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Feather retention force in broilers ante-, peri-, and post-mortem as influenced by carcass orientation, angle of extraction, and slaughter method
Feather Retention Force in Broilers Ante-, Peri-, and Post-Mortem as Influenced by Carcass Orientation, Angle of Extraction, and Slaughter Method R. J. BUHR,*,1 J. A. CASON,† and G. N. ROWLAND* *Department of Avian Medicine, College of Veterinary Medicine, The University of Georgia, Athens, Georgia 30602-4875, and †USDA, Agricultural Research Service, Richard B. Russell Agricultural Research Center, P.O. Box 5633, Athens, Georgia 30604-5677 greater FRF (9 to 29%) than feathers extracted at a perpendicular angle, at all sample periods. Broilers suspended on shackles ante- and peri-mortem had higher FRF values (5 to 30%) than those restrained in shackles in a supine position on a table. Other parameters resulted in minor and inconsistent alterations in FRF. Electrical stunning, when not followed by bleeding, resulted in small reductions in FRF (up to 7%). Bleeding after stunning without or with spinal cord transection resulted in variable peri-mortem FRF changes (+7 to –11% and +11 to –11%, respectively). Only in the pectoral feather tract was there a significant increase (5 to 6%) in FRF as broilers went from the anteto peri-mortem state. At 2 and 6 min after stunning and initiation of exsanguination, post-mortem FRF was unaffected by carcass orientation for the pectoral and femoral tracts.
(Key words: feather retention force, electrical stunning, slaughter orientation, broiler, spinal cord) 1997 Poultry Science 76:1591–1601
INTRODUCTION Feather retention force (FRF), the force required to remove a feather from the feather follicle, is diminished during scalding (81 to 99% reduction, Klose et al., 1961; Dickens and Shackleford, 1988; Walker and Griffis, 1994) to facilitate defeathering during the picking process. Feathers are normally seated tightly in their follicles, whether the feathers are growing or mature. Feather tension in conscious and unconscious poultry appears in part to depend on tonus nerve impulses from the central nervous system to the multiunit smooth muscle fibers attached via tendons to the feather follicle (Ostmann et al., 1964; Smith and Helbacka, 1968). In addition, the friction between the corneous sheets of the follicle and the feather contributes to feather tension as the bird goes from ante- through the post-mortem state.
Received for publication November 12, 1996. Accepted for publication June 1, 1997. 1To whom correspondence should be addressed.
Alternative methods have been used prior to slaughter (ante-mortem) to enhance efficient removal of feathers from the carcass during post-mortem processing. Some of these methods involve mechanical or chemical stunning procedures that disable the portion of the central nervous system responsible for feather follicle muscle tension, the medulla oblongata (King, 1921). Others have used neurological blocking agents or anesthetics, in addition to peri-mortem electrical stunning and carcass stimulation as a means of decreasing FRF. King (1921) demonstrated that induced lesions of the medulla oblongata in anesthetized broilers resulted in a slackening of 57% in feather pulling force. Kuenzel et al. (1985), chemically stunned broilers by injecting ammonium acetate into the medulla oblongata and measured a FRF reduction of 23% following a 60 s bleed-out. Klose et al. (1962), reported that when restrained hens (15-moold White Leghorn) were pithed and bled, FRF was reduced 58% within 30 s, but the depression of FRF persisted for less than 30 s. The immediate reduction and subsequent restoration of FRF following pithing
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ABSTRACT Stunning and slaughter trials were conducted to evaluate the influence of carcass orientation (inverted or supine), angle of feather extraction (parallel or perpendicular to the carcass surface), and slaughter method (exsanguination without or with spinal cord transection) on feather retention force (FRF) in commercial broilers sampled ante-, peri-, and post-mortem. The pectoral, sternal, and femoral feather tracts were sampled before and after stunning contralaterally, with a maximum indicating force gauge, from broilers suspended on a shackle (inverted) or laying on a table (supine). For all trials and sample periods FRF was consistently greater in the femoral area (547 to 679 g) than in the pectoral area (273 to 391 g), with the sternal feather tract requiring the least force at 246 to 343 g. Feathers extracted parallel to the carcass resulted in consistently
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addition, in all of the experiments by Levinger and Angel (1977), FRF values recorded after bleeding (2.5 min) remained unchanged after an additional 30 min post-mortem holding period for both anesthetized and unanesthetized spinal cord transected and untransected Leghorn chickens (8 to 10 wk of age). These results indicate that within the time period from 2 to 30 min post-mortem, FRF is not measurably changed. Peri-mortem sampling of broilers at 20 or 120 s after electrical stunning (in the absence of bleeding) resulted in a lower FRF of 16 to 18% compared to prestunning values, when broilers were restrained and sampled on a table (Dickens and Shackleford, 1988). Following stunning (50 V alternating current) and bleeding (90 s) Kuenzel et al. (1986) reported that post-mortem FRF was reduced 10%, or in conjunction with an additional secondary post-stunner reduced by as much as 28%. However, Mahoney et al. (1971) found no significant differences in carcass picking scores, following scalding and picking, among electrically stunned (whole body, head, or back), debrained, or semi-Kosher slaughtered broilers. These reports indicate that electrical stunning had little effect on FRF as compared to anesthesia. In contrast, electrical stimulation during bleed-out (1 to 4 min) or following scalding (24 min) consistently resulted in smaller reduction in wing FRF (63 to 80%) than unstimulated controls after scalding (85 to 99%, Walker and Griffis, 1994). Previous reports indicated that even under ideal conditions, the time period for reduction in FRF after the pithing procedure is short followed by a return of FRF with the onset of death. The relaxation of ante-mortem FRF following anesthesia or stunning indicates that the central nervous system maintains a tonic influence on FRF in conscious birds. In addition, the further reduction of FRF following spinal cord transection in lightly anesthetized birds indicates that the central nervous system continues to be involved in unconscious birds. Poultry are commonly shackled and electrically stunned prior to bleeding in most processing plants in the U.S. The primary objective of stunning is to achieve immobilization of the bird during the killing and bleeding process. The objective of this study was to measure FRF ante-, peri-, and post-mortem and to further clarify factors that influence FRF in commercial broilers during processing. Implementation of environmental or neurobiological parameters, ante-mortem or peri-mortem, that consistently reduce post-mortem FRF would enable minimization of defeathering processing procedures (scalding and picking) and the potential for broiler carcass microbial cross-contamination during defeathering.
MATERIALS AND METHODS
Broilers and Body Weight Measurements On each processing day, 16 or 18 live male broiler chickens were obtained from a commercial processor,
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indicates the presence of a temporary peri-mortem period within which FRF may be influenced by mechanical trauma to the medulla prior to death. Administration of anesthetics and tranquilizers have been shown to reduce ante-mortem FRF by more than 80% (Klose et al., 1961; Ostmann et al., 1963); however, these effects do not seem to be retained after death, just prior to or after scalding. A positive relationship appears to exist between FRF peri-mortem and FRF post-mortem following scalding. This relationship was demonstrated by Klose et al. (1961), in which anesthetized (sodium pentobarbital) roosters and spent hens displayed reduced FRF values (44 to 76%) and a further reduction occurred when anesthetized birds were subscalded at 50 or 53 C (57 to 90%). These reductions in FRF were greater than those obtained from nonanesthetized, bled, and subscalded birds (26 to 61%). However, any additive benefit of anesthesia was not detectable at a higher scalding temperature of 60 C (92 to 98% reduction in FRF). Spinal cord transection in anesthetized White Leghorn hens further reduced FRF (66%) in feather tracts innervated by spinal nerves located caudal to the lesion. This reduction in FRF was beyond the decrease (22%) associated with the light anesthesia measured from feather tracts innervated by spinal nerves located cranial to the lesion (Ostmann et al., 1964). Crude electrical stimulation of the caudal end of the severed spinal cord restored FRF to a 13% reduction from preanesthetic values. The increase in FRF following spinal cord stimulation demonstrated the capability of the nervous system to mediate increases in FRF. When death was induced in anesthetized and spinal cord transected hens by an overdose of anesthetic (sodium pentobarbital), an immediate additional post-mortem decrease (37%) in FRF occurred. However, after 5 min post-mortem FRF was restored by 94% (approximately 31% lower than the unanesthetized value) when compared to the anesthetized and spinal cord transected value. In contrast, when death was induced by exsanguination and clonic convulsions (death struggle) occurred, there was an immediate increase in FRF of 160% (approximately 5% lower than the unanesthetized value) for anesthetized and spinal cord transected hens (Ostmann et al., 1964). These results indicate the absence of substantial carryover effects post-mortem from spinal cord transection (for anesthetized birds) and that the occurrence of clonic convulsions is associated with rapid return of FRF post-mortem. This premise is further supported by the report from Levinger and Angel (1977), in which a significant reduction in FRF (61%) was recorded following anesthesia, but the reduction was diminished to only 10% following exsanguination. However, when the spinal cord was transected (at the first cervical vetebra) prior to or immediately after exsanguination (for 2.5 min) FRF remained 13 to 18% below unanesthetized ante-mortem values. The application of spinal cord severing did not significantly reduce post-mortem FRF, but eliminated clonic convulsions and the associated rapid return of FRF post-mortem. In
FEATHER RETENTION FORCE
transferred into plastic coops, and transported in a covered vehicle to the pilot processing facility. Broilers were removed from coops and individually weighed prior to initiation of assigned treatment, and a second weight was taken following pulling the final set of feathers. Body weight loss was determined by difference in initial and final weight. Final weight was not adjusted for water pickup during electrical stunning or for cloacal discharge, because reweighing immediately following stunning would have delayed exsanguination and spinal cord transection. Body weight was measured to assure uniformity in broiler size and feather development among assigned treatments. Body weight loss was determined for comparison of blood loss during bleeding among slaughter methods.
Pretreatment feather samples pulled from conscious broilers were considered ante-mortem. Ante-mortem values were collected to enable determination of the relative depression or elevation in FRF peri- or postmortem following treatment for each broiler. Feather removal initiated at 0.5 min after stunning was considered peri-mortem and was concurrent with the bleed-out period. Feather extraction initiated at 2 or 6 min after stunning was considered post-mortem. Peri- and postmortem samples were taken to determine the relative depression or elevation in FRF immediately following stunning and after death. Sampling rate was approximately four broilers per hour, requiring 4 min to pull six feathers unilaterally from each of the three feather tracts. Preliminary experiments indicated that ante-mortem FRF was influenced by the time that broilers remained in the plastic coop after delivery. Therefore, broilers were assigned to treatments sequentially (forward and reverse, i.e., 1st, 6th, 7th, 12th, 13th, and 18th) resulting in first and last broiler sampled each day being assigned to the same treatment. Feather samples from conscious broilers in Table 1 were taken within the first 2 h of transport or between 4 to 6 h of transport to record “time in coop” effect on FRF. In addition, initial sampling side (left or right) was alternated for each successive broiler as was the initial feather tract sampled (pectoral, sternal, or femoral). These three feather tracts were chosen as representative of covert feathers varying in size from different regions of the body. Feather sampling periods were restricted between the hanging and scalding steps for broiler processing. This time period was chosen in consideration of the work reported by Klose et al. (1961) indicating that a lower FRF prior to scalding resulted in a lower FRF after subscalding at 50 or 53 C. However, Dickens and Schackleford (1988) reported positive effects of scalding time (1, 1.5, and 2 min)
2Shimpo
America Corp., Lincolnwood, IL 60659.
and temperature (52 and 56 C) in the reduction of postscald FRF. The severe reduction in FRF after scalding (81 to 99%, Klose et al., 1961; Dickens and Shackleford, 1988; Walker and Griffis, 1994) would overwhelm the detection of minor factors as angle of feather extraction, sampling side, stunning, spinal cord severing, or carcass orientation.
Carcass Orientation Feathers were pulled from broilers suspended in shackles (inverted) or on a table (supine) prior to stunning, following stunning during bleeding, and after bleeding. Broilers oriented on the table ante-mortem were shackled and wings taped at the carpal joint to the table. The head and neck of the broiler extended over the edge of the table and remained unsupported. During stunning and bleedout broilers were suspended on shackles and otherwise unrestricted, except for trials reported in Table 2. Trials presented in Table 2 were conducted to determine whether bleed-out orientation (inverted or supine) influenced bleed-out weight loss or FRF, and therefore broilers were positioned on a table or shackle during bleed-out.
Feather Tracts Sampled Six feathers were pulled in series at each sampling period from the pectoral, sternal, and femoral feather tracts. For the pectoral feather tract, feathers were sampled from the second or third rows adjacent to the marginal feather row along the apteria pectorale (Baumel et al., 1979). For the sternal feather tract, feathers from the first or second rows (whichever was larger) were selected adjacent to the apteria sternale along the midline of the breast. For the femoral feather tract, feathers were pulled proximal (second or third rows) to the caudal-distal marginal row, adjacent to the apteria curale. Preliminary experiments indicated that marginal rows of feathers had lower FRF than the second or third rows.
Angle of Feather Extraction Feathers were extracted from the carcass at an angle parallel or perpendicular to the carcass (and floor) while the carcass was oriented supine on a table or inverted on a shackle. Feather extraction measurements taken perpendicular to the floor (against the force of gravity) were adjusted by 75 g (the combined weight of the internal components of the force gauge and the hemostat used to grasp the feather) prior to analysis.
Measuring Feather Retention Force A maximum indicating force gauge2 was used to record the force (grams) required to remove a late-immature feather from the feather follicle. Individual feathers were clamped above the follicle umbilicus with a hemostatic
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Feather Sampling Periods (Ante-, Peri-, and Post-Mortem)
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BUHR ET AL. TABLE 1. Ante-mortem initial and final feather retention force in conscious broilers influenced by carcass orientation and holding time for the pectoral, sternal, and femoral feather tracts
Parameter
Initial ante-mortem
Final ante-mortem
Feather tract
Feather tract
Pectoral
Sternal
Femoral
Pectoral
Sternal
Femoral
(g) Orientation of carcass Supine Inverted Holding time 0 to 2 h 4 to 6 h Side Left Right Pooled SEM
385b 407a
313 322
607b 664a
369b 406a
316 341
566b 677a
411a 381b
336a 300b
599b 672a
394 380
342a 315b
610 633
415a 377b 20
338a 297b 21
683a 588b 35
396 378 24 Probability
317 340 22
576b 668a 37
0.0091 0.3192 0.2035
0.0533 0.0339 0.0750
0.0001 0.2855 0.0001
a,bMeans within a column and parameter contrast with no common superscript differ significantly (P < 0.05); n = 4 broilers. 1Order compares initial ante-mortem to final ante-mortem feather retention force values.
tissue forceps, attached to the force gauge, and the forceps-gauge moved away from the carcass. Six feathers were pulled in sequence unilaterally from the pectoral, sternal, and femoral feather tracts for each sampling period. Feather retention force was averaged per feather tract for individual broilers and for each sampling period. The difference between sampling periods was expressed as percentage change in FRF.
individually head to shanks. All broilers were removed from the stunning shackle and transferred to the bleeding shackle or table, and bled by severing both carotid arteries and at least one jugular vein within 10 s after stunning. Broilers that were assigned spinal cord severing had the spinal column and cord transected with hand shears, within the second and third cervical vertebra region, immediately following hanging on the bleed-out shackle.
Stunning and Slaughter
Statistical Analysis
Electrical stunning was applied using a brine stunner (saturated salt concentration) with voltage set at 50 V, alternating current, for 10 s, with an average current drawn of 30 mA per bird. Broilers were stunned
Feather retention force was determined on broilers subjected to different carcass orientations (inverted and supine), angles of feather extraction (parallel or perpendicular), sample sides (left and right), feather tracts
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Source of variation Orientation 0.0481 0.4292 0.0054 Holding time 0.0110 0.0038 0.0005 Side 0.0012 0.0011 0.0001 Combined initial and final ante-mortem feather sampling periods (g) Orientation of carcass 314 587b Supine 377b Inverted 407a 332 671a Holding time 339a 605b 0 to 2 h 402a 4 to 6 h 381b 307b 653a Side 327 629 Left 406a 319 628 Right 378b Order Initial 396 318 635 Final 387 328 622 Pooled SEM 15 16 28 Probability Source of variation Orientation 0.0010 0.0576 0.0001 Holding time 0.0165 0.0006 0.0038 Side 0.0022 0.3239 0.9207 Order1 0.3409 0.2351 0.4059
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FEATHER RETENTION FORCE TABLE 2. Post-mortem feather retention force influenced by carcass orientation during slaughter and feather sampling for the pectoral, sternal, and femoral feather tracts Initial post-mortem1 (2 min)
Final post-mortem (6 min)
Feather tract
Feather tract
Slaughter orientation
Sample orientation
Pectoral
Sternal
Femoral
Supine
Supine Inverted Supine Inverted
425 423 422 380
311 363 344 366
396 429 40
337 355 37
Pectoral
Sternal
Femoral
618 631 667 663
434 424 437 405
338ab 367ab 325b 394a
677 649 637 709
632 657 49
433 417 40 Probability
372 340 41
667 669 59
(g)
Inverted Side Left Right Pooled SEM
0.5076 0.3109
0.0193 0.0517
0.1570 0.9532
a,bMeans within a column and parameter contrast with no common superscript differ significantly (P < 0.05), n = 4 broilers. 1Post-mortem 2 or 6 min after stunning and bleed-out. All broilers were stunned inverted on a shackle and bled as indicated. 2Order compares initial post-mortem (2 min) to final post-mortem (6 min) feather retention force values.
(pectoral, sternal, and femoral), and slaughter methods (stun; stun and bled; stun, bled and spinal cord severed), at ante-, peri-, and post-mortem sampling periods. All treatment variables were replicated on 2 or more processing d, n = 4 to eight broilers per treatment. Mean FRF for the six feathers per feather tract per birds per sample period was analyzed using the General Linear Models procedure SAS, and the means separated using the Tukey’s Studentized range (HSD) Test (SAS Institute, 1994). For all analyses, significance was determined at P < 0.05 level. Feather tracts consistently differed in FFR and therefore the data were reanalyzed and are reported by feather tract. Sources of variation in the model included the following main effects: angle of feather extraction, sample side, carcass orientation, and slaughter methods. Interaction terms for main effects were tested by residual
error. Initial ante-mortem FRF varied among replications, but interactions between replications and main effects were not significant.
RESULTS AND DISCUSSION
Feather Tracts Feather retention force (FRF) for all trials and sample periods (ante-, peri-, and post-mortem) was consistently greater in the femoral (547 to 679 g) than the pectoral (273 to 391 g) feather tract, and both were greater than the sternal (246 to 342 g) tract (Tables 1 to 5). Therefore data are reported for each discrete feather tract. This ranking in FRF appears to be associated with feather maturity and
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Source of variation Slaughter-Sample orientation 0.1434 0.0524 0.2337 Side 0.0557 0.2220 0.2402 Combined 2 min and 6 min post-mortem feather sampling periods (g) Slaughter orientation Supine 426 345 644 Inverted 411 357 669 Sample orientation 650 Supine 430 330b 663 Inverted 408 372a Side Left 415 355 650 Right 423 348 663 Order 2 min 413 346 645 6 min 425 356 668 Pooled SEM 20 20 27 Probability Source of variation Slaughter orientation 0.1846 0.2667 0.1105 Sample orientation 0.0612 0.0002 0.3934 Side 0.4922 0.5317 0.4271 Order2 0.2880 0.3758 0.1400
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size among the three feather tracts for market age broilers. Differences in FRF between covert feather tracts have previously been reported for broilers (Dickens and Shackleford, 1988) and White Leghorn hens (Ostmann et al., 1964).
Angle of Feather Extraction
Orientation of the Carcass Broilers oriented inverted on shackles had greater FRF than those oriented supine on a table both ante-mortem (11 to 30%) and peri-mortem (13 to 26%, Table 3). Change in carcass orientation from supine to inverted position, between initial and final sampling periods generally increased FRF (–7 to +53%) and the opposite change from inverted to supine decreased FRF (0 to –26%, Table 3). Post-mortem, at 2 and 6 min after stunning, the orientation of the carcass did not influence FRF (Table 4) for the pectoral and femoral feather tracts. However, FRF in the
TABLE 3. Ante-mortem and peri-mortem feather retention force influenced by angle of feather extraction and carcass orientation for the pectoral, sternal, and femoral feather tracts Final peri-mortem1
Initial ante-mortem Angle of feather extraction
Orientation of carcass Pectoral
Feather tract Sternal
(g) Parallel Supine 294bc 245abc Perpendicular Supine 226de 183c Parallel Supine 335ab 247abc Perpendicular Supine 197e 238abc Parallel Inverted 366a 289ab Perpendicular Inverted 264cd 237abc bcd Parallel Inverted 285 324a Perpendicular Inverted 251cde 232bc Pooled SEM 34 51 Probability 0.0001 0.0007 Angle of feather extraction (combined orientation of carcass) 276a Parallel 320a Perpendicular 235b 223b Orientation of carcass (combined angle feather extraction) 228b Supine 263b Inverted 292a 270a Side (combined angle of feather extraction and orientation of carcass) Left 284 264a Right 270 235b Pooled SEM 19 25
Femoral
Orientation of carcass Pectoral
Feather tract Sternal
Femoral
338ab 254cd 330abc 250cd 345a 290abc 264bcd 204d 45 0.0001
(g) 235bc 192c 280b 221bc 372a 256bc 248bc 220bc 41 0.0001
570a 401b 586a 472ab 581a 512ab 543a 398b 72 0.0001
572a 426b
319a 250b
284a 222b
570a 446b
433b 565a
265b 304a
224b 282a
478b 538a
502 495 38
288 281 24
250 256 23
537 479 32
577a 311b 533a 309b 634a 548a 542a 535a 67 0.0001
Supine Supine Inverted Inverted Inverted Inverted Supine Supine
Probability Source of variation Angle of feather extraction Orientation of carcass Side Order2 a–eMeans
0.0001 0.0100 0.5180 0.5157
0.0001 0.0040 0.0038 0.7411
0.0001 0.0001 0.1155 0.6396
0.0001 0.0050 0.0897
0.0001 0.0001 0.5405
0.0001 0.0016 0.6396
within a column and parameter contrast with no common superscript differ significantly (P < 0.05), n = 4 broilers. 0.5 to 4 min after stunning during bleed-out. All broilers were stunned and bled inverted on a shackle. 2Order compares initial ante-mortem to final peri-mortem feather retention force values. 1Peri-mortem
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The angle at which the feather was extracted from the carcass significantly affected FRF at all measurement periods (ante-, peri-, and post-mortem; Tables 3 and 4). In Tables 3, 4, and 5, initial and final FRF values (noncombined) collected from the same group of broilers are presented within a row of the table. Feathers that were extracted parallel to the longitudinal axis of the carcass had consistently greater FRF values (pectoral 9 to 29%, sternal 19 to 23%, femoral 14 to 26%) than feathers that were extracted at a perpendicular angle. The difference in FRF between angles of feather extraction was nonsignificant only at 2 min after stunning for the pectoral tract (Table 4). Changing feather extraction angle from parallel to perpendicular (from initial to final samples, Table 4) resulted in lower FRF (–9 to –31%), whereas
change from perpendicular to parallel resulted in an increase in FRF (3 to 24%). The difference associated with the angle of feather extraction were present for both supine and inverted carcass orientation. The consistently lower FRF for feathers extracted perpendicular to the carcass (for all sample periods) indicates that the angle of feather removal should be evaluated in the design of commercial picking equipment. In Tables 1, 2, and 3, feathers were extracted parallel to the carcass in order to measure maximum FRF.
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orientation from inverted (for all broilers) during stunning to supine during feather sampling may have influenced this increase. The influence of carcass orientation on FRF appears to differ for conscious and unconscious broilers. Carcass orientation was further examined with initial and final samples collected entirely within the antemortem (Table 1) or post-mortem periods (2 and 6 min after stunning, Table 2). Carcass orientation of all broilers was changed between initial and final sampling in order that each broiler was sampled while oriented supine and inverted. Therefore, in Tables 1 and 2, initial and final FRF values collected from the same group of broilers are presented transposed between adjacent rows of the table. Initial and final ante-mortem FRF values for the pectoral and femoral tracts were higher for broilers inverted on shackles than those shackled in the supine position on a table, whereas the differences for the sternal tract was not significant. These results indicate that FRF in conscious (ante-mortem) broilers can be altered depending on carcass orientation (Table 1), and that orientation (supine or inverted) is differentiated by the broiler and not simply a change in orientation. In addition, in Table 2 the
TABLE 4. Post-mortem1 feather retention force influenced by carcass orientation and angle of feather extraction for the pectoral, sternal, and femoral feather tracts Initial post-mortem (2 min) Orientation of carcass
Angle of feather extraction
Final post-mortem (6 min)
Feather tract Pectoral
Sternal
(g) Supine Parallel 328 270abc Supine Perpendicular 293 201abc Supine Parallel 321 269abc Supine Perpendicular 269 232abc Inverted Parallel 288 272ab Inverted Perpendicular 276 200c Inverted Parallel 313 294a Inverted Perpendicular 299 222bc Pooled SEM 54 39 Probability 0.4984 0.0001 Orientation of carcass (combined angle of feather extraction) Supine 303 245 Inverted 294 247 Angle of feather extraction (combined orientation of carcass) Parallel 312 276a Perpendicular 284 216b Side (combined orientation of carcass and angle of feather extraction) Left 293 237 Right 303 256 Pooled SEM 27 19
Femoral
Angle of feather extraction
Feather tract Pectoral
Sternal
Femoral
357a 308ab 286ab 352a 343ab 306ab 260b 341ab 49 0.0076
(g) 276abc 215c 244bc 245bc 316ab 226c 224c 346a 44 0.0001
558bc 471cd 424d 665ab 568bc 542c 413d 676a 62 0.0001
541 553
326 313
245b 278a
529 550
587a 507b
348a 290b
296a 227b
617a 462b
565a 529b 29
331 307 24
289 234 22
584 495 29
548abc 524abc 615a 475c 570abc 512bc 614ab 516abc 57 0.0002
Parallel Perpendicular Perpendicular Parallel Parallel Perpendicular Perpendicular Parallel
Probability Source of variation Orientation of carcass Angle of feather extraction Side Order2 a–dMeans
0.5756 0.0716 0.5378 0.0541
0.8394 0.0001 0.0910 0.1261
0.4520 0.0001 0.0336 0.6409
0.3469 0.0003 0.0711
0.0109 0.0001 0.5773
0.3114 0.0001 0.1319
within a column and parameter contrast with no common superscript differ significantly (P < 0.05), n = 4 broilers. 2 or 6 min after stunning and bleed-out. All broilers were stunned and bled inverted on a shackle. 2Order compares initial post-mortem (2 min) to final post-mortem (6 min) feather retention force values. 1Post-mortem
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sternal tract at 6 min post-mortem was higher for broilers that were oriented inverted (13%) as opposed to those in a supine position. Additional ante-mortem orientation FRF values are presented in Table 5 (n = 64) and broilers oriented in an inverted position had higher (5%) FRF values for the femoral tract only, whereas the pectoral and sternal tracts were not significantly affected by orientation. Perimortem (0.5 to 6 min after stunning), only the pectoral tract was significantly affected by orientation, supine having greater (6%) values than inverted. This perimortem difference was not anticipated. With only stunned broilers (excluding stunned and bled, and stunned, bled, and spinal cord severed), the difference in FRF between supine and inverted orientation peri-mortem for the pectoral tract was 4% and was not significant (355 and 344 g). Stunned but not bled (unconscious) broilers oriented inverted on shackles consistently had small reductions in FRF for all three feather tracts ante-mortem (–4.4, –3.5, and –7%, Table 5). Stunned but not-bled broilers shackled supine on a table generally displayed an increase in FRF peri-mortem (+5, –1, and +5%). Change in carcass
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BUHR ET AL. TABLE 5. Ante-mortem and peri-mortem feather retention force influenced by carcass orientation and slaughter treatment for the pectoral, sternal, and femoral feather tracts Final peri-mortem1
Initial ante-mortem Feather tract Pectoral
Sternal
Supine Supine
365ab 379a
295 314
577abc 584abc
Supine
329bc
315
567abc
Supine
358abc
297
567abc
Supine
316c
288
528c
Supine Inverted Inverted
369ab 339abc 354abc
317 287 305
547bc 543bc 608ab
Inverted
341abc
318
592abc
Inverted
335abc
332
591abc
Inverted
355abc
329
632a
Femoral
Feather tract
Slaughter treatment
Orientation of carcass
Pectoral
Sternal
Femoral
Stunned Stunned Stunned Bled Stunned Bled Stunned Bled Cord Stunned Bled Cord Stunned Stunned Stunned Bled Stunned Bled Stunned Bled Cord Stunned Bled Cord
Supine Inverted
384a 355ab
(g) 292bc 295bc
606ab 558bc
Supine
356ab
299bc
602ab
Inverted
334ab
299bc
613ab
Supine
350ab
289bc
569abc
Inverted Inverted Supine
328b 324b 362ab
288bc 277c 332ab
595ab 504c 608ab
Inverted
347ab
353a
637ab
Supine
341ab
300bc
610ab
Inverted
366ab
339ab
648a
Supine
384a 27 0.0005
312abc 28 0.0001
605ab 42 0.0001
363a 342b
304 308
600 593
356 345 357
299 313 307
569b 616a 604a
360a 345b 14
312 300 14
621a 571b 21
(g)
Inverted 371ab 291 589abc Pooled SEM 23 25 36 Probability 0.0001 0.0791 0.0001 Orientation of carcass (combined slaughter treatment) Supine 353 304 567b Inverted 349 310 592a Slaughter treatment (combined orientation of carcass) Stunned 359a 300 578 Stunned and bled 341b 311 579 Stunned, bled, and cord 353ab 315 574 Side (combined orientation of carcass and slaughter treatment) 307 597a Left 359a Right 343b 308 557b Pooled SEM 12 13 18
Probability Source of variation Slaughter treatment Orientation of carcass Side Order2
0.0273 0.5380 0.0036 0.4313
0.1088 0.3003 0.8785 0.6257
0.8759 0.0004 0.0001 0.0001
0.2109 0.0015 0.0237
0.2325 0.5056 0.0711
0.0005 0.4546 0.0001
a–cMeans
within a column and parameter contrast with no common superscript differ significantly (P < 0.05). 0.5 or 4 min after stunning and during bleed-out. 2Order compares initial ante-mortem to final peri-mortem feather retention force values. Slaughter treatments stunned and stunned, bled, and spinal cord severed n = 8 broilers; stunned and bled n = 16. 1Peri-mortem
orientation of the carcass during bleed-out was examined. Post-mortem FRF values, 2 and 6 min after stunning and bleeding, were not significantly influenced by orientation of the carcass during bleed-out or carcass orientation during feather sampling (Table 2). For the sternal tract, at 2 min after stunning, broilers oriented inverted during slaughter and sampled inverted had greater FRF (21%) than those sampled supine. Change in orientation from supine to inverted resulted in a 5 to 12% increase in FRF from initial to final samples. In contrast, change in orientation from inverted to supine resulted in a 2 to 15% decrease in FRF from initial to final samples.
In Table 5, after stunning unconscious broilers orientation on a shackle had lower FRF, whereas unconscious broilers oriented supine on a table had elevated FRF. In contrast, conscious broilers initially sampled supine then inverted had increases in FRF, whereas broilers initially sampled inverted and then supine resulted in decreases in FRF (Table 1). The difference between carcass orientation, greater for inverted than for supine for the sternal tract and not the pectoral and femoral tracts is unexplained. Our preliminary investigations have indicated that heart rate is higher for conscious broilers oriented inverted on a shackle than supine on a table after removal from the
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Orientation of carcass
FEATHER RETENTION FORCE
transport coop (R. J. Buhr, unpublished data). Factors resulting in an increased heart rate in conscious broilers may accompany the increase in FRF for broiler oriented supine ante- and peri-mortem. Heart rate of unconscious broilers after stunning has not been determined.
Side of Feather Extraction
Stunning and Slaughter The influence of stunning and bleeding with and without spinal cord severing are presented in Table 5. These three treatments resulted in minimal changes in FRF (–3 to 7%) within the same carcass orientation anteand peri-mortem. Only for the femoral feather tract was peri-mortem FRF significantly lower for stunned broilers than for bled broilers (7%). The absence of a reduction in FRF following spinal cord transection immediately after stunning indicates that spinal cord-brain integration is not necessary for the small increase (5 to 6%) in FRF antemortem to peri-mortem, or to maintain peri-mortem FRF tone. Separation of the connections between the spinal cord and cutaneous nerves will determine whether the
spinal cord mediates FRF peri-mortem. These results agree with those reported by Ostmann et al. (1964), in which when death was induced by exsanguination and clonic convulsions occurred there was an immediate increase in FRF to approximately 5% lower than the nonanesthetized value. However, noticeable clonic convulsions did not occur in our trials after stunning and bleeding with or without spinal cord transection.
Holding Time Holding time in the coop prior to sampling significantly influenced initial and final ante-mortem FRF values, but the effect was not uniform for the three feather tracts (Table 1). In the pectoral and sternal tracts, FRF was greater for broilers held 0 to 2 h (402 and 339 g), whereas broilers held 4 to 6 h had lower values (381 and 307 g). With regard to the femoral tract, broilers held 0 to 2 h had lower FRF (605 g) than higher values after 4 to 6 h in the coop (653 g). The prolonged crouching position and minimal wing movement of the broiler in the coop may influence FRF differently among the feather tracts. The difference may have resulted from alteration in neural tone to feather follicle smooth muscles for the three feather tracts. This unavoidable source of variability “time in coop” was minimized by assigning one broiler to each treatment group sequentially on the day of processing.
Feather Sampling Periods The order of sample collection (initial or final) did not detectably affect FRF ante-mortem (Table 4) or postmortem at 2 and 6 min after stunning and bleeding (Tables 2, and 4). The absence of a difference in FRF between initial and final sampling periods ante-mortem (Table 1) indicate that handling during removal from the transportation coop did not inflate the initial FRF samples over the final samples. In addition, the ante-mortem sequential pulling of 18 feathers from the 3 feathers tracts and then switching sides and body orientation did not significantly influence the FRF for the final 18 feathers from the contralateral three feather tracts. All feathers sampled were small and immature, and the vast majority of the broilers showed little or no outward reaction to removal of the feathers. In Table 3, no differences between initial ante-mortem and final peri-mortem FRF values were detected. Similarly in Table 4, the differences between initial postmortem (2 min) and final post-mortem (6 min) FRF values were not significant. The absence of a peri-mortem increase in FRF was again demonstrated for the pectoral and sternal feather tracts in Table 5. However, a small but significant increase (5 to 6%) in FRF was detected for the femoral tract peri-mortem. In our experiments, there does not appear to be substantial increase or decrease in FRF from ante- to peri- or post-mortem periods following stunning or stunning and bleeding.
Body Weight Measurements Pretreatment broiler body weight did not differ among slaughter treatments for any processing trial (Table 6).
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When significant differences occurred between sampling sides, usually the left side had significantly greater FRF values than the right (9 of 10 instances; Tables 1 to 5). When all four sample periods were combined (ante-, peri-, and post-mortem, Tables 3 and 4) only the femoral tract differed significantly between the left and right side (9.5%). Inconsistent differences in FRF for sample side was anticipated from preliminary experiments, and therefore initial and final feather samples were alternated left and right for each broiler to account for this variability. In Table 5, the effect of sample side was significant for the pectoral and femoral feather tracts ante- and peri-mortem. Changing from the left to right side between initial and final samples resulted in a lower FRF (–3%). In contrast, change from initial sampling on the right and final sampling on the left increased FRF (6%). Comparing initial and final samples both during the ante-mortem period (Table 1), the initial samples from the left side were greater than those samples taken from the right side for all three tracts (10 to 16%). Final ante-mortem sample values did not differ between sides for the pectoral and sternal tracts, but in the femoral tract, samples from the right side were greater than the left (14%). If FRF was not influenced by sample side but only by individual variation among broilers, the higher initial FRF values for the left side would result in correspondingly higher FRF values for the final right side samples. However, significantly higher final values for samples from the right side occurred once (Table 1). Comparing FRF post-mortem (at 2 and 6 min after stunning and bleeding, Table 2), no difference was detected between left and right side samples. Significant differences in FRF for sample sides occurred ante- and peri-mortem. These results demonstrate the influence of sample side, and change in sides between initial and final sampling ante-mortem can influence FRF –9 to +7%.
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BUHR ET AL. TABLE 6. Body weight and percentage weight loss after feather sampling with and without bleeding, and spinal cord severing Treatment and carcass orientation
Ante-mortem
Peri- or post-mortem (kg)
Not stunned or bled Oriented supine Oriented inverted Stunned and bled Oriented supine Oriented inverted Pooled SEM
Percentage change
n
(%)
1.944 2.061
1.940 2.057
–0.18b –0.18b
8 8
2.110 1.988 0.036
2.032 1.918 0.035 Probability
–3.50a –3.64a 0.01
8 8
Source of variation Treatment Orientation Oriented inverted Stunned Stunned and bled Stunned, bled, and spinal cord severed Pooled SEM
0.3753 0.9615
0.6383 0.9850
2.042 2.024 2.004 0.026
2.046a 1.952b 1.951b 0.026 Probability
Source of variation Treatment
0.6224
0.0277
Therefore, similar body size and degree of feather maturity among slaughter treatments can be assumed. Body weight for broilers that were not stunned and feathers extracted ante-mortem resulted in a 0.18% decrease in weight (for the 36 feathers extracted). Weight loss for carcasses orientated supine or inverted in the presence or absence of bleeding did not differ. Carcass orientation during the bleed-out period, inverted (3.7%) or supine (3.5%), did not influence body weight loss. Electrically stunned broilers increased their carcass weight (0.19%) greater than the loss from feathers, apparently due to body surface water pickup during the brine-stunning process. As anticipated broilers that were stunned and bled had greater percentage weight loss than those only stunned. The percentage of body weight loss during the bleed-out period was greater for broilers with intact spinal cords (3.5%) than those that were severed (2.7%) immediately after stunning. It was not determined whether this difference resulted from adhering or pooling of blood from severed blood vessels in spinal cord transected groups. Our experiments have provided additional evidence and described several parameters (carcass orientation, sampling side, “time in coop”, electrical stunning) that can alter FRF ante- or peri-mortem. Identification of a factor that consistently lowers FRF post-mortem was not attained. However, feathers extracted perpendicular from the carcass surface consistently had lower FRF values ante-, peri-, and post-mortem compared to feathers extracted parallel. The alteration in FRF ante-, peri-, and post-mortem influenced by the parameters evaluated was minimal compared to the reported 81 to 99% reduction in
0.19a –3.54c –2.68b 0.14
32 64 32
0.0001
common superscript differ significantly (P < 0.05).
FRF after immersion scalding (Klose et al., 1961; Dickens and Schackleford, 1988; Walker and Griffis, 1994).
ACKNOWLEDGMENT The authors thank V. Allan Savage for technical support and assistance with data collection.
REFERENCES Baumel, J. J., A. S. King, A. M. Lucas, J. E. Breazile, and H. E. Evans, ed. 1979. Nomina Anatomica Avium. Academic Press, London, UK. Dickens, J. A., and A. D. Shackleford, 1988. Feather-releasing force related to stunning, scalding time, and scalding temperature. Poultry Sci. 67:1069–1074. King, C. H., 1921. Physiology of the “stick” in the dry picking of poultry. J. Am. Assoc. Inst. Invest. Poult. Husbandry 7: 55–56, 65–70. Klose, A. A., E. P. Mecchi, and M. F. Pool, 1961. Observations on factors influencing feather release. Poultry Sci. 40: 1029–1036. Klose, A. A., E. P. Mecchi, and M. F. Pool, 1962. Feather release by scalding and other factors. Poultry Sci. 41:1277–1282. Kuenzel, W. J., W. Collins, and C. Meyers, 1985. Feather release in processed broilers and a modification of the standard electrical stunning method used in poultry processing plants. Pages 73–78 in: Proceedings 20th National Meeting Poultry Health Condemnations, Ocean City, MD. Kuenzel, W. J., J. Walther, and W. Collins, 1986. The effect of pre- and post stunning on bleed-out and feather release in processed broilers. Pages 62–66 in: Proceedings 21st National Meeting Poultry Health Condemnations, Ocean City, MD.
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a–cMeans within a column and parameter contrast with no
0.0001 0.6661
FEATHER RETENTION FORCE Levinger, I. M., and S. Angel, 1977. Effect of spinal cord transection on feather release in the slaughtered broiler. Br. Poult. Sci. 18:169–172. Mahoney, W. A., G. W. Newell, and G. Olson, 1971. Feather release as related to stunning methods. The ASAE Paper No. 71-865. American Society of Agricultural Engineers, St. Joseph, MI. Ostmann, O. W., R. A. Peterson, and R. K. Ringer, 1964. Effect of spinal cord transection and stimulation on feather release. Poultry Sci. 43:648–654.
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Ostmann, O. W., R. K. Ringer, and M. Tetzlaff, 1963. The anatomy of the feather follicle and its immediate surroundings. Poultry Sci. 42:958–969. SAS Institute, 1994. SAS/STAT Guide for Personal Computers. Version 7 Edition. SAS Institute Inc., Cary, NC. Smith, C. J., and N.V.L. Helbacka, 1968. The effect of brain lesions on feather release from young chickens. Poultry Sci. 47:711–714. Walker, J. T., and C. L. Griffis, 1994. Effects of electrical stimulation on feather pulling force. ASAE 37:541–544.
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(Key words: feather retention force, electrical stunning, slaughter orientation, broiler, spinal cord) 1997 Poultry Science 76:1591–1601
INTRODUCTION Feather retention force (FRF), the force required to remove a feather from the feather follicle, is diminished during scalding (81 to 99% reduction, Klose et al., 1961; Dickens and Shackleford, 1988; Walker and Griffis, 1994) to facilitate defeathering during the picking process. Feathers are normally seated tightly in their follicles, whether the feathers are growing or mature. Feather tension in conscious and unconscious poultry appears in part to depend on tonus nerve impulses from the central nervous system to the multiunit smooth muscle fibers attached via tendons to the feather follicle (Ostmann et al., 1964; Smith and Helbacka, 1968). In addition, the friction between the corneous sheets of the follicle and the feather contributes to feather tension as the bird goes from ante- through the post-mortem state.
Received for publication November 12, 1996. Accepted for publication June 1, 1997. 1To whom correspondence should be addressed.
Alternative methods have been used prior to slaughter (ante-mortem) to enhance efficient removal of feathers from the carcass during post-mortem processing. Some of these methods involve mechanical or chemical stunning procedures that disable the portion of the central nervous system responsible for feather follicle muscle tension, the medulla oblongata (King, 1921). Others have used neurological blocking agents or anesthetics, in addition to peri-mortem electrical stunning and carcass stimulation as a means of decreasing FRF. King (1921) demonstrated that induced lesions of the medulla oblongata in anesthetized broilers resulted in a slackening of 57% in feather pulling force. Kuenzel et al. (1985), chemically stunned broilers by injecting ammonium acetate into the medulla oblongata and measured a FRF reduction of 23% following a 60 s bleed-out. Klose et al. (1962), reported that when restrained hens (15-moold White Leghorn) were pithed and bled, FRF was reduced 58% within 30 s, but the depression of FRF persisted for less than 30 s. The immediate reduction and subsequent restoration of FRF following pithing
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ABSTRACT Stunning and slaughter trials were conducted to evaluate the influence of carcass orientation (inverted or supine), angle of feather extraction (parallel or perpendicular to the carcass surface), and slaughter method (exsanguination without or with spinal cord transection) on feather retention force (FRF) in commercial broilers sampled ante-, peri-, and post-mortem. The pectoral, sternal, and femoral feather tracts were sampled before and after stunning contralaterally, with a maximum indicating force gauge, from broilers suspended on a shackle (inverted) or laying on a table (supine). For all trials and sample periods FRF was consistently greater in the femoral area (547 to 679 g) than in the pectoral area (273 to 391 g), with the sternal feather tract requiring the least force at 246 to 343 g. Feathers extracted parallel to the carcass resulted in consistently
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addition, in all of the experiments by Levinger and Angel (1977), FRF values recorded after bleeding (2.5 min) remained unchanged after an additional 30 min post-mortem holding period for both anesthetized and unanesthetized spinal cord transected and untransected Leghorn chickens (8 to 10 wk of age). These results indicate that within the time period from 2 to 30 min post-mortem, FRF is not measurably changed. Peri-mortem sampling of broilers at 20 or 120 s after electrical stunning (in the absence of bleeding) resulted in a lower FRF of 16 to 18% compared to prestunning values, when broilers were restrained and sampled on a table (Dickens and Shackleford, 1988). Following stunning (50 V alternating current) and bleeding (90 s) Kuenzel et al. (1986) reported that post-mortem FRF was reduced 10%, or in conjunction with an additional secondary post-stunner reduced by as much as 28%. However, Mahoney et al. (1971) found no significant differences in carcass picking scores, following scalding and picking, among electrically stunned (whole body, head, or back), debrained, or semi-Kosher slaughtered broilers. These reports indicate that electrical stunning had little effect on FRF as compared to anesthesia. In contrast, electrical stimulation during bleed-out (1 to 4 min) or following scalding (24 min) consistently resulted in smaller reduction in wing FRF (63 to 80%) than unstimulated controls after scalding (85 to 99%, Walker and Griffis, 1994). Previous reports indicated that even under ideal conditions, the time period for reduction in FRF after the pithing procedure is short followed by a return of FRF with the onset of death. The relaxation of ante-mortem FRF following anesthesia or stunning indicates that the central nervous system maintains a tonic influence on FRF in conscious birds. In addition, the further reduction of FRF following spinal cord transection in lightly anesthetized birds indicates that the central nervous system continues to be involved in unconscious birds. Poultry are commonly shackled and electrically stunned prior to bleeding in most processing plants in the U.S. The primary objective of stunning is to achieve immobilization of the bird during the killing and bleeding process. The objective of this study was to measure FRF ante-, peri-, and post-mortem and to further clarify factors that influence FRF in commercial broilers during processing. Implementation of environmental or neurobiological parameters, ante-mortem or peri-mortem, that consistently reduce post-mortem FRF would enable minimization of defeathering processing procedures (scalding and picking) and the potential for broiler carcass microbial cross-contamination during defeathering.
MATERIALS AND METHODS
Broilers and Body Weight Measurements On each processing day, 16 or 18 live male broiler chickens were obtained from a commercial processor,
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indicates the presence of a temporary peri-mortem period within which FRF may be influenced by mechanical trauma to the medulla prior to death. Administration of anesthetics and tranquilizers have been shown to reduce ante-mortem FRF by more than 80% (Klose et al., 1961; Ostmann et al., 1963); however, these effects do not seem to be retained after death, just prior to or after scalding. A positive relationship appears to exist between FRF peri-mortem and FRF post-mortem following scalding. This relationship was demonstrated by Klose et al. (1961), in which anesthetized (sodium pentobarbital) roosters and spent hens displayed reduced FRF values (44 to 76%) and a further reduction occurred when anesthetized birds were subscalded at 50 or 53 C (57 to 90%). These reductions in FRF were greater than those obtained from nonanesthetized, bled, and subscalded birds (26 to 61%). However, any additive benefit of anesthesia was not detectable at a higher scalding temperature of 60 C (92 to 98% reduction in FRF). Spinal cord transection in anesthetized White Leghorn hens further reduced FRF (66%) in feather tracts innervated by spinal nerves located caudal to the lesion. This reduction in FRF was beyond the decrease (22%) associated with the light anesthesia measured from feather tracts innervated by spinal nerves located cranial to the lesion (Ostmann et al., 1964). Crude electrical stimulation of the caudal end of the severed spinal cord restored FRF to a 13% reduction from preanesthetic values. The increase in FRF following spinal cord stimulation demonstrated the capability of the nervous system to mediate increases in FRF. When death was induced in anesthetized and spinal cord transected hens by an overdose of anesthetic (sodium pentobarbital), an immediate additional post-mortem decrease (37%) in FRF occurred. However, after 5 min post-mortem FRF was restored by 94% (approximately 31% lower than the unanesthetized value) when compared to the anesthetized and spinal cord transected value. In contrast, when death was induced by exsanguination and clonic convulsions (death struggle) occurred, there was an immediate increase in FRF of 160% (approximately 5% lower than the unanesthetized value) for anesthetized and spinal cord transected hens (Ostmann et al., 1964). These results indicate the absence of substantial carryover effects post-mortem from spinal cord transection (for anesthetized birds) and that the occurrence of clonic convulsions is associated with rapid return of FRF post-mortem. This premise is further supported by the report from Levinger and Angel (1977), in which a significant reduction in FRF (61%) was recorded following anesthesia, but the reduction was diminished to only 10% following exsanguination. However, when the spinal cord was transected (at the first cervical vetebra) prior to or immediately after exsanguination (for 2.5 min) FRF remained 13 to 18% below unanesthetized ante-mortem values. The application of spinal cord severing did not significantly reduce post-mortem FRF, but eliminated clonic convulsions and the associated rapid return of FRF post-mortem. In
FEATHER RETENTION FORCE
transferred into plastic coops, and transported in a covered vehicle to the pilot processing facility. Broilers were removed from coops and individually weighed prior to initiation of assigned treatment, and a second weight was taken following pulling the final set of feathers. Body weight loss was determined by difference in initial and final weight. Final weight was not adjusted for water pickup during electrical stunning or for cloacal discharge, because reweighing immediately following stunning would have delayed exsanguination and spinal cord transection. Body weight was measured to assure uniformity in broiler size and feather development among assigned treatments. Body weight loss was determined for comparison of blood loss during bleeding among slaughter methods.
Pretreatment feather samples pulled from conscious broilers were considered ante-mortem. Ante-mortem values were collected to enable determination of the relative depression or elevation in FRF peri- or postmortem following treatment for each broiler. Feather removal initiated at 0.5 min after stunning was considered peri-mortem and was concurrent with the bleed-out period. Feather extraction initiated at 2 or 6 min after stunning was considered post-mortem. Peri- and postmortem samples were taken to determine the relative depression or elevation in FRF immediately following stunning and after death. Sampling rate was approximately four broilers per hour, requiring 4 min to pull six feathers unilaterally from each of the three feather tracts. Preliminary experiments indicated that ante-mortem FRF was influenced by the time that broilers remained in the plastic coop after delivery. Therefore, broilers were assigned to treatments sequentially (forward and reverse, i.e., 1st, 6th, 7th, 12th, 13th, and 18th) resulting in first and last broiler sampled each day being assigned to the same treatment. Feather samples from conscious broilers in Table 1 were taken within the first 2 h of transport or between 4 to 6 h of transport to record “time in coop” effect on FRF. In addition, initial sampling side (left or right) was alternated for each successive broiler as was the initial feather tract sampled (pectoral, sternal, or femoral). These three feather tracts were chosen as representative of covert feathers varying in size from different regions of the body. Feather sampling periods were restricted between the hanging and scalding steps for broiler processing. This time period was chosen in consideration of the work reported by Klose et al. (1961) indicating that a lower FRF prior to scalding resulted in a lower FRF after subscalding at 50 or 53 C. However, Dickens and Schackleford (1988) reported positive effects of scalding time (1, 1.5, and 2 min)
2Shimpo
America Corp., Lincolnwood, IL 60659.
and temperature (52 and 56 C) in the reduction of postscald FRF. The severe reduction in FRF after scalding (81 to 99%, Klose et al., 1961; Dickens and Shackleford, 1988; Walker and Griffis, 1994) would overwhelm the detection of minor factors as angle of feather extraction, sampling side, stunning, spinal cord severing, or carcass orientation.
Carcass Orientation Feathers were pulled from broilers suspended in shackles (inverted) or on a table (supine) prior to stunning, following stunning during bleeding, and after bleeding. Broilers oriented on the table ante-mortem were shackled and wings taped at the carpal joint to the table. The head and neck of the broiler extended over the edge of the table and remained unsupported. During stunning and bleedout broilers were suspended on shackles and otherwise unrestricted, except for trials reported in Table 2. Trials presented in Table 2 were conducted to determine whether bleed-out orientation (inverted or supine) influenced bleed-out weight loss or FRF, and therefore broilers were positioned on a table or shackle during bleed-out.
Feather Tracts Sampled Six feathers were pulled in series at each sampling period from the pectoral, sternal, and femoral feather tracts. For the pectoral feather tract, feathers were sampled from the second or third rows adjacent to the marginal feather row along the apteria pectorale (Baumel et al., 1979). For the sternal feather tract, feathers from the first or second rows (whichever was larger) were selected adjacent to the apteria sternale along the midline of the breast. For the femoral feather tract, feathers were pulled proximal (second or third rows) to the caudal-distal marginal row, adjacent to the apteria curale. Preliminary experiments indicated that marginal rows of feathers had lower FRF than the second or third rows.
Angle of Feather Extraction Feathers were extracted from the carcass at an angle parallel or perpendicular to the carcass (and floor) while the carcass was oriented supine on a table or inverted on a shackle. Feather extraction measurements taken perpendicular to the floor (against the force of gravity) were adjusted by 75 g (the combined weight of the internal components of the force gauge and the hemostat used to grasp the feather) prior to analysis.
Measuring Feather Retention Force A maximum indicating force gauge2 was used to record the force (grams) required to remove a late-immature feather from the feather follicle. Individual feathers were clamped above the follicle umbilicus with a hemostatic
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Feather Sampling Periods (Ante-, Peri-, and Post-Mortem)
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BUHR ET AL. TABLE 1. Ante-mortem initial and final feather retention force in conscious broilers influenced by carcass orientation and holding time for the pectoral, sternal, and femoral feather tracts
Parameter
Initial ante-mortem
Final ante-mortem
Feather tract
Feather tract
Pectoral
Sternal
Femoral
Pectoral
Sternal
Femoral
(g) Orientation of carcass Supine Inverted Holding time 0 to 2 h 4 to 6 h Side Left Right Pooled SEM
385b 407a
313 322
607b 664a
369b 406a
316 341
566b 677a
411a 381b
336a 300b
599b 672a
394 380
342a 315b
610 633
415a 377b 20
338a 297b 21
683a 588b 35
396 378 24 Probability
317 340 22
576b 668a 37
0.0091 0.3192 0.2035
0.0533 0.0339 0.0750
0.0001 0.2855 0.0001
a,bMeans within a column and parameter contrast with no common superscript differ significantly (P < 0.05); n = 4 broilers. 1Order compares initial ante-mortem to final ante-mortem feather retention force values.
tissue forceps, attached to the force gauge, and the forceps-gauge moved away from the carcass. Six feathers were pulled in sequence unilaterally from the pectoral, sternal, and femoral feather tracts for each sampling period. Feather retention force was averaged per feather tract for individual broilers and for each sampling period. The difference between sampling periods was expressed as percentage change in FRF.
individually head to shanks. All broilers were removed from the stunning shackle and transferred to the bleeding shackle or table, and bled by severing both carotid arteries and at least one jugular vein within 10 s after stunning. Broilers that were assigned spinal cord severing had the spinal column and cord transected with hand shears, within the second and third cervical vertebra region, immediately following hanging on the bleed-out shackle.
Stunning and Slaughter
Statistical Analysis
Electrical stunning was applied using a brine stunner (saturated salt concentration) with voltage set at 50 V, alternating current, for 10 s, with an average current drawn of 30 mA per bird. Broilers were stunned
Feather retention force was determined on broilers subjected to different carcass orientations (inverted and supine), angles of feather extraction (parallel or perpendicular), sample sides (left and right), feather tracts
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Source of variation Orientation 0.0481 0.4292 0.0054 Holding time 0.0110 0.0038 0.0005 Side 0.0012 0.0011 0.0001 Combined initial and final ante-mortem feather sampling periods (g) Orientation of carcass 314 587b Supine 377b Inverted 407a 332 671a Holding time 339a 605b 0 to 2 h 402a 4 to 6 h 381b 307b 653a Side 327 629 Left 406a 319 628 Right 378b Order Initial 396 318 635 Final 387 328 622 Pooled SEM 15 16 28 Probability Source of variation Orientation 0.0010 0.0576 0.0001 Holding time 0.0165 0.0006 0.0038 Side 0.0022 0.3239 0.9207 Order1 0.3409 0.2351 0.4059
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FEATHER RETENTION FORCE TABLE 2. Post-mortem feather retention force influenced by carcass orientation during slaughter and feather sampling for the pectoral, sternal, and femoral feather tracts Initial post-mortem1 (2 min)
Final post-mortem (6 min)
Feather tract
Feather tract
Slaughter orientation
Sample orientation
Pectoral
Sternal
Femoral
Supine
Supine Inverted Supine Inverted
425 423 422 380
311 363 344 366
396 429 40
337 355 37
Pectoral
Sternal
Femoral
618 631 667 663
434 424 437 405
338ab 367ab 325b 394a
677 649 637 709
632 657 49
433 417 40 Probability
372 340 41
667 669 59
(g)
Inverted Side Left Right Pooled SEM
0.5076 0.3109
0.0193 0.0517
0.1570 0.9532
a,bMeans within a column and parameter contrast with no common superscript differ significantly (P < 0.05), n = 4 broilers. 1Post-mortem 2 or 6 min after stunning and bleed-out. All broilers were stunned inverted on a shackle and bled as indicated. 2Order compares initial post-mortem (2 min) to final post-mortem (6 min) feather retention force values.
(pectoral, sternal, and femoral), and slaughter methods (stun; stun and bled; stun, bled and spinal cord severed), at ante-, peri-, and post-mortem sampling periods. All treatment variables were replicated on 2 or more processing d, n = 4 to eight broilers per treatment. Mean FRF for the six feathers per feather tract per birds per sample period was analyzed using the General Linear Models procedure SAS, and the means separated using the Tukey’s Studentized range (HSD) Test (SAS Institute, 1994). For all analyses, significance was determined at P < 0.05 level. Feather tracts consistently differed in FFR and therefore the data were reanalyzed and are reported by feather tract. Sources of variation in the model included the following main effects: angle of feather extraction, sample side, carcass orientation, and slaughter methods. Interaction terms for main effects were tested by residual
error. Initial ante-mortem FRF varied among replications, but interactions between replications and main effects were not significant.
RESULTS AND DISCUSSION
Feather Tracts Feather retention force (FRF) for all trials and sample periods (ante-, peri-, and post-mortem) was consistently greater in the femoral (547 to 679 g) than the pectoral (273 to 391 g) feather tract, and both were greater than the sternal (246 to 342 g) tract (Tables 1 to 5). Therefore data are reported for each discrete feather tract. This ranking in FRF appears to be associated with feather maturity and
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Source of variation Slaughter-Sample orientation 0.1434 0.0524 0.2337 Side 0.0557 0.2220 0.2402 Combined 2 min and 6 min post-mortem feather sampling periods (g) Slaughter orientation Supine 426 345 644 Inverted 411 357 669 Sample orientation 650 Supine 430 330b 663 Inverted 408 372a Side Left 415 355 650 Right 423 348 663 Order 2 min 413 346 645 6 min 425 356 668 Pooled SEM 20 20 27 Probability Source of variation Slaughter orientation 0.1846 0.2667 0.1105 Sample orientation 0.0612 0.0002 0.3934 Side 0.4922 0.5317 0.4271 Order2 0.2880 0.3758 0.1400
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size among the three feather tracts for market age broilers. Differences in FRF between covert feather tracts have previously been reported for broilers (Dickens and Shackleford, 1988) and White Leghorn hens (Ostmann et al., 1964).
Angle of Feather Extraction
Orientation of the Carcass Broilers oriented inverted on shackles had greater FRF than those oriented supine on a table both ante-mortem (11 to 30%) and peri-mortem (13 to 26%, Table 3). Change in carcass orientation from supine to inverted position, between initial and final sampling periods generally increased FRF (–7 to +53%) and the opposite change from inverted to supine decreased FRF (0 to –26%, Table 3). Post-mortem, at 2 and 6 min after stunning, the orientation of the carcass did not influence FRF (Table 4) for the pectoral and femoral feather tracts. However, FRF in the
TABLE 3. Ante-mortem and peri-mortem feather retention force influenced by angle of feather extraction and carcass orientation for the pectoral, sternal, and femoral feather tracts Final peri-mortem1
Initial ante-mortem Angle of feather extraction
Orientation of carcass Pectoral
Feather tract Sternal
(g) Parallel Supine 294bc 245abc Perpendicular Supine 226de 183c Parallel Supine 335ab 247abc Perpendicular Supine 197e 238abc Parallel Inverted 366a 289ab Perpendicular Inverted 264cd 237abc bcd Parallel Inverted 285 324a Perpendicular Inverted 251cde 232bc Pooled SEM 34 51 Probability 0.0001 0.0007 Angle of feather extraction (combined orientation of carcass) 276a Parallel 320a Perpendicular 235b 223b Orientation of carcass (combined angle feather extraction) 228b Supine 263b Inverted 292a 270a Side (combined angle of feather extraction and orientation of carcass) Left 284 264a Right 270 235b Pooled SEM 19 25
Femoral
Orientation of carcass Pectoral
Feather tract Sternal
Femoral
338ab 254cd 330abc 250cd 345a 290abc 264bcd 204d 45 0.0001
(g) 235bc 192c 280b 221bc 372a 256bc 248bc 220bc 41 0.0001
570a 401b 586a 472ab 581a 512ab 543a 398b 72 0.0001
572a 426b
319a 250b
284a 222b
570a 446b
433b 565a
265b 304a
224b 282a
478b 538a
502 495 38
288 281 24
250 256 23
537 479 32
577a 311b 533a 309b 634a 548a 542a 535a 67 0.0001
Supine Supine Inverted Inverted Inverted Inverted Supine Supine
Probability Source of variation Angle of feather extraction Orientation of carcass Side Order2 a–eMeans
0.0001 0.0100 0.5180 0.5157
0.0001 0.0040 0.0038 0.7411
0.0001 0.0001 0.1155 0.6396
0.0001 0.0050 0.0897
0.0001 0.0001 0.5405
0.0001 0.0016 0.6396
within a column and parameter contrast with no common superscript differ significantly (P < 0.05), n = 4 broilers. 0.5 to 4 min after stunning during bleed-out. All broilers were stunned and bled inverted on a shackle. 2Order compares initial ante-mortem to final peri-mortem feather retention force values. 1Peri-mortem
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The angle at which the feather was extracted from the carcass significantly affected FRF at all measurement periods (ante-, peri-, and post-mortem; Tables 3 and 4). In Tables 3, 4, and 5, initial and final FRF values (noncombined) collected from the same group of broilers are presented within a row of the table. Feathers that were extracted parallel to the longitudinal axis of the carcass had consistently greater FRF values (pectoral 9 to 29%, sternal 19 to 23%, femoral 14 to 26%) than feathers that were extracted at a perpendicular angle. The difference in FRF between angles of feather extraction was nonsignificant only at 2 min after stunning for the pectoral tract (Table 4). Changing feather extraction angle from parallel to perpendicular (from initial to final samples, Table 4) resulted in lower FRF (–9 to –31%), whereas
change from perpendicular to parallel resulted in an increase in FRF (3 to 24%). The difference associated with the angle of feather extraction were present for both supine and inverted carcass orientation. The consistently lower FRF for feathers extracted perpendicular to the carcass (for all sample periods) indicates that the angle of feather removal should be evaluated in the design of commercial picking equipment. In Tables 1, 2, and 3, feathers were extracted parallel to the carcass in order to measure maximum FRF.
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FEATHER RETENTION FORCE
orientation from inverted (for all broilers) during stunning to supine during feather sampling may have influenced this increase. The influence of carcass orientation on FRF appears to differ for conscious and unconscious broilers. Carcass orientation was further examined with initial and final samples collected entirely within the antemortem (Table 1) or post-mortem periods (2 and 6 min after stunning, Table 2). Carcass orientation of all broilers was changed between initial and final sampling in order that each broiler was sampled while oriented supine and inverted. Therefore, in Tables 1 and 2, initial and final FRF values collected from the same group of broilers are presented transposed between adjacent rows of the table. Initial and final ante-mortem FRF values for the pectoral and femoral tracts were higher for broilers inverted on shackles than those shackled in the supine position on a table, whereas the differences for the sternal tract was not significant. These results indicate that FRF in conscious (ante-mortem) broilers can be altered depending on carcass orientation (Table 1), and that orientation (supine or inverted) is differentiated by the broiler and not simply a change in orientation. In addition, in Table 2 the
TABLE 4. Post-mortem1 feather retention force influenced by carcass orientation and angle of feather extraction for the pectoral, sternal, and femoral feather tracts Initial post-mortem (2 min) Orientation of carcass
Angle of feather extraction
Final post-mortem (6 min)
Feather tract Pectoral
Sternal
(g) Supine Parallel 328 270abc Supine Perpendicular 293 201abc Supine Parallel 321 269abc Supine Perpendicular 269 232abc Inverted Parallel 288 272ab Inverted Perpendicular 276 200c Inverted Parallel 313 294a Inverted Perpendicular 299 222bc Pooled SEM 54 39 Probability 0.4984 0.0001 Orientation of carcass (combined angle of feather extraction) Supine 303 245 Inverted 294 247 Angle of feather extraction (combined orientation of carcass) Parallel 312 276a Perpendicular 284 216b Side (combined orientation of carcass and angle of feather extraction) Left 293 237 Right 303 256 Pooled SEM 27 19
Femoral
Angle of feather extraction
Feather tract Pectoral
Sternal
Femoral
357a 308ab 286ab 352a 343ab 306ab 260b 341ab 49 0.0076
(g) 276abc 215c 244bc 245bc 316ab 226c 224c 346a 44 0.0001
558bc 471cd 424d 665ab 568bc 542c 413d 676a 62 0.0001
541 553
326 313
245b 278a
529 550
587a 507b
348a 290b
296a 227b
617a 462b
565a 529b 29
331 307 24
289 234 22
584 495 29
548abc 524abc 615a 475c 570abc 512bc 614ab 516abc 57 0.0002
Parallel Perpendicular Perpendicular Parallel Parallel Perpendicular Perpendicular Parallel
Probability Source of variation Orientation of carcass Angle of feather extraction Side Order2 a–dMeans
0.5756 0.0716 0.5378 0.0541
0.8394 0.0001 0.0910 0.1261
0.4520 0.0001 0.0336 0.6409
0.3469 0.0003 0.0711
0.0109 0.0001 0.5773
0.3114 0.0001 0.1319
within a column and parameter contrast with no common superscript differ significantly (P < 0.05), n = 4 broilers. 2 or 6 min after stunning and bleed-out. All broilers were stunned and bled inverted on a shackle. 2Order compares initial post-mortem (2 min) to final post-mortem (6 min) feather retention force values. 1Post-mortem
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sternal tract at 6 min post-mortem was higher for broilers that were oriented inverted (13%) as opposed to those in a supine position. Additional ante-mortem orientation FRF values are presented in Table 5 (n = 64) and broilers oriented in an inverted position had higher (5%) FRF values for the femoral tract only, whereas the pectoral and sternal tracts were not significantly affected by orientation. Perimortem (0.5 to 6 min after stunning), only the pectoral tract was significantly affected by orientation, supine having greater (6%) values than inverted. This perimortem difference was not anticipated. With only stunned broilers (excluding stunned and bled, and stunned, bled, and spinal cord severed), the difference in FRF between supine and inverted orientation peri-mortem for the pectoral tract was 4% and was not significant (355 and 344 g). Stunned but not bled (unconscious) broilers oriented inverted on shackles consistently had small reductions in FRF for all three feather tracts ante-mortem (–4.4, –3.5, and –7%, Table 5). Stunned but not-bled broilers shackled supine on a table generally displayed an increase in FRF peri-mortem (+5, –1, and +5%). Change in carcass
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BUHR ET AL. TABLE 5. Ante-mortem and peri-mortem feather retention force influenced by carcass orientation and slaughter treatment for the pectoral, sternal, and femoral feather tracts Final peri-mortem1
Initial ante-mortem Feather tract Pectoral
Sternal
Supine Supine
365ab 379a
295 314
577abc 584abc
Supine
329bc
315
567abc
Supine
358abc
297
567abc
Supine
316c
288
528c
Supine Inverted Inverted
369ab 339abc 354abc
317 287 305
547bc 543bc 608ab
Inverted
341abc
318
592abc
Inverted
335abc
332
591abc
Inverted
355abc
329
632a
Femoral
Feather tract
Slaughter treatment
Orientation of carcass
Pectoral
Sternal
Femoral
Stunned Stunned Stunned Bled Stunned Bled Stunned Bled Cord Stunned Bled Cord Stunned Stunned Stunned Bled Stunned Bled Stunned Bled Cord Stunned Bled Cord
Supine Inverted
384a 355ab
(g) 292bc 295bc
606ab 558bc
Supine
356ab
299bc
602ab
Inverted
334ab
299bc
613ab
Supine
350ab
289bc
569abc
Inverted Inverted Supine
328b 324b 362ab
288bc 277c 332ab
595ab 504c 608ab
Inverted
347ab
353a
637ab
Supine
341ab
300bc
610ab
Inverted
366ab
339ab
648a
Supine
384a 27 0.0005
312abc 28 0.0001
605ab 42 0.0001
363a 342b
304 308
600 593
356 345 357
299 313 307
569b 616a 604a
360a 345b 14
312 300 14
621a 571b 21
(g)
Inverted 371ab 291 589abc Pooled SEM 23 25 36 Probability 0.0001 0.0791 0.0001 Orientation of carcass (combined slaughter treatment) Supine 353 304 567b Inverted 349 310 592a Slaughter treatment (combined orientation of carcass) Stunned 359a 300 578 Stunned and bled 341b 311 579 Stunned, bled, and cord 353ab 315 574 Side (combined orientation of carcass and slaughter treatment) 307 597a Left 359a Right 343b 308 557b Pooled SEM 12 13 18
Probability Source of variation Slaughter treatment Orientation of carcass Side Order2
0.0273 0.5380 0.0036 0.4313
0.1088 0.3003 0.8785 0.6257
0.8759 0.0004 0.0001 0.0001
0.2109 0.0015 0.0237
0.2325 0.5056 0.0711
0.0005 0.4546 0.0001
a–cMeans
within a column and parameter contrast with no common superscript differ significantly (P < 0.05). 0.5 or 4 min after stunning and during bleed-out. 2Order compares initial ante-mortem to final peri-mortem feather retention force values. Slaughter treatments stunned and stunned, bled, and spinal cord severed n = 8 broilers; stunned and bled n = 16. 1Peri-mortem
orientation of the carcass during bleed-out was examined. Post-mortem FRF values, 2 and 6 min after stunning and bleeding, were not significantly influenced by orientation of the carcass during bleed-out or carcass orientation during feather sampling (Table 2). For the sternal tract, at 2 min after stunning, broilers oriented inverted during slaughter and sampled inverted had greater FRF (21%) than those sampled supine. Change in orientation from supine to inverted resulted in a 5 to 12% increase in FRF from initial to final samples. In contrast, change in orientation from inverted to supine resulted in a 2 to 15% decrease in FRF from initial to final samples.
In Table 5, after stunning unconscious broilers orientation on a shackle had lower FRF, whereas unconscious broilers oriented supine on a table had elevated FRF. In contrast, conscious broilers initially sampled supine then inverted had increases in FRF, whereas broilers initially sampled inverted and then supine resulted in decreases in FRF (Table 1). The difference between carcass orientation, greater for inverted than for supine for the sternal tract and not the pectoral and femoral tracts is unexplained. Our preliminary investigations have indicated that heart rate is higher for conscious broilers oriented inverted on a shackle than supine on a table after removal from the
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Orientation of carcass
FEATHER RETENTION FORCE
transport coop (R. J. Buhr, unpublished data). Factors resulting in an increased heart rate in conscious broilers may accompany the increase in FRF for broiler oriented supine ante- and peri-mortem. Heart rate of unconscious broilers after stunning has not been determined.
Side of Feather Extraction
Stunning and Slaughter The influence of stunning and bleeding with and without spinal cord severing are presented in Table 5. These three treatments resulted in minimal changes in FRF (–3 to 7%) within the same carcass orientation anteand peri-mortem. Only for the femoral feather tract was peri-mortem FRF significantly lower for stunned broilers than for bled broilers (7%). The absence of a reduction in FRF following spinal cord transection immediately after stunning indicates that spinal cord-brain integration is not necessary for the small increase (5 to 6%) in FRF antemortem to peri-mortem, or to maintain peri-mortem FRF tone. Separation of the connections between the spinal cord and cutaneous nerves will determine whether the
spinal cord mediates FRF peri-mortem. These results agree with those reported by Ostmann et al. (1964), in which when death was induced by exsanguination and clonic convulsions occurred there was an immediate increase in FRF to approximately 5% lower than the nonanesthetized value. However, noticeable clonic convulsions did not occur in our trials after stunning and bleeding with or without spinal cord transection.
Holding Time Holding time in the coop prior to sampling significantly influenced initial and final ante-mortem FRF values, but the effect was not uniform for the three feather tracts (Table 1). In the pectoral and sternal tracts, FRF was greater for broilers held 0 to 2 h (402 and 339 g), whereas broilers held 4 to 6 h had lower values (381 and 307 g). With regard to the femoral tract, broilers held 0 to 2 h had lower FRF (605 g) than higher values after 4 to 6 h in the coop (653 g). The prolonged crouching position and minimal wing movement of the broiler in the coop may influence FRF differently among the feather tracts. The difference may have resulted from alteration in neural tone to feather follicle smooth muscles for the three feather tracts. This unavoidable source of variability “time in coop” was minimized by assigning one broiler to each treatment group sequentially on the day of processing.
Feather Sampling Periods The order of sample collection (initial or final) did not detectably affect FRF ante-mortem (Table 4) or postmortem at 2 and 6 min after stunning and bleeding (Tables 2, and 4). The absence of a difference in FRF between initial and final sampling periods ante-mortem (Table 1) indicate that handling during removal from the transportation coop did not inflate the initial FRF samples over the final samples. In addition, the ante-mortem sequential pulling of 18 feathers from the 3 feathers tracts and then switching sides and body orientation did not significantly influence the FRF for the final 18 feathers from the contralateral three feather tracts. All feathers sampled were small and immature, and the vast majority of the broilers showed little or no outward reaction to removal of the feathers. In Table 3, no differences between initial ante-mortem and final peri-mortem FRF values were detected. Similarly in Table 4, the differences between initial postmortem (2 min) and final post-mortem (6 min) FRF values were not significant. The absence of a peri-mortem increase in FRF was again demonstrated for the pectoral and sternal feather tracts in Table 5. However, a small but significant increase (5 to 6%) in FRF was detected for the femoral tract peri-mortem. In our experiments, there does not appear to be substantial increase or decrease in FRF from ante- to peri- or post-mortem periods following stunning or stunning and bleeding.
Body Weight Measurements Pretreatment broiler body weight did not differ among slaughter treatments for any processing trial (Table 6).
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When significant differences occurred between sampling sides, usually the left side had significantly greater FRF values than the right (9 of 10 instances; Tables 1 to 5). When all four sample periods were combined (ante-, peri-, and post-mortem, Tables 3 and 4) only the femoral tract differed significantly between the left and right side (9.5%). Inconsistent differences in FRF for sample side was anticipated from preliminary experiments, and therefore initial and final feather samples were alternated left and right for each broiler to account for this variability. In Table 5, the effect of sample side was significant for the pectoral and femoral feather tracts ante- and peri-mortem. Changing from the left to right side between initial and final samples resulted in a lower FRF (–3%). In contrast, change from initial sampling on the right and final sampling on the left increased FRF (6%). Comparing initial and final samples both during the ante-mortem period (Table 1), the initial samples from the left side were greater than those samples taken from the right side for all three tracts (10 to 16%). Final ante-mortem sample values did not differ between sides for the pectoral and sternal tracts, but in the femoral tract, samples from the right side were greater than the left (14%). If FRF was not influenced by sample side but only by individual variation among broilers, the higher initial FRF values for the left side would result in correspondingly higher FRF values for the final right side samples. However, significantly higher final values for samples from the right side occurred once (Table 1). Comparing FRF post-mortem (at 2 and 6 min after stunning and bleeding, Table 2), no difference was detected between left and right side samples. Significant differences in FRF for sample sides occurred ante- and peri-mortem. These results demonstrate the influence of sample side, and change in sides between initial and final sampling ante-mortem can influence FRF –9 to +7%.
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BUHR ET AL. TABLE 6. Body weight and percentage weight loss after feather sampling with and without bleeding, and spinal cord severing Treatment and carcass orientation
Ante-mortem
Peri- or post-mortem (kg)
Not stunned or bled Oriented supine Oriented inverted Stunned and bled Oriented supine Oriented inverted Pooled SEM
Percentage change
n
(%)
1.944 2.061
1.940 2.057
–0.18b –0.18b
8 8
2.110 1.988 0.036
2.032 1.918 0.035 Probability
–3.50a –3.64a 0.01
8 8
Source of variation Treatment Orientation Oriented inverted Stunned Stunned and bled Stunned, bled, and spinal cord severed Pooled SEM
0.3753 0.9615
0.6383 0.9850
2.042 2.024 2.004 0.026
2.046a 1.952b 1.951b 0.026 Probability
Source of variation Treatment
0.6224
0.0277
Therefore, similar body size and degree of feather maturity among slaughter treatments can be assumed. Body weight for broilers that were not stunned and feathers extracted ante-mortem resulted in a 0.18% decrease in weight (for the 36 feathers extracted). Weight loss for carcasses orientated supine or inverted in the presence or absence of bleeding did not differ. Carcass orientation during the bleed-out period, inverted (3.7%) or supine (3.5%), did not influence body weight loss. Electrically stunned broilers increased their carcass weight (0.19%) greater than the loss from feathers, apparently due to body surface water pickup during the brine-stunning process. As anticipated broilers that were stunned and bled had greater percentage weight loss than those only stunned. The percentage of body weight loss during the bleed-out period was greater for broilers with intact spinal cords (3.5%) than those that were severed (2.7%) immediately after stunning. It was not determined whether this difference resulted from adhering or pooling of blood from severed blood vessels in spinal cord transected groups. Our experiments have provided additional evidence and described several parameters (carcass orientation, sampling side, “time in coop”, electrical stunning) that can alter FRF ante- or peri-mortem. Identification of a factor that consistently lowers FRF post-mortem was not attained. However, feathers extracted perpendicular from the carcass surface consistently had lower FRF values ante-, peri-, and post-mortem compared to feathers extracted parallel. The alteration in FRF ante-, peri-, and post-mortem influenced by the parameters evaluated was minimal compared to the reported 81 to 99% reduction in
0.19a –3.54c –2.68b 0.14
32 64 32
0.0001
common superscript differ significantly (P < 0.05).
FRF after immersion scalding (Klose et al., 1961; Dickens and Schackleford, 1988; Walker and Griffis, 1994).
ACKNOWLEDGMENT The authors thank V. Allan Savage for technical support and assistance with data collection.
REFERENCES Baumel, J. J., A. S. King, A. M. Lucas, J. E. Breazile, and H. E. Evans, ed. 1979. Nomina Anatomica Avium. Academic Press, London, UK. Dickens, J. A., and A. D. Shackleford, 1988. Feather-releasing force related to stunning, scalding time, and scalding temperature. Poultry Sci. 67:1069–1074. King, C. H., 1921. Physiology of the “stick” in the dry picking of poultry. J. Am. Assoc. Inst. Invest. Poult. Husbandry 7: 55–56, 65–70. Klose, A. A., E. P. Mecchi, and M. F. Pool, 1961. Observations on factors influencing feather release. Poultry Sci. 40: 1029–1036. Klose, A. A., E. P. Mecchi, and M. F. Pool, 1962. Feather release by scalding and other factors. Poultry Sci. 41:1277–1282. Kuenzel, W. J., W. Collins, and C. Meyers, 1985. Feather release in processed broilers and a modification of the standard electrical stunning method used in poultry processing plants. Pages 73–78 in: Proceedings 20th National Meeting Poultry Health Condemnations, Ocean City, MD. Kuenzel, W. J., J. Walther, and W. Collins, 1986. The effect of pre- and post stunning on bleed-out and feather release in processed broilers. Pages 62–66 in: Proceedings 21st National Meeting Poultry Health Condemnations, Ocean City, MD.
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a–cMeans within a column and parameter contrast with no
0.0001 0.6661
FEATHER RETENTION FORCE Levinger, I. M., and S. Angel, 1977. Effect of spinal cord transection on feather release in the slaughtered broiler. Br. Poult. Sci. 18:169–172. Mahoney, W. A., G. W. Newell, and G. Olson, 1971. Feather release as related to stunning methods. The ASAE Paper No. 71-865. American Society of Agricultural Engineers, St. Joseph, MI. Ostmann, O. W., R. A. Peterson, and R. K. Ringer, 1964. Effect of spinal cord transection and stimulation on feather release. Poultry Sci. 43:648–654.
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Ostmann, O. W., R. K. Ringer, and M. Tetzlaff, 1963. The anatomy of the feather follicle and its immediate surroundings. Poultry Sci. 42:958–969. SAS Institute, 1994. SAS/STAT Guide for Personal Computers. Version 7 Edition. SAS Institute Inc., Cary, NC. Smith, C. J., and N.V.L. Helbacka, 1968. The effect of brain lesions on feather release from young chickens. Poultry Sci. 47:711–714. Walker, J. T., and C. L. Griffis, 1994. Effects of electrical stimulation on feather pulling force. ASAE 37:541–544.
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