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Relationship between feed withdrawal and viscera condition of broilers
Relationship Between Feed Withdrawal and Viscera Condition of Broilers J. K. NORTHCUTT,*,1 S. I. SAVAGE,† and L. R. VEST‡ *Department of Poultry Science, The University of Georgia, Athens, Georgia 30602, †Department of Poultry Science, The University of Georgia, Tifton, Georgia 31793, and ‡Department of Poultry Science, The University of Georgia, Calhoun, Georgia 30703
(Key words: broiler quality, feed withdrawal, gastrointestinal tract, liver color) 1997 Poultry Science 76:410–414
Mast, 1989; Papa, 1991; Lyon et al., 1991). To be effective, the withdrawal period must be long enough to allow the tract to clear, but short enough to limit live weight and carcass yield losses from feed withdrawal (Veerkamp, 1986; Lyon et al., 1991). Research on feed withdrawal has shown that broilers deprived of feed for 8 to 12 h before slaughter have the lowest incidence of carcass contamination and minimal eviscerated carcass yield losses (Smidt et al., 1964; Wabeck, 1972; Veerkamp, 1986; Lyon et al., 1991). Most plants attempt to process broilers after a 10-h feed withdrawal period; however, feed withdrawal is frequently longer than 10 h and birds are processed according to a variety of withdrawal schedules (Benoff, 1982; Ang and Hamm, 1985; Bilgili, 1988; Lyon et al., 1991). Studies on the condition of the gastrointestinal tract of broilers after long term (> 12 h) feed withdrawal have given conflicting results. Wabeck (1972) reported that feed withdrawal periods of 12 to 24 h resulted in birds with an increase in intestinal moisture and fecal material. This result contrasted with the observations of Kamus and Farr (1981), who found that intestinal moisture and amount of fecal material decreased after 10 to 20 h of feed withdrawal. In more recent studies, longterm feed withdrawal had no effect on intestinal moisture, but intestinal content was found to increase with longer withdrawal times (Papa and Dickens, 1989; Papa, 1991). The discrepancies in the feed withdrawal
INTRODUCTION Broiler carcasses may be contaminated with the contents of the gastrointestinal tracts during processing. When contamination occurs, affected carcasses are reprocessed (washed or trimmed), or in extreme cases, condemned (May et al., 1990). Carcass reprocessing or carcass condemnation delays the operation of the processing plant and increases the cost of producing a quality product; therefore, considerable attention has been given to the development of methods that reduce carcass contamination (Benoff, 1982; Bilgili, 1988; Papa and Dickens, 1989; Papa, 1991). One of the production management techniques frequently used to minimize carcass contamination is the withdrawal of feed and water from broilers before catching, loading, and transportation to the processing plant (Wabeck, 1972; Bilgili, 1988; May and Deaton, 1989; Papa and Dickens, 1989; Rasmussen and Mast, 1989; Papa, 1991; Lyon et al., 1991). During the withdrawal period, the crop and digestive tract are emptied, and there is less material available for contamination in the plant (Bilgili, 1988; May and Deaton, 1989; Papa and Dickens, 1989; Rasmussen and
Received for publication May 9, 1996. Accepted for publication September 20, 1996. 1To whom correspondence should be addressed.
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time by replication did not affect the crop contents or the incidence of bile contamination in the digestive tract. Results also suggested that the integrity of the intestines declined after 12 to 14 h feed withdrawal, as indicated by heavy intestinal sloughing. Color analyses of livers showed that length of feed withdrawal did not affect lightness (L* values), but livers became less red (lower positive a*) as feed withdrawal time increased. It was concluded that length of feed withdrawal significantly affected the gastrointestinal tract; however, variation in the appearance of the liver could not be attributed solely to broiler feed withdrawal time.
ABSTRACT This study was conducted to investigate the effects of feed withdrawal on the viscera of commercial broilers. Birds were withdrawn from feed 0, 3, 9, 12, 14, 16, or 18 h before slaughter. Crop and gizzard contents were determined after dissection, and intestinal shape and villi were subjectively scored. Raw liver color was measured colorimetrically. Length of feed withdrawal (time) and its interaction with grower (time by grower) and replication (time by replication) had a significant effect (P < 0.05) on gizzard contents, intestinal shape, and villi; however, time by grower and
411
FEED WITHDRAWAL EFFECTS ON VISCERA TABLE 1. Criteria for evaluation of crop, gizzard, intestinal shape, intestinal villi, and gizzard bile
Score
Crop
Gizzard
Intestinal shape
Intestinal villi
Gizzard bile
0 1 2 3 4
Missing Feed Water Empty Litter
. . . Feed Water Empty Litter
. . . Early round Early flat Late flat Late round
None Present
5
. . .
Modular feces1
. . .
. . . No sloughing Little sloughing Average sloughing Villi present, heavy sloughing No villi, heavy sloughing
1Modular
feces = fecal material ingested before slaughter while birds are in the holding module.
MATERIALS AND METHODS
Birds The study consisted of a single experiment replicated three times. All birds used in this study were commercially reared broilers (Ross × Ross), 41 to 43 d of age, that were obtained from three to five farms (growers) within each replication. Birds were reared under continuous lighting and given ad libitum access to feed and water. Withdrawal feed contained 17% protein and had a ME level of 1,500 kcal/lb (3,306 kcal/kg).
Treatments and Subjective Scoring Birds were withdrawn from feed 0, 3, 9, 12, 14, 16, and 18 h before slaughter. Water was withdrawn 4 h after the initiation of feed withdrawal. Birds in the 0- and 3-h treatments were necropsied and evaluated on the farms, whereas birds in all other treatments were evaluated at the processing plant. For each replication, 50 to 125 viscera were evaluated using the descriptive analysis listed in Table 1. All evaluations were made immediately post-mortem by a trained panel of three individuals. The contents of the crop and gizzard were scored upon dissection. Gizzard bile was reported as the number of gizzards testing positive for bile divided by the number of gizzards evaluated at the specified feed
withdrawal period. Intestinal shape was scored according to the following descriptions: 1) Early Round refers to a round intestine in the process of passing digesta. 2) Early Flat refers to a completely flat intestine void of digesta. 3) Late Flat means the intestines are contracting and may contain a slight amount of digesta. This score applies to intestines that are not as compressed as those with a score of 2. 4) Late Round shape develops when bacterial fermentation produces intestinal gas, and bubbles emerge during evaluation of the villi. Before evaluating intestinal villi, the panel was given three 30-min training and practice sessions and three 30-min validation sessions to familiarize them with the different scores. Intestinal villi were analyzed by opening the upper and lower ileum lengthwise on either side of yolk stalk remnant (Meckel’s diverticulum). After removal of digesta from the intestines, the trained panel evaluated villi using their index and middle fingers, which were placed under the open intestine with the mucosal lining facing up. Forceps were drawn across the mucosal lining, and villi were scored based upon ability to transmit a perceptible vibratory sensation to the panelists. Panelists assigned scores to the villi by comparing them to the standards used during the training sessions. Sloughing of the mucosal lining was determined based upon presence of intact lining and the amount of the lining that was removed under the light pressure of the forceps. The following scale was used to score villi: 1) A score of 1 was assigned to well developed, finger-like villi, with no sloughing of the lining, and a readily perceived vibratory sensation. 2) A score of 2 was assigned to villi with little or no sloughing of the mucosal lining, but perceived vibration was slightly less than villi receiving a score of 1. 3) A score of 3 was assigned to villi with average sloughing and average villi vibration. 4) A score of 4 indicated only a minor amount of villi vibration could be detected with heavy intestinal sloughing. 5) A score of 5 indicated no perceived villi were present, and there was heavy intestinal sloughing.
Liver Color Measurement The C.I.E. (1978) L*, +a*, and +b* color values were measured on raw livers immediately post-mortem using a
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data may be attributed to differences in broiler catching, holding, and manure consumption before slaughter, which alters intestinal contents and may slow digestive tract clearance. In addition, it has been suggested that increased intestinal moisture in broilers held off feed for longer periods of time develops from accelerated metabolic breakdown of the tissues (Ang and Hamm, 1985). Because the condition and contents of the intestines are important in poultry processing, the present study was designed to 1) establish a method for viscera evaluation that is applicable in a commercial plant, and 2) to use that method to determine the effects of various commercial feed withdrawal schedules on the condition of the viscera of broilers.
412
NORTHCUTT ET AL. TABLE 2. Effect of time off feed on the condition of the crop, gizzard, shape of intestines, intestinal villi, and gizzard bile1
Time off feed (h) 0
Crop
3 9 12 14 16 18 1n
Score 1, 2 (Feed, water) Score 1, 2 (Feed, water) Score 4 (Litter) Score 4 (Litter) Score 4 (Litter) Score 4, 5 (Litter, modular feces) Score 4, 5 (Litter, modular feces)2
Shape of intestines
Intestinal villi
Score 1 (Early round) Score 1 (Early round) Score 2–3 (Early to late flat) Score 2–3 (Early to late flat) Score 3–4 (Late flat to late round) Score 3–4 (Late flat to late round) Score 3–4 (Late flat to late round)
Score 1 (No sloughing) Score 1 (No sloughing) Score 2–3 (Mild sloughing) Score 3 (Average sloughing) Score 3–4 (Average to heavy sloughing) Score 3–4 (Average to heavy sloughing) Score 3–4 (Average to heavy sloughing)
Bile (%) 0 0 30 30 35 40 70
= 275.
2Modular
feces = fecal material ingested before slaughter while birds are in the holding module.
Minolta colorimeter.2 The colorimeter was standardized throughout the study using white3 and pink ceramic tiles.4 One color reading was recorded per liver (n = 220), and the readings were reported as averages. Color difference (DE) was calculated using the following formula: DE = [(L*1 – L*2)2 + (a*1 – a*2)2 + (b*1 – b*2)2]Ø where L*1, a*1, and b*1 represent color parameters measured on liver from birds with no feed withdrawal, and L*2, a*2, and b*2 represent color parameters measured after one of the feed withdrawal treatments (3, 9, 12, 14, 16, or 18 h).
Statistical Analyses All data were statistically analyzed using an analysis of variance to test the main effects of length of feed withdrawal (time) and grower (farm). Replication was used as the error term for the analysis (SAS Institute, 1994). For each replication, viscera were evaluated from 50 to 125 broilers grown on three to five different farms. Farms varied with replication, eliminating the grower by replication interaction. Correlation among variables was determined using the Pearson product-moment correlation coefficient (Sokal and Rohlf, 1969). Differences among means for liver color were separated using the TukeyKramer Means Comparison test at a significance level of P < 0.05 (Neter et al., 1990).
2Minolta Chroma Meter CR-2000, Minolta Camera Co., Ltd., 30, 2 Chrome, Azuchi Machi, Kagashi-Ku, Japan. 3Reference number 13533123. Y = 92.7, x = 0.3133, y = 0.3193. 4Reference number 16332113. Y = 28.7, x = 0.363, y = 0.317.
RESULTS AND DISCUSSION Scores for the various traits measured at the different feed withdrawal times are presented in Table 2. Birds in the 0- and 3-h feed withdrawal groups had similar viscera scores. These birds had ingesta in their gastrointestinal tracts at the time of death, which would more likely result in carcass contamination during processing. Birds processed after 9 and 12 h of feed withdrawal had litter with some bile (30%) in their gastrointestinal tracts; however, the intestines of these birds were optimal for processing because they were empty (flattened shape) and had mild sloughing. Birds with empty intestines have less potential for carcass contamination during processing (Bilgili, 1988; May and Deaton, 1989; Papa and Dickens, 1989; Rasmussen and Mast, 1989; Papa, 1991; Lyon et al., 1991). In addition, the mild intestinal sloughing suggests these intestines retained their integrity and were stronger. The results were consistent with those of Bilgili (1988), who found that there was a significant (P < 0.05) relationship between shear strength of the gastrointestinal tract of broilers and the length of feed withdrawal. According to Bilgili (1988), shear strength of the duodenum of the intestines was greatest in birds that did not eat for 6 or 12 h, and lowest in birds that did not eat for 0, 18, or 24 h before processing. In the present study, intestines of birds that did not eat for 14, 16, and 18 h had heavy sloughing (loss of intestinal mucosal lining), and appeared to be affected by bacterial fermentation, as indicated by the rounded intestinal shape and visible production of intestinal gas (Table 2). When data were analyzed statistically, length of feed withdrawal (time) and its interaction with grower (time by grower) and replication (time by rep) were found to have a significant effect (P < 0.05) on crop contents, intestinal shape, and intestinal villi (Table 3). Although incidence of bile contamination appeared to increase
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Score 1 (Feed) Score 1 (Feed) Score 2 (Water) Score 3 (Empty) Score 3 (Empty) Score 3 (Empty) Score 3 (Empty)
Gizzard
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FEED WITHDRAWAL EFFECTS ON VISCERA TABLE 3. Probability values for the indicated sources Source1
Crop
Gizzard
Shape
Villi
Bile
Time Grower Time × grower Time × replicate
0.0285 0.0302 0.0070 0.0066
0.7762 0.0025 0.0774 0
0 0.0093 0.0024 0
0 0.0956 0.0034 0.0282
0.6550 0.4098 0.3813 0.0261
1Time
refers to length of feed withdrawal.
livers became less red (lower +a* values). The yellowness (+b*) color parameter appeared to follow a cubic pattern, because it decreased initially (3 to 9 h withdrawal), then leveled off (9 to 12 h withdrawal), and finally increased again (18 h withdrawal). Color of livers removed from birds left on feed (0 h group) before slaughter was compared to color of livers removed from birds after 3, 9, 12, 14, 16, and 18 h of feed withdrawal by calculating color difference (DE). As the length of feed withdrawal increased, DE values also increased, indicating a greater difference between colors (Table 5). Liver color difference may have been higher in birds with longer feed withdrawal because liver yield loss may have concentrated the pigments. However, the effect of feed withdrawal on liver yields was not determined during the present investigation. Jensen et al. (1984) showed that birds given feed withdrawal periods less than 8 h had the same liver yields, but increasing feed withdrawal from 12 to 16 h caused a significant loss in liver yields (6.7 and 21% loss, respectively). When these guidelines are applied to the present study, broilers that did not eat for 0 to 3 h, and 9 to 18 h should have different colored livers because of yield loss; however, there was no significant difference in DE values for livers from birds that did not eat for 3, 9, 12, or 16 h. Because of the complexity of liver metabolism, it was concluded that variations in its appearance could not be attributed solely to length of broiler feed withdrawal, and additional research would be required. This study demonstrates that extensive feed withdrawal times can cause a rapid deterioration in the condition of the viscera, which would increase the likelihood of carcass contamination problems during processing. Moreover, the methods for viscera evaluation that were presented in this study may be beneficial to production and processing plant management as they monitor and optimize their feed withdrawal programs.
TABLE 4. Pearson product-moment correlation (r) coefficients (P < 0.05) for crop, gizzard, intestinal shape, intestinal villi, and gizzard bile Variable
Crop
Crop Gizzard Shape Villi Bile
0.100 0.123 0.049 0.059
Gizzard
Shape
Villi
Bile
0.100
0.123 0.428
0.049 0.280 0.725
0.059 0.138 0.175 0.133
0.428 0.280 0.138
0.725 0.175
0.133
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with length of feed withdrawal, reporting it as present or not present prohibited us from finding a distinct significant effect. Farm to farm (grower) variation was found to affect (P < 0.05) crop, gizzard, and intestinal shape. Differences observed in the data because of grower may not only be related to time spent managing the flock, but also to other associated but uncontrollable factors that affect broiler feeding patterns and digestive tract emptying, such as environmental stress. Determining the extent of the involvement of the other contributing factors requires additional research. Correlation coefficients (r) were determined for crop, gizzard, intestinal shape, intestinal villi, and bile contamination because these parameters were descriptive and may be considered as effects of a common cause (Table 4). No significant correlation was found between crop contents or bile contamination and the other measurements. This lack of association may be due to differences in crop contents at the time of catching or other bird-to-bird variations that were not controlled. Changes in the intestinal shape were found to correlate positively with gizzard contents (r = 0.428) and intestinal villi scores (r = 0.725). These findings are similar to those reported by May and Deaton (1989), Papa and Dickens (1989), and Papa (1991) in their studies on digestive tract contents after varying feed withdrawal periods. During the present study, extreme variation in color of raw chicken liver was observed. It was suggested that length of feed withdrawal possibly affects the color of liver because it affects liver glycogen and carcass yields. Color measurements of raw chicken liver after various feed withdrawal periods are presented in Table 5. No significant difference in the lightness (L* values) color parameter of livers was found due to feed withdrawal; however, feed withdrawal affected redness and yellowness values. As length of feed withdrawal increased,
414
NORTHCUTT ET AL. TABLE 5. Effect (x ± SE) of time off feed on color measurement (L, +a*, +b*) or raw chicken livers Time off feed
L (Lightness)1
(h) 0 3 9 12 14 16 19
35.22 36.26 34.23 33.59 33.77 34.67 34.77 a–cMeans
± ± ± ± ± ± ±
3.22 3.32 2.20 1.49 1.85 2.59 2.67
+a* (Redness)1 17.78 17.52 13.87 13.46 12.44 13.11 12.50
± ± ± ± ± ± ±
1.63a 2.40a 1.51b 1.77b 1.48b 1.53b 1.37b
+b* (Yellowness)1 7.45 8.52 6.69 5.77 6.89 6.24 8.44
± ± ± ± ± ± ±
2.52a,b 2.47a 2.00b 1.69b 2.00a,b 2.10a,b 3.17a
Color difference (DE) . . . 4.52 5.03 5.54 6.20 5.97 6.65
± ± ± ± ± ±
0.57b,c 0.22c 0.28a,b 0.19a 0.51a,b 0.35a
within a column with no common superscript differ significantly (P < 0.05).
REFERENCES
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Ang, C.Y.W., and D. Hamm, 1985. Influence of length of feed withdrawal times on proximate composition and levels of selected vitamins and minerals in broiler breast meat. Poultry Sci. 64:1491–1493. Benoff, F. H., 1982. The “live-shrink” trap: Catch weights a must. Broiler Ind. 41(1):56, 60. Bilgili, S. F., 1988. Research note: Effect of feed and water withdrawal on shear strength of broiler gastrointestinal tract. Poultry Sci. 67:845–847. C.I.E., 1978. International Commission on Illumination, Recommendations on Uniform Color Spaces, Color Difference Equations, Psychometric Color Terms. Supplement No. 15 to C.I.E. publication No. 15 (E-1.3.1) 1971/(To-1.3). Bureau Central de la C.I.E., Paris France. Jensen, L. S., H. M. Cervantes, and K. Takahashi, 1984. Liver lipid content in broilers as affected by time without feed or feed and water. Poultry Sci. 63:2404–2407. Kamus, N. L., and A. J. Farr, 1981. Withdrawal and haul effects on moisture uptake, retention and intestinal scores. Poultry Sci. 60:1604. (Abstr.) Lyon, C. E., C. M. Papa, and R. L. Wilson, Jr., 1991. Effect of feed withdrawal on yields, muscle pH, and texture of broiler breast meat. Poultry Sci. 70:1020–1025. May, J. D., and J. W. Deaton, 1989. Digestive tract clearance of broilers cooped or deprived of water. Poultry Sci. 68: 627–630.
May, J. D., B. D. Lott, and J. W. Deaton, 1990. The effect of light and environmental temperature on broiler digestive tract contents after feed withdrawal. Poultry Sci. 69:1681–1684. Neter, J., W. Wasserman, and M. H. Kutner, 1990. Applied Linear Statistical Methods, 3rd ed. Richard D. Irwin, Inc., Homewood, IL. Papa, C. M., 1991. Lower gut contents of broiler chickens withdrawn from feed and held in cages. Poultry Sci. 70: 375–380. Papa, C. M., and J. A. Dickens, 1989. Lower gut contents and defecatory responses of broiler chickens as affected by feed withdrawal and electrical treatment at slaughter. Poultry Sci. 68:1478–1484. Rasmussen, A. L., and M. G. Mast, 1989. Effect of feed withdrawal on composition and quality of broiler meat. Poultry Sci. 68:1109–1113. SAS Institute, 1994. SAS/STAT Guide for Personal Computers. Version 7 edition. SAS Institute, Inc., Cary, NC. Smidt, M. J., S. D. Formica, and J. C. Fritz, 1964. Effect of fasting prior to slaughter on yield of broilers. Poultry Sci. 43:931–934. Sokal, R. R., and F. J. Rohlf, 1969. Biometry: The principles and practice of statistics in biological research. W. H. Freeman and Co., San Francisco, CA. Veerkamp, C. H., 1986. Fasting and yields of broilers. Poultry Sci. 65:1299–1304. Wabeck, C. J., 1972. Feed and water withdrawal time relationship to processing yield and potential fecal contamination of broilers. Poultry Sci. 51:1119–1121.
(Key words: broiler quality, feed withdrawal, gastrointestinal tract, liver color) 1997 Poultry Science 76:410–414
Mast, 1989; Papa, 1991; Lyon et al., 1991). To be effective, the withdrawal period must be long enough to allow the tract to clear, but short enough to limit live weight and carcass yield losses from feed withdrawal (Veerkamp, 1986; Lyon et al., 1991). Research on feed withdrawal has shown that broilers deprived of feed for 8 to 12 h before slaughter have the lowest incidence of carcass contamination and minimal eviscerated carcass yield losses (Smidt et al., 1964; Wabeck, 1972; Veerkamp, 1986; Lyon et al., 1991). Most plants attempt to process broilers after a 10-h feed withdrawal period; however, feed withdrawal is frequently longer than 10 h and birds are processed according to a variety of withdrawal schedules (Benoff, 1982; Ang and Hamm, 1985; Bilgili, 1988; Lyon et al., 1991). Studies on the condition of the gastrointestinal tract of broilers after long term (> 12 h) feed withdrawal have given conflicting results. Wabeck (1972) reported that feed withdrawal periods of 12 to 24 h resulted in birds with an increase in intestinal moisture and fecal material. This result contrasted with the observations of Kamus and Farr (1981), who found that intestinal moisture and amount of fecal material decreased after 10 to 20 h of feed withdrawal. In more recent studies, longterm feed withdrawal had no effect on intestinal moisture, but intestinal content was found to increase with longer withdrawal times (Papa and Dickens, 1989; Papa, 1991). The discrepancies in the feed withdrawal
INTRODUCTION Broiler carcasses may be contaminated with the contents of the gastrointestinal tracts during processing. When contamination occurs, affected carcasses are reprocessed (washed or trimmed), or in extreme cases, condemned (May et al., 1990). Carcass reprocessing or carcass condemnation delays the operation of the processing plant and increases the cost of producing a quality product; therefore, considerable attention has been given to the development of methods that reduce carcass contamination (Benoff, 1982; Bilgili, 1988; Papa and Dickens, 1989; Papa, 1991). One of the production management techniques frequently used to minimize carcass contamination is the withdrawal of feed and water from broilers before catching, loading, and transportation to the processing plant (Wabeck, 1972; Bilgili, 1988; May and Deaton, 1989; Papa and Dickens, 1989; Rasmussen and Mast, 1989; Papa, 1991; Lyon et al., 1991). During the withdrawal period, the crop and digestive tract are emptied, and there is less material available for contamination in the plant (Bilgili, 1988; May and Deaton, 1989; Papa and Dickens, 1989; Rasmussen and
Received for publication May 9, 1996. Accepted for publication September 20, 1996. 1To whom correspondence should be addressed.
410
Downloaded from http://ps.oxfordjournals.org/ at North Dakota State University on June 23, 2015
time by replication did not affect the crop contents or the incidence of bile contamination in the digestive tract. Results also suggested that the integrity of the intestines declined after 12 to 14 h feed withdrawal, as indicated by heavy intestinal sloughing. Color analyses of livers showed that length of feed withdrawal did not affect lightness (L* values), but livers became less red (lower positive a*) as feed withdrawal time increased. It was concluded that length of feed withdrawal significantly affected the gastrointestinal tract; however, variation in the appearance of the liver could not be attributed solely to broiler feed withdrawal time.
ABSTRACT This study was conducted to investigate the effects of feed withdrawal on the viscera of commercial broilers. Birds were withdrawn from feed 0, 3, 9, 12, 14, 16, or 18 h before slaughter. Crop and gizzard contents were determined after dissection, and intestinal shape and villi were subjectively scored. Raw liver color was measured colorimetrically. Length of feed withdrawal (time) and its interaction with grower (time by grower) and replication (time by replication) had a significant effect (P < 0.05) on gizzard contents, intestinal shape, and villi; however, time by grower and
411
FEED WITHDRAWAL EFFECTS ON VISCERA TABLE 1. Criteria for evaluation of crop, gizzard, intestinal shape, intestinal villi, and gizzard bile
Score
Crop
Gizzard
Intestinal shape
Intestinal villi
Gizzard bile
0 1 2 3 4
Missing Feed Water Empty Litter
. . . Feed Water Empty Litter
. . . Early round Early flat Late flat Late round
None Present
5
. . .
Modular feces1
. . .
. . . No sloughing Little sloughing Average sloughing Villi present, heavy sloughing No villi, heavy sloughing
1Modular
feces = fecal material ingested before slaughter while birds are in the holding module.
MATERIALS AND METHODS
Birds The study consisted of a single experiment replicated three times. All birds used in this study were commercially reared broilers (Ross × Ross), 41 to 43 d of age, that were obtained from three to five farms (growers) within each replication. Birds were reared under continuous lighting and given ad libitum access to feed and water. Withdrawal feed contained 17% protein and had a ME level of 1,500 kcal/lb (3,306 kcal/kg).
Treatments and Subjective Scoring Birds were withdrawn from feed 0, 3, 9, 12, 14, 16, and 18 h before slaughter. Water was withdrawn 4 h after the initiation of feed withdrawal. Birds in the 0- and 3-h treatments were necropsied and evaluated on the farms, whereas birds in all other treatments were evaluated at the processing plant. For each replication, 50 to 125 viscera were evaluated using the descriptive analysis listed in Table 1. All evaluations were made immediately post-mortem by a trained panel of three individuals. The contents of the crop and gizzard were scored upon dissection. Gizzard bile was reported as the number of gizzards testing positive for bile divided by the number of gizzards evaluated at the specified feed
withdrawal period. Intestinal shape was scored according to the following descriptions: 1) Early Round refers to a round intestine in the process of passing digesta. 2) Early Flat refers to a completely flat intestine void of digesta. 3) Late Flat means the intestines are contracting and may contain a slight amount of digesta. This score applies to intestines that are not as compressed as those with a score of 2. 4) Late Round shape develops when bacterial fermentation produces intestinal gas, and bubbles emerge during evaluation of the villi. Before evaluating intestinal villi, the panel was given three 30-min training and practice sessions and three 30-min validation sessions to familiarize them with the different scores. Intestinal villi were analyzed by opening the upper and lower ileum lengthwise on either side of yolk stalk remnant (Meckel’s diverticulum). After removal of digesta from the intestines, the trained panel evaluated villi using their index and middle fingers, which were placed under the open intestine with the mucosal lining facing up. Forceps were drawn across the mucosal lining, and villi were scored based upon ability to transmit a perceptible vibratory sensation to the panelists. Panelists assigned scores to the villi by comparing them to the standards used during the training sessions. Sloughing of the mucosal lining was determined based upon presence of intact lining and the amount of the lining that was removed under the light pressure of the forceps. The following scale was used to score villi: 1) A score of 1 was assigned to well developed, finger-like villi, with no sloughing of the lining, and a readily perceived vibratory sensation. 2) A score of 2 was assigned to villi with little or no sloughing of the mucosal lining, but perceived vibration was slightly less than villi receiving a score of 1. 3) A score of 3 was assigned to villi with average sloughing and average villi vibration. 4) A score of 4 indicated only a minor amount of villi vibration could be detected with heavy intestinal sloughing. 5) A score of 5 indicated no perceived villi were present, and there was heavy intestinal sloughing.
Liver Color Measurement The C.I.E. (1978) L*, +a*, and +b* color values were measured on raw livers immediately post-mortem using a
Downloaded from http://ps.oxfordjournals.org/ at North Dakota State University on June 23, 2015
data may be attributed to differences in broiler catching, holding, and manure consumption before slaughter, which alters intestinal contents and may slow digestive tract clearance. In addition, it has been suggested that increased intestinal moisture in broilers held off feed for longer periods of time develops from accelerated metabolic breakdown of the tissues (Ang and Hamm, 1985). Because the condition and contents of the intestines are important in poultry processing, the present study was designed to 1) establish a method for viscera evaluation that is applicable in a commercial plant, and 2) to use that method to determine the effects of various commercial feed withdrawal schedules on the condition of the viscera of broilers.
412
NORTHCUTT ET AL. TABLE 2. Effect of time off feed on the condition of the crop, gizzard, shape of intestines, intestinal villi, and gizzard bile1
Time off feed (h) 0
Crop
3 9 12 14 16 18 1n
Score 1, 2 (Feed, water) Score 1, 2 (Feed, water) Score 4 (Litter) Score 4 (Litter) Score 4 (Litter) Score 4, 5 (Litter, modular feces) Score 4, 5 (Litter, modular feces)2
Shape of intestines
Intestinal villi
Score 1 (Early round) Score 1 (Early round) Score 2–3 (Early to late flat) Score 2–3 (Early to late flat) Score 3–4 (Late flat to late round) Score 3–4 (Late flat to late round) Score 3–4 (Late flat to late round)
Score 1 (No sloughing) Score 1 (No sloughing) Score 2–3 (Mild sloughing) Score 3 (Average sloughing) Score 3–4 (Average to heavy sloughing) Score 3–4 (Average to heavy sloughing) Score 3–4 (Average to heavy sloughing)
Bile (%) 0 0 30 30 35 40 70
= 275.
2Modular
feces = fecal material ingested before slaughter while birds are in the holding module.
Minolta colorimeter.2 The colorimeter was standardized throughout the study using white3 and pink ceramic tiles.4 One color reading was recorded per liver (n = 220), and the readings were reported as averages. Color difference (DE) was calculated using the following formula: DE = [(L*1 – L*2)2 + (a*1 – a*2)2 + (b*1 – b*2)2]Ø where L*1, a*1, and b*1 represent color parameters measured on liver from birds with no feed withdrawal, and L*2, a*2, and b*2 represent color parameters measured after one of the feed withdrawal treatments (3, 9, 12, 14, 16, or 18 h).
Statistical Analyses All data were statistically analyzed using an analysis of variance to test the main effects of length of feed withdrawal (time) and grower (farm). Replication was used as the error term for the analysis (SAS Institute, 1994). For each replication, viscera were evaluated from 50 to 125 broilers grown on three to five different farms. Farms varied with replication, eliminating the grower by replication interaction. Correlation among variables was determined using the Pearson product-moment correlation coefficient (Sokal and Rohlf, 1969). Differences among means for liver color were separated using the TukeyKramer Means Comparison test at a significance level of P < 0.05 (Neter et al., 1990).
2Minolta Chroma Meter CR-2000, Minolta Camera Co., Ltd., 30, 2 Chrome, Azuchi Machi, Kagashi-Ku, Japan. 3Reference number 13533123. Y = 92.7, x = 0.3133, y = 0.3193. 4Reference number 16332113. Y = 28.7, x = 0.363, y = 0.317.
RESULTS AND DISCUSSION Scores for the various traits measured at the different feed withdrawal times are presented in Table 2. Birds in the 0- and 3-h feed withdrawal groups had similar viscera scores. These birds had ingesta in their gastrointestinal tracts at the time of death, which would more likely result in carcass contamination during processing. Birds processed after 9 and 12 h of feed withdrawal had litter with some bile (30%) in their gastrointestinal tracts; however, the intestines of these birds were optimal for processing because they were empty (flattened shape) and had mild sloughing. Birds with empty intestines have less potential for carcass contamination during processing (Bilgili, 1988; May and Deaton, 1989; Papa and Dickens, 1989; Rasmussen and Mast, 1989; Papa, 1991; Lyon et al., 1991). In addition, the mild intestinal sloughing suggests these intestines retained their integrity and were stronger. The results were consistent with those of Bilgili (1988), who found that there was a significant (P < 0.05) relationship between shear strength of the gastrointestinal tract of broilers and the length of feed withdrawal. According to Bilgili (1988), shear strength of the duodenum of the intestines was greatest in birds that did not eat for 6 or 12 h, and lowest in birds that did not eat for 0, 18, or 24 h before processing. In the present study, intestines of birds that did not eat for 14, 16, and 18 h had heavy sloughing (loss of intestinal mucosal lining), and appeared to be affected by bacterial fermentation, as indicated by the rounded intestinal shape and visible production of intestinal gas (Table 2). When data were analyzed statistically, length of feed withdrawal (time) and its interaction with grower (time by grower) and replication (time by rep) were found to have a significant effect (P < 0.05) on crop contents, intestinal shape, and intestinal villi (Table 3). Although incidence of bile contamination appeared to increase
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Score 1 (Feed) Score 1 (Feed) Score 2 (Water) Score 3 (Empty) Score 3 (Empty) Score 3 (Empty) Score 3 (Empty)
Gizzard
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FEED WITHDRAWAL EFFECTS ON VISCERA TABLE 3. Probability values for the indicated sources Source1
Crop
Gizzard
Shape
Villi
Bile
Time Grower Time × grower Time × replicate
0.0285 0.0302 0.0070 0.0066
0.7762 0.0025 0.0774 0
0 0.0093 0.0024 0
0 0.0956 0.0034 0.0282
0.6550 0.4098 0.3813 0.0261
1Time
refers to length of feed withdrawal.
livers became less red (lower +a* values). The yellowness (+b*) color parameter appeared to follow a cubic pattern, because it decreased initially (3 to 9 h withdrawal), then leveled off (9 to 12 h withdrawal), and finally increased again (18 h withdrawal). Color of livers removed from birds left on feed (0 h group) before slaughter was compared to color of livers removed from birds after 3, 9, 12, 14, 16, and 18 h of feed withdrawal by calculating color difference (DE). As the length of feed withdrawal increased, DE values also increased, indicating a greater difference between colors (Table 5). Liver color difference may have been higher in birds with longer feed withdrawal because liver yield loss may have concentrated the pigments. However, the effect of feed withdrawal on liver yields was not determined during the present investigation. Jensen et al. (1984) showed that birds given feed withdrawal periods less than 8 h had the same liver yields, but increasing feed withdrawal from 12 to 16 h caused a significant loss in liver yields (6.7 and 21% loss, respectively). When these guidelines are applied to the present study, broilers that did not eat for 0 to 3 h, and 9 to 18 h should have different colored livers because of yield loss; however, there was no significant difference in DE values for livers from birds that did not eat for 3, 9, 12, or 16 h. Because of the complexity of liver metabolism, it was concluded that variations in its appearance could not be attributed solely to length of broiler feed withdrawal, and additional research would be required. This study demonstrates that extensive feed withdrawal times can cause a rapid deterioration in the condition of the viscera, which would increase the likelihood of carcass contamination problems during processing. Moreover, the methods for viscera evaluation that were presented in this study may be beneficial to production and processing plant management as they monitor and optimize their feed withdrawal programs.
TABLE 4. Pearson product-moment correlation (r) coefficients (P < 0.05) for crop, gizzard, intestinal shape, intestinal villi, and gizzard bile Variable
Crop
Crop Gizzard Shape Villi Bile
0.100 0.123 0.049 0.059
Gizzard
Shape
Villi
Bile
0.100
0.123 0.428
0.049 0.280 0.725
0.059 0.138 0.175 0.133
0.428 0.280 0.138
0.725 0.175
0.133
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with length of feed withdrawal, reporting it as present or not present prohibited us from finding a distinct significant effect. Farm to farm (grower) variation was found to affect (P < 0.05) crop, gizzard, and intestinal shape. Differences observed in the data because of grower may not only be related to time spent managing the flock, but also to other associated but uncontrollable factors that affect broiler feeding patterns and digestive tract emptying, such as environmental stress. Determining the extent of the involvement of the other contributing factors requires additional research. Correlation coefficients (r) were determined for crop, gizzard, intestinal shape, intestinal villi, and bile contamination because these parameters were descriptive and may be considered as effects of a common cause (Table 4). No significant correlation was found between crop contents or bile contamination and the other measurements. This lack of association may be due to differences in crop contents at the time of catching or other bird-to-bird variations that were not controlled. Changes in the intestinal shape were found to correlate positively with gizzard contents (r = 0.428) and intestinal villi scores (r = 0.725). These findings are similar to those reported by May and Deaton (1989), Papa and Dickens (1989), and Papa (1991) in their studies on digestive tract contents after varying feed withdrawal periods. During the present study, extreme variation in color of raw chicken liver was observed. It was suggested that length of feed withdrawal possibly affects the color of liver because it affects liver glycogen and carcass yields. Color measurements of raw chicken liver after various feed withdrawal periods are presented in Table 5. No significant difference in the lightness (L* values) color parameter of livers was found due to feed withdrawal; however, feed withdrawal affected redness and yellowness values. As length of feed withdrawal increased,
414
NORTHCUTT ET AL. TABLE 5. Effect (x ± SE) of time off feed on color measurement (L, +a*, +b*) or raw chicken livers Time off feed
L (Lightness)1
(h) 0 3 9 12 14 16 19
35.22 36.26 34.23 33.59 33.77 34.67 34.77 a–cMeans
± ± ± ± ± ± ±
3.22 3.32 2.20 1.49 1.85 2.59 2.67
+a* (Redness)1 17.78 17.52 13.87 13.46 12.44 13.11 12.50
± ± ± ± ± ± ±
1.63a 2.40a 1.51b 1.77b 1.48b 1.53b 1.37b
+b* (Yellowness)1 7.45 8.52 6.69 5.77 6.89 6.24 8.44
± ± ± ± ± ± ±
2.52a,b 2.47a 2.00b 1.69b 2.00a,b 2.10a,b 3.17a
Color difference (DE) . . . 4.52 5.03 5.54 6.20 5.97 6.65
± ± ± ± ± ±
0.57b,c 0.22c 0.28a,b 0.19a 0.51a,b 0.35a
within a column with no common superscript differ significantly (P < 0.05).
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