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Effect of Feed Withdrawal on Composition and Quality of Broiler Meat1
Effect of Feed Withdrawal on Composition and Quality of Broiler Meat 1 A. L. RASMUSSEN2 and M. G. MAST Department of Food Science, The Pennsylvania State University, University Park, Pennsylvania 16802 (Received for publication April 13, 1987)
1989 Poultry Science 68:1109-1113 INTRODUCTION
Prior to slaughter, broiler chickens are usually subjected to a period of fasting between the end of the growing period and the beginning of processing. Withdrawal periods of 8 to 12 h result in the highest eviscerated yields and minimize the potential for fecal contamination of the carcasses (Smidt et ai, 1964; Wabeck, 1972; Murphy and Goodwin, 1978; Benoff, 1982). Farr (1979) recommended that birds be taken off feed for 10 to 12 h, but that water be available throughout the fasting period. Chickens that have fasted longer than 12 h prior to slaughter have significantly lower eviscerated yields than birds subjected to shorter withdrawal periods (May and Branson, 1955; Branson, 1957). The composition and quality of broiler meat are affected by the duration and type of withdrawal. Muscle moisture decreased when feed and water withdrawal periods were lengthened from 10 to 20 h (Kamus and Farr, 1981), but feed withdrawal periods of 15 h did not influence protein, fat, or ash contents of the carcasses (Ngoka et ai, 1982). The
Authorized for publication on April 3, 1987, as Paper Number 7664 in the Journal Series of the Pennsylvania Agricultural Experiment Station. 2 Present address: Department Nutrition and Food Science, University of Arizona, Tucson, AZ 85721.
purpose of this study was to evaluate the effect of feed and water withdrawal on the yields, composition, texture, and flavor of broiler meat. MATERIALS AND METHODS
Approximately 120 female Hubbard x Hubbard cross broiler chickens were used in each of three replications of this experiment. Dayold broiler chicks were obtained from a local commercial source, individually wingbanded for identification, and reared on The Pennsylvania State University Poultry Research Farm. All birds in each experiment were brooded on the floor of a 2.13 m x 4.26-m pen and fed Agway Country Chick Starter. This feed contained 18% protein and had an ME level of 1,325 to 1,375 kcal/lb (2,915 to 3,025 kcal/kg). Bird density in the pen was 760 cm2/bird. When birds were 6.5 to 7 wk old they were caught, crated, and transferred to 1.2 m x 1.2 m x .5 m cages where they were fed using automatic conveyer-type feeders and given water on demand until they reached 7 to 7.5 wk of age. Birds were then separated randomly into treatment groups using wingband numbers for identification. One cage was used for each of the seven treatments, with 17 to 20 birds per treatment for each replication of the experiment. Birds were either fed ad libitum to slaughter (0-h treatment) or subjected to the following withdrawal periods: 6, 12, or 18 h
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ABSTRACT The effect of feed withdrawal or total withdrawal (simultaneous feed and water withdrawal) on the composition and quality of broiler meat was evaluated. Feed or water or both were withdrawn 0,6,12, or 18 h before slaughter. A gradual and significant (P<.05) increase in weight loss was seen as hours of withdrawal increased. Overall, birds subjected to feed withdrawal treatments experienced a 3.8% shrinkage; birds on total withdrawal treatments lost 4.4% in body weight. Percentage of water uptake during chilling increased gradually as feed withdrawal time increased. Birds on total withdrawal absorbed water in this fashion until 18 h of chilling, when there was a sharp and significant drop in water uptake. No significant differences were found among treatments for precook and cooked weights, cooking loss, total loss, proximate analysis, and shear. Withdrawal times for feed or feed and water did not influence the tenderness or flavor of breast or thigh meat. (Key words: broilers, quality, feed withdrawal, composition)
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RASMUSSEN AND MAST
each treatment; the meat from two of the birds was then combined, keeping breast meat separate from thigh meat. The meat in each sample was cut into small pieces (2.4 cm2) and ground in a Waring commercial food processor (Model 621A; Waring Products Division Dynamics Corp. of America, New Hartford, CT) using the cutting blade for 10 s. This ground meat was used in the determinations of moisture, protein, fat, and ash (Association of Official Analytical Chemists, 1980). The pH was evaluated using the method described in the Handbook for Meat Chemists (Koniecko, 1979). Tenderness and flavor tests were performed on cooked meat from fresh or frozen broilers. Frozen birds were thawed at 2 C for 48 h prior to cooking, and were used 1 mo after slaughter. Each bird was weighed before cooking (163 C oven) to an internal temperature of 85 C in the thigh. The cooked carcass weight was determined for each bird after removal from the oven; pan drippings were excluded from the cooked carcass weight. A 12-member sensory panel, comprised of graduate students with experience in evaluating a variety of foods, was trained in two preliminary sessions to familiarize them with test treatments and scoring procedures. The panel evaluated p. major and b. femoris muscles for tenderness, and p. major and thigh muscles for flavor. Each panelist received four samples at a time, each one taken from a composite of meat from 5 to 8 birds per treatment. The multiple comparison test was used in all cases, with the 6-h withdrawal treatment serving as a reference. The panelists compared meat samples from birds deprived of feed separately from those deprived of both feed and water. During each session panelists evaluated four samples in each of eight multiple comparisons tests. Pectoralis major and b. femoris muscles from five birds per treatment in each replication were used for shear evaluation. Trimmed samples (1.5 cm x 6 cm), two per bird and 10 per treatment, were first weighed, then sheared on a Texturepress (Model TP-2, Food Technology Corp., Rockville, MD) using a multiplebladed shear cell (Model CS-1); the velocity of the crosshead was 30 cm/s. To determine the force required to shear a chicken meat sample, peak height was used to calculate Newtons/ gram (N/g) of sample. The total area under the
Downloaded from http://ps.oxfordjournals.org/ at Michigan State University on February 25, 2015
feed withdrawal or 6, 12, or 18 h feed and water withdrawal (total withdrawal) prior to slaughter. At the beginning of the withdrawal period birds were caught and immediately weighed. Before birds were returned to their respective cages, feed conveyors were turned off and troughs were vacuumed. In the cases where birds were to be deprived of water, the watering cups were removed also. The 0-h birds were not deprived of feed or water before slaughter. Just prior to the scheduled slaughter time, birds in each treatment group were crated and moved to the University poultry processing facility. Each bird was weighed as soon as it reached the kill area to determine the live shrinkage due to withdrawal. Exsanguination was performed by severing the carotid artery with a hand-held knife; birds were bled for 3 min. Birds were then scalded six at a time in a rotary batch-type scalder for 90 s at 55 C and defeathered in an automatic feather picker for 30 s. Carcasses were eviscerated by hand. Eviscerated (shell) weight was measured for each carcass, i.e., excluding giblets, feet, and neck. Carcasses were chilled in a nonagitating ice water bath; after chilling for 1.5 h, carcasses (temperature, 3 to 4 C) were drained for 15 min and weighed to obtain the chilled weight. Withdrawal shrinkage was calculated as the loss in weight between farm weight and slaughter weight, i.e., loss due to deprivation of feed or water or both before slaughter. Other data calculated included eviscerated yield, ready-to-cook yield, percentage of water uptake, loss calculated on a slaughter weight basis, and total loss based on a farm weight basis. After the carcasses were drained they were again separated by wingband number into two groups, those to be kept fresh (nonfrozen) and those to be frozen. Birds to be kept fresh were placed in crushed ice tubs and held in a 2 C cooler for no longer than 3 days. Birds for freezing were individually packaged in Cryovac bags (W. R. Grace Co., Apex, NC) and frozen in a blast freezer (-23 C). Five to eight birds from each treatment in each replication were frozen for later use in shear tests and taste panel evaluations. For the compositional tests, the pectoralis major and the biceps femoris muscles were removed from the carcasses of four birds from
FEED WITHDRAWAL AND BROILER QUALITY
RESULTS AND DISCUSSION
Processing weights and yields of broilers subjected to feed withdrawal or simultaneous feed and water withdrawal can be seen in Table 1. Farm weights, taken just prior to application of each treatment, ranged from 1,168 g to 1,207 g and did not differ significantly among treatments. In addition, no significant differences were observed among treatments for slaughter weight (1,119 to 1,173 g), eviscerated weight (718 to 753 g), and chilled weight (762 to 801 g). Withdrawal shrinkage represents the percentage of weight loss due to withdrawal before slaughter. A gradual and significant (P<.05) increase in withdrawal shrinkage was observed as hours of withdrawal increased
(Table 1). Similar results were obtained by Wabeck (1972) and Scott et al. (1978), who reported that live weight shrinkage increased linearly with increasing withdrawal times. Overall, birds in the feed withdrawal treatments in this study experienced a 3.8% average withdrawal shrinkage, whereas birds given total withdrawal shrank 4.4%. Eviscerated yield was not affected by increasing withdrawal time. The 0-h treatment (no withdrawal) had a sigmficandy lower (P<.05) eviscerated yield than all other treatment groups (Table 1). There were no significant differences in the pooled means for eviscerated yield of birds on feed withdrawal (63.9%) or total withdrawal (63.4%). The ready-to-cook yield of birds on the 0-h treatment was significantly lower (P<.05) than yields of all other treatments (Table 1). Pooled ready-to-cook yields indicate that the feed withdrawal treatments experienced a 68.4% yield, whereas total withdrawal treatments had a 67.5% yield. Scott et al. (1978) reported a 1.5% yield difference between 6-h and 14-h treatments. In the present study, a 1.1% difference was observed between yields of the 6-h and 18-h total withdrawal treatments. The percentage of water uptake during chilling increased gradually as the time off feed increased (Table 1). However, for total withdrawal, this trend was not observed; water uptake during chilling for the total withdrawal birds decreased slighdy at 6-h, increased to 7.6% at the 12-h mark, and finally dropped to
TABLE 1. Processing weights and yields of broilers subjected to varying periods of feed (F), water (W), or both feed and water withdrawal
Withdrawal treatment No withdrawal 6-h F 6-h F + W 12-h F 12-h F + W 18-h F 18-h F + W
n
Farm weight
EvisSlaughter cerated weight weight
63 55 56 56 53 56 54
1,171* 1,207* 1,199* 1,168* 1,194* 1,204* 1,191*
1,171* 1,173* 1,167* 1,131* 1,136* 1,136* 1,119*
Chilled weight
WithEviscerated drawal shrinkage1 yield"1
(Til
a_c
729* 753* 740* 728* 720* 731* 718*
Ready-toWater cook uptake4 yield3
776* 801* 785* 778* 774* 786* 762*
.0°b
2.8 2.6b 3.1 b 4.7* 5.4* 5.9*
61.7b 63.7* 63.1* 63.8* 63.0* 64.1* 64.0*
Means within a column with no common superscripts differ significantly (P<.05). (Farm weight - slaughter weight/farm weight) x 100. 2 (Eviscerated weight/slaughter weight) x 100. 3 (Chilled weight/slaughter weight) x 100. 4 (Chilled weight - eviscerated weight/eviscerated weight) x 100.
65.8C 67.8*b 67.0b 68.4*b 67.7 ab 68.9* 67.8 ab
6.6 abc 6.6 abc 6.1 bc 7 3a^ 7.6* 7.6* 5.9°
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curve was used to calculate the work to shear the sample; work was reported as millijoules/ gram (mJ/g; 1 mJ = .239 Meal). Analysis of variance was performed on the yield data, compositional data, taste panel data, and shear data using the general linear models program of the Statistical Analysis System (SAS, 1985) computer package. The main effects tested were treatments and replicates, with the treatment x replicate interaction used as the error term. The Student-Newman-Keuls mean separation technique was applied to evaluate all mean differences. Data were compiled from individual bird values in all three replications.
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RASMUSSEN AND MAST
The final pH of the breast muscle, measured 5 days after slaughter, averaged 5.77 for all treatments, which agrees with results of Kahn, and Nakamura (1970), which showed an ultimate pH of approximately 5.76 for maintenance of poultry breast muscle quality. The mean pH of thigh muscle was 6.44. No significant differences were found among withdrawal treatments in either force or total work required to shear the chicken meat. Samples prepared from fresh or frozen meat also showed no significant treatment variation. Force values ranged from 2.56 to 4.19 N/g (x = 3.19) for breast meat, and 2.18 to 3.10 N/g (x = 2.71) for thigh meat. The total work required to shear breast meat varied from 25.5 to 40.6 mJ/g (x = 32.2), and 13.2 to 22.2 mJ/g (x = 15.9) for thigh meat. When hours of withdrawal, type of meat (i.e., breast or thigh), and storage values were pooled, feed withdrawal was found to be significantly higher (P<.05) than total withdrawal in force and total work. Panelists evaluated the tenderness and flavor of samples of cooked fresh (nonfrozen) meat as well as samples that had been frozen for 1 mo. The 6-h treatments were used as the reference samples in all cases. Panelists evaluated the feed withdrawal treatments separately from the total withdrawal treatments. No significant differences in tenderness or flavor were found among treatments or between fresh and frozen samples. The fact that no significant differences were seen in the taste panel results for either tenderness or flavor is important for the poultry industry. In this study, varying feed and water withdrawal times up to 18 h did not
TABLE 2. Cooking losses of broilers subjected to varying periods of feed (F), water (W), or both feed and water withdrawal Withdrawal treatment No withdrawal 6-h F 6-h F + W 12-h F 12-h F + W 18-h F 18-h F + W
Precook weight 48 39 36 35 35 35 36
780* 808* 825* 819* 809* 801* 783*
Cooked weight — (g) 562* 590* 590* 586* 586* 570* 584*
Cooking loss1
Loss z
28.0* 27.1* 28.3* 28.7* 27.6* 28.8* 25.5*
53.9* 51.3*b 52.6 ab 52.1*b 51.6*b 52.4 ab 50.4 b
Total loss
(%) -
*,bMeans within a column with no common superscripts differ significantly (P<05). 'Cooking loss = 1 - (cooked weight/precook weight) x 100. 2 Loss = 1 - (cooked weight/slaughter weight) x 100. 3 Total loss = 1 - (cooked weight/farm weight) x 100.
53.9* 52.9* 54.0* 53.9* 54.1* 55.4* 53.4*
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5.9% after 18-h withdrawal. Salmon (1979) reported that weight gain of turkey carcasses during chilling in ice water was not influenced by feed withdrawal or total withdrawal treatments of 12 and 24 h. Other researchers (May and Brunson, 1955; Brunson, 1957; Smidt et al., 1964; Wabeck, 1972; Murphy and Goodwin, 1978; Scott et al., 1978) also failed to mention a drop in water uptake after 18-h withdrawal. Weights and cooking losses of broilers subjected to feed or water withdrawal treatments or both are presented in Table 2. No significant differences were found among the seven treatments in precook weights, cooked weights, cooking losses, or total losses. A significant difference (P<.05) was observed in the percentage of loss based on slaughter weight; the 0-h withdrawal treatment had the highest loss (53.9%). The lowest loss was observed in the 18-h total withdrawal treatment (50.4%), with all other points not significandy different from either of these two. This is not surprising, as birds not subjected to feed or water withdrawal should have a fuller gastrointestinal tract when slaughtered and, therefore, lose a greater percentage of weight. Significant differences were not observed in any of me proximate analysis determinations performed on meat from these broiler chickens subjected to feed or water withdrawal. Kamus and Farr (1981) reported a decrease in muscle moisture with increasing hours of withdrawal, but this was not observed in the present study. These results instead support those of Ngoka et al. (1982), which failed to show a decline in muscle moisture over time.
FEED WITHDRAWAL AND BROILER QUALITY
affect the chicken enough for a trained sensory panel to perceive any treatment differences in tenderness or flavor. If this is also true for consumer evaluations, the poultry industry will have greater flexibility in terms of feed and water withdrawal, without influencing the ultimate quality of the chicken meat. REFERENCES
Koniecko, E. S., 1979. Handbook for Meat Chemists. Avery Publ. Group, Inc., Wayne, NJ. May, K. N., and C. C. Brunson, 1955. Effect of length of starvation period on eviscerated yield of broilers. Poultry Sci. 34:1210. (Abstr.) Murphy, B. D., and T. L. Goodwin, 1978. Effect of food and water withdrawal from broilers on weight loss and carcass yields. Arkansas Farm Res. 27(5):9. Ngoka, D. A., G. W. Froning, S. R. Lowry, and A. S. Babji, 1982. Effects of sex, age, preslaughter factors, and holding conditions on the quality and chemical composition of turkey breast muscles. Poultry Sci. 61: 1996-2203. Salmon, R. E., 1979. Effect of food and water deprivation on live-weight shrinkage, eviscerated carcass yield and water absorption during chilling of turkey carcasses. Br. Poult. Sci. 20:303-306. SAS, 1985. SAS User's Guide: Statistics. Version 5 ed. SAS Inst. Inc., Cary, NC. Scott, T. R., N. L. Kamus, A. J. Farr, and W. A. Johnson, 1978. Study on simultaneous and staggered feed and water withdrawal schedules on processing factors. Poultry Sci. 57:1161. (Abstr.) 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. Wabeck, C. J., 1972. Feed and water withdrawal time relationship to processing yield and potential fecal contamination in broilers. Poultry Sci. 51:1119-1121.
Downloaded from http://ps.oxfordjournals.org/ at Michigan State University on February 25, 2015
Association of Official Analytical Chemists, 1980. Official Methods of Analysis. 13th ed. Association of Official Analytical Chemists, Washington, DC. Benoff, F. H., 1982. The "live-shrink" trap: Catch weights a must. Broiler Ind. 41(1):56, 60. Brunson, C. C , 1957. Effect of length of fasting period with subsequent ice-chilling on eviscerated yield and moisture content of broiler carcasses. Poultry Sci. 36:1107. (Abstr.) Farr, A. J., 1979. The broiler's last 48 hours: Feed withdrawal time can affect weight, shrink, dressed yield and contamination upon slaughter. Poult. Dig. 38: 638-639. Kahn, A. W., and R. Nakamura, 1970. Effects of pre- and postmortem glycosis on poultry tenderness. J. Food Sci. 35:266-267. Kamus, N. L., and A. J. Farr, 1981. Withdrawal and haul effects on moisture uptake, retention and intestinal scores. Poultry Sci. 60:1604. (Abstr.)
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1989 Poultry Science 68:1109-1113 INTRODUCTION
Prior to slaughter, broiler chickens are usually subjected to a period of fasting between the end of the growing period and the beginning of processing. Withdrawal periods of 8 to 12 h result in the highest eviscerated yields and minimize the potential for fecal contamination of the carcasses (Smidt et ai, 1964; Wabeck, 1972; Murphy and Goodwin, 1978; Benoff, 1982). Farr (1979) recommended that birds be taken off feed for 10 to 12 h, but that water be available throughout the fasting period. Chickens that have fasted longer than 12 h prior to slaughter have significantly lower eviscerated yields than birds subjected to shorter withdrawal periods (May and Branson, 1955; Branson, 1957). The composition and quality of broiler meat are affected by the duration and type of withdrawal. Muscle moisture decreased when feed and water withdrawal periods were lengthened from 10 to 20 h (Kamus and Farr, 1981), but feed withdrawal periods of 15 h did not influence protein, fat, or ash contents of the carcasses (Ngoka et ai, 1982). The
Authorized for publication on April 3, 1987, as Paper Number 7664 in the Journal Series of the Pennsylvania Agricultural Experiment Station. 2 Present address: Department Nutrition and Food Science, University of Arizona, Tucson, AZ 85721.
purpose of this study was to evaluate the effect of feed and water withdrawal on the yields, composition, texture, and flavor of broiler meat. MATERIALS AND METHODS
Approximately 120 female Hubbard x Hubbard cross broiler chickens were used in each of three replications of this experiment. Dayold broiler chicks were obtained from a local commercial source, individually wingbanded for identification, and reared on The Pennsylvania State University Poultry Research Farm. All birds in each experiment were brooded on the floor of a 2.13 m x 4.26-m pen and fed Agway Country Chick Starter. This feed contained 18% protein and had an ME level of 1,325 to 1,375 kcal/lb (2,915 to 3,025 kcal/kg). Bird density in the pen was 760 cm2/bird. When birds were 6.5 to 7 wk old they were caught, crated, and transferred to 1.2 m x 1.2 m x .5 m cages where they were fed using automatic conveyer-type feeders and given water on demand until they reached 7 to 7.5 wk of age. Birds were then separated randomly into treatment groups using wingband numbers for identification. One cage was used for each of the seven treatments, with 17 to 20 birds per treatment for each replication of the experiment. Birds were either fed ad libitum to slaughter (0-h treatment) or subjected to the following withdrawal periods: 6, 12, or 18 h
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Downloaded from http://ps.oxfordjournals.org/ at Michigan State University on February 25, 2015
ABSTRACT The effect of feed withdrawal or total withdrawal (simultaneous feed and water withdrawal) on the composition and quality of broiler meat was evaluated. Feed or water or both were withdrawn 0,6,12, or 18 h before slaughter. A gradual and significant (P<.05) increase in weight loss was seen as hours of withdrawal increased. Overall, birds subjected to feed withdrawal treatments experienced a 3.8% shrinkage; birds on total withdrawal treatments lost 4.4% in body weight. Percentage of water uptake during chilling increased gradually as feed withdrawal time increased. Birds on total withdrawal absorbed water in this fashion until 18 h of chilling, when there was a sharp and significant drop in water uptake. No significant differences were found among treatments for precook and cooked weights, cooking loss, total loss, proximate analysis, and shear. Withdrawal times for feed or feed and water did not influence the tenderness or flavor of breast or thigh meat. (Key words: broilers, quality, feed withdrawal, composition)
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RASMUSSEN AND MAST
each treatment; the meat from two of the birds was then combined, keeping breast meat separate from thigh meat. The meat in each sample was cut into small pieces (2.4 cm2) and ground in a Waring commercial food processor (Model 621A; Waring Products Division Dynamics Corp. of America, New Hartford, CT) using the cutting blade for 10 s. This ground meat was used in the determinations of moisture, protein, fat, and ash (Association of Official Analytical Chemists, 1980). The pH was evaluated using the method described in the Handbook for Meat Chemists (Koniecko, 1979). Tenderness and flavor tests were performed on cooked meat from fresh or frozen broilers. Frozen birds were thawed at 2 C for 48 h prior to cooking, and were used 1 mo after slaughter. Each bird was weighed before cooking (163 C oven) to an internal temperature of 85 C in the thigh. The cooked carcass weight was determined for each bird after removal from the oven; pan drippings were excluded from the cooked carcass weight. A 12-member sensory panel, comprised of graduate students with experience in evaluating a variety of foods, was trained in two preliminary sessions to familiarize them with test treatments and scoring procedures. The panel evaluated p. major and b. femoris muscles for tenderness, and p. major and thigh muscles for flavor. Each panelist received four samples at a time, each one taken from a composite of meat from 5 to 8 birds per treatment. The multiple comparison test was used in all cases, with the 6-h withdrawal treatment serving as a reference. The panelists compared meat samples from birds deprived of feed separately from those deprived of both feed and water. During each session panelists evaluated four samples in each of eight multiple comparisons tests. Pectoralis major and b. femoris muscles from five birds per treatment in each replication were used for shear evaluation. Trimmed samples (1.5 cm x 6 cm), two per bird and 10 per treatment, were first weighed, then sheared on a Texturepress (Model TP-2, Food Technology Corp., Rockville, MD) using a multiplebladed shear cell (Model CS-1); the velocity of the crosshead was 30 cm/s. To determine the force required to shear a chicken meat sample, peak height was used to calculate Newtons/ gram (N/g) of sample. The total area under the
Downloaded from http://ps.oxfordjournals.org/ at Michigan State University on February 25, 2015
feed withdrawal or 6, 12, or 18 h feed and water withdrawal (total withdrawal) prior to slaughter. At the beginning of the withdrawal period birds were caught and immediately weighed. Before birds were returned to their respective cages, feed conveyors were turned off and troughs were vacuumed. In the cases where birds were to be deprived of water, the watering cups were removed also. The 0-h birds were not deprived of feed or water before slaughter. Just prior to the scheduled slaughter time, birds in each treatment group were crated and moved to the University poultry processing facility. Each bird was weighed as soon as it reached the kill area to determine the live shrinkage due to withdrawal. Exsanguination was performed by severing the carotid artery with a hand-held knife; birds were bled for 3 min. Birds were then scalded six at a time in a rotary batch-type scalder for 90 s at 55 C and defeathered in an automatic feather picker for 30 s. Carcasses were eviscerated by hand. Eviscerated (shell) weight was measured for each carcass, i.e., excluding giblets, feet, and neck. Carcasses were chilled in a nonagitating ice water bath; after chilling for 1.5 h, carcasses (temperature, 3 to 4 C) were drained for 15 min and weighed to obtain the chilled weight. Withdrawal shrinkage was calculated as the loss in weight between farm weight and slaughter weight, i.e., loss due to deprivation of feed or water or both before slaughter. Other data calculated included eviscerated yield, ready-to-cook yield, percentage of water uptake, loss calculated on a slaughter weight basis, and total loss based on a farm weight basis. After the carcasses were drained they were again separated by wingband number into two groups, those to be kept fresh (nonfrozen) and those to be frozen. Birds to be kept fresh were placed in crushed ice tubs and held in a 2 C cooler for no longer than 3 days. Birds for freezing were individually packaged in Cryovac bags (W. R. Grace Co., Apex, NC) and frozen in a blast freezer (-23 C). Five to eight birds from each treatment in each replication were frozen for later use in shear tests and taste panel evaluations. For the compositional tests, the pectoralis major and the biceps femoris muscles were removed from the carcasses of four birds from
FEED WITHDRAWAL AND BROILER QUALITY
RESULTS AND DISCUSSION
Processing weights and yields of broilers subjected to feed withdrawal or simultaneous feed and water withdrawal can be seen in Table 1. Farm weights, taken just prior to application of each treatment, ranged from 1,168 g to 1,207 g and did not differ significantly among treatments. In addition, no significant differences were observed among treatments for slaughter weight (1,119 to 1,173 g), eviscerated weight (718 to 753 g), and chilled weight (762 to 801 g). Withdrawal shrinkage represents the percentage of weight loss due to withdrawal before slaughter. A gradual and significant (P<.05) increase in withdrawal shrinkage was observed as hours of withdrawal increased
(Table 1). Similar results were obtained by Wabeck (1972) and Scott et al. (1978), who reported that live weight shrinkage increased linearly with increasing withdrawal times. Overall, birds in the feed withdrawal treatments in this study experienced a 3.8% average withdrawal shrinkage, whereas birds given total withdrawal shrank 4.4%. Eviscerated yield was not affected by increasing withdrawal time. The 0-h treatment (no withdrawal) had a sigmficandy lower (P<.05) eviscerated yield than all other treatment groups (Table 1). There were no significant differences in the pooled means for eviscerated yield of birds on feed withdrawal (63.9%) or total withdrawal (63.4%). The ready-to-cook yield of birds on the 0-h treatment was significantly lower (P<.05) than yields of all other treatments (Table 1). Pooled ready-to-cook yields indicate that the feed withdrawal treatments experienced a 68.4% yield, whereas total withdrawal treatments had a 67.5% yield. Scott et al. (1978) reported a 1.5% yield difference between 6-h and 14-h treatments. In the present study, a 1.1% difference was observed between yields of the 6-h and 18-h total withdrawal treatments. The percentage of water uptake during chilling increased gradually as the time off feed increased (Table 1). However, for total withdrawal, this trend was not observed; water uptake during chilling for the total withdrawal birds decreased slighdy at 6-h, increased to 7.6% at the 12-h mark, and finally dropped to
TABLE 1. Processing weights and yields of broilers subjected to varying periods of feed (F), water (W), or both feed and water withdrawal
Withdrawal treatment No withdrawal 6-h F 6-h F + W 12-h F 12-h F + W 18-h F 18-h F + W
n
Farm weight
EvisSlaughter cerated weight weight
63 55 56 56 53 56 54
1,171* 1,207* 1,199* 1,168* 1,194* 1,204* 1,191*
1,171* 1,173* 1,167* 1,131* 1,136* 1,136* 1,119*
Chilled weight
WithEviscerated drawal shrinkage1 yield"1
(Til
a_c
729* 753* 740* 728* 720* 731* 718*
Ready-toWater cook uptake4 yield3
776* 801* 785* 778* 774* 786* 762*
.0°b
2.8 2.6b 3.1 b 4.7* 5.4* 5.9*
61.7b 63.7* 63.1* 63.8* 63.0* 64.1* 64.0*
Means within a column with no common superscripts differ significantly (P<.05). (Farm weight - slaughter weight/farm weight) x 100. 2 (Eviscerated weight/slaughter weight) x 100. 3 (Chilled weight/slaughter weight) x 100. 4 (Chilled weight - eviscerated weight/eviscerated weight) x 100.
65.8C 67.8*b 67.0b 68.4*b 67.7 ab 68.9* 67.8 ab
6.6 abc 6.6 abc 6.1 bc 7 3a^ 7.6* 7.6* 5.9°
Downloaded from http://ps.oxfordjournals.org/ at Michigan State University on February 25, 2015
curve was used to calculate the work to shear the sample; work was reported as millijoules/ gram (mJ/g; 1 mJ = .239 Meal). Analysis of variance was performed on the yield data, compositional data, taste panel data, and shear data using the general linear models program of the Statistical Analysis System (SAS, 1985) computer package. The main effects tested were treatments and replicates, with the treatment x replicate interaction used as the error term. The Student-Newman-Keuls mean separation technique was applied to evaluate all mean differences. Data were compiled from individual bird values in all three replications.
1111
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RASMUSSEN AND MAST
The final pH of the breast muscle, measured 5 days after slaughter, averaged 5.77 for all treatments, which agrees with results of Kahn, and Nakamura (1970), which showed an ultimate pH of approximately 5.76 for maintenance of poultry breast muscle quality. The mean pH of thigh muscle was 6.44. No significant differences were found among withdrawal treatments in either force or total work required to shear the chicken meat. Samples prepared from fresh or frozen meat also showed no significant treatment variation. Force values ranged from 2.56 to 4.19 N/g (x = 3.19) for breast meat, and 2.18 to 3.10 N/g (x = 2.71) for thigh meat. The total work required to shear breast meat varied from 25.5 to 40.6 mJ/g (x = 32.2), and 13.2 to 22.2 mJ/g (x = 15.9) for thigh meat. When hours of withdrawal, type of meat (i.e., breast or thigh), and storage values were pooled, feed withdrawal was found to be significantly higher (P<.05) than total withdrawal in force and total work. Panelists evaluated the tenderness and flavor of samples of cooked fresh (nonfrozen) meat as well as samples that had been frozen for 1 mo. The 6-h treatments were used as the reference samples in all cases. Panelists evaluated the feed withdrawal treatments separately from the total withdrawal treatments. No significant differences in tenderness or flavor were found among treatments or between fresh and frozen samples. The fact that no significant differences were seen in the taste panel results for either tenderness or flavor is important for the poultry industry. In this study, varying feed and water withdrawal times up to 18 h did not
TABLE 2. Cooking losses of broilers subjected to varying periods of feed (F), water (W), or both feed and water withdrawal Withdrawal treatment No withdrawal 6-h F 6-h F + W 12-h F 12-h F + W 18-h F 18-h F + W
Precook weight 48 39 36 35 35 35 36
780* 808* 825* 819* 809* 801* 783*
Cooked weight — (g) 562* 590* 590* 586* 586* 570* 584*
Cooking loss1
Loss z
28.0* 27.1* 28.3* 28.7* 27.6* 28.8* 25.5*
53.9* 51.3*b 52.6 ab 52.1*b 51.6*b 52.4 ab 50.4 b
Total loss
(%) -
*,bMeans within a column with no common superscripts differ significantly (P<05). 'Cooking loss = 1 - (cooked weight/precook weight) x 100. 2 Loss = 1 - (cooked weight/slaughter weight) x 100. 3 Total loss = 1 - (cooked weight/farm weight) x 100.
53.9* 52.9* 54.0* 53.9* 54.1* 55.4* 53.4*
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5.9% after 18-h withdrawal. Salmon (1979) reported that weight gain of turkey carcasses during chilling in ice water was not influenced by feed withdrawal or total withdrawal treatments of 12 and 24 h. Other researchers (May and Brunson, 1955; Brunson, 1957; Smidt et al., 1964; Wabeck, 1972; Murphy and Goodwin, 1978; Scott et al., 1978) also failed to mention a drop in water uptake after 18-h withdrawal. Weights and cooking losses of broilers subjected to feed or water withdrawal treatments or both are presented in Table 2. No significant differences were found among the seven treatments in precook weights, cooked weights, cooking losses, or total losses. A significant difference (P<.05) was observed in the percentage of loss based on slaughter weight; the 0-h withdrawal treatment had the highest loss (53.9%). The lowest loss was observed in the 18-h total withdrawal treatment (50.4%), with all other points not significandy different from either of these two. This is not surprising, as birds not subjected to feed or water withdrawal should have a fuller gastrointestinal tract when slaughtered and, therefore, lose a greater percentage of weight. Significant differences were not observed in any of me proximate analysis determinations performed on meat from these broiler chickens subjected to feed or water withdrawal. Kamus and Farr (1981) reported a decrease in muscle moisture with increasing hours of withdrawal, but this was not observed in the present study. These results instead support those of Ngoka et al. (1982), which failed to show a decline in muscle moisture over time.
FEED WITHDRAWAL AND BROILER QUALITY
affect the chicken enough for a trained sensory panel to perceive any treatment differences in tenderness or flavor. If this is also true for consumer evaluations, the poultry industry will have greater flexibility in terms of feed and water withdrawal, without influencing the ultimate quality of the chicken meat. REFERENCES
Koniecko, E. S., 1979. Handbook for Meat Chemists. Avery Publ. Group, Inc., Wayne, NJ. May, K. N., and C. C. Brunson, 1955. Effect of length of starvation period on eviscerated yield of broilers. Poultry Sci. 34:1210. (Abstr.) Murphy, B. D., and T. L. Goodwin, 1978. Effect of food and water withdrawal from broilers on weight loss and carcass yields. Arkansas Farm Res. 27(5):9. Ngoka, D. A., G. W. Froning, S. R. Lowry, and A. S. Babji, 1982. Effects of sex, age, preslaughter factors, and holding conditions on the quality and chemical composition of turkey breast muscles. Poultry Sci. 61: 1996-2203. Salmon, R. E., 1979. Effect of food and water deprivation on live-weight shrinkage, eviscerated carcass yield and water absorption during chilling of turkey carcasses. Br. Poult. Sci. 20:303-306. SAS, 1985. SAS User's Guide: Statistics. Version 5 ed. SAS Inst. Inc., Cary, NC. Scott, T. R., N. L. Kamus, A. J. Farr, and W. A. Johnson, 1978. Study on simultaneous and staggered feed and water withdrawal schedules on processing factors. Poultry Sci. 57:1161. (Abstr.) 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. Wabeck, C. J., 1972. Feed and water withdrawal time relationship to processing yield and potential fecal contamination in broilers. Poultry Sci. 51:1119-1121.
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Association of Official Analytical Chemists, 1980. Official Methods of Analysis. 13th ed. Association of Official Analytical Chemists, Washington, DC. Benoff, F. H., 1982. The "live-shrink" trap: Catch weights a must. Broiler Ind. 41(1):56, 60. Brunson, C. C , 1957. Effect of length of fasting period with subsequent ice-chilling on eviscerated yield and moisture content of broiler carcasses. Poultry Sci. 36:1107. (Abstr.) Farr, A. J., 1979. The broiler's last 48 hours: Feed withdrawal time can affect weight, shrink, dressed yield and contamination upon slaughter. Poult. Dig. 38: 638-639. Kahn, A. W., and R. Nakamura, 1970. Effects of pre- and postmortem glycosis on poultry tenderness. J. Food Sci. 35:266-267. Kamus, N. L., and A. J. Farr, 1981. Withdrawal and haul effects on moisture uptake, retention and intestinal scores. Poultry Sci. 60:1604. (Abstr.)
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