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Chemical Composition, Carcass Yield and Tenderness of Broilers as Influenced by Rearing Methods and Genetic Strains
Chemical Composition, Carcass Yield and Tenderness of Broilers as Influenced by Rearing Methods and Genetic Strains D. G.
E V A N S , 1 T.
L. GOODWIN AND L. D.
ANDREWS
Department of Animal Sciences, University of Arkansas, Fayetteville, Arkansas 72701 (Received for publication July 18, 1975)
POULTRY SCIENCE 55: 748-755,
T
1976
H E improvement in genetics, nutrition and production practices in the poultry industry in r e c e n t years has created a need to reevaluate existing carcass data. The rearing of broilers in cages has resulted in increased numbers of breast blisters, a rougher finish, increased leg and breast bone deformities and the a p p e a r a n c e of " s l a b - s i d e d " birds (Welch et al., 1971; and R e e c e et al., 1971). W a b e c k and Littlefield (1972) reported that wing and leg breakage after processing was higher for broilers reared in cages, and the highest proportion of breakage was noted in the wings. T h e s e results were substantiated by A n d r e w s and G o o d w i n (1973).
accompanied by a decrease in protein, ash and water in the leg muscle as well as in the remaining edible portion. H a r s h a w and Rector (1940) concluded that age and sex affected the chemical composition only as they affected the deposition of fat.
H a r s h a w (1938) observed in cockerels at 8, 12, 16 or 20 w e e k s of age the percentage of protein, ash and water remained practically constant in breast muscle in relation to both age and fattening. An increase in fat was
T h e purposes of the studies were to provide information on the chemical composition, c a r c a s s yields, and tenderness of different strains of broilers grown in cages or on the floor as well as color sexed broilers grown separated by sex or in equal n u m b e r s .
Increased levels of dietary protein increased the carcass protein and d e c r e a s e d the carcass fat, while increased dietary fat levels significantly increased the carcass fat (Summer et al., 1965). Similar observations have been found by other workers (Essary et al., 1965; Marion and Woodroof, 1966; G o o d w i n et al., 1969; and E d w a r d s et al., 1973).
1. Present address, College of Veterinary Medicine, Louisiana State University, Baton Rouge, La. Published with the approval of the Director of the Arkansas Agricultural Experiment Station.
EXPERIMENTAL PROCEDURE General. Broilers used in these e x p e r i m e n t s were fed a commercial ration and were raised 748
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ABSTRACT Experiments were conducted to determine the influence of cage and floor rearing and strains as well as the rearing of sexes separately or in equal numbers on chemical composition, yield and tenderness. The sexed birds were processed at 6, 7 and 8 weeks of age with measurements made at these ages. The shear values from the iliotibialis of the males were higher than those of the same muscle from the female. This difference in shear values was the only one noted. The second slice of the pectoralis muscle from birds reared in cages produced lower shear values than the corresponding slice from floor reared birds. The shear values from the broilers reared separately by sex or combined were influenced by both the sex of the individual bird as well as rearing method. Shear values from males grown separately were lower than those obtained from the females or those values from birds grown with equal numbers of sexes per pen. Shear values from the 8 week old broilers were lower than either 6 or 7 week old birds. The highest values were obtained from the 7 week old broilers. Females had a higher percentage of total meat as well as a greater meat-to-bone ratio for light meat, but no statistical difference was found between sexes for the dark meat portions. Yield of the sex separated birds increased as they increased in age.
CHEMICAL COMPOSITION AND YIELD
Experiment 1. Five strains designated as 1 to 5 of equal numbers male and female broilers were grown either in cages or on the floor. The management of these birds was described by Andrews et al. (1975). All broilers were processed at 8 weeks of age.
Seven halves from each group and sex were cooked for 20 minutes and evaluated by the shear press method for tenderness. The remaining halves were used for yield and chemical composition determination. The percent meat and meat-to-bone ratios were determined as a composite of light and dark meat parts. Experiment 2. Cobb color-sexed broilers were divided into three groups consisting of all males, all females, or an equal number of males and females. There were eight pens of each group consisting of 120 birds per pen. These broilers were grown in floor pens, and pen weights were obtained at 5, 6, 7 and 8 weeks of age. At 6, 7 and 8 weeks of age, 50 birds were taken from 1 pen of each group and processed. After evisceration, giblet harvesting and chilling, carcasses were weighed to obtain a processed weight. Twenty of the processed birds from each group at each age were evaluated for tenderness. The 6, 7 and 8 week old broilers were cooked for 16, 18 and 20 minutes, respectively. Yield and chemical composition were determined as previously described. EXPERIMENTAL RESULTS Experiment I. Carcasses obtained from males were heavier than those of the females (P < 0.01), and there was a rearing method vs. sex interaction. The floor reared males produced heavier carcasses than those obtained from the cage reared males; however, the opposite was true for the females (Table 1). TABLE 1.—Dressed weight of carcasses grown in cages or on the floor'—Experiment 1 Sex
Rearing method Cage Floor Female 383.8 372.3 Male 456.3 487.9 'Weights represent 1/2 carcasses. Weight in g.
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under commercial conditions unless stated otherwise. All birds were processed in a commercial processing plant, and the carcasses were frozen until they could be analyzed. Thawed birds were halved longitudinally and quartered on a meat saw. Quarters were cooked (Wyche and Goodwin, 1971) and samples were prepared (Wise and Stadelman, 1959) for tenderness determination. A AlloKramer shear press equipped with a 1136 kg. ring and attached to a Varian recorder was used to obtain the shear readings. Differences in shear values were determined by least-square analysis (Steel and Torrie, 1960). For yield and chemical analysis the thawed birds were cut into the following portions: wings, breast with ribs and scapula attached, legs with pelvic meat and back (Agriculture Handbook No. 31). Total weight for each piece was obtained to the nearest 0.1 g. prior to the removal of the meat from the bone, after which separate weights for the meat and bone of each part were recorded. The meat from the parts was separated into light meat (wings and breast portion) and dark meat (legs with pelvic meat and the back). The abdominal fat was included with the light meat. Moisture and fat content of the samples were determined by A.O.A.C. (1965) except the in vacuo temperature was 75° C. and the drying time was 48 hours. Ash content of the meat was determined by heating a 2 g. sample at 600° C. for 16 hours. Protein percent was calculated by differences. Factorial analysis of variance was used as the statistical method on the yield and chemical composition data.
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D. G. EVANS, T. L. GOODWIN AND L. D. ANDREWS TABLE 2.—Sihear values for the iliotibialis and pectoralis major1-—Experiment 1 Rearing method
Sex
Female Male Average
I2
Cage 1st
2nd
I
5.2 6.4 5.8
13.2 13.2 13.2
13.0 13.3 13.2
5.8 5.6 5.7
Floor 1st 13.7 13.4 13.6
2nd 14.7 14.3 14.5
'Shear values expressed as kg. force 1 g. sample. 1—Iliotibialis. 1st—first slice of pectoralis major. 2nd—second slice of pectoralis major.
2
TABLE 4.—Ash content of broiler meat--Experiment I Female
Male Light
Dark
Light
Dark
Strain
%
%
%
%
1 2 3 4 5 Avg.
0.79 0.76 0.85 0.81 0.81 0.80
0.72 0.80 0.81 0.77 0.74 0.77
0.82 0.79 0.74 0.81 0.90 0.81
0.75 0.79 0.72 0.71 0.80 0.75
1 2 3 4 5 Avg.
0.76 0.88 0.77 0.75 0.74 0.78
0.76 0.80 0.77 0.78 0.78 0.78
0.84 0.79 0.77 0.85 0.87 0.82
0.75 0.75 0.80 0.83 0.72 0.77
Cage
Floor
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TABLE 3.—Means of the percentage of total meat were not affected by any of the factors and meat-to-bone ratio of light meat—Experiment studied. The second 3 mm. layer of the 1 pectoralis major muscle from birds reared Males Females in the cages produced shear values that were Percentage of total lower than corresponding values obtained meat 71.2 72.8 from the floor reared broilers. Wabeck (1973) Meat-to-bone ratio 2.6 2.8 reported breast meat from males reared in cages to be more tender than the breast meat The shear values obtained from the ilio- from floor reared males. Neither strain nor rearing method had any tibalis were affected by both sex of the bird influence on either the percentage of total (P < 0.05) and by the interaction of rearing method vs. sex (P < 0.01). The iliotibalis meat or the meat-to-bone ratio for light or dark meat. The females had a higher percentof the males had higher shear values than age of light meat and a higher light meat-tothose of the females. This same trend in shear bone ratio than the males (Table 3). There values was produced for birds reared in cages; was no difference in yield between sexes with however, the males reared on the floor yieldregard to dark meat. ed shear values that were lower than those from the iliotibalis of the females reared on The strain of the bird tested, mode of the floor (Table 2). The shear values of the rearing, sex of the individual and color of outer 3 mm. slice of the pectoralis major the meat influenced one or more of the
751
CHEMICAL COMPOSITION AND YIELD
cage reared birds had a higher moisture content than floor reared birds in both light and dark meat. Sex of the broilers and color of the meat had no influence on moisture content. The interaction between rearing method and strain (P < 0.01) was caused by the meat from strain 3 being higher in moisture content in floor reared broilers than its counter part obtained from the cage reared birds. The fat content of meat from the cage reared broilers was lower than that obtained from floor reared birds (Table 6). Meat from males reared in cages was lower in fat content than the meat from females in cages; however, males reared on the floor produced meat with a higher fat content than females.
TABLE 5.—Moisture content of broiler meat—Experiment 1 Female
Male Light
Dark
Light
Dark
Strain
%
%
%
%
1 2 3 4 5 Avg.
69.22 66.41 68.51 66.55 67.51 67.64
68.92 69.20 69.79 68.43 67.97 64.86
65.47 66.65 65.63 65.81 65.94 65.90
67.63 68.00 64.69 68.60 67.72 67.33
1 2 3 4 5 Avg.
63.35 64.22 61.98 64.25 64.06 64.37
66.21 67.30 66.04 66.17 66.15 64.37
65.25 62.35 64.26 67.61 65.20 64.93
66.19 66.48 66.05 68.86 65.54 66.62
Cage
Floor
TABLE 6.—Fat content of broiler meat--Experiment 1 Male
Female
Light
Dark
Light
Dark
Strain
%
%
%
%
1 2 3 4 5 Avg.
9.74 12.58 9.80 12.94 10.75 11.16
11.96 11.69 10.76 12.71 12.15 11.85
14.07 12.93 14.34 13.76 12.31 13.48
13.77 13.31 17.25 12.72 12.88 13.99
1 2 3 4 5 Avg.
16.09 15.46 18.37 15.55 15.45 16.18
14.99 13.95 15.07 15.12 15.24 14.87
14.12 18.34 15.53 11.59 13.75 14.66
15.43 15.42 15.92 12.19 16.00 14.99
Cage
Floor
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chemical components of the meat. The percentage of ash was affected by color of meat (P < 0.01), strain vs. sex (P < 0.01) and sex vs. color of the meat (P < 0.05) interactions. The light meat was higher in percent ash than the dark meat (Table 4). The percent ash in strains 2 and 3 were higher in the males than females; however for strains 1, 4 and 5 the reverse was true. The females contained a higher percentage of ash in the light meat, but a lower percentage of ash in the dark meat. Moisture content was affected (P < 0.05) by strain and rearing method (Table 5). Carcasses representing strain 3 had the lowest moisture content of the strains tested. The
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D. G. EVANS, T. L. GOODWIN AND L. D. ANDREWS
TABLE 7.—Protein content of broiler meat—Experiment 1 Female
Male Light
Dark
Light
Dark
Strain
%
%
%
%
1 2 3 4 5 Avg.
20.24 20.25 20.83 19.70 20.93 20.39
18.39 18.31 18.63 18.09 19.14 18.51
19.65 19.63 19.30 19.64 20.84 19.81
17.80 17.90 17.34 17.98 18.59 17.92
1 2 3 4 5 Avg.
19.80 19.43 18.88 19.59 19.74 19.49
18.04 19.68 18.12 17.93 17.83 18.32
19.79 18.52 19.45 19.95 20.18 19.56
17.59 17.36 17.23 18.10 17.73 17.60
Cage
Floor
Age in weeks Sex Males xKg. C.V. Females xKg. C.V. Mixed xKg. C.V.
5
6
7
8
0.83 15.07
1.18 12.59
1.48 10.28
1.77 10.50
0.75 13.61
1.03 12.15
1.31 11.32
1.51 10.07
0.80 14.03
1.12 10.47
1.39 13.64
1.60 13.72
When considering the fat content of males vs. females, irrespective of where they were grown, females contained more fat than males. Protein content of meat was higher for males than for females, and protein content was lower in dark meat than light meat (Table 7). Only in one instance, strain 4, were the males lower in protein content than the females. Meat from broilers reared in cages contained more protein than meat from floor reared birds. Cage reared males were lower in protein content than floor reared males, but the cage reared females were higher in protein content than the floor reared females. Protein content of dark meat from females was the lowest tested. Experiment 2. The weight means and the coefficient of variation for weights of the
5, 6, 7 and 8 week old color-sexed broilers are given in Table 8. The males grown separately were the heaviest at all weighing periods. Female pens were the lightest and mixed pens were intermediate. The coefficients of variation was greatest in the mixed pens and lowest in the female pens. The male group had the largest gain per week followed
TABLE 9.—Mean processing yield of broilers—Experiment 2' Age: in weeks Sex Males Females Mixed
6
7
8
%
%
%
62.99 60.96 63.17
64.44 64.48 64.46
64.97 65.70 66.12
1 % yield expressed as chilled wt. of carcass w / o . giblets
Live wt. of broiler
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TABLE 8.—Mean weight and coefficient of variation of the different rearing groups—-Experiment 2
753
CHEMICAL COMPOSITION AND YIELD
TABLE 10.—Shear value means for Iliotibialis, first and second slice of Pectoralis Major—Experiment 2' Iliotibialis Age
Females
Males
Mixed
Average
6 wks. 7 wks. 8 wks. Avg.
7.2 8.0 7.8 7.7
7.2 8.0 6.4 7.2
7.8 10.6 7.9 8.8
7.4 8.9 7.4
6 wks. 7 wks. 8 wks. Avg.
13.6 14.6 13.7 14.0
12.2 13.6 11.5 12.4
13.4 14.7 11.3 13.1
13.0 14.3 12.2
6 wks. 7 wks. 8 wks. Avg.
13.0 15.1 13.4 13.8
11.6 13.0 11.5 12.0
13.3 14.8 10.2 12.8
12.6 14.3 11.7
1st slice
2nd slice
•Shear values expressed as kg. force/g. sample. TABLE 11.—Percentage of total meat and meat-to-bone ratio—Experiment 2 % 6 wks. 7 wks. 8 wks.
52.5 54.5 54.9
Wing
M:B
%
1.1 1.2 1.2
74.2 75.0 75.8
Breast
M:B
%
2.9 3.0 3.2
71.3 72.3 72.5
Leg
M:B
%
2.5 2.6 2.7
41.3 41.1 43.7
Back
M:B 0.7 0.7 0.8
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by the age of the broilers (Table 11, P < .01). As the bird increased in age, the total amount of meat was increased due to the larger size broiler. Broiler leg meat increased in total percentage from 6 to 8 weeks (P < 0.01) as well as the meat-to-bone ratio (P < .05). Age and sex of the individual, rearing method and color of the meat had an influence on some chemical components of the meat. As in experiment 1, light meat was higher in percentage ash than was the dark meat (Table 12). The 7 week-old broilers had the highest percent ash followed in decreasing order by the 6 and 8 week old broilers, respectively. As age increased from 6 to 8 weeks moisture content of the meat decreased and fat content increased (Table 12). The males in this study had a higher moisture content and less fat in the meat than did meat from the
by the mixed sex groups with the females exhibiting the least gain. Processing yield increased with age due to the increase in size of the bird (Table 9). The broilers grown in the mixed sex group had the highest processed yield. Females grown separately increased the greatest in processed yield from 6 to 8 weeks and the males showed the least increase. Broilers processed at 7 weeks of age had the highest shear values of any age tested, and the 8 week old broilers had the lowest values. Shear values from males grown separately had the lowest values of any group for the iliotibialis muscle, but the highest values for the first and second slice of the pectoralis major. Carcasses from the females produced lowest shear readings for both slices of the breast (Table 10). Percentage meat and meat-to-bone ratio of the breast, back and wing were influenced
754
D. G.
E V A N S , T. L. GOODWIN AND L. D,
ANDREWS
TABLE 12.—Chemical composition of broiler meat—Experiment Ash
2
Age
Light %
Dark %
Light %
Dark %
Moisture Males Females Light Dark Light Dark % % % %
6 7 8 Avg.
0.84 0.94 0.88 0.88
0.87 0.86 0.83 0.85
0.81 0.97 0.88 0.88
0.78 0.84 0.86 0.82
66.52 67.58 64.66 66.25
Males
Females
Fat Males Dark % 13.00 12.18 14.66 13.28
Females Light Dark % % 14.59 13.43 15.26 14.22 13.45 13.09 14.43 13.58
females. Light meat samples were lower in moisture and higher in fat than the dark meat samples. The abdominal fat was included with t h e light meat samples and may have accounted for the increased fat content of the light meat. Broiler carcasses exhibited a difference in moisture a n d fat content with a difference in age. T h e females processed at 7 w e e k s were higher in fat content than any other birds p r o c e s s e d . O n e would expect fat content to increase with age, but this particular strain of birds may peak at 7 weeks of age for fat deposition. Protein c o n t e n t increased as the broilers increased with age. T h e light meat samples contained approximately 1 percent more protein than did the dark meat samples. ACKNOWLEDGEMENT T h e authors wish to acknowledge the financial support of C o b b , Inc., C o n c o r d , M a . , for this s t u d y , and to Tyson F o o d s I n c . , Springdale, AR., for growing and processing the broilers. REFERENCES Agriculture Handbook No. 31., 1971. U.S.D.A., Consumer and marketing service. Washington, D.C. Andrews, L. D., and T. L. Goodwin, 1973. Perform-
ance of broilers in cages. Poultry Sci. 52: 723-728. Andrews, L. D., G. S. Nelson, G. C. Harris, Jr. and T. L. Goodwin, 1975. Performance of five strains of broilers in a four-tier cage system with plastic mat floors. Poultry Sci. 54: 54-58. Association Official Agricultural Chemists, 1965. Official Methods of Analysis, 10th edition, A.O.A.C, Washington, D.C. Edwards, H. M., Jr., F. Denman, A. Abou-Ashour and D. Nugara, 1973. Carcass composition studies. 1. Influence of age, sex, and type of dietary fat supplementation on total carcass and fatty acid composition. Poultry Sci. 52: 934-948. Essary, E. O., L. E. Dawson, E. L. Wisman and C. E. Holmes, 1965. Influence of different levels of fat and protein in broiler rations on live weight dressing percentage and specific gravity of carcasses. Poultry Sci. 44: 924-930. Goodwin, T. L., L. D. Andrews and J. E. Webb, 1969. The influence of age, sex and energy level on the tenderness of broilers. Poultry Sci. 48: 548-552. Harshaw, H. M., 1938. The effect of fattening at different ages on the composition of cockerels. Poultry Sci. 17: 163-169. Harshaw, H. M., and R. R. Rector, 1940. The composition of turkeys as affected by age and sex. Poultry Sci. 19:404-411. Marion, J. E., and J. G. Woodroof, 1966. Composition and stability of broiler carcasses as affected by dietary protein and fat. Poultry Sci. 45: 241-247. Reece, F. N., J. W. Deaton, J. D. May and K. N. May, 1971. Cage versus floor rearing of broiler chickens. Poultry Sci. 50: 1786-1790. Steel, R. G. D., and J. H. Torrie, 1960. Principles
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Age 6 7 8 Avg.
Light % 13.95 11.88 15.27 13.70
68.38 65.35 67.70 68.44 64.62 67.29 66.74 65.63 67.72 67.85 65.20 67.57 Protein Males Females Light Dark Light Dark % % % % 18.69 17.75 19.24 18.09 19.61 18.52 19.15 17.66 19.21 17.74 20.04 18.29 19.17 18.00 19.47 18.01
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CHEMICAL COMPOSITION AND YIELD
and Procedures of Statistics. McGraw-Hill Book Co. Inc. Summers, J. D., S. J. Slinger and G. C. Ashton, 1965. The effect of dietary energy and protein on carcass composition with a note on a method for estimating carcass composition. Poultry Sci. 44: 501-509. Wabeck, C. J., 1973. Breast muscle tenderness of male broilers reared in cages and floor pens. Poultry Sci. 52: 2098-2099. Wabeck, C. J., and L. H. Littlefield, 1972. Bone strength of broilers reared in floor pens and cages
having different bottoms. Poultry Sci. 51: 897-899. Welch, S. W., P. F. Metcalfe and R. W. Wesley, 1971. Broilers in cages. World's Poultry Sci. J. 27: 132-142. Wise, R. G., and W. J. Stadelman, 1959. Tenderness at various muscle depths associated with poultry processing techniques. Food Technol. 13: 689-691. Wyche, R. C , and T. L. Goodwin, 1971. The effect of retort cooking pressure and breading technique on yield and per cent breading of broiler parts. J. Milk Food Technol. 34: 347-348.
J. B . COOPER
Department of Poultry Science, Clemson University, Clemson, South Carolina 29631 (Received for publication July 18, 1975)
ABSTRACT Four light intensities were used in completely enclosed pigeon houses for 14 hours per 24 hours. Open front pens with only natural light were also used. There were four pens per treatment and five pairs of young, breeding age, White Carneaux per pen for 420 days, Results per treatment, 16, 30, 44 and 61 lumens per sq. m. and open pens, were respectively as follows for each objective: squabs raised—252, 220, 288, 203, and 212 with no significant differences except for the 44 lumen treatment which was higher than all others except 16; body wt./squab in g.—522, 526, 522, 508, and 531 at four weeks of age with no significant differences; feed per squab in kg.—4.7, 5.3, 4.5, 5.5, and 5.1 with only a significant difference between treatments 44 and 61 lumens; percent hatchability—89.7, 82.1, 89.6, 78.0, and 82.9 with no significant differences; percent squabs raised—93.7, 88.7, 97.9, 91.0, and 89.5 with no significant differences. The average number of squabs raised per treatment for all enclosed artificially lighted pens was 241 compared to 212 for the open pens with only natural light. POULTRY SCIENCE 55: 755-757, 1976
INTRODUCTION
P
I G E O N lofts generally use fly pens and natural light. R e s e a r c h involving lighting and enclosed housing is seriously lacking. Levi (1941) reported no advantage using artificial light t w o hours in the morning and late afternoon with 425 pairs of White Carneaux at Sumter, South Carolina. Piatt and Dare (1937) had doubtful conclusions that lights increased egg production, higher hatchability, and larger s q u a b s because of small
1. Published with the approval of the Director of the South Carolina Agric. Experiment Station as Technical Contribution No. 1283.
n u m b e r s , five pairs per treatment and no replication. Since little information on lighting was found in the literature, this experiment was designed to determine if lighting had any advantage in t h e production of s q u a b s . PROCEDURE Variations in light intensity were used. T o control duration a n d intensity of the light, completely enclosed artificially ventilated h o u s e s were used. In addition, and as a control, open front pens with fly pens were used with only natural light. Total pen size w a s the same as that for the completely enclosed p e n s . It was recognized that tem-
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Light Intensity and Housing for Pigeons'
E V A N S , 1 T.
L. GOODWIN AND L. D.
ANDREWS
Department of Animal Sciences, University of Arkansas, Fayetteville, Arkansas 72701 (Received for publication July 18, 1975)
POULTRY SCIENCE 55: 748-755,
T
1976
H E improvement in genetics, nutrition and production practices in the poultry industry in r e c e n t years has created a need to reevaluate existing carcass data. The rearing of broilers in cages has resulted in increased numbers of breast blisters, a rougher finish, increased leg and breast bone deformities and the a p p e a r a n c e of " s l a b - s i d e d " birds (Welch et al., 1971; and R e e c e et al., 1971). W a b e c k and Littlefield (1972) reported that wing and leg breakage after processing was higher for broilers reared in cages, and the highest proportion of breakage was noted in the wings. T h e s e results were substantiated by A n d r e w s and G o o d w i n (1973).
accompanied by a decrease in protein, ash and water in the leg muscle as well as in the remaining edible portion. H a r s h a w and Rector (1940) concluded that age and sex affected the chemical composition only as they affected the deposition of fat.
H a r s h a w (1938) observed in cockerels at 8, 12, 16 or 20 w e e k s of age the percentage of protein, ash and water remained practically constant in breast muscle in relation to both age and fattening. An increase in fat was
T h e purposes of the studies were to provide information on the chemical composition, c a r c a s s yields, and tenderness of different strains of broilers grown in cages or on the floor as well as color sexed broilers grown separated by sex or in equal n u m b e r s .
Increased levels of dietary protein increased the carcass protein and d e c r e a s e d the carcass fat, while increased dietary fat levels significantly increased the carcass fat (Summer et al., 1965). Similar observations have been found by other workers (Essary et al., 1965; Marion and Woodroof, 1966; G o o d w i n et al., 1969; and E d w a r d s et al., 1973).
1. Present address, College of Veterinary Medicine, Louisiana State University, Baton Rouge, La. Published with the approval of the Director of the Arkansas Agricultural Experiment Station.
EXPERIMENTAL PROCEDURE General. Broilers used in these e x p e r i m e n t s were fed a commercial ration and were raised 748
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ABSTRACT Experiments were conducted to determine the influence of cage and floor rearing and strains as well as the rearing of sexes separately or in equal numbers on chemical composition, yield and tenderness. The sexed birds were processed at 6, 7 and 8 weeks of age with measurements made at these ages. The shear values from the iliotibialis of the males were higher than those of the same muscle from the female. This difference in shear values was the only one noted. The second slice of the pectoralis muscle from birds reared in cages produced lower shear values than the corresponding slice from floor reared birds. The shear values from the broilers reared separately by sex or combined were influenced by both the sex of the individual bird as well as rearing method. Shear values from males grown separately were lower than those obtained from the females or those values from birds grown with equal numbers of sexes per pen. Shear values from the 8 week old broilers were lower than either 6 or 7 week old birds. The highest values were obtained from the 7 week old broilers. Females had a higher percentage of total meat as well as a greater meat-to-bone ratio for light meat, but no statistical difference was found between sexes for the dark meat portions. Yield of the sex separated birds increased as they increased in age.
CHEMICAL COMPOSITION AND YIELD
Experiment 1. Five strains designated as 1 to 5 of equal numbers male and female broilers were grown either in cages or on the floor. The management of these birds was described by Andrews et al. (1975). All broilers were processed at 8 weeks of age.
Seven halves from each group and sex were cooked for 20 minutes and evaluated by the shear press method for tenderness. The remaining halves were used for yield and chemical composition determination. The percent meat and meat-to-bone ratios were determined as a composite of light and dark meat parts. Experiment 2. Cobb color-sexed broilers were divided into three groups consisting of all males, all females, or an equal number of males and females. There were eight pens of each group consisting of 120 birds per pen. These broilers were grown in floor pens, and pen weights were obtained at 5, 6, 7 and 8 weeks of age. At 6, 7 and 8 weeks of age, 50 birds were taken from 1 pen of each group and processed. After evisceration, giblet harvesting and chilling, carcasses were weighed to obtain a processed weight. Twenty of the processed birds from each group at each age were evaluated for tenderness. The 6, 7 and 8 week old broilers were cooked for 16, 18 and 20 minutes, respectively. Yield and chemical composition were determined as previously described. EXPERIMENTAL RESULTS Experiment I. Carcasses obtained from males were heavier than those of the females (P < 0.01), and there was a rearing method vs. sex interaction. The floor reared males produced heavier carcasses than those obtained from the cage reared males; however, the opposite was true for the females (Table 1). TABLE 1.—Dressed weight of carcasses grown in cages or on the floor'—Experiment 1 Sex
Rearing method Cage Floor Female 383.8 372.3 Male 456.3 487.9 'Weights represent 1/2 carcasses. Weight in g.
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under commercial conditions unless stated otherwise. All birds were processed in a commercial processing plant, and the carcasses were frozen until they could be analyzed. Thawed birds were halved longitudinally and quartered on a meat saw. Quarters were cooked (Wyche and Goodwin, 1971) and samples were prepared (Wise and Stadelman, 1959) for tenderness determination. A AlloKramer shear press equipped with a 1136 kg. ring and attached to a Varian recorder was used to obtain the shear readings. Differences in shear values were determined by least-square analysis (Steel and Torrie, 1960). For yield and chemical analysis the thawed birds were cut into the following portions: wings, breast with ribs and scapula attached, legs with pelvic meat and back (Agriculture Handbook No. 31). Total weight for each piece was obtained to the nearest 0.1 g. prior to the removal of the meat from the bone, after which separate weights for the meat and bone of each part were recorded. The meat from the parts was separated into light meat (wings and breast portion) and dark meat (legs with pelvic meat and the back). The abdominal fat was included with the light meat. Moisture and fat content of the samples were determined by A.O.A.C. (1965) except the in vacuo temperature was 75° C. and the drying time was 48 hours. Ash content of the meat was determined by heating a 2 g. sample at 600° C. for 16 hours. Protein percent was calculated by differences. Factorial analysis of variance was used as the statistical method on the yield and chemical composition data.
749
750
D. G. EVANS, T. L. GOODWIN AND L. D. ANDREWS TABLE 2.—Sihear values for the iliotibialis and pectoralis major1-—Experiment 1 Rearing method
Sex
Female Male Average
I2
Cage 1st
2nd
I
5.2 6.4 5.8
13.2 13.2 13.2
13.0 13.3 13.2
5.8 5.6 5.7
Floor 1st 13.7 13.4 13.6
2nd 14.7 14.3 14.5
'Shear values expressed as kg. force 1 g. sample. 1—Iliotibialis. 1st—first slice of pectoralis major. 2nd—second slice of pectoralis major.
2
TABLE 4.—Ash content of broiler meat--Experiment I Female
Male Light
Dark
Light
Dark
Strain
%
%
%
%
1 2 3 4 5 Avg.
0.79 0.76 0.85 0.81 0.81 0.80
0.72 0.80 0.81 0.77 0.74 0.77
0.82 0.79 0.74 0.81 0.90 0.81
0.75 0.79 0.72 0.71 0.80 0.75
1 2 3 4 5 Avg.
0.76 0.88 0.77 0.75 0.74 0.78
0.76 0.80 0.77 0.78 0.78 0.78
0.84 0.79 0.77 0.85 0.87 0.82
0.75 0.75 0.80 0.83 0.72 0.77
Cage
Floor
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TABLE 3.—Means of the percentage of total meat were not affected by any of the factors and meat-to-bone ratio of light meat—Experiment studied. The second 3 mm. layer of the 1 pectoralis major muscle from birds reared Males Females in the cages produced shear values that were Percentage of total lower than corresponding values obtained meat 71.2 72.8 from the floor reared broilers. Wabeck (1973) Meat-to-bone ratio 2.6 2.8 reported breast meat from males reared in cages to be more tender than the breast meat The shear values obtained from the ilio- from floor reared males. Neither strain nor rearing method had any tibalis were affected by both sex of the bird influence on either the percentage of total (P < 0.05) and by the interaction of rearing method vs. sex (P < 0.01). The iliotibalis meat or the meat-to-bone ratio for light or dark meat. The females had a higher percentof the males had higher shear values than age of light meat and a higher light meat-tothose of the females. This same trend in shear bone ratio than the males (Table 3). There values was produced for birds reared in cages; was no difference in yield between sexes with however, the males reared on the floor yieldregard to dark meat. ed shear values that were lower than those from the iliotibalis of the females reared on The strain of the bird tested, mode of the floor (Table 2). The shear values of the rearing, sex of the individual and color of outer 3 mm. slice of the pectoralis major the meat influenced one or more of the
751
CHEMICAL COMPOSITION AND YIELD
cage reared birds had a higher moisture content than floor reared birds in both light and dark meat. Sex of the broilers and color of the meat had no influence on moisture content. The interaction between rearing method and strain (P < 0.01) was caused by the meat from strain 3 being higher in moisture content in floor reared broilers than its counter part obtained from the cage reared birds. The fat content of meat from the cage reared broilers was lower than that obtained from floor reared birds (Table 6). Meat from males reared in cages was lower in fat content than the meat from females in cages; however, males reared on the floor produced meat with a higher fat content than females.
TABLE 5.—Moisture content of broiler meat—Experiment 1 Female
Male Light
Dark
Light
Dark
Strain
%
%
%
%
1 2 3 4 5 Avg.
69.22 66.41 68.51 66.55 67.51 67.64
68.92 69.20 69.79 68.43 67.97 64.86
65.47 66.65 65.63 65.81 65.94 65.90
67.63 68.00 64.69 68.60 67.72 67.33
1 2 3 4 5 Avg.
63.35 64.22 61.98 64.25 64.06 64.37
66.21 67.30 66.04 66.17 66.15 64.37
65.25 62.35 64.26 67.61 65.20 64.93
66.19 66.48 66.05 68.86 65.54 66.62
Cage
Floor
TABLE 6.—Fat content of broiler meat--Experiment 1 Male
Female
Light
Dark
Light
Dark
Strain
%
%
%
%
1 2 3 4 5 Avg.
9.74 12.58 9.80 12.94 10.75 11.16
11.96 11.69 10.76 12.71 12.15 11.85
14.07 12.93 14.34 13.76 12.31 13.48
13.77 13.31 17.25 12.72 12.88 13.99
1 2 3 4 5 Avg.
16.09 15.46 18.37 15.55 15.45 16.18
14.99 13.95 15.07 15.12 15.24 14.87
14.12 18.34 15.53 11.59 13.75 14.66
15.43 15.42 15.92 12.19 16.00 14.99
Cage
Floor
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chemical components of the meat. The percentage of ash was affected by color of meat (P < 0.01), strain vs. sex (P < 0.01) and sex vs. color of the meat (P < 0.05) interactions. The light meat was higher in percent ash than the dark meat (Table 4). The percent ash in strains 2 and 3 were higher in the males than females; however for strains 1, 4 and 5 the reverse was true. The females contained a higher percentage of ash in the light meat, but a lower percentage of ash in the dark meat. Moisture content was affected (P < 0.05) by strain and rearing method (Table 5). Carcasses representing strain 3 had the lowest moisture content of the strains tested. The
752
D. G. EVANS, T. L. GOODWIN AND L. D. ANDREWS
TABLE 7.—Protein content of broiler meat—Experiment 1 Female
Male Light
Dark
Light
Dark
Strain
%
%
%
%
1 2 3 4 5 Avg.
20.24 20.25 20.83 19.70 20.93 20.39
18.39 18.31 18.63 18.09 19.14 18.51
19.65 19.63 19.30 19.64 20.84 19.81
17.80 17.90 17.34 17.98 18.59 17.92
1 2 3 4 5 Avg.
19.80 19.43 18.88 19.59 19.74 19.49
18.04 19.68 18.12 17.93 17.83 18.32
19.79 18.52 19.45 19.95 20.18 19.56
17.59 17.36 17.23 18.10 17.73 17.60
Cage
Floor
Age in weeks Sex Males xKg. C.V. Females xKg. C.V. Mixed xKg. C.V.
5
6
7
8
0.83 15.07
1.18 12.59
1.48 10.28
1.77 10.50
0.75 13.61
1.03 12.15
1.31 11.32
1.51 10.07
0.80 14.03
1.12 10.47
1.39 13.64
1.60 13.72
When considering the fat content of males vs. females, irrespective of where they were grown, females contained more fat than males. Protein content of meat was higher for males than for females, and protein content was lower in dark meat than light meat (Table 7). Only in one instance, strain 4, were the males lower in protein content than the females. Meat from broilers reared in cages contained more protein than meat from floor reared birds. Cage reared males were lower in protein content than floor reared males, but the cage reared females were higher in protein content than the floor reared females. Protein content of dark meat from females was the lowest tested. Experiment 2. The weight means and the coefficient of variation for weights of the
5, 6, 7 and 8 week old color-sexed broilers are given in Table 8. The males grown separately were the heaviest at all weighing periods. Female pens were the lightest and mixed pens were intermediate. The coefficients of variation was greatest in the mixed pens and lowest in the female pens. The male group had the largest gain per week followed
TABLE 9.—Mean processing yield of broilers—Experiment 2' Age: in weeks Sex Males Females Mixed
6
7
8
%
%
%
62.99 60.96 63.17
64.44 64.48 64.46
64.97 65.70 66.12
1 % yield expressed as chilled wt. of carcass w / o . giblets
Live wt. of broiler
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TABLE 8.—Mean weight and coefficient of variation of the different rearing groups—-Experiment 2
753
CHEMICAL COMPOSITION AND YIELD
TABLE 10.—Shear value means for Iliotibialis, first and second slice of Pectoralis Major—Experiment 2' Iliotibialis Age
Females
Males
Mixed
Average
6 wks. 7 wks. 8 wks. Avg.
7.2 8.0 7.8 7.7
7.2 8.0 6.4 7.2
7.8 10.6 7.9 8.8
7.4 8.9 7.4
6 wks. 7 wks. 8 wks. Avg.
13.6 14.6 13.7 14.0
12.2 13.6 11.5 12.4
13.4 14.7 11.3 13.1
13.0 14.3 12.2
6 wks. 7 wks. 8 wks. Avg.
13.0 15.1 13.4 13.8
11.6 13.0 11.5 12.0
13.3 14.8 10.2 12.8
12.6 14.3 11.7
1st slice
2nd slice
•Shear values expressed as kg. force/g. sample. TABLE 11.—Percentage of total meat and meat-to-bone ratio—Experiment 2 % 6 wks. 7 wks. 8 wks.
52.5 54.5 54.9
Wing
M:B
%
1.1 1.2 1.2
74.2 75.0 75.8
Breast
M:B
%
2.9 3.0 3.2
71.3 72.3 72.5
Leg
M:B
%
2.5 2.6 2.7
41.3 41.1 43.7
Back
M:B 0.7 0.7 0.8
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by the age of the broilers (Table 11, P < .01). As the bird increased in age, the total amount of meat was increased due to the larger size broiler. Broiler leg meat increased in total percentage from 6 to 8 weeks (P < 0.01) as well as the meat-to-bone ratio (P < .05). Age and sex of the individual, rearing method and color of the meat had an influence on some chemical components of the meat. As in experiment 1, light meat was higher in percentage ash than was the dark meat (Table 12). The 7 week-old broilers had the highest percent ash followed in decreasing order by the 6 and 8 week old broilers, respectively. As age increased from 6 to 8 weeks moisture content of the meat decreased and fat content increased (Table 12). The males in this study had a higher moisture content and less fat in the meat than did meat from the
by the mixed sex groups with the females exhibiting the least gain. Processing yield increased with age due to the increase in size of the bird (Table 9). The broilers grown in the mixed sex group had the highest processed yield. Females grown separately increased the greatest in processed yield from 6 to 8 weeks and the males showed the least increase. Broilers processed at 7 weeks of age had the highest shear values of any age tested, and the 8 week old broilers had the lowest values. Shear values from males grown separately had the lowest values of any group for the iliotibialis muscle, but the highest values for the first and second slice of the pectoralis major. Carcasses from the females produced lowest shear readings for both slices of the breast (Table 10). Percentage meat and meat-to-bone ratio of the breast, back and wing were influenced
754
D. G.
E V A N S , T. L. GOODWIN AND L. D,
ANDREWS
TABLE 12.—Chemical composition of broiler meat—Experiment Ash
2
Age
Light %
Dark %
Light %
Dark %
Moisture Males Females Light Dark Light Dark % % % %
6 7 8 Avg.
0.84 0.94 0.88 0.88
0.87 0.86 0.83 0.85
0.81 0.97 0.88 0.88
0.78 0.84 0.86 0.82
66.52 67.58 64.66 66.25
Males
Females
Fat Males Dark % 13.00 12.18 14.66 13.28
Females Light Dark % % 14.59 13.43 15.26 14.22 13.45 13.09 14.43 13.58
females. Light meat samples were lower in moisture and higher in fat than the dark meat samples. The abdominal fat was included with t h e light meat samples and may have accounted for the increased fat content of the light meat. Broiler carcasses exhibited a difference in moisture a n d fat content with a difference in age. T h e females processed at 7 w e e k s were higher in fat content than any other birds p r o c e s s e d . O n e would expect fat content to increase with age, but this particular strain of birds may peak at 7 weeks of age for fat deposition. Protein c o n t e n t increased as the broilers increased with age. T h e light meat samples contained approximately 1 percent more protein than did the dark meat samples. ACKNOWLEDGEMENT T h e authors wish to acknowledge the financial support of C o b b , Inc., C o n c o r d , M a . , for this s t u d y , and to Tyson F o o d s I n c . , Springdale, AR., for growing and processing the broilers. REFERENCES Agriculture Handbook No. 31., 1971. U.S.D.A., Consumer and marketing service. Washington, D.C. Andrews, L. D., and T. L. Goodwin, 1973. Perform-
ance of broilers in cages. Poultry Sci. 52: 723-728. Andrews, L. D., G. S. Nelson, G. C. Harris, Jr. and T. L. Goodwin, 1975. Performance of five strains of broilers in a four-tier cage system with plastic mat floors. Poultry Sci. 54: 54-58. Association Official Agricultural Chemists, 1965. Official Methods of Analysis, 10th edition, A.O.A.C, Washington, D.C. Edwards, H. M., Jr., F. Denman, A. Abou-Ashour and D. Nugara, 1973. Carcass composition studies. 1. Influence of age, sex, and type of dietary fat supplementation on total carcass and fatty acid composition. Poultry Sci. 52: 934-948. Essary, E. O., L. E. Dawson, E. L. Wisman and C. E. Holmes, 1965. Influence of different levels of fat and protein in broiler rations on live weight dressing percentage and specific gravity of carcasses. Poultry Sci. 44: 924-930. Goodwin, T. L., L. D. Andrews and J. E. Webb, 1969. The influence of age, sex and energy level on the tenderness of broilers. Poultry Sci. 48: 548-552. Harshaw, H. M., 1938. The effect of fattening at different ages on the composition of cockerels. Poultry Sci. 17: 163-169. Harshaw, H. M., and R. R. Rector, 1940. The composition of turkeys as affected by age and sex. Poultry Sci. 19:404-411. Marion, J. E., and J. G. Woodroof, 1966. Composition and stability of broiler carcasses as affected by dietary protein and fat. Poultry Sci. 45: 241-247. Reece, F. N., J. W. Deaton, J. D. May and K. N. May, 1971. Cage versus floor rearing of broiler chickens. Poultry Sci. 50: 1786-1790. Steel, R. G. D., and J. H. Torrie, 1960. Principles
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Age 6 7 8 Avg.
Light % 13.95 11.88 15.27 13.70
68.38 65.35 67.70 68.44 64.62 67.29 66.74 65.63 67.72 67.85 65.20 67.57 Protein Males Females Light Dark Light Dark % % % % 18.69 17.75 19.24 18.09 19.61 18.52 19.15 17.66 19.21 17.74 20.04 18.29 19.17 18.00 19.47 18.01
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CHEMICAL COMPOSITION AND YIELD
and Procedures of Statistics. McGraw-Hill Book Co. Inc. Summers, J. D., S. J. Slinger and G. C. Ashton, 1965. The effect of dietary energy and protein on carcass composition with a note on a method for estimating carcass composition. Poultry Sci. 44: 501-509. Wabeck, C. J., 1973. Breast muscle tenderness of male broilers reared in cages and floor pens. Poultry Sci. 52: 2098-2099. Wabeck, C. J., and L. H. Littlefield, 1972. Bone strength of broilers reared in floor pens and cages
having different bottoms. Poultry Sci. 51: 897-899. Welch, S. W., P. F. Metcalfe and R. W. Wesley, 1971. Broilers in cages. World's Poultry Sci. J. 27: 132-142. Wise, R. G., and W. J. Stadelman, 1959. Tenderness at various muscle depths associated with poultry processing techniques. Food Technol. 13: 689-691. Wyche, R. C , and T. L. Goodwin, 1971. The effect of retort cooking pressure and breading technique on yield and per cent breading of broiler parts. J. Milk Food Technol. 34: 347-348.
J. B . COOPER
Department of Poultry Science, Clemson University, Clemson, South Carolina 29631 (Received for publication July 18, 1975)
ABSTRACT Four light intensities were used in completely enclosed pigeon houses for 14 hours per 24 hours. Open front pens with only natural light were also used. There were four pens per treatment and five pairs of young, breeding age, White Carneaux per pen for 420 days, Results per treatment, 16, 30, 44 and 61 lumens per sq. m. and open pens, were respectively as follows for each objective: squabs raised—252, 220, 288, 203, and 212 with no significant differences except for the 44 lumen treatment which was higher than all others except 16; body wt./squab in g.—522, 526, 522, 508, and 531 at four weeks of age with no significant differences; feed per squab in kg.—4.7, 5.3, 4.5, 5.5, and 5.1 with only a significant difference between treatments 44 and 61 lumens; percent hatchability—89.7, 82.1, 89.6, 78.0, and 82.9 with no significant differences; percent squabs raised—93.7, 88.7, 97.9, 91.0, and 89.5 with no significant differences. The average number of squabs raised per treatment for all enclosed artificially lighted pens was 241 compared to 212 for the open pens with only natural light. POULTRY SCIENCE 55: 755-757, 1976
INTRODUCTION
P
I G E O N lofts generally use fly pens and natural light. R e s e a r c h involving lighting and enclosed housing is seriously lacking. Levi (1941) reported no advantage using artificial light t w o hours in the morning and late afternoon with 425 pairs of White Carneaux at Sumter, South Carolina. Piatt and Dare (1937) had doubtful conclusions that lights increased egg production, higher hatchability, and larger s q u a b s because of small
1. Published with the approval of the Director of the South Carolina Agric. Experiment Station as Technical Contribution No. 1283.
n u m b e r s , five pairs per treatment and no replication. Since little information on lighting was found in the literature, this experiment was designed to determine if lighting had any advantage in t h e production of s q u a b s . PROCEDURE Variations in light intensity were used. T o control duration a n d intensity of the light, completely enclosed artificially ventilated h o u s e s were used. In addition, and as a control, open front pens with fly pens were used with only natural light. Total pen size w a s the same as that for the completely enclosed p e n s . It was recognized that tem-
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Light Intensity and Housing for Pigeons'