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The Effect of Four Stocking Densities on Broiler Carcass Grade, the Incidence of Breast Blisters, and Other Performance Traits1
The Effect of Four Stocking Densities on Broiler Carcass Grade, the Incidence of Breast Blisters, and Other Performance Traits1 F. G. PROUDFOOT 2 , H. W. HULAN 2 , and D. R. RAMEY3 Research Station, Agriculture Canada, Kentville, Nova Scotia
(Received for publication November 28, 1978)
INTRODUCTION With the gradual expansion of broiler production and the increasing costs of construction, there has been a tendency to increase stocking densities rather than expand into newly constructed broiler buildings. The Nova Scotia Chicken Marketing Board recommended regular broilers be allotted 7.44 dm 2 of floor space per bird. The object of this investigation was to estimate the effects of four stocking densities on carcass grade, incidence of breast blisters, mortality, body weights, feed conversion, and monetary returns. MATERIALS AND METHODS
A total of 3544 broiler chicks were housed in this experiment. The broiler chicks were a commercial genotype widely used in the industry. The four stocking densities consisted of 9.27, 7.44, 5.55, and 3.72 dm 2 (1.0, .8, .6, and .4 ft 2 ) of floor area per bird with 552, 692, 920, and 1380 birds housed per treatment, respectively. The sexes were intermingled in equal numbers. Each pen had a floor area of 2564 dm 2 (276 ft 2 ). Feeder space was allotted so that each bird was exposed to equivalent feeder space regardless of the stocking density treatment (Table 1). Waterer space was also pro-
Contribution No. 1657. Research Station, Agriculture Canada, Kentville, Nova Scotia, Canada. New Brunswick Department of Agriculture and Rural Development, Fredericton, New Brunswick, Canada.
vided so that each bird had adequate watering space (Table 1). Birds were vent sexed so that equal numbers of each sex were housed in each pen. Each stocking density group was duplicated with pen location picked at random. Commercial starter, developer, and finisher diets were fed to all birds in the experiment. Warm room, hot water brooding temperatures were supplemented by using two infra-red heat lamps up to 3 weeks of age. Birds were started under a light intensity of 25 lux which was gradually reduced so that by 21 days of age light intensity was reduced to 5 lux. Fresh wood shavings approximately 6 cm deep were used as litter. Traits measured were percentage mortality of males and females from 0 to 51 days of age and body weights of males and females at 51 days of age. Feed consumption was recorded and feed conversion was calculated as the unit weight of feed per unit body weight. At time of slaughter carcasses were graded in a commercial processing plant according to Canadian Grade Standards. The number of carcasses graded into the different grade classes was determined, and these data were used to calculate the percent Grade A carcasses originating from each pen. Carcasses down-graded because of breast blisters were listed separately and these data were used to calculate the incidence of breast blisters (Table 2). The calculation of monetary returns over the cost of feed and chicks was based on current market prices. Feed prices were as follows: starter — 27.0^/kg; developer — 25.8c/kg; and finisher — 24.8<^/kg. Chick cost was 24^ each 791
Downloaded from http://ps.oxfordjournals.org/ at University of Texas at San Antonio on June 29, 2015
ABSTRACT A total of 3544 chicken broilers were used in an experiment in which chickens were housed at 3.72, 5.55, 7.44, and 9.27 dm2 floor area per bird. Increased bird density resulted in a significant (P<.05) linear reduction in body weight of both males and females and adversely affected carcass quality. There was a significant (P<.05) increase in the incidence of breast blisters in females with the linear effect approaching significance for males. With increased stocking density, the monetary returns per bird started, declined linearly. An opposite and significant (P<.05) effect occurred when returns were based on units of floor area. 1979 Poultry Science 58:791-793
PROUDFOOTETAL.
792
TABLE 2. The effects of four stocking densities on mortality, body weights, feed conversion, carcass grades, incidence of breast blisters, and monetary returns3,
Stocking density dm 2 /bird
Mortality Female Male
Feed Body weights converMale Female sion
(%) 9.27 8.3 7.44 3.8 9.4 5.55 8.0 3.72 SEMb ±1.66 Sign.(5%)e NS
3.3 1.8 4.2 4.8 ±2.15 NS
2275 2209 2146 2016 ±29 L
(g) 1867 1826 1828 1658 ±19 L,Q
Grade A carcasses Male Female:
Mean monetary returns over feed and chick cost Breast Per Per dm 2 blisters bird floor Male Female started space
l'/o)
2.13 2.09 2.12 2.15 ±.02 NS
58.4 52.1 51.8 27.6 ±1.13 L,Q,C
80.5 76.1 74.2 58.6 ±2.03 L
18.0 25.6 25.7 40.0 ±4.04 NS
5.0 4.7 10.8 16.3 ±2.72 L
37.8 39.6 35.0 28.7 ±.81 L,Q
\t) 4.07 5.34 6.28 7.72 ±.20 L
All percentage data were converted to angles for the statistical analysis. SEM, standard error of the means. C Sign. — significant, linear — L, quadratic — 0_, or cubic — C effects over different stocking densities and NS — mean not significant at the 5% level of probability.
Downloaded from http://ps.oxfordjournals.org/ at University of Texas at San Antonio on June 29, 2015
TABLE 1. Feeders and waterers installed in each pen tion in male and female body weights. There housing either 276, 346, 460, or 690 birds per pen was also evidence of a significant quadratic trend for females relative to increased stocking Birds housed Feeders Waterers density. These results are similar to those reper pen per pen per pen a ported earlier by Proudfoot (1973) and by Weaver^ al. (1973). (No.) The percentage of Grade A carcasses, origi2 276 5 nating as both male and female birds, were sig346 7 4 nificantly affected by stocking density. As 460 4 9 14 690 6 stocking density was increased, the percent Grade A carcasses originating as males declined Cylinder type feeders were used with a feeder pan somewhat erratically, showing significant linear, diameter of 36.8 cm (14.5"). quadratic, and cubic trends. As stocking density Bell shaped waterers were used with a pan diam- increased Grade A carcasses originating as feeter of 35.6 cm (14"). males declined linearly. The percentage of birds graded down because of breast blisters increased linearly as stocking density increased. This trend was significant at the 5% level for feand meat revenue was based on a price of males and approached significance at the 5% 87.1c/kg of live weight. level for males. The analyses of variance were based on pen It was observed that birds housed under low means and linear, quadratic, and cubic trends density conditions exhibited smooth healthy were calculated where appropriate using a probplumage, whereas feathering in birds in high ability of < .05 to designate significant trends. stocking density pens were rough and tattered. The litter in pens with high stocking densities RESULTS AND DISCUSSION tended to be damp and packed. The lack of Mortality of both male and female broiler full, smooth feathering coupled with damp, chicks and feed conversion were not significant- hard packed litter probably related to the high incidence of breast blisters under high stocking ly affected by the different treatments. Body weights of both males and females densities. Mean monetary returns per bird started dewere significantly affected with higher stocking densities, resulting in a significant linear reduc- clined linearly and also exhibited a significant
STOCKING DENSITIES AND PERFORMANCE TRAITS
duced body weights, has an adverse effect on carcass quality, increases the incidence of breast blisters, and reduces monetary returns based on the number of birds started. However, when monetary returns are based on returns per unit of floor area, high stocking densities result in increased returns, when based on live weight only. This economic gain is at least partially offset by the reduction in carcass quality, particularly when floor space per bird is reduced from 5.55 to 3.72 d m 2 . REFERENCES Parkhurst, C. R., G. R. Boughman, J. P. Thaxton, J. D. Garlick, and F. W. Edens, 1977. A comparison of broilers grown in environmentally modified and conventional housing at different population densities. 1. Production performance and economic analysis. Poultry Sci. 56:883-885. Proudfoot, F. G., 1973. Response of broilers to variations in waterer, feeder and floor space under continuous and intermittent photoperiods. Can. J. Anim. Sci. 53:349-354. Weaver, W. D., Jr., W. L. Beane, and P. B. Siegel, 1973. Methods of rearing sexes and stocking densities on broiler performance: an experiment conducted by a Poultry Science curriculum club. Poultry Sci. 52: 2100-2101.
Downloaded from http://ps.oxfordjournals.org/ at University of Texas at San Antonio on June 29, 2015
quadratic trend as stocking density increased. However, when monetary returns were calculated on the basis of returns per unit of floor area, the reverse effect occurred; monetary returns increased as stocking density increased. Although extremely high stocking densities were tested, the point of diminishing returns was not reached despite the reduction in growth rate. Since meat revenues were based on a price per unit of live weight, obviously some growth rate reduction can be sacrificed, but the long term effect of reduced carcass quality may nullify short-term economic gains. Parkhurst et al. (1977) reported that broiler performance was unaffected by stocking density; however, it should be noted that in their trial stocking densities were restricted to a comparison of 6 and 7 dm 2 of floor space per bird. In the experiment reported here a much wider range of stocking densities was tested. The data presented demonstrate that the greatest impact on performance occurred between birds housed at 5.55 dm 2 and those housed at 3.72 dm 2 of floor area. It is concluded that high stocking densities in broiler chicks grown to 51 days results in re-
793
(Received for publication November 28, 1978)
INTRODUCTION With the gradual expansion of broiler production and the increasing costs of construction, there has been a tendency to increase stocking densities rather than expand into newly constructed broiler buildings. The Nova Scotia Chicken Marketing Board recommended regular broilers be allotted 7.44 dm 2 of floor space per bird. The object of this investigation was to estimate the effects of four stocking densities on carcass grade, incidence of breast blisters, mortality, body weights, feed conversion, and monetary returns. MATERIALS AND METHODS
A total of 3544 broiler chicks were housed in this experiment. The broiler chicks were a commercial genotype widely used in the industry. The four stocking densities consisted of 9.27, 7.44, 5.55, and 3.72 dm 2 (1.0, .8, .6, and .4 ft 2 ) of floor area per bird with 552, 692, 920, and 1380 birds housed per treatment, respectively. The sexes were intermingled in equal numbers. Each pen had a floor area of 2564 dm 2 (276 ft 2 ). Feeder space was allotted so that each bird was exposed to equivalent feeder space regardless of the stocking density treatment (Table 1). Waterer space was also pro-
Contribution No. 1657. Research Station, Agriculture Canada, Kentville, Nova Scotia, Canada. New Brunswick Department of Agriculture and Rural Development, Fredericton, New Brunswick, Canada.
vided so that each bird had adequate watering space (Table 1). Birds were vent sexed so that equal numbers of each sex were housed in each pen. Each stocking density group was duplicated with pen location picked at random. Commercial starter, developer, and finisher diets were fed to all birds in the experiment. Warm room, hot water brooding temperatures were supplemented by using two infra-red heat lamps up to 3 weeks of age. Birds were started under a light intensity of 25 lux which was gradually reduced so that by 21 days of age light intensity was reduced to 5 lux. Fresh wood shavings approximately 6 cm deep were used as litter. Traits measured were percentage mortality of males and females from 0 to 51 days of age and body weights of males and females at 51 days of age. Feed consumption was recorded and feed conversion was calculated as the unit weight of feed per unit body weight. At time of slaughter carcasses were graded in a commercial processing plant according to Canadian Grade Standards. The number of carcasses graded into the different grade classes was determined, and these data were used to calculate the percent Grade A carcasses originating from each pen. Carcasses down-graded because of breast blisters were listed separately and these data were used to calculate the incidence of breast blisters (Table 2). The calculation of monetary returns over the cost of feed and chicks was based on current market prices. Feed prices were as follows: starter — 27.0^/kg; developer — 25.8c/kg; and finisher — 24.8<^/kg. Chick cost was 24^ each 791
Downloaded from http://ps.oxfordjournals.org/ at University of Texas at San Antonio on June 29, 2015
ABSTRACT A total of 3544 chicken broilers were used in an experiment in which chickens were housed at 3.72, 5.55, 7.44, and 9.27 dm2 floor area per bird. Increased bird density resulted in a significant (P<.05) linear reduction in body weight of both males and females and adversely affected carcass quality. There was a significant (P<.05) increase in the incidence of breast blisters in females with the linear effect approaching significance for males. With increased stocking density, the monetary returns per bird started, declined linearly. An opposite and significant (P<.05) effect occurred when returns were based on units of floor area. 1979 Poultry Science 58:791-793
PROUDFOOTETAL.
792
TABLE 2. The effects of four stocking densities on mortality, body weights, feed conversion, carcass grades, incidence of breast blisters, and monetary returns3,
Stocking density dm 2 /bird
Mortality Female Male
Feed Body weights converMale Female sion
(%) 9.27 8.3 7.44 3.8 9.4 5.55 8.0 3.72 SEMb ±1.66 Sign.(5%)e NS
3.3 1.8 4.2 4.8 ±2.15 NS
2275 2209 2146 2016 ±29 L
(g) 1867 1826 1828 1658 ±19 L,Q
Grade A carcasses Male Female:
Mean monetary returns over feed and chick cost Breast Per Per dm 2 blisters bird floor Male Female started space
l'/o)
2.13 2.09 2.12 2.15 ±.02 NS
58.4 52.1 51.8 27.6 ±1.13 L,Q,C
80.5 76.1 74.2 58.6 ±2.03 L
18.0 25.6 25.7 40.0 ±4.04 NS
5.0 4.7 10.8 16.3 ±2.72 L
37.8 39.6 35.0 28.7 ±.81 L,Q
\t) 4.07 5.34 6.28 7.72 ±.20 L
All percentage data were converted to angles for the statistical analysis. SEM, standard error of the means. C Sign. — significant, linear — L, quadratic — 0_, or cubic — C effects over different stocking densities and NS — mean not significant at the 5% level of probability.
Downloaded from http://ps.oxfordjournals.org/ at University of Texas at San Antonio on June 29, 2015
TABLE 1. Feeders and waterers installed in each pen tion in male and female body weights. There housing either 276, 346, 460, or 690 birds per pen was also evidence of a significant quadratic trend for females relative to increased stocking Birds housed Feeders Waterers density. These results are similar to those reper pen per pen per pen a ported earlier by Proudfoot (1973) and by Weaver^ al. (1973). (No.) The percentage of Grade A carcasses, origi2 276 5 nating as both male and female birds, were sig346 7 4 nificantly affected by stocking density. As 460 4 9 14 690 6 stocking density was increased, the percent Grade A carcasses originating as males declined Cylinder type feeders were used with a feeder pan somewhat erratically, showing significant linear, diameter of 36.8 cm (14.5"). quadratic, and cubic trends. As stocking density Bell shaped waterers were used with a pan diam- increased Grade A carcasses originating as feeter of 35.6 cm (14"). males declined linearly. The percentage of birds graded down because of breast blisters increased linearly as stocking density increased. This trend was significant at the 5% level for feand meat revenue was based on a price of males and approached significance at the 5% 87.1c/kg of live weight. level for males. The analyses of variance were based on pen It was observed that birds housed under low means and linear, quadratic, and cubic trends density conditions exhibited smooth healthy were calculated where appropriate using a probplumage, whereas feathering in birds in high ability of < .05 to designate significant trends. stocking density pens were rough and tattered. The litter in pens with high stocking densities RESULTS AND DISCUSSION tended to be damp and packed. The lack of Mortality of both male and female broiler full, smooth feathering coupled with damp, chicks and feed conversion were not significant- hard packed litter probably related to the high incidence of breast blisters under high stocking ly affected by the different treatments. Body weights of both males and females densities. Mean monetary returns per bird started dewere significantly affected with higher stocking densities, resulting in a significant linear reduc- clined linearly and also exhibited a significant
STOCKING DENSITIES AND PERFORMANCE TRAITS
duced body weights, has an adverse effect on carcass quality, increases the incidence of breast blisters, and reduces monetary returns based on the number of birds started. However, when monetary returns are based on returns per unit of floor area, high stocking densities result in increased returns, when based on live weight only. This economic gain is at least partially offset by the reduction in carcass quality, particularly when floor space per bird is reduced from 5.55 to 3.72 d m 2 . REFERENCES Parkhurst, C. R., G. R. Boughman, J. P. Thaxton, J. D. Garlick, and F. W. Edens, 1977. A comparison of broilers grown in environmentally modified and conventional housing at different population densities. 1. Production performance and economic analysis. Poultry Sci. 56:883-885. Proudfoot, F. G., 1973. Response of broilers to variations in waterer, feeder and floor space under continuous and intermittent photoperiods. Can. J. Anim. Sci. 53:349-354. Weaver, W. D., Jr., W. L. Beane, and P. B. Siegel, 1973. Methods of rearing sexes and stocking densities on broiler performance: an experiment conducted by a Poultry Science curriculum club. Poultry Sci. 52: 2100-2101.
Downloaded from http://ps.oxfordjournals.org/ at University of Texas at San Antonio on June 29, 2015
quadratic trend as stocking density increased. However, when monetary returns were calculated on the basis of returns per unit of floor area, the reverse effect occurred; monetary returns increased as stocking density increased. Although extremely high stocking densities were tested, the point of diminishing returns was not reached despite the reduction in growth rate. Since meat revenues were based on a price per unit of live weight, obviously some growth rate reduction can be sacrificed, but the long term effect of reduced carcass quality may nullify short-term economic gains. Parkhurst et al. (1977) reported that broiler performance was unaffected by stocking density; however, it should be noted that in their trial stocking densities were restricted to a comparison of 6 and 7 dm 2 of floor space per bird. In the experiment reported here a much wider range of stocking densities was tested. The data presented demonstrate that the greatest impact on performance occurred between birds housed at 5.55 dm 2 and those housed at 3.72 dm 2 of floor area. It is concluded that high stocking densities in broiler chicks grown to 51 days results in re-
793