The effect of commercial selection on the growth, efficiency,
and yield of broilers was studied using 2 University of ...
Alberta Meat Control strains unselected since 1957 and 1978,
and a commercial Ross 308 strain (2005).
Mixed-sex chicks (n = 180 per strain) were placed into 4 replicate
pens per strain, and grown on a current nutritional program
to 56 d of age.
Weekly front and side profile photographs of 8 birds per strain
were collected.
Growth rate, feed intake, and measures of feed efficiency including
feed conversion ratio, residual feed intake, and residual
maintenance energy requirements were characterized.
A nonlinear mixed Gompertz growth model was used to predict BW
and BW variation, useful for subsequent stochastic growth simulation.
Dissections were conducted on 8 birds per strain semiweekly from
21 to 56 d of age to characterize allometric growth of pectoralis muscles,
leg meat, abdominal fat pad, liver, gut, and heart.
A novel nonlinear analysis of covariance was used to test the hypothesis
that allometric growth patterns have changed as a result of commercial
selection pressure.
From 1957 to 2005, broiler growth increased by over 400%,
with a concurrent 50% reduction in feed conversion ratio, corresponding
to a compound annual rate of increase in 42 d live BW of 3.30%.
Forty-two-day FCR decreased by 2.55% each year over the same
48-yr period. Pectoralis major growth potential increased, whereas
abdominal fat decreased due to genetic selection pressure over the
same time period.
From 1957 to 2005, pectoralis minor yield at 42 d of age was 30%
higher in males and 37% higher in females; pectoralis major yield
increased by 79% in males and 85% in females.
Over almost 50 yr of commercial quantitative genetic selection pressure,
intended beneficial changes have been achieved.
Unintended changes such as enhanced sexual dimorphism are likely inconsequential, though musculoskeletal, immune function,
and parent stock management challenges may require additional
attention in future selection programs.
Alberta Meat Control strains unselected since 1957 and 1978,
and a commercial Ross 308 strain (2005).
Mixed-sex chicks (n = 180 per strain) were placed into 4 replicate
pens per strain, and grown on a current nutritional program
to 56 d of age.
Weekly front and side profile photographs of 8 birds per strain
were collected.
Growth rate, feed intake, and measures of feed efficiency including
feed conversion ratio, residual feed intake, and residual
maintenance energy requirements were characterized.
A nonlinear mixed Gompertz growth model was used to predict BW
and BW variation, useful for subsequent stochastic growth simulation.
Dissections were conducted on 8 birds per strain semiweekly from
21 to 56 d of age to characterize allometric growth of pectoralis muscles,
leg meat, abdominal fat pad, liver, gut, and heart.
A novel nonlinear analysis of covariance was used to test the hypothesis
that allometric growth patterns have changed as a result of commercial
selection pressure.
From 1957 to 2005, broiler growth increased by over 400%,
with a concurrent 50% reduction in feed conversion ratio, corresponding
to a compound annual rate of increase in 42 d live BW of 3.30%.
Forty-two-day FCR decreased by 2.55% each year over the same
48-yr period. Pectoralis major growth potential increased, whereas
abdominal fat decreased due to genetic selection pressure over the
same time period.
From 1957 to 2005, pectoralis minor yield at 42 d of age was 30%
higher in males and 37% higher in females; pectoralis major yield
increased by 79% in males and 85% in females.
Over almost 50 yr of commercial quantitative genetic selection pressure,
intended beneficial changes have been achieved.
Unintended changes such as enhanced sexual dimorphism are likely inconsequential, though musculoskeletal, immune function,
and parent stock management challenges may require additional
attention in future selection programs.
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