Dynamic behavior of early body weight in meat type chickens with different age at the same target slaughter weight
Keywords:
initial body weight, target slaughter weight, exponential function, growth rate, free-range chickenAbstract
In order to characterize the dynamic behavior of body weight in two populations of slow-growing chickens (Casilda CP and Campero INTA) compared to the commercial broiler Cobb 500; 20 males and 20 females of each group were weighed individually at weekly intervals between birth and slaughter. Body weight-age data were fit to an exponential model and the values of the parameter estimates, S (start value) and k (growth rate), for each bird were used as new random variables. In both sexes Cobb 500 showed a higher value of S than Casilda CP y Campero INTA with no apparent differences between the groups of slow growth. There were no significant differences among groups in k values. Artificial selection for growth rate applied to heavy breeders populations, responsible for reducing the number of days required to reach a target slaughter weight, would have affected the regulation of the process in a very primary level of the chain of events linked to body weight phenogenesis, setting a higher level of this variable response without changing the relative growth rate.
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