the effect of early feed restriction on performance and serum thyroxin concentration of broiler chickens

an experiment was conducted to evaluate the effect of early feed restriction on performance and serum thyroxin concentration of broiler chicks. the experiment was designed in a 2×2 factorial with 5 replicates of floor pens with 12 male or female chicks in each. 240 male and/or female day-old chicks of a commercial strain (hybrow) were wing banded, weighed and randomly allocated to two treatment groups of each sex. two treatments involved, one control group (no restriction) and one restricted group, which were fed a mixture of 50:50 rice hulls and commercial starter diet with supplementation of trace minerals & vitamin premixes from 4 to 11 days of age. all groups were fed the same starter, grower & finisher diets from 11 to 56 days of age. live body weight (lbw) of restricted birds was compensated on day 42 of age and was greater than restricted group at 49 and 56 days of age. mean daily feed intake and feed conversion ratio up to 42, 49 and 56 days of age wasn't affected significantly by treatments. feed cost per kg of lbw in restricted birds markedly improved in compare to control group. furthermore, feed cost per kg of lbw for male chicks was lower than of female chicks. carcass fat content of restricted birds was significantly lower than of control birds. also, carcass fat content of male chicks was significantly lower than of female chicks. abdominal fat of restricted birds at 49 and 56 days of age was significantly lower than of control birds. mean lbw up to 42, 49 and 56 days of age, weight gain and feed intake for male chicks was more than female chicks. serum thyroxin concentration on day 11 in restricted group was significantly lower than control group but its concentration during accelerated growth period (28-49 days of age) in restricted group was nonsignificantly more than control group. results of this experiment showed that, broiler chickens after early feed restriction compensated the retarded growth and showed less abdominal and carcass fat content.