GROWTH AND CARCASS COMPOSITION IN BROILER-TYPE CHICKENS FOLLOWING PASSIVE-IMMUNIZATION OF INSULIN-LIKE GROWTH FACTOR-II (IGF-2) BETWEEN 2 AND 4 WEEKS OF AGE

Ten broiler-type chickens at 2 weeks of age were injected daily with 0 .5 mi of normal sheep serum while 10 others were similarly injected wi th 0.5 mi of a sheep anti-IGF-2 serum. Immunization with anti-IGF-2 se rum had no significant effect upon body weight gain, on carcass compos ition, on appetite or food conversion. Liver weight was significantly increased (P < 0.05) in the anti-IGF-2 birds, but there was-no effect on the weight of any other organ measured. The proportion of breast mu scle in the carcass of anti-IGF-2 treated birds was significantly lowe r (P < 0.01) than in the controls and they also had 27% less abdominal fat. In acute studies, anti-IGF-2 administration caused an elevation in plasma GH, but in the longer term neither plasma GH nor plasma T-3 concentrations were significantly affected by immunization against IGF -2. These results suggest that circulating IGF-2 is not a major regula tor of overall somatic growth in chickens, but may have an effect on m uscle and fat deposition. (C) 1997 Elsevier Science Inc.