Abdominal fat pad mass reduction by in ovo administration of anti-adipocyte monoclonal antibodies in chickens

The effect of in ovo administration of anti-adipocyte monoclonal antibodies (MAb) on growth and adipose tissue development in chickens was investigate d. In Trial 1,60 fertilized eggs from layer-type chickens were injected int o allantoic circulation with different amounts of MAb against chicken adipo cyte plasma membranes (0, 0.05, 0.1, 0.2, and 0.4 mg) on Day 15 of embryoge nesis. In Trial 2, 180 fertilized broiler eggs were injected into allantoic circulation with 0.2 mg MAb on Day 15 of embryogenesis. In Trial 1, high d oses (0.2 and 0.4 mg) of MAb in-in ovo injection reduced (P less than or eq ual to 0.05) abdominal fat pad weight without affecting total body weight a t 42 d of age. Only the highest dose (0.4 mg) significantly reduced hatch r ate. In Trial 2, adipose tissue (pectoral, femoral, and abdominal), major o rgan (heart, liver, and spleen), and total body weights at 14 d of age were not affected by in ovo injection. Hatch success rate of eggs was not signi ficantly different among treatments. However, by 6 wk of age, in ovo inject ion of MAb significantly reduced (P less than or equal to0.05) abdominal fa t pad weight by more than 28%. This relative fat pad mass reduction occurre d without affecting femoral or pectoral fat tissues. Total body weight and feed intake were not affected among treatments. Our experiments demonstrate d for the first time that in ovo administration of anti-adipocyte MAb on Da y 15 of embryogenesis reduced the chicken abdominal fat pad mass by 42 d of age without affecting growth or body weight.