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

The effect of in ovo administration of antiadipocyte monoclonal antibodies (MAb) on growth and adipose tissue development in chickens was investigated. In Trial 1, 60 fertilized eggs from layer-type chickens were injected into allantoic circulation with different amounts of MAb against chicken adipocyte plasma membranes (0, 0.05, 0.1, 0.2, and 0.4 mg) on Day 15 of embryogenesis. 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 doses (0.2 and 0.4 mg) of MAb in in ovo injection reduced (P < or = 0.05) abdominal fat pad weight without affecting total body weight at 42 d of age. Only the highest dose (0.4 mg) significantly reduced hatch rate. In Trial 2, adipose tissue (pectoral, femoral, and abdominal), major organ (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 significantly different among treatments. However, by 6 wk of age, in ovo injection of MAb significantly reduced (P < or = 0.05) abdominal fat pad weight by more than 28%. This relative fat pad mass reduction occurred without affecting femoral or pectoral fat tissues. Total body weight and feed intake were not affected among treatments. Our experiments demonstrated for the first time that in ovo administration of anti-adipocyte MAb on Day 15 of embryogenesis reduced the chicken abdominal fat pad mass by 42 d of age without affecting growth or body weight.