Abstract：Excess fat deposition in livestock is of major concern to the meat industry. Various approaches have been attempted to solve this excessive fat deposition problem. In this paper, 150 female(♀) SD rats(Rattus norvegicus) weighting (110±10) g were allotted randomly into five groups (basic diet adding 0, 75, 500, 1 000 and 6 000 mg/kg of yolk powder containing antibody against adipocyte plasma membranes(APM), respectively. The trial lasted for 75 days after rats were slaughtered for carcass analysis and blood, and three different white adipose tissue depots (mesenteric fat, parametrial fat and perirenal fat) and hypothalamus were sampled. Concentrations of serum insulin and serum leptin were determined by radioimmunoassay (RIA). The total RNA was extracted from tissues to measure the abundance of Leptin, Bcl-2 and Bax mRNA in different adipose tissue depots and Ob-Rb mRNA in hypothalamus by RT-PCR with 18S rRNA internal standard. DNA and RNA content in different adipose tissue depots were determined. The results showed that yolk antibody treatment decreased celiac fat weight and index, but did no affect body weight gain, food intake of rats and gastrocnemius muscle weight. Basic diet adding 6000 mg/kg positive yolk powder decreased serum triglycerides concentration, increased serum free fatty acids (FFA) concentrations, reduced DNA content and concentration of parametrial fat and perirenal fat. Basic diet adding 75 mg/kg positive yolk powder reduced DNA content of parametrial fat and perirenal fat. Yolk antibody treatment decreased serum insulin, down-regulated Leptin mRNA expression in parametrial fat and perirenal fat, up-regulated Ob-Rb mRNA expression in hypothalamus, decreased Bcl-2 and Bax mRNA expression in parametrial fat, but did no affect Bcl-2 mRNA /Bax mRNA. The results also showed that the expression of Leptin mRNA in perirenal fat was higher than that in parametrial fat, latter was higher than that in mesenteric fat, and Bcl-2 and Bax gene expressions in parametrial and perirenal fat were higher than that in mesenteric fat. The results suggested that oral administration of yolk antibody against APM can decrease adipose tissue depots, and its possible mechanisms are: 1) IgY directly destory adipocyte and decline proliferation of preadipocyte; 2) IgY decrease fat deposition through metabolic changes of adipocytes.
