Identifying genes involved in the variability of genetic fatness in the growing chicken.

A precise knowledge of the genome involved in the expression of a quantitative trait could provide a useful tool in breeding programs; molecular genetic methods are capable of yielding this kind of information. An experimental procedure is presented here for identifying genes whose expression is related to weight variability of abdominal adipose tissue in the growing chicken. Quantitative traits are the result of metabolic pathways exhibiting some major regulation stages that are controlled genetically. These steps involve genes that may act as "major genes". With regard to chicken fat metabolism, most fatty acids are synthesized in the liver and incorporated into very low density lipoprotein (VLDL) particles before their secretion into the plasma. Accordingly, the present study focused on the expression of liver genes. The mRNA of lipogenic enzymes (acetyl-coenzyme-A carboxylase, fatty acid synthase, malic enzyme, and delta 9-desaturase) were analyzed. Also studied were apoprotein (apo)A1, apoVLDL-II, and apoB mRNA from 9-wk-old male chickens from two lines selected for high and low abdominal fat pads. Significant differences for apoA1 mRNA levels occurred between fat and lean birds. Moreover, the total quantity of mRNA provided an accurate estimation of the abdominal fat pad (r = .74 with P < .05).