Preliminary association studies between EBVs and SNPs in 5 candidate genes for milk fat in goats

Fat yield and content play a major role in the technological and nutritional quality of goat milk, influencing nutritional, aromatic and technological characteristics, like firmness, color and flavor, of milk and milk-derived products (Delacroix-Buchet and Lamberet 2000). These traits are relevant factors for the market value of dairy goat products and make milk fat a considerable component of the economic efficiency of goat production. Moreover, fatty acid composition of milk is of great interest, considering the implications for human health (Garcìa-Fernandez et al. 2009). This work aims to present some preliminary results of the association studies between a panel of SNPs identified in candidate genes for milk fat and estimated breeding values for fat yield (kg) and fat content (%), calculated by the National Breeders Association (ASSONAPA) on a sample of 80 Alpine and Saanen bucks reared in Italy. The five candidate genes investigated are well known for their role. Acetyl-coenzyme A carboxylase alpha (ACACA) is part of a multifunctional complex enzyme system which catalyzes the rate-limiting step in fatty acid synthesis. Badaoui et al. (2007a) observed in ACACA gene a polymorphism associated with fat yield, lactose content and somatic cell count in 4 Spanish goat breeds. Diacilglycerol acyl transferase 1 (DGAT1) is a key enzyme in triacylglycerol synthesis in the mammary gland, well known in cattle for its effects on fat and protein yield (Grisart et al. 2004), whereas in goat Angiolillo et al. (2007) identified only a SNP. Fatty acid synthase (FASN) encodes a multifunctional protein catalyzing the synthesis of palmitate into long-chain saturated fatty acids. In cattle SNP on FASN gene showed a significant association with milk fat yield and content (Roy et al. 2006). Lipoprotein lipase (LPL) encodes homonymous lipase with the dual functions of triglyceride hydrolase and ligand/binding factor for receptor-mediated lipoprotein uptake. In this gene Badaoui et al. (2007) observed one SNP associated with fat content in 4 Spanish goat breeds. Stearoyl-CoA desaturase (SCD) is the key enzyme involved in the endogenous synthesis of conjugated linoleic acid (CLA) in ruminants. It is well studied in cattle whereas in goat only some SNPs are known (Badaoui et al. 2007b; Moioli et al. 2007).