Associations between candidate gene polymorphisms and milk production traits in Alpine goats farmed in Italy

Milk fat yield and composition have a great economic importance in the goat industry being most of milk destined to cheese processing. The identification of genes associated with these traits could provide useful indications for breeding programs. In this work, an association study between 11 SNP polymorphisms at 3 candidate genes (acetyl-coenzyme A carboxylase, ACACA; stearoyl-CoA desaturase, SCD; lipoprotein lipase, LPL) was carried out on 59 Alpine bucks. Data from 13,331 daily records, for milk, fat, and protein yields (kg/d) and fat and protein contents (%) of 2,220 lactations were recorded on 946 goats, daughters of the 59 bucks. Associations were tested with a mixed linear model that included the fixed effects of flock, date of the test, lactation stage, kidding season, age of the goat at kidding, SNP genotype of the sire and the random effect of the goat. Four SNPs were found to be significantly associated to milk production traits (Bonferroni gene-wide adjusted significance P < 0.01). The GC substitution at exon 1 of the LPL locus had the highest effect on milk yield (difference of about 0.6 kg/day between the 2 homozygotes CC and GG, respectively, P < 0.01). The CT substitution at exon 45 of the ACACA locus affected milk yield and fat percentage. The deletion at the 3′ untranslated region of the SCD locus affected milk, and protein (undeleted homozygotes produced about 16 g/d more than deleted ones) yield and fat percentage. Finally, the CT mutation at exon 5 of the SCD gene was associated to milk yield. These interesting associations should be obviously validated on a larger sample. Moreover, effect on other traits as milk fatty acid composition could be considered in future analyses.