Milk traits characterization and association studies with DGAT1 polymorphisms in Bagnolese sheep

The Bagnolese sheep is an authochtonous dual-purpose breed (milk and meat) reared in the Campania region, whose milk is used to produce Pecorino Bagnolese cheese. Genetic information on this sheep is extremely limited, especially regarding genes affecting productions. The aim of this study was to investigate milk production traits in Bagnolese sheep and the variability of diacylglycerol acyltransferase 1 (DGAT1) gene and its effects on milk production.

Milk quantity was recorded during the morning milking, while Kjeldahl and Gerber methods were used to assess protein and fat percentage (w/v) of collected milk samples. Two polymerase chain reaction-restriction fragment length polymorphism protocols using BamHI and MspI endonucleases for genotyping of g.5553C>T and g.8539C>T at DGAT1 locus, respectively, were set up.

Bagnolese sheep milk shows high fat and protein concentrations. Genotyping revealed a high frequency of the g.5553C and g.8539C alleles (0.56 and 0.95, respectively). The association study between the single nucleotide polymorphism (SNP) g.5553C>T and milk traits showed that animals with the CT genotype had a higher percentage of fat produced per milking than those with the CC and TT genotypes (p<0.01). Similar results were found for protein yield percentage, with CT individuals being more productive than CC individuals (p<0.01).

Bagnolese sheep milk parameters found are associated with high yields in the resulting dairy products. CT genotype at the SNP g.5553 of DGAT1 has shown a positive association with fat and protein milk yield percentage suggesting it could be considered a marker to improve productions of this breed. Finally, the new genotyping techniques used for this study enable a cheap and reliable characterization of two DGAT1 SNPs in sheep.