Genetic polymorphisms of the OLR1 and DGAT1 genes associated with milk components in Holstein Friesian dairy cattle under an intensive management in Central Java

Abstract

Oxidized Low Density Lipoprotein Receptor 1 (OLR1) gene serves to encode the binding vascular surface receptors and to degrade the oxidized low-density lipoprotein. In dairy cattle a nucleotide mutation at 3′UTR location of the OLR1 gene results in C allele of which related to higher milk fat content than A allele. Diacylglycerol O-acyltransferase 1 (DGAT1) gene has a K232A mutation of which K allele also associated with higher milk fat content against A allele. This study was aimed to study the association of variant genotypes of the OLR1 and DGAT1 genes on milk fat and other milk components in Holstein Friesian (HF) dairy cattle. The target of this research was to obtain genotypes of the OLR1 and DGAT1 gene affecting highly to milk fat content and other milk components in domestic HF cattle. Animals observed were Holstein Friesian (HF) lactating cows for 53 heads kept intensively at one government dairy station at BBPTU Baturraden, Central Java. Base mutations at 3′UTR location of the OLR1 gene and at K232A mutation of the DGAT1 gene were identified by PCR-RFLP (polymerase chain reaction - restriction fragment length polymorphism) techniques. Allele frequency of the base mutation of each gene was analyzed by PopGen 32 program. Milk components of fat, protein, solid non-fat (SNF) and lactose were generated from daily milk test for morning, afternoon and average of both. Study of the association of variant genotypes of the OLR1 and DGAT1 genes on individual milk component was analyzed by GLM considering the fixed effects of lactation period (1-3, 4-6), calving season (1-4 mo., and 5-8 mo.) and calving year (2011, 2012). Duncan Multiple Range Test was used to test significant differences of the averages among subclasses. The OLR1 gene resulted in A allele and C allele of whose the frequencies were respectively 0.457 and 0.543, while the DGAT1 gene resulted in A allele and K allele with the frequencies respectively 0.426 and 0.575. Variant genotypes of the OLR1 gene gave a significant different on milk fat production (P<0.05). Genetic polymorphism of the OLR1 gene had a significant effect on milk fat content in the noon, the highest was for CC genotype, followed by AC, and the lowest was AA, with the fat contents of CC and AC genotypes higher to AA one by 4.87% and 1.38% respectively. However variant genotypes of the OLR1 gene had no significant effect on other milk components (P>0.05). Similarly, variant genotypes of the DGAT1 gene consisting of genotype AK and genotype KK did not significantly affect on all of milk components. It was concluded that there was a fairly good control of the OLR1 gene to fat content in HF cows. The base mutation at the 3′UTR location of the OLR1 gene can be considered as an initial information in developing a genetic assisted selection (GAS) technique for milk fat content in domestic HF cows.