Daily milk, fat and protein yield and amount of somatic cells in cow milk are very important factors that influence milk performance traits. An association between polymorphisms in the kappa casein (CSN3) gene and milk production, composition and technical properties has been previously reported; however, this type of information is not available for the bovine β-carotene oxygenase 2 (BCO2) gene - the BCO2 gene has relationship with milk color and meat fat color, which is dependent on content of β-carotene.
Milk performance traits
The signal transducer and activator of transcription (STAT) genes are responsive to a wide range of cytokines, growth factors, and hormones, and thus control important biological processes. In humans, STAT4 mutations have been identified as genetic markers for rheumatoid arthritis, systemic lupus erythematosus, and primary Sjögren’s syndrome, whereas little research has been conducted on bovine STAT4 mutations and their potential effects.
Prolactin (PRL) plays central roles in mammals’ reproduction, gland development, milk secretion, and the expression of milk protein genes. In dairy cattle, the PRL gene is a potential quantitative trait locus and genetic marker related to milk performance traits. Here, a total of 586 randomly selected Chinese Holstein cows were genotyped for locus PRL-RsaI. One haplotype block containing eight SNPs was identified in the region from intron 3 to intron 4 of the PRL gene in Chinese Holstein cows.