Abstract:

 The effect of two mutations in Interleukin-8 (IL-8) gene for 588 Holstein cows from 72 bull families of Haifeng dairy cattle farm imported from Australia were investigated on 7 milking performances: tested day milk yield, milk fat percentage, milk protein percentage, 305 d corrected milk yield, 305 d milk fat yield, 305 d milk protein yield and somatic cell score (SCS). The aim was to explore molecular marker in the breeding of dairy cattle. The polymorphism of IL8 gene was detected by polymerase Chain reaction-single strand conformation polymorphism (PCR-SSCP) technique. The association between polymorphic sites of IL8 gene and milking performances , SCS was analyzed by the least square mean model. The results showed that a mutation from G to A was identified in the 5′ upstream of -180(G/A), the genotypic frequencies of GG, GA and AA were 0.226, 0.476 and 0.298, respectively. The gene frequencies of G and A were 0.464 and 0.536, respectively. No significant effects of mutation were observed on milking performances and SCS except on 305 d milk fat yield. The 305 d milk fat yield for GG genotype was higher than GA (P<0.05). A mutation from A to G was identified in 2 789 of IL8, and the genotypic frequencies of GG, GA and AA were 0.297, 0.506 and 0.197, respectively. The gene frequencies of G and A were 0.550 and 0.450. This mutation showed significant effects on tested day milk fat percentage, milk protein percentage, 305 d corrected milk yield and SCS. The AA genotype had greatly significant higher milk fat percentage than GG and GA genotypes (P<0.01). Milk protein percentage for AA was greatly significant higher than that GA (P<0.01). GG genotype had greatly significant higher SCS than GA and AA (P<0.01). 305 d corrected milk yield for GA was significant higher than AA (P<0.05). The polymorphisms of IL8 gene had a greatly genetic effects on milking traits and mastitis resistance, so this gene could be a useful genetic marker for Holstein cows imported from Australia.