Evaluation of candidate gene effects and environmental factors on reproductive performance of Holstein cows
This study investigated the impact of nine polymorphisms located in the CSN2, CSN3, CSN1S1, CSN1S2, OLR1, LALBA, STAT1, DGAT1 and LGB genes, and environmental factors including calving year, season and parity on reproductive traits. The analysis was conducted on 165 Holstein-Friesian cows. Genotypes were identified using PCR-RFLP. The data of reproductive traits for four lactations were evaluated. Statistical analysis was carried out using least squares of the GLM procedures. Results indicated that CSN2 had significant effects on days before first insemination and first insemination to pregnancy interval. The SNP at the CSN3 was significantly associated with gestation length. A novel effect of OLR1-C223A on age at first calving was observed in the present study. Moreover, DGAT1 and LGB markers were significantly associated with calving interval and days before first insemination, respectively. In addition, significant environmental effects were as follows: calving year with days before first oestrus, days open, and first insemination to pregnancy interval; season with days open, first insemination to pregnancy interval, and calving interval; parity with days before first oestrus and days open. The present results and novel associations may therefore be useful and indicative for future studies on a genetic basis of cattle reproduction traits.
Keywords: cattle, environmental effects, genetic marker, Holstein-Friesian, reproduction parameters