Authors
1
Dep. of Animal Science, Faculty of Animal Science and Fisheries, Sari Agricultural Sciences and Natural Resources University, Sari, Iran
2
Sari Agricultural Sciences and Natural Resources University
Abstract
Background and objectives: Reproductive efficiency is one of the most important factors influencing dairy cow performance. In the present study, relationship between the nucleotide polymorphisms in interleukin 2 (IL-2: exon 6) and interleukin 10 (IL-10: exon 5) genes with reproductive traits including days open, calving interval, days from calving to first service, gestation length, service success, stillbirth and calving difficulty were examined.
Materials and methods: In the present study, the selective genotyping method was used to investigate the relationship between interleukin 2 and 10 candidate genes with reproductive traits in Holstein cows. Individuals were selected based on their days open residual distribution obtained from a mixed model analysis. In the used model, the effects of year of birth, year of calving, season of calving and lactation number were taken into account as fixed effects, and the random effects of the animal and the covariate effect of milk yield were also included in the model. A total of 194 cows including 97 cows from each tail of the residual distribution, were selected. The DNA was extracted using a modified salting out procedure. Polymerase chain reactions (PCR) using specific primers were implemented to amplify 172 bp and 325 bp of IL-2 and IL-10, respectively. Banding patterns were identified using the PCR-SSCP technique. The Cox test in SAS was used to examine the association between banding patterns with days open, calving interval, days from calving to first service, gestation length. The logistics regression was implemented in SAS for service success, stillbirths and calving difficulty.
Results: The results showed the existence of polymorphism for both studied loci. Four different banding patterns in IL-2 and seven different banding patterns in IL-10 were observed. For IL-10 locus, banding patterns 5 and 6 had the highest frequency and pattern 3 showed the least frequency in the individuals with residual values below the mean. Also, in this locus, for the second group with residual values above the mean, the highest frequency of banding patterns was observed for pattern 6 which also had the highest frequency in the entire sample. For IL-2, in the individuals with residual values below the mean, patterns 1 and 2 showed the most and the least frequency, respectively and pattern 4 had the least frequency in the entire sample. Statistical results showed that IL-2 gene had a significant effect on days open (P<0.05) and length of gestation (P<0.01). Also, IL-10 gene had a significant effect on days open (P<0.01).
Conclusion: Considering the high polymorphism of the studied regions in the population of Holstein dairy cows and the relationship of these polymorphisms with reproductive traits, these genes can be considered in breeding programs by confirming the results with the aid of sequencing.
Keywords