A polymorphism in the insulin-like growth factor 1 gene is associated with postpartum resumption of ovarian cyclicity in Holstein-Friesian cows under grazing conditions

Abstract

Background: Insulin-like growth factor 1 (IGF-1) gene is considered as a promising candidate for the identification of polymorphisms affecting cattle performance. The objectives of the current study were to determine the association of the single nucleotide polymorphism (SNP) IGF-1/SnaBI with fertility, milk production and body condition traits in Holstein-Friesian dairy cows under grazing conditions.

Methods: Seventy multiparous cows from a commercial herd were genotyped for the SNP IGF-1/SnaBI. Fertility measures evaluated were: interval to commencement of luteal activity (CLA), calving to first service (CFS) and calving to conception (CC) intervals. Milk production and body condition score were also evaluated. The study period extended from 3 wk before calving to the fourth month of lactation.

Results and discussion: Frequencies of the SNP IGF-1/SnaBI alleles A and B were 0.59 and 0.41, respectively. Genotype frequencies were 0.31, 0.54 and 0.14 for AA, AB and BB, respectively. Cows with the AA genotype presented an early CLA and were more likely to resume ovarian cyclicity in the early postpartum than AB and BB ones. No effect of the SNP IGF-1/SnaBI genotype was evidenced on body condition change over the experimental period, suggesting that energy balance is not responsible for the outcome of postpartum ovarian resumption in this study. Traditional fertility measures were not affected by the SNP IGF-1/SnaBI.

Conclusion: To our knowledge this is the first report describing an association of the SNP IGF-1/SnaBI with an endocrine fertility measure like CLA in cattle. Results herein remark the important role of the IGF-1gene in the fertility of dairy cows on early lactation and make the SNP IGF-1/SnaBI an interesting candidate marker for genetic improvement of fertility in dairy cattle.

Figure 1

Agarose gel electrophoresis showing the SNP IGF-1/SnaBI in 5^′-noncoding region of cattle IGF-1 gene. Lanes 1 and 8: molecular size marker 50-bp ladder (Fermentas); lanes 2 and 3: AA (TT) genotype (223-bp); lanes 4 and 5: AB (TC) genotype (249 and 223-bp); lanes 6 and 7: BB (CC) genotype (249-bp). The 26-bp fragment in AA and AB genotypes is undetectable.

Figure 2

Percentage of cows cycling across SNP IGF-1/SnaBI genotypes (AA, AB, BB) within the same day postpartum. Superscripts differ by: ^{a, b} P ≤ 0.05, ^{x, y, z} P ≤ 0.1.