Association between Bovine GDF9 SNPs and Calving Rate (Superovulation) in Holstein-Friesian Cows

The present study aimed to assess the relationship of Growth Differentiation Factor 9 (GDF9) genotypes with calving rate, Follicle-stimulating hormone (FSH), and Estradiol (E2) in the Iraqi Holstein-Friesian breed. A number of 15 blood samples were collected from a mother of dizygotic twin birth (DZTB) (with high calving rate records), and another blood sample was collected from 15 single birth (SB) cows. The DNA was extracted and six primers were designed for PCR and sequencing analysis. The FSH and E2 levels were tested through the estrus phase for the two groups (n=10 in each group). The sequence evaluation revealed the presence of two single nucleotide polymorphisms (SNPs) in exon II: A (1109) T and G (1133) A. The genotypic frequency for mutant genotypes was higher significantly (P<0.01) in DZTB cows (with calving rate), as compared to wild genotypes at the same loci. On the other hand, the wild genotypes recorded a significant increment (P<0.01) for SB cows, when compared to mutant genotypes in the same loci. Moreover, a significant rise (P<0.05) was reported in E2 and FSH levels for DZTB cows and mutant genotypes (P<0.01) against SB cows and wild genotypes in 0 and 24 h of estrus phase, respectively. Furthermore, non-significant differences were recorded in E2 concentration among the same genotypes at the same period. In conclusion, the GDF9 exon II SNPs increased the calving rate in Holstein-Friesian cows. The blood FSH and E2 concentrations were higher in the DZTB cows and control the superovulation. Finally, these SNPs can be regarded as markers to accelerate the breeding programs and used in embryo transfer and in vitro embryo production for Iraqi Holstein-Friesian cow breed.