Exploring the relationship between polymorphisms of leptin and IGF-1 genes with milk yield in indicine and taurine crossbred cows

Genome-wide association study of Nelore and Angus heifers with low and high ovarian follicle counts

The number of antral follicles is considered an important fertility trait because animals with a high follicle count (HFC) produce more oocytes and embryos per cycle. Identification of these animals by genetic markers such as single nucleotide polymorphisms (SNPs) can accelerate selection of future generations. The aim of this study was to perform a genome wide association study (GWAS) on Nelore and Angus heifers with HFC and low (LFC) antral follicle counts. The groups HFC and LFC for genotyping were formed based on the average of total follicles (≥ 3 mm) counted in each breed consistently ± standard deviation. A total of 72 Nelore heifers (32 HFC and 40 LFC) and 48 Angus heifers (21 HFC and 27 LFC) were selected and the DNA was extracted from blood and hair bulb. Genotyping was done using the Illumina Bovine HD 770K BeadChip. The GWAS analysis showed 181 and 201 SNPs with genotype/phenotype association (P ≤ 0.01) in Nelore and Angus heifers, respectively. Functional enrichment analysis was performed on candidate genes that were associated with SNPs. A total of 97 genes were associated to the 181 SNPs in the Nelore heifers and the functional analysis identified genes (ROBO1 and SLIT3) in the ROBO-SLIT pathway that can be involved in the control of germ cell migration in the ovary as it is involved in lutheal cell migration and fetal ovary development. In the Angus heifers, 57 genes were associated with the 201 SNPs, highlighting Fribilin 1 (FBN1) gene, involved in regulation of growth factors directly involved in follicle activation and development. In summary, GWAS for Nelore and Angus heifers showed SNPs associated with higher follicle count phenotype. Furthermore, these findings offer valuable insights for the further investigation of potential mechanism involved in follicle formation and development, important for breeding programs for both breeds.

Study of milk production genes and their association with production traits in Rathi cattle

The study aimed to identify polymorphism of LEP, and STAT5A milk-producing genes and their association with production traits in Rathi cattle. An overall 160 animals were selected from a population of Rathi cattle from Livestock Research Station, Rajasthan University of Veterinary and Animals Sciences, Bikaner (Rajasthan). The phenotypic information on total milk yield, peak yield and lactation length were recorded from the years 2012- 2018. Each animal’s milk sample (100 ml) was analysed for milk composition parameters. Genomic DNA was extracted from the whole blood sample through the spin column method and association analysis was done. The polymorphism have been observed in exon-3 (454 bp) of LEP gene, intron 9-10 (224 bp) and intron-15-exon-16 (379 bp) of STAT5A genes by PCR-SSCP and revealed two types of genotypic pattern. The STAT5A exon-7 (215 bp) also showed polymorphism with three genotypic patterns. The AB pattern of LEP exon-3 and AA pattern of intron 9-10 and intron-15-exon-16 of STAT5A genes showed a significant effect on total milk yield. The BB genotypic pattern of the STAT5A exon-7 gene showed a significant impact on peak yield. The AB pattern of LEP and STAT5A genes were associated with more milk fat % in the studied population of Rathi cattle. All these genes showed a significant effect on total solids. The association analysis of LEP and STAT5A genes with different milk production and milk composition traits illustrated the worth of these genes for marker-assisted selection of dairy cattle. Thus, the present study was designed to unmask the relevant genetic factors responsible for variation in milk performance traits.