Casein (CSN) gene variants and parity affect the milk protein traits in crossbred (Bos taurus x Bos indicus) cows in sub-tropical climate.

Genotypes at four casein (CSN) loci-A26181G of CSN1S1, C6227T of CSN1S2, A8101C of CSN2, and A13104C of CSN3-along with non-genetic factors were studied for their effects on various milk protein traits in 100 crossbred cows with major inheritance of Holstein Frisian (Bos taurus) and Tharparkar (Bos indicus). Results demonstrated the presence of all CSN genotypes with a predominance of heterozygotes. At CSN2 (A8101C; His67Pro) locus, the A2 allele, desirable for human health, was present in 62% as heterozygous and 29% in homozygous condition. Among non-genetic factors, parity of the cows had a significant influence on the milk protein traits in these crossbreds. The genotypes at CSN1S1, CSN2, and CSN3 loci were found to influence (p<0.05 to 0.01) the casein and whey protein yields and composition traits. The casein index and total milk yield were most influenced by the CSN1S2 locus. The AA (A1 milk) genotype of CSN2 had significantly higher yields and percentages of casein and whey proteins. Positive influence of CC genotype of CSNS3 on milk proteins of was observed similar to Bos taurus cows; however, such influence of AA genotype of CSN2 locus may be distinctive to the crossbred cows maintained in subtropical condition. Overall, the results revealed the diverse effects of CSN genotypes on milk proteins in crossbred cattle.

Genome-Wide Runs of Homozygosity Revealed Selection Signatures in Bos indicus.

Genome-wide runs of homozygosity (ROH) are suitable for understanding population history, calculating genomic inbreeding, deciphering genetic architecture of complex traits and diseases as well as identifying genes linked with agro-economic traits. Autozygosity and ROH islands, genomic regions with elevated ROH frequencies, were characterized in 112 animals of seven Indian native cattle breeds (B. indicus) using BovineHD BeadChip. In total, 4138 ROH were detected. The average number of ROH per animal was maximum in draft breed, Kangayam (63.62 ± 22.71) and minimum in dairy breed, Sahiwal (24.62 ± 11.03). The mean ROH length was maximum in Vechur (6.97 Mb) and minimum in Hariana (4.04 Mb). Kangayam revealed the highest ROH based inbreeding (FROH > 1Mb = 0.113 ± 0.059), whereas Hariana (FROH > 1Mb = 0.042 ± 0.031) and Sahiwal (FROH > 1Mb = 0.043 ± 0.048) showed the lowest. The high standard deviation observed in each breed highlights a considerable variability in autozygosity. Out of the total autozygous segments observed in each breed except Vechur, > 80% were of short length (< 8 Mb) and contributed almost 50% of the genome proportion under ROH. However, in Vechur cattle, long ROH contributed 75% of the genome proportion under ROH. ROH patterns revealed Hariana and Sahiwal breeds as less consanguineous, while recent inbreeding was apparent in Vechur. Maximum autozygosity observed in Kangayam is attributable to both recent and ancient inbreeding. The ROH islands were harbouring higher proportion of QTLs for production traits (20.68% vs. 14.64%; P≤ 0.05) but lower for reproductive traits (11.49% vs. 15.76%; P≤ 0.05) in dairy breeds compared to draft breed. In draft cattle, genes associated with resistant to diseases/higher immunity (LYZL1, SVIL, and GPX4) and stress tolerant (CCT4) were identified in ROH islands; while in dairy breeds, for milk production (PTGFR, CSN1S1, CSN2, CSN1S2, and CSN3). Significant difference in ROH islands among large and short statured breeds was observed at chromosome 3 and 5 involving genes like PTGFR and HMGA2 responsible for milk production and stature, respectively. PCA analysis on consensus ROH regions revealed distinct clustering of dairy, draft and short stature cattle breeds.