Genomic breakthrough: ‘Identifying markers for high fertility bulls’

Pakistan possesses a large livestock population, which holds a critical position in the economic policy of the country. Livestock contributes 62.68% to agriculture and 14.36% to GDP (Pakistan Economic Survey 2022-23). Pakistan is ranked among the largest milk-producing countries globally.

Reproductive efficiency is a highly important factor in determining dairy profitability. Maintaining a short and well-defined calving season is crucial for efficient and economical herd management, achieved through highly fertile bulls and females. The economics and sustainability of animal agriculture depend on achieving the highest conception rate from genetically superior sires. Sire fertility is crucial in bovine reproduction, as a single bull is typically used to breed several cows. Bulls may represent only 2-5% of breeding stock but are responsible for 50% of herd fertility, influencing herd genetics, dynamics, and production. Nearly one in every five bulls possesses poor physical soundness, semen quality, or both, while approximately one in four bulls has unsatisfactory serving capacity. A reduction in bull fertility affects the number of culled females, reduces calf weaning weights, prolongs the calving season, delays conception, and decreases productivity and profit. Therefore, predicting bull fertility at an early age offers numerous benefits for the economic success of livestock businesses by improving pregnancy rates.

Fertility can be affected by environmental factors (nutrition, stress, disease), age, genetics, epigenetics, epistasis, hormonal disturbances, and congenital factors. High fertility bulls can be selected by identifying genomic markers of male fertility in the bull genome. Various approaches, such as candidate gene studies, comparative genomic approaches, and whole-genome scans, have been employed to identify genomic regions, polymorphisms, and their associations with service sire fertility.

In a recent research study at the University of Veterinary and Animal Sciences, Lahore, Mr. Kashif Hameed Anjum (Ph.D. Scholar), under the supervision of Dr. Asif Nadeem, conducted genomic and transcriptomic profiling of breeding bulls. This study identified genomic markers associated with semen quality traits. These identified genomic markers will be immensely helpful for selecting calves at an early age in calf raising centres (CRCs), reared to serve as high-fertility bulls for semen production units. This early selection and identification of calves with the best genetic makeup regarding semen quality traits will not only save labour, fodder, and management difficulties but also reduce the time wasted in selecting calves in CRCs established for raising bulls for semen production units. Further genomic research is necessary to explore the genetic potential of the native Sahiwal cattle breed to maximise the economic benefits of dairy production and earn foreign remittances.