Comparative Reproductive Efficiencies of Cows and Heifers Artificially Inseminated with Sex-Sorted and Conventional Semen in Bhutan

Abstract

The study objective was to compare conception rates and sex of calf at birth from Artificial Insemination [AI] of cows and heifers, using sex-sorted [sexed] and conventional [unsexed] semen. Imported frozen semen from two sire lines for both sexed and conventional semen that had equivalent Post Thaw Motility of 40% was used. Predictors of conception rates and sex of calf at birth were semen type, animal type, insemination sire, number of AI per conception, AI Technician and breed. In total, 422 AI was done in 160 heifers and 130 cows of Jersey pure, Jersey cross and local cattle, of which 151 and 271 were sexed semen and conventional semen, respectively. The conception rates of 44% and 48% were recorded for sexed and unsexed semen, respectively. Although, the conception rate was higher in conventional semen, difference was not statically significant. Sexed sorted semen gave birth to 89.6% female calves as compared to 51.5% for conventional semen, indicating a strong influence of semen type on birth of female calves. Conception rate was significantly influenced by animal type; cow and heifer and not by other predictors. Conception rate was significantly lower in cows than in heifers. Hence, expensive sexed semen can be recommended for use in first-service heifers than in cows for optimizing conception rates.