Growth trends in Bos grunniens (yak) raised in pasture-based systems in Eastern Kentucky

Bos grunniens (yak) are a unique ruminant species adapted to the rugged, high-altitude regions of Asia that could diversify livestock production in the Southeastern United States, however, limited research has been conducted on the yak in North America. The objective of this study was to evaluate the performance of male and female growing yaks in pasture-based systems in the mixed humid transition zone of the United States. Six males (beginning weight 132.8 ± 13.5 kg) and six females (beginning weight 124.3 ± 34.4 kg) were grazed in Year 1, and four males (beginning weight 157.3 ± 15.0 kg) and four females (beginning weight 160.9 ± 26.4 kg) were grazed in Year 2, allowing two pasture replicates per sex. Pastures were monitored throughout the study to assess forage availability, botanical composition, and nutritive value. In Year 1, males gained at a greater rate than females (0.45 kg/day vs. 0.23 kg/day; p < 0.01). In Year 2, a similar difference was observed for seasonal gains between sexes with males gaining 0.61 kg/day and females gaining 0.25 kg/day (p < 0.01). A significant year effect for growth rates of male yaks was seen (0.45 kg/day vs. 0.61 kg/day; p < 0.01) but not observed in females. Sex can impact weight gain in growing yaks raised in pasture-based systems with males gaining more rapidly than females.