Abstract
This study explores biological rhythms in Himalayan yaks. Indicators of reproductive, physiological rhythms and health were evaluated in 26 representative yaks from as many yak herds in 26 villages/hamlets of Changthang Ladakh (India). Average life span (20.57 ± 0.39 years), body weight (200-650 kg), age of puberty (2.1-2.9 years), oestrus period (21.1 ± 0.29 days), oestrus duration (16.9 ± 0.7 h), and gestation length (259.73 ± 1.48 days) was recorded. Seasonal breeding (spring/summer) with parturition cycle starting in spring season, was noticed. Single calving and singlet births were noted. Migration starts in April-May and returns in September-October. Common feeding practice includes pasture grazing. Hemoglobin (g/dl), packed cell volume (%), total erythrocytic count (x10
6
) and total leucocytic count (x10
3
) ranged from 12.29-14.56, 36.88-43.7, 7.28-7.79, and 8.43-7.15 during summer and winter, respectively. Rectal temperature (◦F) was 99.78-101.13, respiration rate (breaths per minute) was 34.23-65.38 and heart rate (beats per minute) was 68.65-99.04 during winter and summer, respectively. Seasonal cyclicity of common infectious and non-infectious diseases was noted. In conclusion, this study provides baseline data of biological rhythms of yaks and elaborates their seasonal variation with emphasis on future management prospects.