It was found that mean GH among the age groups differ
(pb0.05). With increasing age and BW, GH level decreased. The age groups with higher plasma GH showed higher growth rates(r=0.73). In conclusion, a highly sensitive enzymeimmunoassay procedure has been developed for the first time to determine plasma GH levels in bovine (yak) plasma. A close relationship of plasma GH concentration with age, BW and growth rates was
found in yaks.