Postpartum oestrous cycling resumption of yak cows following different calf weaning strategies under range conditions.

Early weaning can improve body condition and reproductive performance of cows. The objectives of this study were to examine and compare oestrous cycling resumption, behaviour and blood parameters of yak cows following four different strategies of calf weaning. Twenty-six yak cows (4-8 years) and their calves (94.3 ± 2.4 days) were studied in which calves were: weaned naturally with free access to their mothers (NW; n = 13); weaned abruptly and separated permanently from their mothers (PW; n = 5); separated temporarily from their mothers for 15 days (TW; n = 5); and fitted with nose plates for 15 days, but allowed free access to their mothers (NP; n = 3). Yak cows with sucking calves (NW) spent more time grazing in the cold season (from d 39 to 84). Based on serum progesterone concentrations, none of nine NW yak cows resumed oestrous cycling during the study, while seven of nine yak cows with weaned calves resumed cycling (3/3 for PW; 2/3 for TW; and 2/3 for NP yaks). We concluded that early weaning improved postpartum reproductive performance of yak cows on the Qinghai-Tibetan plateau and that abrupt and permanent weaning was an appropriate strategy.