Effects Of Early Weaning Strategies On Yak Cows And Yak Calves

Yak cows had low reproductive capacity under the harsh environmental conditions of the Qinghai-Tibetan plateau.The objectives of this study were to characterize the behavioral and hematological responses to weaning stress in yak cows and calves and the estrus condition of yak cows for evaluating a practicable way to improve postpartum reproductive performance of yak cows.Twenty-six yak cows(4-8 years)and 26 yak calves(94.3±2.4 days)were studied in the experiment.The cows and calves were assigned to four weaning treatments: calves allowed free access to their cows and ad libitum sucking(NW,n=13);calves permanently weaned and separated from their cows(PW,n=5);calves temporarily separated from their cows for 15 days(TW,n=5);calves allowed free access to their cows,but fitted with nose plates for 15 days(NP,n=3).The weaning day was assigned as d 0.The results showed:Part 1 The effect of yak calves' early weaning on the grazing behavior,stress response to calves' weaning,estrus activity and nutrition metabolic in yak cows1)The results of walking activities of yak cows showed that the daily walking distance of PW yak cows was significant higher compared with NW on d 1(P<0.05).The walking distance of NW yak cows were higher than PW at 22:00 and 1:00(P<0.05),and the walking space was larger for NW compared with PW from d 58 to 84.2)The results of grazing behavior of yak cows showed that the total ruminating time of PW yak cows was lower than NW on d 1(P<0.05).The total eating time of NW yak cows was higher than PW from d 39 to 84.However,the total ruminating time of yak cows were higher in NW compared with PW from d 0 to 19 and d 19 to 84(P<0.05).3)The results of blood physiological parameters in yak cows showed that the blood WBC were higher for NP compared with PW on d 14(P<0.05).4)The results of blood physiological parameters in yak cows showed that the INS and NEFA of yak cows were higher in NW and NP compared with PW and TW on d 14(P<0.05),and the INS and NEFA of yak cows were higher in NP compared with NW on d 70 and 84(P<0.05).5)The results of blood progestone concentration in yak cows showed that all yak cows of the four treatments went into the first luteal phase in the test.Otherwise,the NW yak cows did not show normal luteal phase,and part of the yak cows in TW and NP groups went into the normal luteal phase.All yak cows in PW went into the normal luteal phase.Part 2 The effect of early weaning on growth performance,the stress response to calves' weaning and nutrition metabolic in yak cows1)The breast girth of yak calves was measured to estimate the growth performance,which showed no significant difference between PW and NW groups(P>0.05).However,it was smaller in TW compared with NW and PW on d 70(P<0.05).The breast girth of yak calves in NP was smaller than PW,NW and NP were bigger than TW on d 84(P<0.05).2)The observed behavior results showed that the yak calves which suffered early weaning significantly increased standing and walking time(P<0.05)and significantly decreased playing time(P<0.05).Yak calves in PW and TW group all returned to the similar level of NW yak calves before d 5,however,the playing behavior of NP yak calves still significantly higher compared with NW yak calves on d 8(P<0.05).3)The results of blood physiological parameters in yak calves showed that the WBC,HGB and HCT in PW,TW and NP significantly increased(P<0.05)after weaning,and returned to the similar level before weaning in 19 days.4)In yak calves,the blood INS in TW yak calves were lower than NW on d 19(P<0.05).In conclusion,the early weaning of yak calves can result a short-term stress response,but the cows can quickly adapt to the absence of their calves.The yak cows with calves and those without calves should graze separately in cold season.The early weaning of yak calves helped to improve the estrus of yak cows,and the permanent weaning method has the most obvious effect on the yak cows' estrus compared with other weaning practices.Early weaning can induce the yak calves suffer weaning stress and wearing nose plates would make the yak calves suffer longer weaning stress.Under grazing conditions,permanent weaning with supplementing concentrates is the best practice for yak calves' growth.The temporary weaning and wearing nose plates for 15 days can restrict the yak calves' growth,especially in the cold season.