Honig Hen, Ofer Lior, Elbaz Michal, Kaim Moshe, Shinder Dima, Gershon Eran
Institute of Animal Sciences, Agricultural Research Organization, PO Box 6, Bet-Dagan 50250, Israel.
Department of Ruminant Science, Agricultural Research Organization, PO Box 6, Bet Dagan 50250, Israel.
Gen Comp Endocrinol. 2016 Sep 1;235:64-69. doi: 10.1016/j.ygcen.2016.06.006. Epub 2016 Jun 8.
In dairy cows, heat stress depresses appetite, leading to decreased food intake, a negative energy balance, and modifies ghrelin levels. Ghrelin is a gut-brain peptide with two major forms: acylated, with an O-n-octanoylated serine in position 3, and nonacylated. To date, the effect of heat stress and estrous cycle on ghrelin secretion in dairy cows has not been studied. We characterized ghrelin secretion during the estrous cycle in each, the winter and the summer seasons. We further examined the effects of parity on ghrelin secretion. Blood was collected from 10 primiparous or multiparous Israeli-Holstein dairy cows throughout the estrous cycle, in both, the hot and cold seasons. The levels of acylated and total ghrelin were measured in the blood samples. We found that both acylated and total ghrelin levels during heat stress were lower than their respective levels in the winter in both, primiparous and multiparous cows. No differences in acylated and total ghrelin levels were found between primiparous and multiparous cows in both seasons. We further found that in multiparous but not primiparous cows acylated ghrelin secretion oscillated during the estrous cycle in both seasons. Its levels peaked on the last days of the first follicular wave and on the days before and during ovulation. Interestingly, we found that elevated acylated ghrelin levels correlated with conception success and increased total ghrelin levels were associated with successful conception from first insemination. Our data is the first to demonstrate seasonal variation in ghrelin secretion. This study provides evidence for the yet unfamiliar link between heat stress, ghrelin and fertility. Increased circulating acylated ghrelin may contribute to improved fertility in dairy cows. It further raises the possibility of a link between ghrelin levels and successful inseminations. Further research is required to determine the effects of ghrelin on dairy cow performance.
在奶牛中，热应激会抑制食欲，导致采食量减少、能量负平衡，并改变胃饥饿素水平。胃饥饿素是一种肠脑肽，有两种主要形式：酰化型，第3位丝氨酸被O-正辛酰化；非酰化型。迄今为止，尚未研究过热应激和发情周期对奶牛胃饥饿素分泌的影响。我们对每个季节（冬季和夏季）发情周期中的胃饥饿素分泌进行了表征。我们还进一步研究了胎次对胃饥饿素分泌的影响。在炎热和寒冷季节，从10头初产或经产以色列荷斯坦奶牛整个发情周期中采集血液。测量血样中酰化胃饥饿素和总胃饥饿素的水平。我们发现，在热应激期间，初产和经产奶牛的酰化胃饥饿素和总胃饥饿素水平均低于冬季各自的水平。在两个季节中，初产和经产奶牛的酰化胃饥饿素和总胃饥饿素水平均未发现差异。我们还发现，在经产奶牛而非初产奶牛中，两个季节发情周期中酰化胃饥饿素的分泌都会波动。其水平在第一个卵泡波的最后几天以及排卵前和排卵期间达到峰值。有趣的是，我们发现酰化胃饥饿素水平升高与受孕成功相关，而总胃饥饿素水平升高与首次输精后的成功受孕相关。我们的数据首次证明了胃饥饿素分泌存在季节性变化。本研究为热应激、胃饥饿素与繁殖力之间尚不为人熟知的联系提供了证据。循环中酰化胃饥饿素增加可能有助于提高奶牛的繁殖力。这进一步增加了胃饥饿素水平与输精成功之间存在联系的可能性。需要进一步研究以确定胃饥饿素对奶牛生产性能的影响。
