Tauck Shaun A, Olsen Jesse R, Berardinelli James G
Department of Animal and Range Sciences, Montana State University, 119 Linfield Hall, Bozeman, MT 59715, USA.
Reprod Biol Endocrinol. 2007 Aug 13;5:33. doi: 10.1186/1477-7827-5-33.
The objective was to evaluate if cortisol concentrations are associated with the resumption of luteal activity in postpartum, primiparous cows exposed to bulls. The hypotheses were that 1) interval from start of exposure to resumption of luteal activity; 2) proportions of cows that resumed luteal function during the exposure period; and 3) cortisol concentrations do not differ among cows exposed or not exposed to bulls (Exp. 1), and cows continuously exposed to bull or steer urine (Exp. 2).
In Exp. 1, 28 anovular cows were exposed (BE; n = 13) or not exposed (NE; n = 15) to bulls for 30 d at 58 d after calving. In Exp. 2, 38 anovular cows were fitted with a controlled urine delivery device at 45 d after calving and exposed continuously (24 h/d) to bull (BUE; n = 19) or steer (SUE; n = 19) urine. Length of exposure was ~64 d. Blood samples were collected from each cow on D 0 and every 3 d throughout exposure periods in both experiments and assayed for progesterone. Cortisol was assayed in samples collected on D 0, 8, 16, and 24 in Exp. 1; and, D 0, 19, 38, and 57 in Exp. 2.
In Exp. 1, interval from the start of exposure to resumption of luteal activity was shorter (P < 0.05) for BE cows than NE cows, similarly, more (P < 0.05) BE cows than NE cows resumed luteal function during the exposure period. In Exp. 2, there was no difference in intervals from the start of exposure to resumption of luteal activity and proportions of cows that resumed luteal function during the exposure period between BUE and SUE cows. In Exp. 1, there was no difference in cortisol concentrations between BE and NE cows at the start of the experiment (D 0), however, cortisol concentrations were greater (P < 0.05) in BE cows than NE cows on D 9, 18, and 27. In Exp. 2, cortisol concentrations were higher for BUE than SUE cows on D 0 (P < 0.05), thereafter cortisol decreased (P < 0.05) but did not differ between BUE and SUE cows.
We conclude that the physical presence of bulls stimulates resumption of luteal activity and is coincident with increased cortisol concentrations, and hypothesize a possible association between adrenal activation and the biostimulatory effect of bulls.
目的是评估产后初产母牛接触公牛后皮质醇浓度是否与黄体活动恢复有关。假设如下：1）从开始接触到黄体活动恢复的间隔时间；2）接触期间恢复黄体功能的母牛比例；3）接触或未接触公牛的母牛（实验1）以及持续接触公牛尿液或阉牛尿液的母牛（实验2）之间的皮质醇浓度没有差异。
在实验1中，28头无排卵母牛在产后58天被暴露于公牛（暴露组；n = 13）或不暴露于公牛（非暴露组；n = 15）30天。在实验2中，38头无排卵母牛在产后45天安装了可控尿液输送装置，并持续（每天24小时）暴露于公牛尿液（公牛尿液暴露组；n = 19）或阉牛尿液（阉牛尿液暴露组；n = 19）。暴露时间约为64天。在两个实验的暴露期间，从每头母牛在第0天以及此后每3天采集血样并检测孕酮。在实验1中，对第0、8、16和24天采集的样本检测皮质醇；在实验2中，对第0、19、38和57天采集的样本检测皮质醇。
在实验1中，暴露组母牛从开始接触到黄体活动恢复的间隔时间比非暴露组母牛短（P < 0.05），同样，在接触期间恢复黄体功能的暴露组母牛比非暴露组母牛多（P < 0.05）。在实验2中，公牛尿液暴露组和阉牛尿液暴露组母牛从开始接触到黄体活动恢复的间隔时间以及接触期间恢复黄体功能的母牛比例没有差异。在实验1中，实验开始时（第0天）暴露组和非暴露组母牛的皮质醇浓度没有差异，然而，在第9、18和27天，暴露组母牛的皮质醇浓度高于非暴露组母牛（P < 0.05）。在实验2中，第0天公牛尿液暴露组母牛的皮质醇浓度高于阉牛尿液暴露组母牛（P < 0.05），此后皮质醇浓度下降（P < 0.05），但公牛尿液暴露组和阉牛尿液暴露组母牛之间没有差异。
我们得出结论，公牛的实际存在刺激了黄体活动的恢复，并且与皮质醇浓度升高同时发生，并推测肾上腺激活与公牛的生物刺激作用之间可能存在关联。
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