Reksen O, Gröhn Y T, Havrevoll Ø, Bolstad T, Waldmann A, Ropstad E
Department of Reproduction and Forensic Medicine, Norwegian School of Veterinary Science, PO Box 8146 Dep, N-0033 Oslo, Norway.
Anim Reprod Sci. 2002 Oct 16;73(3-4):169-84. doi: 10.1016/s0378-4320(02)00146-x.
Relationships among milk progesterone, concentrate allocation, energy balance (EB), milk yield and conception rate were studied in 146 lactations in 94 moderate yielding cows. All animals were of the dual purpose breed Norwegian cattle, and were monitored through their first and second lactations. The cows were assigned three different concentrate allocations and had free access to grass silage. Energy balance was estimated by subtracting energy required for maintenance and lactation from energy intake. Milk progesterone concentration was determined three times weekly from calving until pregnancy. The cumulative progesterone concentration was calculated as area under the progesterone curve for the first three luteal phases postpartum. The conception rate increased linearly by rising milk progesterone for values of cumulative progesterone in the lowest third of the range, whereas the likelihood of conception did not differ between milk progesterone concentrations within the upper two-thirds. This implies that the progesterone values were below a threshold value for optimal reproductive success in one-third of the services performed in this study. Milk progesterone concentrations during the third luteal phase postpartum were low when the high-energy diet was fed. Negative EB was associated with reduced values for milk progesterone during the third luteal phase in second parity cows. Likewise, milk yield was inversely related to progesterone levels during both the first and third luteal phases postpartum in second parity cows. Energy balance was higher and milk yield lower during peak lactation among second parity cows that conceived compared to cows that remained open after the first artificial insemination. The present study have demonstrated an association between likelihood of conception and the energy coverage in Norwegian cattle. This relationship is possibly mediated through progesterone deficiency.
在94头中产奶牛的146次泌乳期内，研究了牛奶孕酮、精饲料分配、能量平衡（EB）、产奶量和受孕率之间的关系。所有动物均为兼用型挪威牛品种，并在其第一个和第二个泌乳期进行监测。给奶牛分配三种不同的精饲料量，并让它们自由采食青贮草。能量平衡通过从能量摄入量中减去维持和泌乳所需能量来估算。从产犊到怀孕期间，每周三次测定牛奶孕酮浓度。累积孕酮浓度计算为产后前三个黄体期孕酮曲线下的面积。对于累积孕酮值处于范围最低三分之一的情况，受孕率随牛奶孕酮升高呈线性增加，而在范围较高的三分之二内，牛奶孕酮浓度之间的受孕可能性没有差异。这意味着在本研究中三分之一的配种中，孕酮值低于实现最佳繁殖成功率的阈值。在饲喂高能日粮时，产后第三个黄体期的牛奶孕酮浓度较低。二胎奶牛产后第三个黄体期，负能量平衡与牛奶孕酮值降低有关。同样，二胎奶牛产后第一个和第三个黄体期的产奶量均与孕酮水平呈负相关。与首次人工授精后未受孕的奶牛相比，受孕的二胎奶牛在泌乳高峰期能量平衡更高，产奶量更低。本研究证明了挪威牛受孕可能性与能量供应之间的关联。这种关系可能是通过孕酮缺乏介导的。
