Caixeta L S, Ospina P A, Capel M B, Nydam D V
Department of Population Medicine and Diagnostic Sciences, College of Veterinary Medicine, Cornell University, Ithaca, NY, 14853, USA.
Perry Veterinary Clinic, Perry, NY, 14530, USA.
Theriogenology. 2017 May;94:1-7. doi: 10.1016/j.theriogenology.2017.01.039. Epub 2017 Jan 25.
The objective of this study was to determine the effects of subclinical hypocalcemia on reproductive performance in dairy cows. In a prospective cohort study, 97 cows on 2 dairy farms with automatic milking systems were monitored for subclinical hypocalcemia. Animals were enrolled 7 ± 3 days prior to estimated calving date and three parity groups were defined based on the lactation that the animals were going to start: lactation = 1, lactation = 2, and lactation ≥3. Serum calcium concentration (Ca) was measured in all animals in the first 3 DIM and subclinical hypocalcemia (SCH) was defined as Ca ≤ 8.6 mg/dL; animals that presented a low Ca level during all 3 days were classified as chronic SCH (cSCH). Return to cyclicity during the voluntary waiting period was analyzed based on weekly progesterone concentrations measured in serum. Information on reproductive outcomes (i.e., number of breedings, pregnancy status, days open, etc.), were collected from on-farm software after all study cows had completed their study period. Chronic SCH was present in all parity groups with higher incidence in multiparous animals (20% of parity = 1, 32% of parity = 2; and 46% of parity ≥ 3 animals). The cSCH animals took longer to show active ovaries when compared to eucalcemic and SCH animals. In a multivariable Cox's Proportional Hazard model animals with normal Ca were 1.8 times more likely to return to cyclicity by the end of the voluntary waiting period when compared to cSCH animals. Animals with cSCH also had 0.27 odds of being pregnant at first service compared to eucalcemic cows when analyzed by multivariable logistic regression. Subclinical hypocalcemia had a negative effect on return of ovarian function during the voluntary waiting period and decreased the odds of pregnancy at first service. Those cows with cSCH had an even more pronounced impaired reproductive function than those with one subclinical measurement.
本研究的目的是确定亚临床低钙血症对奶牛繁殖性能的影响。在一项前瞻性队列研究中，对2个配备自动挤奶系统的奶牛场的97头奶牛进行了亚临床低钙血症监测。在预计产犊日期前7±3天纳入动物，并根据动物即将开始的泌乳情况定义了三个胎次组：泌乳=1、泌乳=2和泌乳≥3。在产后第1天至第3天对所有动物测量血清钙浓度（Ca），亚临床低钙血症（SCH）定义为Ca≤8.6mg/dL；在所有3天中Ca水平均低的动物被分类为慢性SCH（cSCH）。根据血清中每周测量的孕酮浓度分析自愿等待期内的发情周期恢复情况。在所有研究奶牛完成研究期后，从农场软件收集繁殖结果信息（即配种次数、妊娠状态、空怀天数等）。所有胎次组中均存在慢性SCH，经产动物的发病率更高（泌乳=1的动物中占20%，泌乳=2的动物中占32%；泌乳≥3的动物中占46%）。与血钙正常和SCH动物相比，cSCH动物出现活跃卵巢的时间更长。在多变量Cox比例风险模型中，与cSCH动物相比，血钙正常的动物在自愿等待期结束时恢复发情周期的可能性高1.8倍。通过多变量逻辑回归分析，与血钙正常的奶牛相比，cSCH动物首次配种时怀孕的几率也为0.27。亚临床低钙血症对自愿等待期内卵巢功能的恢复有负面影响，并降低了首次配种时怀孕的几率。那些患有cSCH的奶牛的繁殖功能受损比那些有一次亚临床测量结果的奶牛更明显。
