Lopez H, Bunch T D, Shipka M P
Department of Animal Dairy and Veterinary Sciences, Utah State University, Logan, UT 84322, USA.
Anim Reprod Sci. 2002 Jul 15;72(1-2):37-46. doi: 10.1016/s0378-4320(02)00074-x.
The objective of this study was to determine the efficacy of using milk estradiol-17beta (E(2)) sampled during regular milking periods as a predictor of estrus in dairy cows. Twenty-three primiparous Holstein cows received radiotelemetric transmitters on day 16 of the estrous cycle (day 0 = estrus) for continuous monitoring of behavioral estrus. Milk and blood samples were collected every 12h at each milking, from day 18 of the estrous cycle until the fourth milking after the onset of estrus, for radioimmunoassay of E(2). Onset of estrus was indicated by the first standing event identified by radiotelemetry. Ultrasound examination of ovaries was conducted daily in a subset of cows (n = 17) from day 18 until ovulation was confirmed. Statistical analysis involved utilization of Pearson correlation to observe any association of mean plasma and milk E(2) concentrations. Intervals from highest measured plasma and highest measured milk E(2) until the first expression of standing behavior and intervals from highest measured plasma and highest measured milk E(2) until ovulation were compared using Student's t-test. Repeated measures were utilized to evaluate the effect of day and time on milk E(2) concentration. Chi-square procedures were utilized to detect differences in actual time of onset of estrus compared to the expectation of random time of onset of estrus throughout the 24 h day. Mean duration from highest measured milk E(2) until onset of standing behavior was 21+/-3.7h and until ovulation was 46.7+/-5.3h. Mean duration from onset of standing behavior until ovulation was 26.4+/-4.2h. Mean milk E(2) concentrations increased (P<0.01) from the fourth milking period before estrus to the milking period immediately before the first expression of standing behavior, followed by a reduction (P<0.01) in mean concentrations at the milking immediately after the onset of estrus.
本研究的目的是确定在常规挤奶期间采集的牛奶中雌二醇-17β（E₂）作为奶牛发情预测指标的有效性。23头初产荷斯坦奶牛在发情周期的第16天（第0天=发情期）佩戴无线电遥测发射器，以持续监测行为发情情况。从发情周期的第18天到发情开始后的第四次挤奶，每次挤奶时每12小时采集一次牛奶和血液样本，用于E₂的放射免疫分析。发情开始由无线电遥测确定的第一次站立事件指示。从第18天到确认排卵，每天对一部分奶牛（n = 17）进行卵巢超声检查。统计分析采用Pearson相关性分析，以观察平均血浆和牛奶E₂浓度之间的任何关联。使用Student's t检验比较从最高测量血浆和最高测量牛奶E₂到首次出现站立行为的间隔时间，以及从最高测量血浆和最高测量牛奶E₂到排卵的间隔时间。采用重复测量来评估日期和时间对牛奶E₂浓度的影响。采用卡方检验来检测发情实际开始时间与全天随机发情开始时间预期之间的差异。从最高测量牛奶E₂到站立行为开始的平均持续时间为21±3.7小时，到排卵为46.7±5.3小时。从站立行为开始到排卵的平均持续时间为26.4±4.2小时。平均牛奶E₂浓度从发情前的第四个挤奶期到首次出现站立行为前的挤奶期升高（P<0.01），随后在发情开始后的第一次挤奶时平均浓度降低（P<0.01）。
