Randi Federico, McDonald Michael, Duffy Pat, Kelly Alan K, Lonergan Patrick
School of Agriculture and Food Science, University College Dublin, Belfield, Dublin 4, Ireland.
School of Agriculture and Food Science, University College Dublin, Belfield, Dublin 4, Ireland.
Theriogenology. 2018 Apr 1;110:175-181. doi: 10.1016/j.theriogenology.2018.01.001. Epub 2018 Jan 9.
The aim of this study was to evaluate the relationship of body temperature fluctuations, as measured by external auditory canal temperature, to the onset of estrus and ovulation. Beef heifers (n = 44, mean age 23.5 ± 0.4 months, mean weight 603.3 ± 5.7 kg) were fitted with a Boviminder ear tag 2 weeks before the start of the estrous synchronization protocol to allow acclimatization. The device recorded the temperature, accurate to 0.01° Fahrenheit, every 10 min and transmitted the data via a base station over the internet where it could be accessed remotely. The estrous cycles of all heifers were synchronized using an 8-day progesterone-based synchronization program; on day 0 a PRID was inserted in conjunction with an injection of GnRH, and PGF2α was administered the day before PRID removal. Heifers were checked for signs of estrus at 4-h intervals (i.e., 6 times per day) commencing 24 h after PRID withdrawal. Beginning 12 h after the onset of estrus, the ovaries were ultrasound scanned at 4-h intervals to determine the time of ovulation. Body temperature was recorded every 10 min and averaged to hourly means for the following 4 periods relative to the detected oestrus onset (=Time 0): Period I: -48 h to -7 h, Period II: -6 h to +6 h, Period III +7 h to ovulation, and Period IV: ovulation to 48 h post ovulation. Data were analysed using a Mixed Model ANOVA in SAS in a completely randomized design to observe effects of induced estrus on external auditory canal temperature. The mean (±SD) interval from removal of the PRID to onset of estrus activity was 46.6 ± 14.7 h. The mean duration of estrus was 16.0 ± 5.67 h and the mean interval from estrus onset to ovulation was 27.9 ± 7.68 h. Highest temperatures (100.95 ± 0.03 °F) were observed in Period II around estrus onset, whereas lowest temperatures were observed in the 48 h preceding estrus onset (100.28 ± 0.03 °F; Period I) and around ovulation (100.30 ± 0.2 °F; Period III)(P < .001). Indeed, around the time of estrus onset (Period II) mean temperature was 0.66 °F (P < .001) higher compared with Period I. Diurnal temperature rhythms were similar (P > .10) before (Period I) and after oestrus (Period III). In conclusion, a significant elevation in external auditory canal temperature was associated with estrus in beef heifers and was followed by a decline in temperature leading up to ovulation approximately 28 h later. Future studies are required to assess pregnancy rates following AI based on changes in external auditory canal temperature.
本研究的目的是评估通过外耳道温度测量的体温波动与发情和排卵开始之间的关系。在发情同步方案开始前2周，给44头肉用小母牛（平均年龄23.5±0.4个月，平均体重603.3±5.7千克）佩戴Boviminder耳标，以便使其适应。该设备每10分钟记录一次温度，精确到0.01华氏度，并通过基站经互联网传输数据，可远程访问这些数据。使用基于孕酮的8天同步程序使所有小母牛的发情周期同步；在第0天，插入孕酮释放装置（PRID）并注射促性腺激素释放激素（GnRH），在取出PRID的前一天给予前列腺素F2α（PGF2α）。在取出PRID后24小时开始，每隔4小时（即每天6次）检查小母牛的发情迹象。从发情开始后12小时起，每隔4小时对卵巢进行超声扫描，以确定排卵时间。每10分钟记录一次体温，并将其平均为相对于检测到的发情开始（=时间0）的以下4个时间段的每小时平均值：第I期：-48小时至-7小时，第II期：-6小时至+6小时，第III期：+7小时至排卵，第IV期：排卵至排卵后48小时。在SAS中使用混合模型方差分析对数据进行完全随机设计分析，以观察诱导发情对外耳道温度的影响。从取出PRID到发情活动开始的平均（±标准差）间隔为46.6±14.7小时。发情的平均持续时间为16.0±5.67小时，从发情开始到排卵的平均间隔为27.9±7.68小时。在发情开始前后的第II期观察到最高温度（100.95±0.03华氏度），而在发情开始前的48小时（100.28±0.03华氏度；第I期）和排卵前后（100.30±0.2华氏度；第III期）观察到最低温度（P<0.001）。实际上，在发情开始时（第II期），平均温度比第I期高0.66华氏度（P<0.001）。发情前（第I期）和发情后（第III期）的昼夜温度节律相似（P>0.10）。总之，肉用小母牛的外耳道温度显著升高与发情有关，随后温度下降，大约28小时后排卵。需要进一步的研究来评估基于外耳道温度变化进行人工授精后的妊娠率。
