Gazal O S, Guzman-Vega G A, Williams G L
Animal Reproduction Laboratory, Texas A&M University Agricultural Research Station, Beeville 78102-9410, USA.
J Anim Sci. 1999 May;77(5):1044-7. doi: 10.2527/1999.7751044x.
Previously published reports have indicated that postpartum anovulatory intervals can be markedly reduced and rebreeding performance enhanced in Bos taurus cows by eliminating nighttime suckling. We sought to confirm this hypothesis by examining the effects of day, nighttime, and ad libitum suckling on suckling behavior of calves, duration of the postpartum anovulatory interval, and pregnancy rates in 45 fall-calving Brahman x Hereford (F1) cows. Beginning on d 9 to 12 postpartum, calves were removed from lactating cows from 0700 to 1900 (Night-Suckled, n = 15) or from 1900 to 0700 (Day-Suckled, n = 15), or remained with their dams continuously (Ad Libitum-Suckled, n = 15). Cows in each group were maintained with fertile Angus bulls from d 10 postpartum until the first normal luteal phase or 100 d postpartum, whichever occurred first. Cows were observed for estrous behavior twice daily, and jugular blood samples were collected twice weekly for the determination of serum progesterone concentration. Mean number of suckling episodes per 24 h was greater (P < .0001) for the Ad Libitum-Suckled group than either Night- or Day-Suckled groups (5.9+/-.42 vs 3.8+/-.14, and 3.9+/-.32, respectively). Hourly analysis of suckling episodes in the Ad Libitum group indicated that they were not skewed toward a particular period, with suckling occurring at a periodicity of 4 to 6 h. Intervals to the first rise in progesterone > or = 1 ng/mL (32+/-2.5, 32+/-4.5, and 31+/-1.7 d, respectively), first normal luteal phase (38+/-3.1, 38+/-3.8, and 37+/-2.5 d, respectively), and first estrus (43+/-3.5, 40+/-3.9, and 36+/-1.1 d, respectively) did not differ (P > .05) among the three groups. Similarly, cumulative pregnancy rates within 100 d after calving did not differ (P > .05). These results in Bos indicus x Bos taurus (F1) cattle do not support the previous conclusions in Bos taurus that eliminating nighttime suckling reduces the postpartum anovulatory interval.
先前发表的报告指出，通过消除夜间哺乳，可以显著缩短黄牛产后无排卵间隔，并提高其再次繁殖的性能。我们试图通过研究白天、夜间和自由哺乳对犊牛哺乳行为、产后无排卵间隔持续时间以及45头秋季产犊的婆罗门牛×赫里福德牛（F1）母牛妊娠率的影响，来证实这一假设。产后第9至12天开始，将犊牛从泌乳母牛身边带走，带走时间为0700至1900（夜间哺乳组，n = 15）或1900至0700（白天哺乳组，n = 15），或者让犊牛一直与母牛待在一起（自由哺乳组，n = 15）。每组母牛从产后第10天开始与可育的安格斯公牛饲养在一起，直到出现第一个正常黄体期或产后100天，以先出现者为准。每天观察母牛两次发情行为，每周采集两次颈静脉血样以测定血清孕酮浓度。自由哺乳组每24小时的平均哺乳次数比夜间哺乳组和白天哺乳组都多（P <.0001）（分别为5.9±0.42次、3.8±0.14次和3.9±0.32次）。对自由哺乳组的哺乳次数进行每小时分析表明，哺乳次数没有偏向特定时间段，哺乳周期为4至6小时。三组中，孕酮首次升高至≥1 ng/mL的间隔时间（分别为32±2.5天、32±4.5天和31±1.7天）、第一个正常黄体期的间隔时间（分别为38±3.1天、38±3.8天和37±2.5天）以及第一次发情的间隔时间（分别为43±3.5天、40±3.9天和36±1.1天）没有差异（P>.05）。同样，产犊后100天内累计妊娠率也没有差异（P>.05）。这些婆罗门牛×黄牛（F1）牛的结果不支持先前在黄牛中得出的结论，即消除夜间哺乳可缩短产后无排卵间隔。
