Tauck S A, Berardinelli J G
Department of Animal and Range Sciences, Montana State University, Bozeman, Montana 59717, USA.
J Anim Sci. 2007 Jul;85(7):1669-74. doi: 10.2527/jas.2006-849. Epub 2007 Mar 5.
The objective of this study was to determine if factors associated with the biostimulatory effect of bulls alter breeding performance of primiparous, suckled beef cows using a progestin-based estrous synchronization protocol. We tested the hypotheses that the estrous synchronization response and AI pregnancy rates differ among cows exposed to bulls, continuously exposed to bull urine, and exposed to fence-line contact with bulls or cows not exposed to bulls or bull urine. Data were collected from 3 experiments performed over consecutive years. Cows were assigned to the following treatments: bull exposure (BE; n = 26) or no bull exposure (NB; n = 25) in Exp. 1, bull urine exposure (BUE; n = 19) or steer urine exposure (SUE; n = 19) in Exp. 2, and fence-line contact with bulls (BFL; n = 26) or no bull exposure (NB; n = 26) in Exp. 3. Synchronization protocols in each experiment included the use of a controlled internal drug release device (d -10), PGF(2alpha) (d -3), and GnRH and fixed-time AI (TAI; d 0). Cows that were observed in estrus by 60 h after PGF(2alpha) were inseminated 12 h later. Cows not observed in estrus by 60 h after PGF(2alpha) were TAI at 72 h and given GnRH (100 mug). Pregnancy was determined by ultrasonography 35 d after TAI. In Exp. 1, 2, and 3, cows were exposed directly to bulls, bull urine, or bull fence-line contact for 35, 64, and 42 d, respectively. Data were analyzed between treatments within each experiment. The proportion of estrous cycling cows did not differ between treatments at the beginning of each experiment; however, more (P < 0.05) BE and BFL cows were estrous cycling at the beginning of the estrous synchronization protocol than NB cows in Exp. 1 and 3. The proportion of cows that showed estrus and interval to estrus after PGF(2alpha) did not differ between treatments in Exp. 1 and 3. However, in Exp. 2, more BUE cows tended (P = 0.09) to have shorter intervals to estrus and to exhibit estrus after PGF(2alpha) than SUE cows. Overall, AI pregnancy rates were greater (P < 0.05) for BE and BUE cows than for NB and SUE cows in Exp. 1 and 2, respectively. There was no difference in AI pregnancy rates between BFL and NB cows in Exp. 3. The presence of bulls and exposure to bull urine appeared to improve breeding performance of primiparous beef cows using a progestin-based estrous synchronization protocol, whereas fence-line bull exposure was insufficient to cause this biostimulatory effect. We propose that a novel urinary pheromone of bulls may be responsible for the enhancement of fertility in the primiparous, postpartum cow.
本研究的目的是确定与公牛生物刺激效应相关的因素是否会改变使用基于孕激素的发情同步方案的初产哺乳肉牛的繁殖性能。我们检验了以下假设：暴露于公牛、持续暴露于公牛尿液、与公牛围栏接触的母牛与未暴露于公牛或公牛尿液的母牛相比，发情同步反应和人工授精妊娠率存在差异。数据收集自连续三年进行的3项实验。母牛被分配到以下处理组：实验1中为公牛暴露组（BE；n = 26）或无公牛暴露组（NB；n = 25），实验2中为公牛尿液暴露组（BUE；n = 19）或阉牛尿液暴露组（SUE；n = 19），实验3中为与公牛围栏接触组（BFL；n = 26）或无公牛暴露组（NB；n = 26）。每个实验中的同步方案包括使用可控内部药物释放装置（第 -10天）、PGF(2α)（第 -3天）、GnRH和定时人工授精（TAI；第0天）。在PGF(2α)后60小时内观察到发情的母牛在12小时后进行授精。在PGF(2α)后60小时内未观察到发情的母牛在72小时进行TAI并给予GnRH（100微克）。在TAI后35天通过超声检查确定妊娠情况。在实验1、2和3中，母牛分别直接暴露于公牛、公牛尿液或与公牛围栏接触35天、64天和42天。对每个实验中的处理组之间的数据进行分析。在每个实验开始时，处理组之间发情周期母牛的比例没有差异；然而，在实验1和3中，在发情同步方案开始时，发情周期的BE和BFL母牛比NB母牛更多（P < 0.05）。在实验1和3中，处理组之间在PGF(2α)后表现出发情的母牛比例和发情间隔没有差异。然而，在实验2中，与SUE母牛相比，更多的BUE母牛倾向于（P = 0.09）在PGF(2α)后发情间隔更短且表现出发情。总体而言，在实验1和2中，BE和BUE母牛的AI妊娠率分别高于NB和SUE母牛（P < 0.05）。在实验3中，BFL和NB母牛之间的AI妊娠率没有差异。公牛的存在和暴露于公牛尿液似乎可以提高使用基于孕激素的发情同步方案的初产肉牛的繁殖性能，而围栏接触公牛不足以产生这种生物刺激效应。我们提出，公牛一种新的尿液信息素可能是初产产后母牛生育力增强的原因。
