Zúñiga O, Forcada F, Abecia J A
Departamento de Producción Animal y Ciencia de los Alimentos, Universidad de Zaragoza, Miguel Servet 177, 50013 Zaragoza, Spain.
Anim Reprod Sci. 2002 Aug 15;72(3-4):165-74. doi: 10.1016/s0378-4320(02)00117-3.
Rasa Aragonesa ewes were used to evalutate whether treatment with melatonin implants in spring could modify: (i) the response to the male effect in terms of oestrous behaviour and ovulation rate; and (ii) the maintenance of sexual activity and ovulation rate at medium term, i.e. over the next 306 days. On 12 April, 42 ewes were divided into two groups, with (M; n = 21) or without (C; n = 21) a subcutaneous implant containing 18 mg melatonin. On 17 May (day 0), three aproned rams were introduced to each group to induce a ram effect. Ewes were observed for oestrus daily. The rams were removed 40 days later after which one aproned ram was introduced daily. Oestrous detection continued until 28 February, 306 days after the first male-female contact. The ovulation rate was determined by endoscopy in the first three cycles after ram introduction and in September-October and January. Progesterone was assayed from blood samples taken on 6 May, 10 and from day 0 to day 22 after ram introduction. Luteal activity before ram introduction was seen in 33% (M) and 29 (C)% of the ewes, respectively. Significantly more M ewes showed oestrous behaviour during the first 40 days after ram introduction (M: 100%; C: 62%; P < 0.01). Similar differences were observed for ewes anovulatory at ram introduction (M: 100%, C: 47%; P < 0.01). These differences were maintained over the three oestrous cycles in both groups. Treatment with melatonin implants was without detrimental effect on cyclic functions in the following breeding season, after seasonal anoestrus. Melatonin treatment significantly increased (P < 0.05) the mean ovulation rate of the first (1.62 +/- 0.11 versus 1.31 +/- 0.13), second (1.78 +/- 0.15 versus 1.36 +/- 0.15) and third cycles (M: 1.73 +/- 0.12 versus C: 1.27 +/- 0.14). There was a significant interaction between the effects of cyclicity at day 0 and melatonin treatment on the ovulation rate in the first cycle (P < 0.05). The mean ovulation rates of both groups were similar at the beginning (September) and middle (January) of the subsequent breeding season. Overall, the results confirmed that melatonin implants, combined with the ram effect, improved the reproductive parameters of reduced-seasonality ewes during spring mating, without impairing sexual activity or ovulation rate during the subsequent breeding season.
（i）在发情行为和排卵率方面对公羊效应的反应；以及（ii）中期（即接下来的306天）性活动和排卵率的维持情况。4月12日，42只母羊被分为两组，一组（M组；n = 21）皮下植入含18毫克褪黑素的植入物，另一组（C组；n = 21）不植入。5月17日（第0天），每组引入三只带围裙的公羊以诱导公羊效应。每天观察母羊的发情情况。40天后将公羊移走，之后每天引入一只带围裙的公羊。发情检测持续到2月28日，即首次公母接触后的306天。在引入公羊后的前三个周期以及9 - 10月和1月，通过内窥镜检查确定排卵率。在5月6日、10日以及引入公羊后第0天至第22天采集血样检测孕酮。引入公羊前，分别有33%（M组）和29%（C组）的母羊出现黄体活动。引入公羊后的前40天，显著更多的M组母羊表现出发情行为（M组：100%；C组：62%；P < 0.01）。对于引入公羊时不排卵的母羊也观察到类似差异（M组：100%，C组：47%；P < 0.01）。两组在三个发情周期中均保持这些差异。季节性乏情后，在接下来的繁殖季节，褪黑素植入物处理对周期功能没有不利影响。褪黑素处理显著提高了（P < 0.05）第一个周期（1.62 ± 0.11对1.31 ± 0.13）、第二个周期（1.78 ± 0.15对1.36 ± 0.15）和第三个周期的平均排卵率（M组：1.73 ± 0.12对C组：1.27 ± 0.14）。在第0天的周期性效应和褪黑素处理对第一个周期排卵率的影响之间存在显著交互作用（P < 0.05）。在随后繁殖季节开始时（9月）和中期（1月），两组的平均排卵率相似。总体而言，结果证实，褪黑素植入物与公羊效应相结合，改善了季节性降低的母羊在春季配种期间的繁殖参数，且不损害随后繁殖季节的性活动或排卵率。
