Ecole Nationale de Médecine Vétérinaire, 2020, Ariana, Sidi Thabet 2020, Université de la Manouba, Tunisia.
Laboratory of Management and Control of Animal and Environmental Resources in Semi-Arid Area, LR18AG01, Institut Supérieur Agronomique de Chott-Mariem, Université de Sousse, Tunisia.
Animal. 2024 Nov;18(11):101332. doi: 10.1016/j.animal.2024.101332. Epub 2024 Sep 19.
Management of reproduction that relies on naturally based solutions is extremely important to counter the negative perception around hormone-based interventions. In Mediterranean latitudes and wider regions of non-tropical drylands, sheep do not normally ovulate during spring but exposure to a ram can induce oestrus and ovulation. This study assesses the response of maiden Barbarine ewes in drylands to the 'ram effect' during springtime and estimates the genetic parameters of this response. The study uses a database documenting, for 24 consecutive years, the response of nulliparous 18-month-old ewes when mated after stimulation by the 'ram effect.' In addition to the oestrous and fertility database, a pedigree database was also available. Nearly half of the maiden ewes responded to the 'ram effect,' while 24% exhibited spontaneous reproductive activity and displayed oestrus during the first 14 days following the introduction of rams. Nearly 5% of females did not exhibit oestrus, and these animals are proposed for early culling. Average annual values of Normalised Difference Vegetation Index (NDVI), reflecting vegetation cover, and the percent of maiden ewes spontaneously cycling were positively correlated (P = 0.006). Interestingly, NDVI was negatively correlated with the percentage of anoestrus females that did not respond to the 'ram effect' but exhibited oestrus beyond the hypothetical time frame commonly used to describe it. Average fertility was 82.8% and was significantly affected by mating year, live weight at mating, and the response to the 'ram effect.' The highest fertility (88.39%) was for females spontaneously cycling at the time of ram introduction, and the lowest (83.35%) was for females coming into oestrus beyond the time frame for a ram-induced oestrus and ovulation. Heritability from a univariate logit-transformed analysis for fertility was 0.10 and the genetic correlation between fertility and the interval between ram introduction and oestrus was 0.26, suggesting that a shorter interval is associated with higher fertility. Thus, the interval between ram introduction and oestrus is a good candidate for selective breeding for high fertility of maiden ewes in drylands mated out-of-season using the 'ram effect.'
依赖于自然解决方案的生殖管理对于对抗基于激素的干预措施的负面看法非常重要。在地中海纬度和更广泛的非热带干旱地区，绵羊通常不在春季排卵，但暴露于公羊可以诱导发情和排卵。本研究评估了干旱地区处女巴巴里母羊在春季对“公羊效应”的反应，并估计了这种反应的遗传参数。该研究使用一个数据库，该数据库记录了 24 年来，18 月龄的初产母羊在接受“公羊效应”刺激后交配时的发情和生育情况。除了发情和生育数据库外，还有一个系谱数据库。近一半的处女羊对“公羊效应”有反应，而 24%的羊表现出自发性生殖活动，并在公羊引入后的前 14 天内发情。近 5%的母羊没有发情，这些动物建议早期淘汰。归一化差异植被指数（NDVI）的年平均值反映了植被覆盖，与自发循环的处女羊的百分比呈正相关（P=0.006）。有趣的是，NDVI与未对“公羊效应”做出反应但在通常用于描述的时间框架之外发情的无发情母羊的比例呈负相关。平均生育率为 82.8%，并受到配种年份、配种时体重和对“公羊效应”的反应的显著影响。引入公羊时自发发情的母羊的生育率最高（88.39%），而在通常用于描述公羊诱导发情和排卵的时间框架之外发情的母羊的生育率最低（83.35%）。从单变量逻辑转换分析得出的生育力的遗传力为 0.10，生育力与公羊引入和发情之间的间隔的遗传相关性为 0.26，这表明间隔越短，生育力越高。因此，公羊引入和发情之间的间隔是一个很好的候选基因，可用于选择干旱地区的处女羊，使其在淡季使用“公羊效应”交配时具有高生育力。
