Unitat de Cunicultura, Institut de Recerca i Tecnologia Agroalimentàries, Barcelona, Spain.
J Anim Sci. 2011 Dec;89(12):3983-95. doi: 10.2527/jas.2011-3924. Epub 2011 Jul 15.
Animals under environmental thermal stress conditions have reduced fertility due to impairment of some mechanisms involved in their reproductive performance that are different in males and females. As a consequence, the most sensitive periods of time and the magnitude of effect of temperature on fertility can differ between sexes. The objective of this study was to estimate separately the effect of temperature in different periods around the insemination time on male and on female fertility by using the product threshold model. This model assumes that an observed reproduction outcome is the result of the product of 2 unobserved variables corresponding to the unobserved fertilities of the 2 individuals involved in the mating. A total of 7,625 AI records from rabbits belonging to a line selected for growth rate and indoor daily temperature records were used. The average maximum daily temperature and the proportion of days in which the maximum temperature was greater than 25°C were used as temperature descriptors. These descriptors were calculated for several periods around the day of AI. In the case of males, 4 periods of time covered different stages of the spermatogenesis, the transit through the epididymus of the sperm, and the day of AI. For females, 5 periods of time covered the phases of preovulatory follicular maturation including day of AI and ovulation, fertilization and peri-implantational stage of the embryos, embryonic and early fetal periods of gestation, and finally, late gestation until birth. The effect of the different temperature descriptors was estimated in the corresponding male and female liabilities in a set of threshold product models. The temperature of the day of AI seems to be the most relevant temperature descriptor affecting male fertility because greater temperature records on the day of AI caused a decrease in male fertility (-6% in male fertility rate with respect to thermoneutrality). Departures from the thermal zone in temperature descriptors covering several periods before AI until early gestation had a negative effect on female fertility, with the pre- and peri-implantational period of the embryos being especially sensitive (from -5 to -6% in female fertility rate with respect to thermoneutrality). The latest period of gestation was unaffected by the temperature. Overall, magnitude and persistency of the temperatures reached in the conditions of this study do not seem to be great enough to have a large effect on male and female rabbit fertility.
在环境热应激条件下，动物的繁殖能力会降低，这是因为它们的一些生殖性能机制受到了损害，而这些机制在雄性和雌性动物中是不同的。因此，温度对雄性和雌性动物繁殖力的影响在最敏感的时期和程度上可能存在差异。本研究的目的是使用乘积门限模型分别估计授精时间前后不同时期温度对雄性和雌性繁殖力的影响。该模型假设观察到的繁殖结果是两个参与交配的个体的未观察到的繁殖力的乘积。总共使用了 7625 个属于生长速度选择系的兔子的人工授精记录和室内日温度记录。平均最大日温度和最大温度超过 25°C 的天数比例被用作温度描述符。这些描述符是根据授精日前后的几个时期计算的。对于雄性，4 个时期涵盖了精子发生的不同阶段、精子通过附睾的运输以及授精日。对于雌性，5 个时期涵盖了包括授精日和排卵、受精和胚胎着床前阶段、胚胎和早期胎儿期以及最后妊娠晚期直到分娩的促排卵卵泡成熟阶段。在一组乘积门限模型中，对不同的温度描述符在相应的雄性和雌性负债中的影响进行了估计。授精日当天的温度似乎是影响雄性繁殖力的最相关的温度描述符，因为授精日当天较高的温度记录会导致雄性繁殖力下降（相对于热中性，雄性繁殖力下降 6%）。从授精前几个时期到早期妊娠的温度描述符偏离热区对雌性繁殖力有负面影响，胚胎的着床前和着床期尤其敏感（相对于热中性，雌性繁殖力下降 5%至 6%）。妊娠晚期不受温度影响。总体而言，在本研究条件下达到的温度的幅度和持续时间似乎不足以对雄性和雌性兔子的繁殖力产生很大影响。
