Formoso-Rafferty Nora, Gutiérrez Juan Pablo, García-Álvarez Andrés, Pérez Teresa, Cervantes Isabel
Departamento de Producción Agraria, E.T.S. Ingeniería Agronómica Alimentaria y de Biosistemas, Universidad Politécnica de Madrid, Madrid, Spain.
Departamento de Producción Animal, Facultad de Veterinaria, Universidad Complutense de Madrid, Madrid, Spain.
J Anim Breed Genet. 2022 Jul;139(4):370-379. doi: 10.1111/jbg.12676. Epub 2022 Mar 19.
Uniformity, understood as a similar performance in relevant livestock traits, such as birth weight within the litter, is being included as one of the selection objectives in breeding programmes, especially for polytocous livestock species. A divergent selection experiment for birth weight within-litter variability in mice during 23 generations showed that homogeneous animals were better for litter size, survival and feed efficiency but less heavy than heterogeneous animals. The aim of this study was to compare the reproductive longevity in both divergent lines as time to the end of the reproductive period. Two generations from both lines with an initial number of 43 females and 43 males were mated one to one and stayed together to have consecutive parturitions until the end of the reproductive life. Females were discarded when the time elapsed from the last parturition was longer than 63 days. The time to the end of the reproductive period between both lines was compared by fitting a Cox proportional hazard regression model adjusting for line, generation and its interaction. The rate of parturitions in both lines was also compared using a Prentice-Williams-Peterson model adjusted for the same effects. The low variability line was associated with a higher parturition rate, e.g., adjusted hazard ratio was 2.93 (95% CI 2.17-3.94). The Cox model showed that the low variability females also presented benefits of time to the end of the reproductive period, with an adjusted hazard ratio of 0.26 (95% CI 0.16-0.41). The median of reproductive days was 55.50 in the high variability line whilst the median was 252.50 days for the low variability females. The homogeneous line presented important reproductive advantages suggesting higher robustness and animal welfare. Further research should confirm whether the findings presented here of a better performance in the low variability line could be properly applied to some livestock species.
一致性被理解为在相关家畜性状上表现相似，例如同一窝内的出生体重，它正被纳入育种计划的选择目标之一，尤其是对于多胎家畜品种。一项在23代小鼠中针对窝内出生体重变异性的 divergent 选择实验表明，同质动物在窝产仔数、存活率和饲料效率方面表现更好，但体重比异质动物轻。本研究的目的是比较两个 divergent 品系作为繁殖期结束时间的生殖寿命。从两个品系中选取初始数量为43只雌性和43只雄性的两代进行一对一交配，并共同生活以连续产仔，直到生殖寿命结束。当从上一次分娩开始经过的时间超过63天时，雌性被淘汰。通过拟合Cox比例风险回归模型并对品系、世代及其相互作用进行调整，比较了两个品系之间繁殖期结束的时间。还使用针对相同效应进行调整的Prentice-Williams-Peterson模型比较了两个品系的分娩率。低变异性品系与较高的分娩率相关，例如，调整后的风险比为2.93（95%CI 2.17 - 3.94）。Cox模型表明，低变异性雌性在繁殖期结束时间方面也有优势，调整后的风险比为0.26（95%CI 0.16 - 0.41）。高变异性品系的生殖天数中位数为55.50天，而低变异性雌性的中位数为252.50天。同质品系表现出重要的生殖优势，表明具有更高的稳健性和动物福利。进一步的研究应确认这里呈现的低变异性品系表现更好的结果是否能适用于某些家畜品种。
