Studies on a base population of mice were used to establish an index of components of litter size and a physiological model for measuring uterine capacity to be used subsequently in a selection experiment evaluating alternative methods for practicing selection to increase litter size. Heritability estimates of litter size, ovulation rate and ova success (fraction of ova resulting in fully formed pups) were .18, .33 and .15, respectively. No significant genetic or phenotypic correlation was found between overall ovulation rate and ova success. Phenotypic means and genetic variances were higher for characteristics measured on the right than on the left side of the reproductive tract. Linear and quadratic selection indexes, derived for a quadratic definition of breeding value, were compared. The linear index was predicted to be .99 as efficient as the quadratic one. Due to simplicity, the linear index (I = 1.21 x ovulation rate + 9.05 x ova success), scaled to have variance the same as litter size, was chosen for use. Ovulation rate in unilaterally ovariectomized females was .95 of that in females with both ovaries. No hypertrophy of the ipsilateral uterine horn in unilaterally ovariectomized females was found before implantation of embryos. Thus, unilateral ovariectomy appears to provide a physiological state to measure uterine capacity (as litter size) in the mouse.
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机译:对小鼠基本种群的研究用于建立窝产仔数的组成指标和用于测量子宫容量的生理模型,随后将用于选择实验,评估选择实践以增加窝产仔数的替代方法。产仔数,排卵率和卵子成功率(卵子的分数导致完全形成的幼仔)的遗传力估计分别为.18,.33和.15。在总排卵率和卵子成功率之间没有发现显着的遗传或表型相关性。在生殖道的右侧测量的特征的表型均值和遗传方差高于左侧。比较了为育种值的二次定义而得出的线性和二次选择指数。线性指数被预测为是二次指数的0.99。由于简单,选择使用线性指数(I = 1.21 x排卵率+ 9.05 x ova成功),缩放比例使其方差与垫料大小相同。单侧切除卵巢的女性的排卵率是两个卵巢的女性的排卵率的0.95。在植入胚胎之前,在单侧卵巢切除的雌性中未发现同侧子宫角肥大。因此,单侧卵巢切除术似乎提供了一种生理状态以测量小鼠的子宫容量(以产仔数计算)。
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