ten Napel J, de Vries A G, Buiting G A, Luiting P, Merks J W, Brascamp E W
DLO-Research Institute for Animal Science and Health (ID-DLO), Research Branch Zeist, The Netherlands.
J Anim Sci. 1995 Aug;73(8):2193-203. doi: 10.2527/1995.7382193x.
A selection experiment with a selection and a control line maintained for eight generations was set up to study efficacy of selection for a short interval from weaning to estrus after weaning the first litter and to estimate genetic variation in the Dutch Landrace population. Intervals were recorded without truncation (i.e., intervals up to 234 d were observed). A mating scheme with 10 mating groups was used to avoid inbreeding. Distribution of intervals from weaning to estrus was described by a mixture of a normal and an exponential distribution. Between lines, both underlying distributions were similar, but the contribution to the total distribution was different. From generation 4 onward, intervals were significantly shorter in the selection line than in the control line. Variances within lines, generations, and mating groups varied to a large extent. Response per unit selection differential was calculated for original data and three sets of transformed data, both with and without correction for unequal subclass numbers. Standardized responses were more precise and linear, when data were log-transformed, and when corrected for unequal subclass numbers. The assumed best estimate of the realized heritability was .17. The heritability in the foundation population was estimated at .36 +/- .05, using an animal model including all genetic relationships in the data. It was concluded that genetic selection decreases the average interval from weaning to estrus by reducing the number of sows with a record in the exponential part of the distribution.
开展了一项选择实验，设立了一个选择品系和一个对照品系，并维持八代，以研究在第一窝仔猪断奶后从断奶到发情的短时间间隔内的选择效果，并估计荷兰长白猪群体的遗传变异。记录间隔时不进行截断（即观察到最长达234天的间隔）。采用了一种有10个交配组的交配方案以避免近亲繁殖。断奶至发情间隔的分布用正态分布和指数分布的混合来描述。品系间，两种基础分布相似，但对总分布的贡献不同。从第4代起，选择品系的间隔明显短于对照品系。品系内、代次间和交配组内的方差在很大程度上有所不同。针对原始数据和三组变换后的数据计算了单位选择差的响应，有无不等子类数校正均进行了计算。当数据进行对数变换以及进行不等子类数校正时，标准化响应更精确且呈线性。所假定的实现遗传力的最佳估计值为0.17。使用包含数据中所有遗传关系的动物模型，基础群体中的遗传力估计为0.36±0.05。得出的结论是，遗传选择通过减少分布指数部分有记录的母猪数量，降低了从断奶到发情的平均间隔。
