Zhang Hao, Li Jia-Qi, Wang Chong, Liu Xiao-Hong, Chen Yao-Sheng
College of Animal Science, South China Agricultural University, Guangzhou 510642, China.
Yi Chuan Xue Bao. 2005 Jul;32(7):696-703.
The effects of the population size,boar to sow ratio,and the number of pigs tested per litter on the selection response and its coefficient of variation, inbreeding coefficient of sire line selection were studied. Pig populations of 100 to 500 sows were simulated with Monte Carlo method,and the ratios of boar to sow were 1:10 and 1:20. The number of pigs tested per litter were 2 and 4 composed equally of boars and gilts. The traits selected were average daily gain after weaning (ADG) and backfat thickness (BF) at 100 kg live weight. Breeding pigs were selected according to multiple-trait BLUP,and economic weight of BF was set as 2.5 times of that of ADG. After five generation selection, the results showed that the more the number of sows of the breeding population, the higher the cumulative selection response at 5th generation, and the slower the coefficient of inbreeding increment per generation, the smaller the coefficient of variation of the cumulative selection response at 5th generation. Increasing the number of pigs tested per litter and/or the boar to sow ratio increased the cumulative selection response at 5th generation, inbreeding coefficient increment per generation, and the coefficient of variation of the cumulative selection response at 5th generation. The cumulative selection response got higher and the increment of inbreeding coefficient slowed down significantly when the number of sows in the breeding population increased from 100 to 300,and the ratio of boar to sow and the number of pigs tested per litter were fixed. When the sow number of breeding population was increased from 300 to 400 above,the cumulative selection response only increased slightly,and the coefficient of inbreeding continued to decrease but at a diminished rate. In conclusion, for the short-term selection of sire line, it is recommended that the breeding population should be composed of 400 or above sows, 4 pigs tested per litter,and the ratio of boar to sow should be maintained at 1:20.
研究了群体规模、公母猪比例和每窝测定仔猪数对选择反应及其变异系数、父系选择近交系数的影响。采用蒙特卡罗方法模拟了100至500头母猪的猪群，公母猪比例为1:10和1:20。每窝测定的仔猪数为2头和4头，公猪和后备母猪数量相等。选择的性状为断奶后平均日增重（ADG）和100千克活重时的背膘厚（BF）。根据多性状BLUP法选择种猪，将BF的经济权重设为ADG的2.5倍。经过五代选择，结果表明，繁殖群体中母猪数量越多，第五代的累积选择反应越高，每代近交系数增加越慢，第五代累积选择反应的变异系数越小。增加每窝测定仔猪数和/或公母猪比例可提高第五代的累积选择反应、每代近交系数增量以及第五代累积选择反应的变异系数。当繁殖群体中的母猪数量从100头增加到300头，且公母猪比例和每窝测定仔猪数固定时，累积选择反应升高，近交系数增量显著减缓。当繁殖群体的母猪数量从300头增加到400头以上时，累积选择反应仅略有增加，近交系数继续下降但下降速度减缓。总之，对于父系的短期选择，建议繁殖群体应由400头或以上母猪组成，每窝测定4头仔猪，公母猪比例保持在1:20。
