The Selection Effect, Correlation And Path Analysis Of Main Economical Traits In Dian-Lu Pig Line

The data including reproductive traits of 377 first parity sows, growth traits of 119 pigs, fattening and carcass traits of 79 pigs were used to analyze the selection effects of main economical traits in Dian-Lu line. Based on the correlation and path analysis of 3 classes, 26 traits, the optimized regression equations for estimating litter weight of piglets at 42 days (weaning), body weight at 8 months and carcass meat percentage were established. The selection methods used in the breeding of Dian-Lu line were also discussed in this paper. The results showed:1. After 6-generation systematic selection, the main economical traits of Dian-Lu line were all improved in different degrees, which showed that the selection methods used in the breeding of the line were feasible in all. Among the 3-class traits, the improvement of reproductive traits and growth speed were relative higher, but the carcass traits were lower. The average litter size of first parity, body weight at 6 months daily gain during fattening period and carcass meant percentage were 9.96 pigs, 67.66kg, 656.31g and 51.05 percentage, respectively. The main traits were all reach to a relative high level, which showed that the line was good at high prolificacy and maternal performance. It is expected that the satisfied effects will be gain if it is used as maternal parent in cross utilization.2. The results of correlation analysis showed that the correlations between 7 traits of reproductive performance and 12 traits of growth performance were all positive, and some correlation coefficients were reach to a higher level. This means it is possible that improving multiple reproductive or growth traits by reasonable breeding and feeding approaches in practical production. However, the correlation between 7 fattening and carcass traits were negative except that of daily gain and backfat thickness, skin thickness and meat percentage, backfat thickness and fat percentage and dressing percentage. This means that it is difficult to improve all the carcass traits in one breeding scheme.3. The optimized regression equation for estimating piglets litter weight at 42 days (weaning), body weight at 8 months and carcass meat percentage were established by stepwise method, based on the path analysis. It provides some basis and support for simplifying test items and exploring indirect selection to increase breeding benefits.4. Considering the line have already been selected by closed breeding for more years, it will improve the selection effects by opening the population, generation overlapping for excellent individuals and introduce advanced selection methods.