Studies On Application Of Bodysize Appearance Phenotype Measurement In Boar Production

This experiment was based on Landrace-Yorkshire hybrid sows, applying methods with correlation analysis and path analysis to study the correlation between body size traits and body weight and age of weighting at 100 kg, backfat thickness before mating and breeding pregnancy, childbirth breeding rate, reproductive traits. This study was aimed at finding out suitable backfat thickness before mating and the main characters which affected the weight of Landrace-Yorkshire hybrid sows to provide theoretical basis for selecting gilts in farms.This study selected 233 Landrace-Yorkshire hybrid gilts weighting about 100 kg as experimental animals, measuring seven body size traits of body length, body height, body chest, chest width, chest depth, pipe circumference and hip width, and body weight. The experimental animals were divided into 4 group according to backfat thickness before mating, 11~13mm; 14~16mm; 17~20mm; 20~23mm. The results indicate :① Determination of body size traits were correlated with age of weighting at 100 kg. Thereinto hip width and body height, chest girth were the main characters that affected 100 kg weight age, the correlation coefficients were-0.557,-0.534,-0.522(P <0.01); the correlation coefficient between body length and chest depth and age of weighting at 100 kg were not significant(P> 0.05). Chest width and pipe girth affected age of weighting at 100 kg mainly through hip width and body height.② The main characters of body size traits affecting body weight was hip width, chest girth and body height, and the correlation coefficient were 0.614,0.568,0.539(P <0.01).Chest width, chest depth, body height and pipe girth were also significantly correlated with body weight(P <0.01), and which affected body weight through the hip width, chest girth and body weight.③ The breeding rate in group of backfat thickness 14~17mm before mating was the highest in four groups. The breeding rate was 89.19%, which was respectively higher than other groups :22.63%, 1.64%, 17.56%.Breeding pregnancy rate and childbirth breeding rate of backfat thickness 17 ~ 20 mm group were the highest, which respectively were 89.39%, 83.33%.The breeding pregnancy rate was higher than group of 11~13mm, 14~17mm, 20~23mm:33.33%, 2.51%, 9.26%.The breeding bith rate was higher 32.33%, 0.94%, 7.84% than backfat thickness of 11~13mm, 14~17mm, 20~23mm.④ The litter number born alive in group of backfat thickness 17~20mm group before mating was significantly higher than backfat thickness 11 ~ 13 mm group(P <0.05),as compared with the other two groups that was not significant(P> 0.05). Hower, total number born of backfat thickness 17 ~ 20 mm group was significantly higher than the other three groups(P <0.05); and litter weight at birth was also significantly higher than the backfat thickness 11 ~ 13 mm, 20 ~ 23 mm group(P <0.05).There was no significant difference between group of backfat thickness 14~17mm and other three groups in litter weight at birth.In conclusion, the main characters that affected body weight and 100 kg weiht age of Landrace-Yorkshire hybrid sows were hip width, body height, chest girth. The sows with backfat thickness 17-20 mm before breeding has the highest breeding pregnancy rate and the best reproductive performence.