Pathway Analysis Of Body Weight,Body Size And Reproductive Traits Of Yorkshire And Establishment Of Optimal Regression Model

In order to study the correlation between body size and reproductive traits in large body Yorkshire,the direct and indirect effects of body size on body weight and reproductive traits on weaning litter weight at 21 days of age were studied,furthermore,the optimal regression models of body weight and body size,reproductive traits and litter weight at 21 days of age were established.In this experiment,240 large body Yorkshire were selected from the reserve system,body weight,body length,body height,abdominal circumference,hip circumference,hip width,hip length,shank circumference,back fat and chest circumference were measured at 180 and210 days of age,total number born,number born alive,born weight,average birth weight,number of weaned piglets at 21 days,average weaning weight at 21 days and litter weaning weight at 21 days were collected,Pearson Correlation Analysis,Path Analysis and Stepwise Regression Analysis were performed on the above data.The results are as follows:1.Analysis of the difference of body weight and body size in different age,sex:The body weight of boars of the same age and different sex was higher than that of sows,and the difference was very significant（P<0.01）,All body measurements showed that boars were larger than sows.180-day-old Yorkshire hip circumference,hip width,hip length,shank circumference and body length,abdomen circumference,hip width,shank circumference,back fat and chest circumference of 210-day-old Yorkshire were significantly different between boars and sows（P<0.01）.The body weight of 210-day-old Yorkshire was significantly higher than that of 180-day-old Yorkshire（P<0.01）,The body measurements of 210-day-old Yorkshire showed that the size of boars was larger than that of sows,and the difference was very significant（P<0.01）.2.Pearson Correlation Analysis:There was a significant positive correlation between body weight and body size（P<0.01）,there was a positive correlation between body size traits.There was a significant positive correlation between reproductive traits and litter weaning weight at21 days（P<0.01）,except average birth weight.Total number born and average birth weight,total number born and average weaning weight at 21 days,number born alive and average birth weight,number born alive and average weaning weight at 21 days,average birth weight and number of weaned piglets at 21 days,number of weaned piglets at 21 days and average weaning weight at 21 days,there was a negative correlation,the other traits showed positive correlation.3.Path Analysis:The direct effect of abdominal circumference on body weight was greatest in 180-day-old boars,and the indirect effect of hip circumference on body weight was greatest;The direct effect of body length on body weight of 180-day-old sows was the greatest,while the indirect effect of hip width on body weight was the greatest;The direct effect of hip width on body weight was greatest in 210-day-old boars,and the indirect effect of hip circumference on body weight was greatest;The direct effect of body length on body weight was greatest in 210-day-old sows,and the indirect effect of back fat on body weight was greatest;The direct effect of number of weaned piglets at 21 days on litter weaning weight at 21 days was the greatest,and the indirect effect of number born alive on litter weaning weight at 21days was the greatest.The relative determination coefficients of the above 5 groups of path analysis errors were as follows:180-day-old boars d0.e=0.072;180-day-old sows d0.e=0.029;210-day-old boars d0.e=0.014;210-day-old sows d0.e=0.068;reproductive traits d0.e=0.013.4.A Stepwise Regression Analysis was used to establish the optimal regression model:The optimal regression equation of body weight and body size index of 180-d ay-old Yorkshire boars was Y=0.284X₁+1.057X₃+0.6X₈-71.035,in which Y was body weight,X₁ was body length,X₃ was abdominal circumference,X₈ was back fat,R² w as 0.915（P<0.01）;The optimal regression equation of body weight and body size of180-day-old Yorkshire sows was:Y=0.77X₂+0.625X₁+0.25X₆+0.211X₇+0.111X₃-59.178,in which Y was body weight,X₁ was body length,X₂ was body height,X₆ was hip length,X₇ was shank circumference and X₃ was abdominal circumference,R² was 0.957（P<0.01）;The optimal regression equation of body weight and body size index of 210-day-old Yorkshire boars was Y=0.813X₅+0.517X₂+0.462X₃+0.235X₁+0.192X₈-44.049,in which Y was body weight,X₁ was body length,X₂ was body height,X₃ was abdominal circumference,X₅ was hip width and X₈ was back fat,R² was 0.986（P<0.01）;The optimal regression equation of body weight and body size index of 210-da y-old Yorkshire sows was:Y=0.572X₁+0.366X₃+0.582X₄+0.200X₉+0.471X₈+0.147X₂-72.76,in which Y was body weight,X₁ was body length,X₂ was body height,X₃ was abdominal circumference,X₄ was hip width,X₈ was back fat,X₉ was chest circumfer ence,R² was 0.965（P<0.01）;The optimal regression equation of reproductive traits was:Y=8.267X₅+10.453X₆-87.087,in which Y was litter weaning weight at 21 days,X₅ number of weaned piglets at 21 days,X₆ was average weaning weight at 21 days,R² was 0.982（P<0.01）.