Study On Formulation Of Growth Trait Correction Formula And Estimation Of Breeding Values For Etong Two-end-black

Etong Two-End-Black is a new variety being cultivated by our research group,the growth rate and feed efficiency are the target traits of breeding.In this study,we took Etong Two-End-Black as the research object,measured the growth rate and feed efficiency of boars,gilts and castrated boars by using the intelligent growth performance measurement system of pig,used the daily feed intake（FI）and daily body weight（BW）data to calculate the average daily gain（ADG）,average daily feed intake（ADFI）,feed-gain ratio（FG）and residual feed intake（RFI）,construct an analytical model to fit the growth curves of age and body weight,a correction formula was formulated to calculate the corresponding correction coefficient of weight at corrected age and corrected weight at age,and construct the model to calculate RFI.We analyzed factors affecting growth traits as fixed factors to calculate the breeding value,performed the correlation analysis of ADG,RFI,FG and ADFI selected ADG and RFI to estimate the genetic parameters,calculate the comprehensive breeding value of ADG and RFI,which provides a basis for breeding selection of Etong Two-End-Black.The main research results are as follows:（1）Growth trends and growth curves:The BW,ADFI and FG of Etong Two-End-Black all increased with the increase of age,and the relationship between age and BW was in accordance with the"S"type growth law.The absolute growth has two growth peaks,while the relative growth rate decreased rapidly first and then steadily.Comparing the fit degree of different models,the fitting result of Von Bertalanffy model was the closest to the measured value of Etong Two-End-Black.The fitted equation of boars in 90-150 days age was₌95.93(1-0.7637^-0.0086)³,the theoretical inflection point weight is 28.42kg,the theoretical inflection point age was 95.94d;the fitted equation of gilts in 90-180 days age was₌184.7(1-0.8381^-0.0074)³,the theoretical inflection point weight was 54.73kg,the theoretical inflection point age was124.44d;the fitted equation for castrated boars in 90-210 days age was₌189.5(1-0.7872^-0.0073)³,the theoretical inflection point weight was 56.15kg,the theoretical inflection point age was 117.72d.In the equation,t was the day age,W_twas the BW of t day age.We construct the correction equation for ETONG TWO-END-BLACK boars and gilts by the Von Bertalanffy model to obtain the correction coefficients for BW at the entry and exit ages.The correction equation for Etong Two-End-Black castrated boars was100kg BW for day age corrected=Actual age+100kg-Actual BW×_Ac^Actual _{tual BW}^age-55.002.（2）Feed efficiency:Feed efficiency included FG and RFI.FG was equal to the total FI divided by the total weight gain during the growth assay period.The FG of Etong Two-End-Black was increasing with the increase of age.RFI was constructed by multiple linear regression models of growth traits related to FI,and we selected the most suitable model for the calculation of RFI of Etong Two-End-Black by comparing the fit degree.The RFI model of boars was RFI=ADFI-（0.0132*On BW+0.0013*ADG）,the RFI model of gilts was RFI=ADFI--0.287*On BW+0.029*Mid BW+0.264*Off BW-0.023*ADG+0.002*BF,the RFI model of castrated boars was RFI=ADFI--1.9607*On BW+0.0026*Mid BW+1.965*Off BW-0.2347*ADG+0.066*BF.In the model,On BW was the entry weight,Mid BW was the mid-measurement weight,Off BW was the end weight,and BF was the backfat thickness.（3）Influencing factors of growth traits and estimation of genetic parameters:the sex,birth season and production batch had effects on the growth traits of On BW,ADG,ADFI and RFI in Etong Two-End-Black.We selected ADG and RFI to estimate the single-trait model breeding values of Etong Two-End-Black,and then constructed the two-trait model,obtained the heritability of ADG and RFI were 0.233 and 0.442,and the genetic correlation and phenotypic correlation between ADG and RFI were 0.806 and-0.103,respectively.The comprehensive breeding value（CBV）of ADG and RFI was:CBV=0.7×EBV_ADG-0.3×EBV_RFI.EBV in the model was the estimated breeding value for the trait.The Von Bertalanffy model selected in this study can provide the best fit for the growth curve of Etong Two-End-Black,and the calculated growth inflection points provide the basis for the determination of the junction time of Etong Two-End-Black.We discovered the performance pattern of ADG and RFI and the correlation between the two traits in the growth and development stages of Etong Two-End-Black through the calculation and correlation analysis of RFI and ADG for each individual growth measurement period.Therefore,the comprehensive breeding value model of two characters was constructed,which could be used to select the two characters of growth rate and feed efficiency of Etong Two-End-Black.