| Part ?: In the pig production industry,the quality of reproductive traits has a great impact on production efficiency.Genetic improvement to reproductive traits in pigs might effectively improve production efficiency,save environmental resources and increase economic benefits.Therefore,this study aimed to identify the genetic markers and major genes for reproductive traits in domestic pigs.Based on 108 Duroc pigs,597 Landrace pigs,2031 Yorkshire pigs,and 613 Landrace × Yorkshire crossbred pigs from two different breeding companies.12 reproductive traits of 3349 sows,including total number of born,number of born alive,number of born healthy,number of born weak,number of born deformity,number of stillbirths,number of mummified fetuses at birth,gestation length,litter weight at birth,average individual birth weight,farrowing duration,and average birth interval,were studied.In this project,the self-designed CC1 Porcinesnp50 chip was used for genetic analysis of reproductive traits in the study population.Firstly,the genetic parameters of 12 reproductive traits were estimated by GCTA software using animal model and genetic restricted maximum likelihood method(GREML)method.The results showed that the heritability of the 12 reproductive traits(merged population)were 0.07,0.08,0.09,0.09,0.06,0.05,0.03,0.20,0.09,0.26,0.06 and 0.10,respectively;Among them,the total number of born,number of born alive,number of born healthy and the litter weight at birth showed a high positive correlation with correlation coefficients between 0.53?0.96,However,the total number of born,number of born alive,number of born healthy and the average litter interval showed a high negative correlation with correlation coefficients between-0.61?-0.67.Secondly,the genetic analysis of these reproductive traits was carried out.Single-population genome-wide association analysis and joint-population genome-wide association analysis were conducted for 12 reproductive traits in this study using the univariate mixed linear model statistical method of GCTA software.The results showed that 39 SNPs exceeding the chromosome significance level were related to these reproductive traits.The statistical method of a multivariate mixed linear model of GEMMA software was used to conduct a joint population genome-wide association study on 11 reproductive traits of 853 individuals in the study population.The results showed that 61 SNPs were identified that were significantly associated with reproductive traits,and22 of them reached genome-wide significance level.The bioinformatics analysis of the functional genes close to the significantly associated SNPs has screened out some important candidate genes,including ZDHHC14,ZNF608,MSR1,MYCN,TENM3,USP25 and CORIN.The above research results are helpful to understand the genetic mechanism of pig reproductive traits and provide an effective reference for the genetic improvement of reproductive traits in actual production.Part ?: Nowadays,electronic automatic feeding systems are widely used in the automatic feeding of pig breeding and the genetic improvement of related growth traits,and the production efficiency has been significantly improved.In this study,874 individuals including 427 Duroc pigs,163 Landrace pigs,and 284 Yorkshire pigs were used.Osborne's electronic automatic feeding system were used to measure and collect feeding-related data.From the recorded data of the electronic automatic feeding system,we have obtained the number of visits per day,occupation time per visit,feed intake per visit,final body weight,amount of visits per day with the following visit interval being less than 30 s long,daily occupation time,daily feed intake,average daily gain,and days of daily feed intake less than 0.5 kg.The feeding behaviors and social behaviors of domestic pigs were studied and discussed.The average number of visits per day,occupation time per visit,and feed intake per visit values were used to determine the social rank of pigs in each pen.Pigs with longer occupation time per visit,higher feed intake per visit and fewer number of visits per day were defined as the highest social rank(HSR)pigs in the pen.Shorter occupation time per visit,less feed intake per visit and more the number of visits per day were defined as signs of the lowest social rank(LSR)pigs.The lowest social rank pigs had a longer daily occupation time(4167 vs 3131 sec)and more amount of visits per day with the following visit interval being less than 30 s long(6.2 vs 2.6)than the highest social rank pigs.However,no differences were observed for daily feed intake,average daily gain,final body weight and days of daily feed intake less than 0.5 kg between the highest social rank and lowest social rank pigs.This social rank study across pig breeds clarified that there is breed priority on social rank.The highest social rank pigs were mainly Duroc and the lowest social rank pigs were mainly Yorkshire.This suggested that Duroc was at the top of the pig social rankings.The season significantly impacted daily feed intake and average daily gain(P-value < 0.0001).Pigs in autumn had higher daily feed intake and average daily gain compared to the other three seasons,and the patterns were consistent in all three breeds.This may be a biological feeding rhythm of pigs due to autumn being a season with abundant food followed by winter with less food and harsh climatic conditions.Through the analysis of the feeding behaviors of different batches and different breeds of pigs,this study has new insights into the feeding behaviors of pigs and brings certain guiding significance for actual production. |
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