Estimation of Genetic Parameters and Analysis of Season Effects and Age Effects for Semen Traits in Landrace Boars

The purpose of this study was to estimate the genetic parameters of semen traits of Landrace boars in South China and to analyze the influence of the age and season of semen collection on semen traits, so as to provide theoretical basis for formulating reasonable boar breeding program. The Asreml-R was used to analyze the 107 221 semen data of 1 605 Landrace boars from 2 AI stations in Southern China, the single-trait repeatability animal model was used to estimate the variance components, heritability and repeatability of each semen traits, two-trait repeatability animal model was used to estimate genetic correlation and phenotypic correlation of semen volume, semen density, sperm motility and percentage of abnormal sperm. The general linear model of R language program was used to analyze the influence of age and season of semen collection on semen traits. The results showed that the semen volume and percentage of abnormal sperm had medium heritability (0.23 and 0.38), and the variation coefficient of percentage of abnormal sperm was 85.42%, while the other traits had low heritability (0.07-0.19). Semen volume-semen density and sperm motility-percentage of abnormal sperm had extremely significantly negative genetic correlation(-0.77 and -0.90, respectively). Semen density-sperm motility showed extremely significantly positive genetic correlation (0.50). The influence of the age of semen collection on semen traits was significant(P<0.05). After boars reached sexual maturity, semen volume showed a significant increase, semen density and percentage of abnormal sperm showed a general decrease, and total sperm number and functional sperm number were significantly higher in the 13-18-month of age group than those in the other groups (P<0.05). The semen density was the highest in spring, and the total sperm number and functional sperm number were significantly higher in autumn and winter than those in spring and summer (P<0.05). In conclusion, the semen volume and percentage of abnormal sperm of Landrace boars can be selected as candidate traits. In the boar production management, boar whose semen production after 36 months of age decline, will be considered to update. Boar semen quality was significantly higher in autumn and winter than those in spring and summer. It is suggested that cooling work should be done in advance in Southern China in summer.