Studies On The On-farm Genetic Evaluation And Genetic Analysis Of Lean Type Swine

Lean type swine breeding has been done in Hunan Yiyang Swine Breeding Farm and Zhenghong Swine Breeding Farm by us since 2000. Multi-trait animal model BLUP is now the best method of estimating breeding value. We use this method in selecting breeding pigs. On-farm genetic evaluation of lean type swine was carried out in the two breeding farms by using GBS software. In this study, the effects of major traits in genetic evaluation are analysed. Genetic parameters and variance components of gametic imprinting effects are estimated for major traits by using Bayesian method based on Gibbs sampling.The main results of this study are as below:1. The growth curves of replacement pigs in Duroc, Landrace and Large White swine are fitted by the equations of Logistic and Gompertz. The goodness(R~2) is great. The adjusted coefficients from pig weights at about the fourth month to age at 100kg are worked out through Logistic equation. These coefficients are precise and can be used in adjustment.2. After five years' selection which is based on performance test and genetic evaluation, the performances of pig improved fast. In Yiyang Swine Breeding Farm, age at 100kg of replacement pig in Duroc and Large White dropped 16.37 and 16.42 days respectively, population EBV dropped 2.69 and 2.57 days respectively. Backfat thickness at 100kg of replacement pig in Duroc and Large White dropped 1.26 and 1.10mm respectively, population EBV dropped 0.18 and 0.21mm respectively. Paternal index in Duroc raised 7. 12 and maternal index in Large White raised 5.74 from 2000 to 2004.In Zhenghong Swine Breeding Farm, age at 100kg of replacement pig in Duroc, Landrace and Large White dropped 16.67, 20.26 and 20.92 days respectively, population EBV dropped 2.59, 2.67 and 3.11 days respectively. Backfat thickness at 100kg of replacement pig in Duroc, Landrace and Large White dropped 0.72, 0.84 and 0.26mm respectively, population EBV dropped 0.15, 0.17 and 0.14mm respectively. Paternal index in Duroc raised 4.31 , maternal index in Landrace and Large White raised 8.09 and 9.77 respectively from 2000 to 2004.Reproductive performances of sow in these two swine breeding farmsincreased from 2000 to 2004, but the rates are slower than that of growth traits of replacement pig.During fattening period, the growth rate and feed conversion of Duroc, Landrace, Large White and their crosses increased fast, lean percentage of carcass is in a good condition. Body conformation, population tidiness and quality of breeding swine are improved.3. The results of estimating genetic parameters for major traits are as below: (1) litter effect(c2) of age at 100kg in Duroc, Landrace and Large White are 0. 160, 0. 173 and 0. 182 respectively, while \\ are 0. 353, 0. 338 and 0. 346 respectively.(2) litter effect (cz) of backfat thickness at 100kg in Duroc, Landrace and Large White are 0.055, 0.061 and 0.059 respectively, while \\ are 0.482, 0.487 and 0.479 respectively, c" of age at 100kg is bigger than c" of backfat thickness at 100kg. (3) Genetic correlation between age at 100kg and backfat thickness in Duroc, Landrace and Large White are -0. 259, -0. 233 and -0. 249 respectively. (4) h2 of total litter size in Duroc, Landrace and Large White are 0. 108,0. 123 and 0. 119 respectively.4. The results of estimating variance components of gametic imprinting: (1) For age at 100kg, estimates of the proportion of total variance accounted for by paternally transmitted gametes are 2. 3%, 2. 7% and 2. 8% in Duroc, Landrace and Large White swine respectively. Corresponding results for maternally transmitted gametes are 4.0%, 4.4% and 4.1%. The expression of imprinting effects in these three breeds is almost the same, but variance components of maternal game tic effects are bigger than that of paternal gametic effects.(2) For backfat thickness at 100kg, estimates of the proportion of total variance accounted for by paternally transmitted gametes are 5.9%, 5.5% and 5. 6% in Duroc, Landrace and Large White swine respectively. Corresponding results for maternally transmitted gametes are 3. 1%, 2. 0% and 2. 5%. Variance components of paternal gametic effects are bigger than that of maternal gametic effects.(3) For total litter size of sow, estimates of the proportion of totalvariance accounted for by paternally transmitted gametes are 1.0%, 0.7% and 0.9% in Duroc, Landrace and Large White swine respectively. Corresponding results for maternally transmitted gametes are 2. 1%N 1.7% fP 1.8%. Variance components of maternal gametic effects are nearly twice than that of paternal gametic effects.