Genetic improvement in litter sizes at birth at intensive swine farms in Hochiminh city
2000
Tran Thi Dan
Genetic improvements of litter sizes at birth were estimated on data from 8412 litters farrowed by 2023 sows born during 1990-1996 at two breeding swine farms in Ho Chi Minh City. Breeds of sows and litters were purebreds of Duroc, Landrace and Yorkshire, and crossbreds among the three breeds. Traits analyzed were total number of piglets born (TSS), born alive (SSS) and weight of litter born alive (TLSS). Multiple trait animal models including genetic group effects were analyzed using a derivative-free restricted maximum likelihood approach. The models included the fixed effects of herd-year-season, parity, type of mating and number of failed conceptions prior to farrowing the litters along with breed composition of sow and litter, and heterozygosity of sow and litter. Random effects were genetic effects of sows and service sires, and permanent environmental effects associated with the sows. Estimated genetic changes were based on the average of predicted breeding values of animals. Heritabilities were found to be 0.17 for TSS and SSS, and 0.22 for TLSS. Maternal heterosis effects ranged from 3.90 percent to 5.43 percent and were significant for all litter traits. Genetic effects of service sires explained only 2 percent and 1 percent for the variation of litter sizes and litter weight, respectively, in univariate models, but the effects were almost zero in multiple trait models. Estimated genetic changes per year were 0.05 pigs born, 0.04 pigs born alive and 0.08 kg birth weight per alive litter
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