Effects of porcine stress syndrome genotype on maternal traits in swine
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Studies were conducted to evaluate maternal performance differences between females with different porcine stress syndrome (PSS) genotypes. Two data sets were used to conduct this evaluation. The first involved 870 records from 333 females from a synthetic line of pigs selected for their PSS susceptibility. The second data set involved 3100 records from 841 purebred Landrace females. Only records from normal (NN) and carrier (Nn) dams were included;The first study revealed that Nn females farrowed 0.91 and 0.69 more (P < 0.05) live pigs than NN and positive (nn) females, respectively. No difference in litter birth weight of pigs born alive or proportion of pigs surviving from birth to transfer was observed between any dam PSS genotypes;Normal females had 0.57 more (P < 0.05) pigs at birth than did nn females. Normal sows raised 0.49 more (P < 0.05) pigs to 21 d than did nn females. Normal sows produced 6.20 kg and 2.86 kg heavier (P < 0.05) 21-d litter weights than did nn and Nn females, respectively. The proportion of pigs surviving from transfer to 21 d favored (P < 0.05) NN dams by 13.1% and 9.3%, respectively, compared to nn and Nn dams. Normal females had 0.24 more pigs per litter at 42 d although the difference was not significant. Normal and Nn dams produced (P < 0.05) 8.22 kg and 5.16 kg, respectively, heavier litters at 42 d. A 7.69% and 4.48% survival rate to 42 d advantage (P < 0.05) was found in litters of NN and Nn sows, respectively, when compared to nn sows. Normal and Nn dams had similar survival rates of their litters to 42 d;The results from the study involving NN and Nn purebred Landrace dams revealed no significant differences for number born alive, number at 21 d, 21-d litter weight, survival rate to 21 d, and farrowing interval. This data set was also used to estimate genetic parameters for these traits. Heritabilities ranged from 0.04 to 0.06 for number born alive, from 0.21 to 0.32 for number at 21 d, and from 0.14 to 0.21 for 21-d litter weight depending on the method of adjusting for environmental factors. Heritabilities of 0.21 and 0.02 were found for survival rate to 21 d and farrowing interval, respectively.