Characteristics at birth were recorded from 969 litters of F1 Duroc * Large White (82), Large White (651), Meishan (63) and Laconie (173) sows. Models included a random litter effect, the fixed effects of sow genetic type, parity, birth assistance, piglet sex, as well as gestation length, piglet birth weight and litter size as covariates. Stillbirth was assumed binomially distributed. Statistical analyses were performed with standard Generalized Estimating Equations (GEE). The three most important factors involved in stillbirth were difference in piglet birth weight from the litter mean (2.36%), piglet sex (1.01%), and sow genetic type (0.94%). Stillbirth probability was higher for lighter and male piglets. Piglets born from Meishan sows had a lower risk (p<0.0001) and were little affected by the different factors of variation as compared to the three other sow genetic types. Standard and robust GEE approaches gave similar results despite some disequilibrium in the data set structure highlighted with the robust GEE approach.
Proceedings of the World Congress on Genetics Applied to Livestock Production, Volume , , 06.06, 2006
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