Analysis of factors to predict piglet body weight at the end of the nursery phase

In pig production, within-batch variation in body weight (BW) gain of piglets during the nursery period (up to 10 weeks of age) can be high and is of high economic importance. Homogeneity of BW within batches of animals is important as it influences the efficiency of use of the grower and finisher facilities, and provides an extra value for the fattening farms. In the current study, factors for a low BW at the end of the nursery period of pigs were determined by analysing datasets from three different Swine Research Centres in the Netherlands and France. The entire dataset contained information on 77,868 individual piglets born in the period between 2005 and 2010. BW was determined at different time points over the pre- and post-weaning phase, and sex, season of birth; litter information (litter size at day of birth and after cross-fostering, number of piglets born alive per litter, number of total born littermates, sow parity number); cross-fostered animals (yes or no), and pen group size over the post-weaning period were recorded. A risk factor analysis approach was used to analyze the datasets to determine factors that predict piglet BW at the end of the nursery period. BW at the end of the nursery period corrected for age was mainly determined by season (P <0.001), sex (P <0.001), birth weight (P <0.001), weaning weight (P <0.001) and BW at 6 wk of age (P <0.001). These variables were consistent among datasets and explained approximately 70% of the overall variation in BW at the end of the nursery period. Litter information did not significantly (P > 0.05) contribute to explaining the BW at the end of the nursery period. To discard the possibility of intrauterine growth retarded piglets (IUGR) being the reason for the influence of birth weight (BiW) as an explanatory factor in the regression model, a further analysis was performed on the effect of this category of piglets on the results of the regression analysis. Overall, it was concluded that piglet's BW at the end of the nursery phase is mainly determined by season, sex, birth and weaning weight and BW at 6 weeks of age. Piglets with a BiW higher than the mean BiW minus 2.5 times the SD have the potential to compensate during the subsequent phases of growth.