Recursive and simultaneous equation models have a long tradition in the econometrics literature to describe feedback and recursiveness involving two or more variables. Here, a recursive mixed model (RMM) and a standard two-trait mixed model (SMM) were fitted to litter size and average litter weight records from Landrace and Yorkshire pigs. The models were compared using Bayes factors. In Landrace, the SMM was best supported by the data, whereas the opposite was true in Yorkshire. In Landrace, both models led to very similar inferences because the recursive parameter was very close to zero. In Yorkshire, a prediction based on the posterior mean of the recursive parameter indicates that a unit increase in litter size leads to a decline of 23 gr. in average litter weight. The resulting inferences of genetic parameters under both models have a number of important consequences for predicted responses to selection.

D. Sorensen, Luis Varona

Proceedings of the World Congress on Genetics Applied to Livestock Production, Volume , , 24.06, 2006
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