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Partitioning of Multiple-Trait Model Parameters with Respect to Phenotypic Recursion: Case Study of Birth Weight and Calving Ease in Canadian Simmentals
Fully recursive model (RM) is equivalent to a multiple-trait model (MTM). Structural coefficients and other RM parameters can be derived from MTM parameters given a known causal structure. Birth weight (BW) and calving ease (CE) of Canadian Simmental cattle were analyzed by a linear-binary MTM with direct and maternal genetic effects. Direct and indirect (mediated by BW) genetic and environmental effects on CE were quantified by transformation of MTM parameters. An increase of 1 kg of BW resulted in more difficult calving by 0.044 on a liability scale. Variance due to direct effects on CE constituted from 71 to 100% of the total variance for different sources of variability. Random MTM effects were correlated almost perfectly with direct RM effects. Correlations between direct and indirect RM effects on CE were smaller than 0.66.
Keywords:
beef cattle
calving ease
genetic parameters
recursive model
