A structural equation model to analyze energy utilization in lactating dairy cows

Energy balance trials from lactating cows have traditionally been analyzed using the regression approach. However, univariate analysis of mutually interacting animal traits can provide biased parameter estimates if one trait is used as an explanatory variable to model a second trait and the sub-model of the first trait is ignored (Gianola and Sorensen, 2004). Moreover, multivariate methods should be preferred because animal responses are correlated and relationships among responses can be quantified through the use of structural equations. Furthermore, the US current energy evaluation system of dairy cattle (NRC, 2001) relies on energetic parameters from the 1960’s but over the past decades genetic improvement of dairy cattle has substantially increased the ability of cows to produce milk. The objective of the present study was to analyze energy utilization in lactating cows using structural equations