Conformation of 7 667 primiparas derived from herd effects subjected to evaluation in the region of Wielkopolska was estimated. Measurements were taken in 1989-1995. Correlations between body conformation and milk traits in consecutive lactations were compared and genetic and phenotypic correlations were estimated. The study also used a mixed animal model, which helped to demonstrate that conformation traits affect milk production, especially in the first lactation. Of the non-genetic factors, the herd and the year of calving were found to have a very significant impact on milk yield, while the age at first calving exerted a slightly smaller effect. Positive phenotypic and genetic correlations were observed between conformation traits and milk yield and milk composition. Values of correlation coefficients, especially of genetic correlations, decreased with consecutive lactations. Conformation traits alongside non-genetic factors (herd and year of calving) exerted a significant influence on the value of milk traits. Conformation traits should be taken into account when assessing current breeding programs.

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