Genetic parameters for reproductive traits in a beef cattle herd estimated using multitrait analysis

The object of this study was to estimate heritabilities and genetic correlations for reproductive traits in a composite multibreed beef cattle herd using multitrait analysis. A REML procedure fitting a multitrait animal model was used to analyse data. Heritabilities and genetic correlations for calving interval (CI), calving date (CD), calving date with a penalty score (CDP) and age at first calving (AFC) were estimated as traits of the dam. The estimated heritabilities for CI, CD, CDP and AFC obtained in this study were 0.01, 0.04, 0.06 and 0.40 respectively with a repeatability of 0.07, 0.12 and 0.13 for CI, CD and CDP. Genetic correlations between traits varied from low to moderate, except for high correlations between CD and CDP (0.98), CI and CD (0.75) and between CI and CDP (0.79). Heritabilities, genetic correlations and repeatabilities of CD and CDP obtained in this study suggest that CD and CDP are the same traits and that selection for CDP rather then for CD does not have any additional advantages. Due to the additional advantages of CD over CI and the fact that CD is a less biased measurement of the female reproductive complex, CD and AFC (because of its high heritability) may be considered as selection criteria for improvement of reproduction in beef cattle herds.