The relationship between production level and reproductive efficiency in dairy cattle

Nine measures of production and four measures of reproductive efficiency were compared and analyzed on 453 cows over a five year period from 1963 to 1968. The purpose was to ascertain the effect of production level on reproductive efficiency. Data were analyzed by correlation and regression analysis and analysis of variance. Correlation analysis revealed a small positive correlation between most production and reproductive traits. Regression analysis revealed that the influence of 120 day FCM on days to conception tended to be linear and was significant at all age levels with the exception of five year olds. The analysis of variance also confirmed that milk production exerts a significantly depressing effect on reproductive efficiency. The least significant differences between treatment groups state that reproductive efficiency in the top treatment group is significantly different from reproductive efficiency within the two bottom groups. Although R² values indicate that milk production accounts for only a small portion of the variation in reproductive efficiency, it appears from this study that high levels of milk production do exert a significantly depressing effect on reproductive efficiency as measured by days to conception, days from first service to conception, and services per conception.