Evaluation of Sources of Variance in Dairy Herd Fertility

Fertility data were obtained for the first ten cows bred in 23 herds in each of 22 artificial breeding locals for a period of four consecutive years. Analysis of variance and separation of the components indicated that 1.4(~ of the variance was due to differences between years, 4.6% to differences between locals, 7.5% was between herds within locals, 2.1% was due to the interaction between years and locals, and 4.9~/( was due to the interaction between years and herds within locals. The remaining 79.6% of the variance was estimated to be due to sampling error.