The effect of sampling frequency on the accuracy of estimates of milk-fat yields of dairy cows

Estimation of 300-day lactation yields of milk, fat, protein and lactose from combined morning and afternoon milk samples collected at five-weekly intervals is time-consuming, and proportional bulking of morning and evening samples is not always done correctly by farmers. This study was conducted to determine whether samples could be collected once daily without compromising the accuracy of yield estimates. The results of this study support the five-weekly sampling procedure currently used by the South African National Dairy Cattle Performance Testing Scheme. However, replacement of proportional bulking of individual morning and evening samples with a single evening milk sample would not compromise accuracy provided that the relevant corrections are made to prevent over-estimation of milk-fat yields.