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 fr om combined morning and afternoon milk samples collected at five-weekly int ervals is time-consuming, and proportional bulking of morning and evening s amples is not always done correctly by farmers. This study was conducted to determine whether samples could be collected once daily without compromisi ng the accuracy of yield estimates. The results of this study support the f ive-weekly sampling procedure currently used by the South African National Dairy Cattle Performance Testing Scheme. However, replacement of proportion al bulking of individual morning and evening samples with a single evening milk sample would not compromise accuracy provided that the relevant correc tions are made to prevent over-estimation of milk-fat yields.