The recording of total lactation yield for individual cows can be timeconsuming and costly. Periodic sampling at intervals throughout lactation offers an acceptable alternative, and a single day's production can be made to furnish a useful guide, by using an equation relating total to daily production.
Errors of estimation are affected by the degree of consistency of daily production, parity and individual herd management, so that estimates could be biased and have a standard error of nearly 20% if these effects are disregarded. Coefficients in the prediction equation must therefore be developed for individual herds.