Historically, most cows enrolled in a milk recordingprogram in the US have had milk weights recordedmonthly (14). However, practices for collecting milkand component data (fat and protein) have changedrapidly. More than 30 innovative test plans wereproposed and introduced between 1989 and 1995 (P.Dukas, 1995, personal communication). Many of thenew plans require less labor for recording milkweights and collecting component samples (fat andprotein), thereby reducing cost to the producers
Comparison of Test Interval and Best Prediction Methods for Estimation of Lactation Yield from Monthly, a.m.–p.m., and Trimonthly Testing (PDF Download Available). Available from: https://www.researchgate.net/publication/13221765_Comparison_of_Test_Interval_and_Best_Prediction_Methods_for_Estimation_of_Lactation_Yield_from_Monthly_am-pm_and_Trimonthly_Testing [accessed May 8, 2016].