The use of prolonged intervals between milk weighings and butterfat tests in milk recording

Alternative methods of milk recording have been investigated. The aim of the investigation was to examine the significance of simplified and thus less expensive methods of recording. The investigation was based on Danish data from 1146 cows tested at weekly intervals at Progeny Testing Stations and 4196 lactation records from four-weekly tests by Milk Recording Societies.An increase in the intervals between milk weighings and butterfat tests resulted in a small increase in S.D. of bias; however, the bias was not significant for intervals up to 12 weeks. The results indicate that lactation records from bimonthly or trimonthly tests are reasonable alternatives to a traditional recording once a month as far as utilization of data for breeding purposes is concerned.Cases were investigated where milk weighings were fixed to 4- or 8-week intervals and the number of butterfat tests varied during lactation. The results indicate that milk weighing at 4-week intervals and butterfat tests at 12-week intervals gives approximately the same significance of production records as testing for both milk and butterfat with 8-week intervals.Recording in the first part of the lactation may cause a large part of the error of the lactation record. By correcting for length of the interval between calving and first recording it is possible to reduce the S.D. of bias.Possibilities of using butterfat tests from dairy plants were investigated. Even a reduction in butterfat tests to one per cow in each lactation combined with the herd average of butterfat percentage from the dairy plant may give a reasonable significance in data from Milk Recording Societies.