Use of test day milk yields for genetic evaluation in dairy cattle - a review

Abstract

Traditionally, the data collected in milk recording schemes are aggregated into records for entire lactations, most often standardized to a length of 305 days (P305). These records then are used in analyses related to dairy cattle breeding programmes. Recently, interest has been increasing in the use of test day milk yields (PLDC) as alternative criterion in studies involving milk yield. Among other advantages, the use of PLDC allows considering records at their origin, i.e. at the day of recording. Under this approach genetic and environmental effects specific to each single record can be considered. Using PLDC it is possible to evaluate cows before the completion of the lactation without the use of factors to extend partial lactation records and also to improve the accuracy of a sire’s genetic evaluation as there will be more daughters with production records. However, knowledge of the particularities of the methodology is needed in order for it to be recommended and effectively used in milk production research. The objective of this study was to review the literature on the viability of using the PLDC in dairy cattle genetic evaluations. It was concluded that there are more advantages associated with the use of PLDC than of P305.