Accuracy of estimating 305-day milk, fat and protein yields using different milk recording systems through the first three lactations in dairy cattle

Shereen K. Genena1 and A. M. Soliman2

Abstract

Across the first three lactations 47163 records of Austrian Fleckvieh cows were used in this study to estimate 305-day milk , fat and protein yields by comparing bimonthly recording system (BRS2) and trimonthly recording systems (TRS2 and TRS3). Traits studied were recorded milk yields of both monthly test - day and 305-day (MT) and estimated (EMT) 305-day of milk ; fat and protein yield. Three measures of accuracy (ACM) for those systems were (biases (BMT); percentages (PERMT) and percentages bias (PBMT) of estimated from actually recorded 305- day milk traits were calculated. Effects of calving year – season; age at calving; days open and stage of lactation were considered as fixed effects and sire effects as random. Genetic (rG), phenotypic (rP) and environmental (rE) correlations among those estimated and actually recorded traits were estimated. The evaluation criteria for the comparisons between those schemes were relying on the accuracy measurements and the correlations. The results indicated that for the first lactation, using TRS3 and for the second and the third lactations using BRS2 were accurate enough to predict 305 - day milk, fat and protein yields.

Key words

dairy cows, milk recording systems, prediction, accuracy measurements, milk traits.