MONTHLY TEST DAY MILK RECORDS AND YIELD AT 244 DAYS .3. STUDY ON CUMULATIVE AND REMAINING YIELD

With the objective of defining the method for extending lactation yield, a study was carried out on cumulative and remaining production and the relation between them. The first 8 test day milk records of 3,095 first lactation cows were used. A linear model including the effects of dairy unit (45), year (5), seasons (6) the year x season interaction, the linear regression on age at calving and the linear regression on the calving-first test day interval was used for the analysis. The least squares method using the GLM programme of the SAS was employed for the estimation or parameters. With the exception of age at calving, all other factors were highly significant both for cumulative and remaining yield. The phenotypic correlations between test day records and remaining yield are higher than those between cumulative and remaining yield (0.49-0.66 vs 0.27-0.49). These results confirm the use of the last test day record for extending lactation yield since it is the best indicator of remaining yield.