Variance Components for Test-Day Milk, Fat, and Protein Yield, and Somatic Cell Score for Analyzing Management Information

摘要: Test-day (TD) models are used in most countries to perform national genetic evaluations for dairy cattle. The TD estimate lactation curves and their changes as well variation populations. Although potentially useful, little attention has been given the application of management purposes. potential model use depends on its ability describe within- or between-herd that can be linked specific practices. aim this study was variance components milk yield, component yields, somatic cell score (SCS) cows Ragusa Vicenza areas Italy, such relevant sources identified development parameters. available data set contained 1,080,637 records 42,817 471 herds. Variance were estimated with a multilactation, random-regression, animal by using software adopted NRS Dutch evaluation. comprised 5 fixed effects [region x parity days (DIM), year calving season DIM, age at calving, interval stage pregnancy, test calendar week test] random herd date, regressions curve (HCUR), additive effect, permanent environmental effect fourth-order Legendre polynomials. HCUR variances protein yields highest around time peak yield (DIM 50 150), whereas fat relatively constant throughout first decreased following 40 90 DIM lactations 2 3. For SCS, small compared genetic, environmental, residual variances. all traits except explained date much smaller than variance, which indicates parameters should focus during components. within-herd greater suggesting explaining cow level. present showed clear evidence benefits regression decisions.