Genetic Parameters for Milk Production and Persistency for Danish Holsteins Estimated in Random Regression Models using REML

• Published in: Journal of dairy science Vol. 85; no. 6; pp. 1607 - 1616
• Main Authors: Jakobsen, J.H., Madsen, P., Jensen, J., Pedersen, J., Christensen, L.G., Sorensen, D.A.
• Format: Journal Article
• Language: English
• Published: Savoy, IL Elsevier Inc 01.06.2002; Am Dairy Sci Assoc; American Dairy Science Association
• Subjects: Algorithms; Animal productions; Animals; Biological and medical sciences; Cattle - genetics; Fats - analysis; Female; Fundamental and applied biological sciences. Psychology; Lactation - genetics; Likelihood Functions; Milk - chemistry; Milk - secretion; Milk Proteins - analysis; Milk Proteins - genetics; model choice; Models, Genetic; Models, Statistical; persistency; random regression; Regression Analysis; Terrestrial animal productions; test-day milk yield; Vertebrates; Denmark; Europe; test-day milk yield; RR; TMI; DH; persistency; model choice; AI; EM; random regression; EMREML; MILK YIELD; Farming animal; Lactation; Ruminant animal; Dairy cattle; Model study; Genetic character; Milk production; Statistical regression; Vertebrata; Milk protein; Mammalia; Regression model; Genetic improvement; Cow milk; Heritability; Artiodactyla; Milk fat; Ungulata
• ISSN: 0022-0302; 1525-3198
• DOI: 10.3168/jds.S0022-0302(02)74231-8

(Co)variance components for milk, fat, and protein yield of 8075 first-parity Danish Holsteins (DH) were estimated in random regression models by REML. For all analyses, the fixed part of the model was held constant, whereas four different functions were applied to model the additive genetic effect and the permanent environment effect. Homogeneous residual variance was assumed throughout lactation. Univariate models were compared using a minimum of –2 ln(restricted likelihood) as the criterion for best fit. Heritabilities as a function of time were calculated from the estimated curve parameters from univariate analyses. Independent of the function applied and the trait in question, heritabilities were lowest in the beginning of the lactation. Heritabilities for persistency of fat yield were slightly higher than heritabilities for persistency of milk and protein yield. Genetic correlations between persistency and 305-d production were higher for protein and milk yield than for fat yield. Bivariate analyses between the production traits were carried out in sire models using the models with the best 3-parameter curve fit in the univariate analyses. Correlations between traits were calculated from covariance components for curve parameters estimated in bivariate analyses. Genetic correlations between milk and protein yield were higher than between milk and fat yield.