Abstract
Objective of the study was to apply random regression models to daily dry matter intakes (DMI) of 376 beef steers fed for up to 168 days for evaluating genetic parameters and the optimum period of test. Steers were tested in a research station in Canada from 1997 to 2001. Models included fixed effects of biological breed type, test group, herd of origin and starting age and random additive genetic and permanent environmental effects of animal. Legendre polynomials on days of test were fitted for all fixed and random effects, except for biological types, which were estimated as linear regression on biological type composition. Heritability substantially improved from the first week up to 84 days on test (0.23 to 0.49), when it reduced the rate of increase. Genetic correlation between cumulative feed intake in the entire period of test and the intake up to 84 days was high (0.93). Results indicated that a test period of 84 days could be used for evaluating cumulative feed intake of steers for a 168 days growth period. Genetic eigenfunctions revealed that changes to the shape of the feed intake curve seem to be more difficult than changes to the overall level of intake of steers.
Published Version
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