Maternal effects on docility in Limousin cattle

¹ Department of Animal Sciences, Colorado State University, Fort Collins, CO 80523-1171
² Department of Animal Sciences, Colorado State University, Fort Collins, CO 80523-1171; Institute of Veterinary, Animal and Biomedical Sciences, Massey University, Palmerston North, New Zealand

^* To whom correspondence should be addressed. E-mail: mark.enns{at}colostate.edu.

	Abstract

The objective of this study was to quantify the role of maternal effects on docility in Limousin cattle. Docility scores were obtained at weaning while animals were restrained in a squeeze chute. Scores 1 through 6 represented docile to aggressive temperament, respectively, and were provided by the North American Limousin Foundation (NALF). Observations with unknown age of dam, contemporary groups containing less than 10 observations, contemporary groups with no variation, and single-sire contemporary groups were removed, leaving 21,932 observations. A two-generation pedigree file compiled from animals with observations contained 49,459 animals. Fixed effects were weaning contemporary group and age of dam (2, 3 yr). Six animal models encompassed combinations of random factors; direct genetic, maternal genetic and maternal permanent environmental effects. Model (D) was the most basic, containing direct genetic and residual effects, and resembled the method currently used by NALF for genetic evaluation of docility. Maternal genetic or permanent environmental effects were separately added to model (D), denoted as models (DM) and (DC), respectively. Model (DMC) contained all random factors. Models (DM-Zero) and (DMC-Zero) were equivalent to models (DM) and (DMC), respectively, but with zero direct-maternal genetic covariance. Direct heritability estimates were moderate for all models (0.29 ± 0.02 to 0.38 ± 0.03). Maternal heritability estimates were low, ranging from 0.01 ± 0.01 (DM-Zero) to 0.05 ± 0.02 (DM). Negative direct-maternal genetic correlations of -0.41 ± 0.09 and -0.55 ± 0.09 were estimated for models (DM) and (DMC), respectively. The proportion of phenotypic variance accounted for by maternal permanent environmental effects was 0.03 ± 0.01, 0.04 ± 0.01, and 0.02 ± 0.01 for models (DC), (DMC), and (DMC-Zero), respectively. Likelihood ratio tests (LRT) indicated model (DMC) best fit the data. Although maternal genetic and maternal permanent environmental effects were significant, they accounted for only 8% (model DMC) of the phenotypic variance, and a Spearman rank correlation of 0.99 between models (D) and (DMC) showed sires do not rank differently with or without inclusion of these effects. Given these results, inclusion of maternal effects to the genetic evaluation of docility in Limousin cattle does not seem warranted.

Key Words: beef cattle, heritability, maternal effects, temperament