ESTIMATES OF GENETIC-PARAMETERS FOR GROWTH TRAITS OF GOBRA CATTLE

Estimates of (co)variance components and genetic parameters were obtai ned for birth (no. = 3909), weaning (no. 3425), yearling (no. = 2763), and final weight (no. = 2142) for Gobra cattle at the Centre de Reche rches Zootechniques de Dahra (Senegal), using single trait animal mode ls. Data were analysed by restricted maximum likelihood. Four differen t animal models were fitted for each trait. Model I considered the ani mal as the only random effect. Model 2 included in addition to the add itive direct effect of the animal, the environmental effect due to the dam. Model 3 added the maternal additive genetic effects and allowed a covariance between the direct and maternal genetic effects. Model 4 fitted both maternal genetic and permanent environmental effects. Incl usion of both types of maternal effects (genetic and environmental) pr ovided a better fit for birth and weaning weights than models with one maternal effect only. For yearling and final weights, the improvement was not significant. Important maternal effects were found for all tr aits. Estimates of direct heritabilities were substantially higher whe n maternal effects were ignored. Estimates of direct and maternal heri tabilities with model 4 were 0.07 (s.e. 0.03) and 0.04 (s.e. 0.02), 0. 20 (s.e. 0.05) and 0.21 (s.e. 0.05), 0.24 (s.e. 0.07) and 0.21 (s.e. 0 .06), and 0.14 (s.e. 0.06) and 0.16 (s.e. 0.06) for birth, weaning, ye arling and final weights, respectively. Correlations between direct an d maternal genetic effects were negative for all traits, and large for weaning and yearling weights with estimates of -0.61 (s.e. 0.33) and -0.50 (s.e. 0.31), respectively. There was a significant positive line ar phenotypic trend for weaning and yearling weights. Linear trends fo r additive direct and maternal breeding values were not significant fo r any trait except maternal breeding value for yearling weight.