|Van Vleck, Lloyd|
Submitted to: British Society of Animal Production Meetings and Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 10/29/1997
Publication Date: N/A
Interpretive Summary: The Gobra is a local cattle of Senegal. Mass selection primarily on growth performance began in 1963 at the Centre de Recherches Zootechniques de Dahra (Senegal). The cattle are small at birth and slow growing, averaging 25, 108, 158, and 202 kg at birth, 6, 12, and 18 months, respectively. Implementation of an efficient genetic improvement program requires know- ledge of genetic parameters of the traits, especially the genetic corre- lations between animal direct genetic and maternal genetic effects as well as the relative importance of direct and maternal genetic effects. This study suported by USAID of records on 3,909 animals showed that direct and maternal genetic effects are equally important for weaning weight with each accounting for 20% of variation and with a high negative genetic cor- relation of -.61. In contrast to results from European cattle, direct and maternal genetic effects are also equally important at 12 and 18 months and dwith large negative genetic correlations. These results indicate that maternal effects must be considered in design of future selection plans to obtain optimal response to long-term selection.
Technical Abstract: Estimates of (co)variance components and genetic parameters were obtained for birth (n=3909), weaning (n=3425), yearling (n=2763), and final weight (n=2142) for Gobra cattle at the Centre de Recherches Zootechniques de Dahra (Senegal), using single trait animal models. Data were analyzed by restricted maximum likelihood. Six different animal models were fitted for each trait, ranging from a simple model with animals as the only rando effect to the most comprehensive model including both genetic and environ- mental maternal effects and a covariance between direct and maternal genetic effects. The most complete model provided the best fit to the data. For yearling and final weight, models including genetic maternal effects tended to provide better fit than models with environmental mater- nal effects; while for weaning weight, the opposite seemed to prevail. Important maternal effects were found for all traits. Ignoring maternal effects caused direct heritability estimates to increase substantially. Estimates of direct and maternal heritabilities with the most complete model were .074 and .039, .203 and .205, .240 and .213, and .138 and .155 for birth, weaning, yearling and final weight, respectively. Correlations between direct and maternal genetic effects were negative for all traits, and large for weaning and yearling weights with estimates of -.61 and -.50, respectively.