The genetics of docility of the grasscutter (Thryonomys swinderianus)

Abstract

The objectives of this study were to estimate non-genetic effects on docility, and calculate phenotypic and genetic parameters for docility in the grasscutter. The study was carried out at the grasscutter section of the Department of Animal Science Education, University of Education, Winneba, Mampong-Ashanti campus, Ghana from 2006 to 2009. Docility was defined as ability of an animal to accept human presence. A docility test was carried out on 321 animals (162 females and 159 males) which were selected at random at weaning (2 months). Docility was scored on a scale of 1 to 4; docile (1), flighty (2), restless (3) and aggressive (4). Each animal was tested 8 times. Average docility score of the population was 2.6. Litter size, sex, parity, year of birth, season of mating and season of birth, and their interactions did not influence (p>0.05) docility. Moderate direct and maternal genetic variations were observed for docility. The permanent environmental influence due to the dam on offspring accounted for a significant proportion (48.0%) of the phenotypic variation in docility. Direct heritability for docility was high (0.58) while the maternal heritability was medium (0.41).There were low genetic and phenotypic correlations between docility and all traits (body weight, growth rate, days of joining to conception, survival, feed intake and feed conversion ratio), except litter size. Litter size had a moderate negative genetic correlation with docility, but a low negative phenotypic correlation. Repeatability of docility was high (0.84). It was concluded that selection for grasscutters with more favourable docility scores would be effective in producing animals with more acceptable temperaments. Selection for grasscutters belonging to large litters is likely to produce docile animals, which are easier to handle. Addition of maternal effects to the genetic evaluation of docility in the grasscutteris recommended. One or two records on the animal's docility are enough to make selection decisions.