Abstract:
This study was done on three strains of East African goats namely, Dodoma. Kigoma and Mtwara with the aim of estimating heritability for pre-weaning (4 months), post-weaning (8 months) and yearling (12 months) growth rates. Other heritability parameters measured were for weight at birth, 4, 8, and 12 months of age and helminth resistance traits (faecal egg count or FEC and packed cell volume or PCV) at six and twelve months of age. Genetic correlations were also determined between FEC. PCV and growth rate at six and twelve months of age. Genetic correlation and heritability were estimated using the Restricted Maximum likelihood (RFML) of the variance component (Var Comp) procedure of the Statistical Analysis System (SAS) package. Most of the traits were observed to have moderate heritability ranging from 0.32 to 0.39, with exception of weight at weaning (4 months). 8 months, one year of age and PCV, which had high heritability (0.4-0. 44) estimates. Negative genetic correlations were observed between FEC and growth rate at six months (rg = -0.69 ± 0.042), and twelve months of age (rg = -0.8 ± 0.011), whereas, PCV-showed positive genetic correlations with growth rate within the same periods rg = 0.59± 0.010 and rg = 0.45 ± 0.022, respectively. It was concluded that the moderate and high heritabilities obtained for growth rates, weights at different age FEC in this study indicate that improvement of growth rate, body size and genetic resistance to helminthosis could be improved through selection and manipulation of both the additive genetic action and non genetic (ienvironmental) components for tropical goat improvement. It was also recommended that genetic manipulation at molecular level should be employed in identifying and isolating quantitative and qualitative trait loci (QTL) linked to economic and desirable traits which will enable development of goats suitable for different ecological zones.
