Growth performance, genetic parameters and selection index of pure and crossbred populations of Red Sokoto and West African Dwarf goats
In 2008, a breeding programme was designed to develop hybrid goat suitable for the rainforest agro-ecological zone of South-Eastern, Nigeria. Two indigenous goat breeds namely, Red Sokoto (RS) and West African Dwarf (WAD) goats were utilized and mated in a main (RS x WAD), reciprocal (WAD x RS) and pure line (RS x RS and WAD x WAD) fashion. A total of 74 progenies were generated from the matings and were evaluated for 12week growth performance. As part of the ranking procedure, a selection index was constructed based on two major body components namely body weight (BWT) and heart girth (HGT) to objectively determine the genetic worth of the growing pure and crossbred progenies of Red Sokoto and West African Dwarf kids. The results showed that average body weight (BWT) of RS x RS (5.29±0.13kg) and RS x WAD (5.14±0.21kg) buck kids were similar but significantly (P< 0.05) heavier than that of their WAD x RS (4.84 + 0.17kg) and WAD x WAD (4.79 + 0.17kg) counterparts. The performance of crossbred RS x WAD compared to WAD x RS and WAD x WAD buck kids indicate that the main crossbred kids sired by Red Sokoto bucks but nursed by WAD dams received superior sets of genes from their large-sized sire. The RS x WAD buck kids in particular, had significantly longer body length (BLT), height-at-withers (HWT) and HGT than WAD x RS and WAD x WAD kids. The phenotypic and genetic correlations of BWT and HGT in both sexes for the different genotypes were high and positive which were indicative of the nature of association between these conformation traits in goats. Heritability estimates (h2) for BWT and HGT in males and females kids ranged from 0.31 – 0.36 versus 0.28 – 0.30, respectively in most of the growing kids. The relative economic values (REV) of chosen traits were generally higher for male kids compared to their female counterparts. Phenotypic variances for BWT and HGT in male and female kids ranged from 0.65 – 0.80. The selection index values were highest in male and female kids of RS x RS, followed by RS x WAD, while WAD x RS kids ranked low and WAD x WAD kids ranked the least. Thus, indicating that selection and improvement of growth traits in these pure and crossbred kids would be in favour of the RS x RS and RS x WAD individuals.
Key words: Indigenous goats, crossbreeding, genetic parameters, selection index, growth traits.