Sources of variation in fleece traits of Avikalin and Avivastra synthetic breeds of sheep

Abstract

The genetic and phenotypic parameters for fleece traits of 1 299 Avikalin and 1 268 Avivastra lambs over 1975-86 were estimated. The year and season of shearing, generation number, sex and age of lamb contributed 4-29% and 3-35% of the phenotypic variability in the fleece traits of Avikalin and Avivastra lambs, respectively. The least-squares means for the first and second 6-monthly greasy fleece weights, staple length, fibre diameter and medullation pecrcentage of Avikalin lambs were 0.864±0.021 and 0.802±0.019 kg, 4.09±0.06 cm, 25.04±0.20 microns and 36.0.9±0.01%, respectively; and correspondingly, of Avivastra lambs, the means were 0.881±0.018 and 0.813±0.022 kg, 3.72±0.06 cm, 21.77±0.16 microns and 17.79±0.01%, respectively. Corresponding heritability estimates were 0.35±0.09, 0.55±0.16, 0.45±0.12, 0.48±0.10 and 0.26±0.08 for Avikalin lambs, respectively; and 0.80±0.14, 0.63±0.15, 0.41±0.12, 0.50±0.12 and 0.17±0.08 for Avivastra lambs, respectively. The estimates of genetic correlations among fleece traits ranged from medium to high in magnitude in both the breeds and some of them were in the desirable direction and significant. These estimates demonstrate an opportunity for the genetic improvement of these traits in both the breeds through selection.