Genetic studies on fleece weights of Muzaffarnagri sheep

Data on 2742 lambs descended from 132 Muzaffarnagri rams collected from the All India Coordinated Research Project on Sheep Breeding for mutton production at the Central Institute for Research on Goats, Makhdoom, over a period of 23 years (1978–2000), were used to identify the different environmental factors affecting the fleece traits and to estimate the genetic parameters of the traits. Fleece weight at first (6 months of age) and second clip (12 months of age) was recorded by shearing of animals and efficiency of wool production at the first and second clips was also calculated. The overall least squares means of wool yield and efficiency at first and second clips were 533.39±12.83, 493.13±15.75 g and 2.30±0.06, 1.71±0.06 per cent, respectively. The type of management was highly significant (P<0.01) on fleece traits at first clip. Period of birth significantly (P<0.01) affected yield and efficiency of yield at second clip. Parity of dam had significant (P<0.05) effect only on efficiency of wool production at 12 months of age. The lambs born in season 1 (March–April) had higher (P<0.01) fleece yield and efficiency of wool production at first clip as compared to lambs born in season 2 (October–November). The males had heavier (P<0.01) greasy fleece weights and efficiency in production than females at second clip. The regression of 6 and 12 months body weights on first and second clip fleece traits was found to be highly (P<0.01) significant. The heritability estimates of fleece weight and efficiency of wool production were 0.23± 0.05, 0.38±0.06 and 0.45±0.08, 0.50± 0.09 at first and second clips, respectively. Genetic and phenotypic correlations between first and second clip fleece yields were 0.32±0.19 and 0.089, respectively.