Genetic parameters of weight productivity traits of D’Man ewes in Tunisia

Data on weight productivity of 1023 ewes of the D’Man breed calculated using an original file on growth performances of 2026 lambs of the same breed were used in this study. All the lambs were born and raised in Tunisia between 1994 and 1999 in the north of the country (Mateur, Kef) and in the south under an oasian environment (Gabès). The studied variables included weights of the litter at 10, 30, 70 and 90 days of age and respectively designated LW10, LW30, LW70 and LW90. Average calculated figures were 8.22 kg (±2.91), 13.72 kg (±4.64), 24.51 kg (±8.79) and 29.46 kg (±11.11) respectively for LW10, LW30, LW70 and LW90. Analysis of the non genetic sources of variation revealed a highly significant effects (P<0.001) of the factors rank of lambing within station, age of the dam, and type of lambingrearing on all the studied traits. Heritability coefficients estimated using the REML method of variance analysis, were 0.17, 0.23, 0.08 and 0.08 for respectively LW10, LW30, LW70 and LW90. Genetic and Phenotypic correlations between all the studied traits were high and positive respectively varying between 0.81 and 0.94 and between 0.82 and 0.96.