ADJUSTMENT FACTORS AND GENETIC AND PHENOTYPIC PARAMETERS FOR GROWTH TRAITS OF BARBARINE LAMBS IN TUNISIA

Growth data on 8788 Barbarine lambs raised in central Tunisia from 196 8 until 1988 were studied. Sex of lamb, type of birth, age of dam, yea r of birth and ram effects were important sources of variation for gro wth traits from birth to 3 months of age. Male and single lambs grew f aster than female and multiple lambs. Means of lamb growth traits were 3.42, 9.06, 15.40 and 17.75 kg, respectively, at birth, 30, 70 and 90 d of age. Average daily gains were 183, 159 and 146 g/d between 10-30 , 30-70 and 30-90 d, respectively. All growth traits were optimal when age of the dam was 5 years. Multiplicative adjustment factors were co mputed, taking into account sex, type of birth and age of dam. Heritab ility estimates were 0.26 +/- 0.04, 0.14 +/- 0.03, 0.19 +/- 0.03, 0.27 +/- 0.04 and 0.32 +/- 0.04 for weights at birth, 10, 30, 70 and 90 d, respectively. Heritabilities for average daily gains from 10-30, 30-7 0 and 30-90 d were 0.15 +/- 0.03, 0.24 +/- 0.04 and 0.31 +/- 0.05, res pectively. Genetic and phenotypic correlations among growth traits wer e all positive ranging from 0.43 to 0.96 and 0.10 to 0.92, respectivel y. These parameters are useful information to develop genetic evaluati on methods for management within-flock or cross-flock breeding program s.