Influence of some genetic and non-genetic factors on early body weight traits of barbary lambs

الملخص EN

-This study was conducted to evaluate Barbary sheep lambs genetically, during the period 2003 to 2006.

Data were obtained from Sawaf and Gebbenh sheep stations in Tunisia, which are cooperating with the Arab Centre for the Studies of Arid Zones and Dry Lands (ACSAD).

A total of 6802 records, of weight traits of lambs at birth (BWT), 30 (WT30), 60 (WT60) and 90 (WT90) days of ages, were evaluated.

The data were analyzed by Mixed Linear Model, using statistical program (Harvey, 1990), to estimate heritability as well as Genetic and Phenotypic correlations, and to study the impact of genetic (sire) and non genetic (lambing year, station, type of lambing, sex of lamb, age of ewe at lambing) factors on body weight traits.

Heritabilities were 0.061 ± 0.020, 0.056 ± 0.020, 0.018 ± 0.017, and 0.046 ± 0.019 of lamb’s weights at birth (BWT), 30 (WT30), 60 (WT60) and 90 (WT90) days of ages, respectively.

Genetic correlations ranged from 0.018 ± 0.273 to 0.927 ± 0.204, and phenotypic correlations ranged from 0.328±0.320 to 0.7132 ± 0.709 for the studied traits.

The effect of genetic factor (sire) were highly significant (P<0.01) on all weight traits except of WT60, and also for all non-genetic effects were significant (P<0.05), except for stations.

Least squares means and standard error (kg) for body weights were 3.58 ± 0.01, 9.13 ± 0.04, 14.05 ± 0.10 and 18.72±0.06 at birth, 30, 60 and 90 days of age, respectively.

The results indicated that, because genetic and phenotypic correlation were positive, so the selection for lamb weight at any age will help to improve other traits.

Heritability values were low, therefore, the variations in the studied traits were mostly associated with the non genetic factors such as lambing year, birth type, sex of lamb, and age of ewe at lambing