التغيرات الوراثية و البيئية و المظهرية لبعض الصفات الإنتاجية لدى أغنام العواس في سورية

الملخص EN

The objective of this research was to estimate genetic, environmental and phenotypic changes of some productive traits (milk production/ kg, length of lactation/ day, litter size weight at birth/ kg, and litter size weight at weaning/ kg) in order to determine the effectiveness of the selection program applied for improving the genetic productive traits on Awassi Sheep in ACSAD, station of Izraa, Syria.

The data were analyzed statistically in a Least Squares Method using the SAS program based on the General Linear Model to estimate the changes of studied phenotypic traits.

The animal model was also used for the analysis of multiple traits, to estimate breeding and environmental values for each studied trait.

The regression of the breeding values, and environmental values to the effect of years, and the averages of the studied phenotypic traits on the years of ewes lambing during study period (2002 -2010) were also estimated to reflect annual genetic, environment, and phenotypic changes of all studied productive traits which estimated.

The values of genetic changes were (-0.56±0.06, -0.001±0.0006, -0.002±0.0008, 0.003±0.002), environmental values were (-8.48±1.36, -4.56±1.93, -0.031±0.026, 0.043±0.043) and phenotypic values were (-7.86±0.94, -4.22±1.60, -0.026±0.029, -0.049±0.022) for the studied traits (milk production/ kg, length of lactation/ day, litter size weight at birth/ kg, and litter size weight at weaning / kg), respectively during the studied period.

The genetic environment and phenotypic changes were highly significant for milk productive traits.

The phenotypic and genetic changes were significant for lactation length and the litter size weight at birth, respectively.

On the other hand, the genetic and environment changes for the length of lactation, environment and the phenotypic changes of litter size weight at birth, and genetic, environment and phenotypic changes of litter size weight at weaning trait were not significant.

The values of genetic changes were (1.199±0.306, -0.003±0.002, -0.007±0.002, 0.004±0.025) for the studied traits, respectively during 2005 - 2010.

The genetic changes of milk production and litter sizes at birth and weaning were significant, whereas the values of genetic changes of lactation length were insignificant.

The study concluded that, the program of selection is effective for milk production and litter size weight at weaning traits, and ineffectiveness for the length of lactation and the litter size weight at birth traits in sheep flock at ACSAD Research Izraa Station during the study period.

Therefore, the selection strategy should be modified for the studied traits.

Consequently, the study recommended the reliance of the breeding values at animal selection, in addition to phenotypic traits.