Hiba Albadee(1)*
(1). Directorate of Agriculture and Agrarian Reform in Aleppo, Department of Plant Production, Aleppo, Syria.
(*Corresponding author: Dr. Hiba Albadee. E-Mail: hibaalbadee@gmail.com).
Received:30/ 09/ 2023 Accepted:15 / 09/ 2023
Abstract:
In this study, Genetic parameters for total milk traits were estimated, which Heritability, repeatability coefficient, Genetic and phenotypic correlations. Besides, the effect of some non-genetic factors such as age of ewe, weight of ewe at lambing, type of birth, calving month and sex of lamb were evaluated on different milk traits (milk production, fat %, protein %, non-fat solids % and density) of Awassi sheep. For this purpose, 100 ewes of local Awassi sheep were used, in Minyan, west of Aleppo, during the period (2019-2021). Data were gathered according to the different levels of the main environmental variables that were thought to affect milk production and composition in the Awassi sheep conditions. The data were statistically analyzed using (SAS, 2012). Genetic parameters for milk traits were estimated by the REML (restricted maximum likelihood estimation). The Average values were about (113.14 kg) for milk production, (7.20 %) for fat, (6.35 %) for protein, (11.89 %) for non-fat solids and (1.036 g/ cm3) for density. In general, these values are largely within the natural range suggested by several researchers for Awassi sheep. The results of statistical analysis showed that age of ewe, type of birth and calving month had a significant effect on milk production and composition (P<0.01; P<0.05), while weight of ewe at lambing and sex of lamb had a significant effect only on milk composition (P<0.01), but they did not have a significant effect on milk production (P>0.05). Heritability and repeatability estimated for milk production were (0.26 and 0.40), fat % (0.10 and 0.21), protein % (0.31 and 0.38), non-fat solids % (0.11 and 0.34) and density (0.09 and 0.16), respectively. On the whole, Heritability and repeatability estimated in this study fall within the range of the results already published on Awassi sheep for the usual total traits (milk production, fat % and protein %), with the estimates for fat % being low. Our results, however, tend to be lower than others for certain foreign breeds raised under different management conditions. Genetic and phenotypic correlations between milk production and qualitative traits were clearly negative. For milk composition, both genetic and phenotypic correlations were positive and oscillated from (0.13 to 0.55) and (0.15 to 0.55), respectively. The highest estimates of the genetic and phenotypic correlations were found between fat % and protein % (0.55). This result is of great importance for the selection programs of Awassi sheep, as the genetic estimates of the percentage of fat were much lower than those recorded in other milk sheep breeds.
Key words: Heritability, repeatability Genetic and phenotypic, Awassi sheep.
Full paper in Arabic: pdf