Альсалх Мохаммад Альмохаммад The paper presents some material on the extensive use of the Holstein breed in the Syrian Arab Republic to improve local breeds. The results indicate a positive effect of Holstein crossing with indigenous breeds of Shami and Okshi. Milk productivity of crossbred animals has doubled. Crossbred cows of different genotypes and generations have a greater live weight at birth than local breeds. Crossbred cows from crossing the Holstein breed and the Shami breed feature a pregnancy period of 284 days, and crosses of the Holstein breed and the Okshi breed are inferior to them and their duration of embryogenesis is shorter by 4 days. When assessing the relationship of the dry period duration, the following results were found: in the purebred Holstein breed, the relationship in the mother-daughter groups was weak and negative r = -0.131. In cows of the Shami and Okshi breeds and their crosses with the Holstein breed a positive low relationship was observed: r = 0.032, r = of 0.085, r = 0.06. The study of reproductive functions in cows of different genotypes found that significantly small age of one insemination in Holstein cows was 18.0 months (540 days), while the latest one was observed in cows of the Okshi breed - 22 months (660 days), the difference being 4 months. Indicators of milk yield vary in crossbred cows in contrast to the original local breeds, so in crossbred cows from Holstein producers and cows of the Shami breed milk yield was 4426 kg with a duration of embryogenesis from 276 days to 283 days, which is lower than that of Holstein cows by 2700 kg, but higher than that of the Shami breed by 2708 kg. Positive relationship has been determined between the live weight of cows at birth, the average indicator of the Okshi breed r = 0.340. The study has revealed positive correlation in the duration of the calving interval in of mother and daughter cows: r = 0.341.
Научная статья 
embryogenesis