Abstract
This study was conducted in the Department of Animal Production/College of Agriculture and Forestry/University of Mosul from 3/4/2022 to 3/2/2023, by using forty Awassi ewes aged between 3-5 years and with an average weight of (42 kg). The ewes were distributed into two groups depending on the structure of growth hormone genes (AA,AG) to study the effect of genetic structure on milk yield and composition by using PCR-RFLP technique. The growth hormone gene was detected by amplifying the gene based on the genome primer. The number of ewes that are born and have AA genotype were 17ewes, while those have AG gene and were 7 ewes only. Results revealed that ewes that have AA structure of growth hormone gene produced more milk significantly (p ≤ 0.01) the total milk yield during 90 days was 25.19 kg as compared with those that had AG structure for growth hormone which was 19.48 kg. This increase in milk production was accompanied with increase in milk fat significantly at the first and third months of lactation period. Otherwise, the other milk components of protein, lactose and solid non-fat were not affected by the difference in growth hormone genotype. We conclude from the results in this study that the genotype of growth hormone has an important role in causing changes in the amount of milk produced and its fat content in the local Awassi ewes, and this has an additional effect on the growth of lambs and its ability to survive to the weaning.
