الفهرس 
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Abstract
SUMMARY
Three sheep breeds (Finn, Romanov, and Rahmani) and their crosses were collected from Sakha and Mahalet Mousa experimental stations in Kafer El-Sheikh governorate, Egypt. These stations belong to Animal Production Research Institute and Agriculture Research Center.
Sheep is one of the most important types of small ruminants for the production of meat as the main product and for the production of wool and dairy derivatives and its products. Twinning trait plays essential role in increasing the economic production of meat and increasing the number of herds of sheep.
It is noticeable that the Rahmani local Egyptian sheep are less productive in terms of twinning than the international exotic sheep (Romanov and Finn), which led to a need for genetic improvement of the local Egyptian sheep by crossing with the exotic Finn and Romanov sheep.
It was found that the proportion of twins in the Finn breed is about 2.8 and about 2.8 in the Romanov under Egyptian conditions. However, the proportion of twins in Rahmani is about 1.4. These proportions different resulted in crosses half or a quarter crossbred (1.6) of the station.
Therefore, this study aimed to make a comparison to assure which is the best crossbred with Rahmani breed (Finn or Romanov) in the animal stations after adaptation under the Egyptian production conditions. Crossing Finn and Romanov with Rahmani was done to study the genes responsible for the production of twins. The studied genes were growth differentiation factor 9 (GDF9), and the second was bone morphogenetic protein 15 (BMP15). These genes are among the genes belonging to Transforming growth factor β super family, and when mutation occurs in any of these two genes leads to an increase in the ovulation rate or the production of twin or triple lambs.
In this study, 96 ewes from both stations which belong to Animal Production Research Institute, Agriculture Research Center were used, including about 12 ewes for each breed and crossbreds. (Rahmani, Finn, ½ Finn ½Rahmani, and ¼ Finn ¾ Rahmani) from Sakha station and (Rahmani, Romanov, ½ Romanov ½ Rahmani and ¼ Romanov ¾ sheep Rahmani) from Mahalet Mousa station. These ewes were used to give birth for single, twins or triple of lambs. This study also took in consideration type of birth (single, twins and triple) of the dams (ewesor mothers). First, a study was carried out at the level of records for all ewes and their reproduction, then a study at the molecular level was carried out. Deoxyribonucleic acid (DNA) was extracted from the blood, then molecular studies using polymerase chain reaction (PCR) was done after selection of some samples (about 14 ewes) for the analysis of nucleic acid sequencing of the assigned genes.
The major results of this investigation could be summarized as follows:
1) An inventory was made of all the ewes’ records and the data that contains the breed type, date of birth of the ewes, type of birth, season and year of insemination and the number of production per lamb.Because twin trait is a quantitative trait that is affected by more than one gene, the following statistical analysis was performed for the traits and the interaction between them to determine their significancy.
2) Statistical analysis was carried out for all records of ewes from the different breeds and crossbreds under study. It was found that the type of breed and the insemination season had significant effects, and the interaction between these traits were highly significant P< 0.0001, followed by the breed and the year of birth which showed significance of P< 0.0005 followed the interaction between season and year of production (P< 0.002).
3) Sequencing was done and showed that there are differences on the level of GDF9 gene as follows:
On the forward level; 29 mutations were seen in ewes producing single and twins. The same results were found when comparing single and triple producing ewes (29 different mutations).
The most important variations were two single nucleotide polymorphisms (SNPs) that differentiate between ewes producing single and multiple birth.
On the reverse level; 5 mutations were found in ewes producing single and twins. While no mutation was reported for ewes producing single and triple.
4) The results of sequencing of BMP15 gene showed that there are differences in this gene as follows:
On the forward level; 17 mutations were found for ewes producing single and twins. While these mutations was less for ewes producing single and triple (9 different mutations)
On the reverse level; 28 mutations for ewes producing single and twins. And 26 mutations for ewes producing single and triple
• Data analysis showed a significant values for SNP6 (C,T) and SNP8 (G,T) for litter size and SNP7 (A,G) for type of birth in GDF9 gene. However, BMP15 gene showed six SNPs as follows:
SNP8 (A,G), SNP31 (A,C) and SNP36 (A,T) for litter size and SNP4 (G,T), SNP19 (G,T) and SNP39 (A,T) for type of birth.
In conclusion, this study indicated that Romanov crosses are better than Finn crosses with Rahmani in regard to twinning trait.