Objective: The aim of this work was to investigate three different mutations; Fec-B, FecX G , Fec-G H at three candidate genes; Bone morphogenetic protein receptor IB, Bone morphogenetic protein 15 and Growth Differentiation Factor 9, respectively, in six sheep breeds reared in Egypt namely; Rahmani, Barki, Rahmani X Barki cross, Awassi, Awassi X Suffolk cross, and Ossimi and their association with litter size.Results: Genomic DNA of 132 sheep was investigated for the Fec-B, FecX G , and Fec-G H mutations by Restriction Fragment Length Polymorphism, Single-Stranded Conformation Polymorphism and DNA sequencing. The results revealed that all breeds did not carry Fec-B mutation. On the other side, the mutations of FecX G , and Fec-G H were detected in Rahmani, and Rahmani X Barki cross which is associated with the high twinning rate/litter size of Rahmani (1.28) and Rahmani X Barki cross (1.22). While, the average litter size for other breeds had almost a constant values rate over six parities, ranging between 1.00 and 1.04.

Body weights at birth, weaning and six-month and growth performance in lambs are economic traits that could be strongly used in sheep breeding objectives. Moreover, previous genetic studies recommended strong associations between these economic traits and polymorphisms in several candidate genes in different livestock species. The aim of this investigation was to study the polymorphism in IGFBP-3 and GH genes using DNA sequencing and RFLP, and their association with body weights and growth performance of Rahmani, Barki, Rahmani X Barki cross, Awassi/Awassi X Suffolk cross and Ossimi sheep breeds. Digestion of 654 bp for IGFBP-3/HaeIII yielded only one restriction pattern of 8 fragments in all animal groups revealing the absence of polymorphism also, DNA sequencing confirmed that. While, sequencing analysis of the amplified fragment of GH gene revealed polymorphism in nucleotide sequencing, and the amino acid sequences for GH gene of Rahmani were different from those of other breeds in 4 amino acids, while, each of Rahmani X Barki cross and Ossimi amino acid sequences were different in 3 amino acids. The genetic differences in GH gene coincided with differences in birth, weaning and six-month weights of the breeds under study. Thus, the current results suggest that body weights and growth performance of tested sheep breeds at different stages of growth are statistically affected by GH gene which could be considered as a candidate gene for growth in breeding programs.