The most common sheep breeds of Egypt are Ossimi, Rahmani, and Barki breeds. The latter one is well adapted to the challenging desert environment, characterized by food shortage and a high temperature fluctuation. Growth performance of Barki sheep has an important economic value in terms of minimizing the shortage of mutton meat in Egypt. Further, milk production is of great importance for feeding newborn lambs. Eight candidate genes, recently associated with production traits in different breeds, were used to study the effect of genotype on lamb growth and ewe milk traits. The examined genes were LEP, IGF1, DGAT1, STAT5A, PRL, CSN1S2, GHR, and GHRHR, of which one representative single nucleotide polymorphism (SNP) located in the coding region was selected for genotyping. Data from 251 Barki sheep were used in this study. Association analysis between SNPs and lamb growth traits identified rs420693815 of the LEP gene to be significantly associated with weaning weight and average daily gain. In ewes, significant effects on milk yield and composition have been estimated for LEP (rs420693815), STAT5A (rs161082816), PRL (rs422713690), and GHRHR (rs414991449). The results indicated that these genes might be considered as interesting candidates for further investigations to improve growth and milk performance in Barki sheep.

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wenty-three (11 dams and 12 of their offspring; 7 males and 5 females) Maghrabi camels (Camelus dromedaries) belonging to Camel Research Station, Matrouh, Agricultural Research Center, Ministry of Agriculture, Egypt were used to study growth performances (birth BW, weaning WW, yearling YW weights, average daily gain from birth to weaning ADG1 and average daily gain from weaning to yearling ADG2) and to identify the myostatin gene in the second exon polymorphism. The sequence of the myostatin gene was done using heterologous oligonucleotide primers designed from the publicly available sequence of the myostatin gene (NCBI GenBank). Results showed that the average BW (28.9 and 26.3 kg), WW (99.6 and 77 kg), YW (152.3 and 116.5 kg), ADG1 (392.7 and 281.5 g/day) and ADG2 (342.6 and 250.4 g/day) for males and females, respectively. While, phenotypic correlation coefficients between weaning and yearling weights were positive and highly significant (p<0.01) with an estimate of 0.973. Results of this study showed no polymorphism in the 230 bp region of the second exon of the myostatin gene. Thus, there was no relation between myostatin gene sequence and growth performance of Maghrabi camels. Therefore, a complete sequence of the myostatin gene and its relationship with muscle hypertrophy mechanism are needed to be used in genetic improvement programs in Maghrabi camels.

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