Co-Expression of Candidate Genes Regulating Growth Performance and Carcass Traits of Barki Lambs in Egypt

Abstract Sheep are considered one of the main sources of animal protein in Egypt while surviving harsh desert conditions. Therefore, the aim of present study was to link the gene expression profile of selected candidate genes with growth performance and carcass traits of Barki lambs. Thirty-eight Barki lambs were kept and fed individually after weaning till 12 months of age. Lambs were divided into 3 groups (fast, intermediate and slow growing) according to growth performance. Carcass traits were recorded directly after slaughtering. Three samples were taken from different body tissues (eye muscle, liver and fat tail) of each group, directly during slaughtering and stored at -80°C until RNA isolation. Real-time PCR was used to profile selected candidate genes (RPL7, CTP1, FABP4, ADIPOQ and CAPN3) and GAPDH was used as a housekeeping gene. The results indicated that, the final body weight was significantly (P ≤ 0.05) greater in fast (49.9 Kg) and intermediate (40.7 Kg) compared to slow growing animals (30.8 Kg). The hot carcass weight was heavier (P ≤ 0.05) in fast, intermediate (24.57 and 19.07 Kg) than low growing lambs (15.10 Kg). The blood profiles of T3 and T4 hormones showed no significant different among fast (1.1 ng/ml and 8.5 µg/dl), intermediate (0.6 ng/ml and 12.4 µg/dl) and slow growing lambs (1.0 ng/ml and 10.5 µg/dl). In addition, the total protein level was not differ in fast (5.94 g/dl), intermediate (6.52 g/dl) and slow growing lambs (6.9 g/dl). Genes involved in protein biosynthesis (RPL7), fatty acid oxidation (CPT1) and lipolysis (FABP4) were up regulated in fast and intermediate growing lambs in all studied tissues. While, gene-regulating lipogenesis (ADIPOQ) was expressed similarly in fat and liver tissues, but increased its expression in muscle of fast and intermediate growing lambs. Expression of CAPN3 was increased in fast and intermediate growing compared to slow growing lambs. In conclusion, the current study indicated a link between variation in gene expression profile in main body tissues with growth performance and carcass weight of Barki lambs, which induced by the genetic makeup however; this hypothesis required a large population for validation. In addition, the transcriptional profile of CPT1, FABP4 RPL7 and CAPN3 are linked with growth performance and carcass traits of Barki lambs, providing an evidence for the importance of co-expression of these genes in body main tissues involved in this process.