Genetic assessment of litter size, body weight, carcass traits and gene expression profiles in exotic and indigenous rabbit breeds: a study on New Zealand White, Californian, and Gabali rabbits in Egypt

Rabbits are essential for commercial meat production due to their efficient growth and productivity, breeds like New Zealand White (NZW), Californian (CAL), and Gabali (GAB) rabbits offer unique genetic traits in litter, growth, and carcass traits. This study aimed to evaluate heritability (h(2)), genetic and phenotypic correlations (rg and rp) for litter size, body weight and carcass traits across California (CAL), New Zealand white (NZW) and Gabali (GA) rabbits. Along with exploring gene expression profiles of TBC1D1, NPY, AGRP, POMC, Leptin, GH, GHR, IGF-1, CAA, GPR, ACC, CPT1, FAS, and CART in the brain, liver, and meat tissues of different rabbit breeds. The breed genotype had a significant impact on litter size (LS), litter weight (LW), body weight at 12 weeks (BW12), and daily weight gain (DWG) traits. NZW rabbits displayed superior performance in terms of litter size and litter weight, while CAL rabbits recorded the highest values for BW12 and DWG. Heritability estimates (h(2)) were generally low for litter size (ranging from 0.05 to 0.12) and medium for body weight (ranging from 0.16 to 0.31). Both genetic (r(g)) and phenotypic (r(p)) correlations for litter size were positive and moderate (ranging from 0.08 to 0.48), while correlations for body weight ranged from 0.21 to 0.58. Additionally, CAL rabbits exhibited higher carcass traits compared to NZW and GA rabbits. In terms of breed-specific gene expression patterns, New Zealand White (NZW) rabbits displayed the highest expression levels of key genes related to energy metabolism (TBC1D1), appetite regulation (NPY, AGRP, POMC), nutrient transport (CAA), and G protein-coupled receptors (GPR) in both brain and liver tissues. Californian (CAL) rabbits exhibited superior gene expression of the ACC gene in brain tissue and GH, GHR, and IGF-1 genes in brain and meat tissues. Gabali (GAB) rabbits demonstrated the highest expression levels of TBC1D1, NPY, AGRP, GPR, and ACC genes in meat tissues. These breed-specific gene expression differences, combined with genetic evaluation efforts, have the potential to enhance reproductive and productive performance in rabbits, offering valuable insights for rabbit breeding programs and genetic selection.