Two experiments were done to study the effect of partial replacement of berseem hay by ensiled and dried sweet potato vines on the performance of growing rabbits. In the first one, 12 mature male New Zealand (NZW) rabbits with an average body weight of 2.5 kg and 8 months old were used to determine digestibility coefficients and nutritive values of berseem hay (BH), ensiled sweet potato vines (SPVS) and dried sweet potato vines (SPVH). In the second one, 50 NZW growing rabbits of 60 days of age were used in a complete randomized design experiment with five treatments. The first group fed commercial rabbit diet including 40% BH (control diet), while in the other groups fed diets contained 20% BH + 20% SPVS (group 2), 40% SPVS (group 3), and 20% BH + 20% SPVH (group 4) and 40% SPVH (group 4), throughout the 70 days of experiment. Results of the first experiment showed that the contents of crude protein (CP) and nitrogen free extract (NFE) of SPVS were nearly similar to that of BH. While, the contents of both extract (EE) and ash were higher and crude fiber (CF) content was lower in SPVS and SPVH and CP content was lower in SPVH compared to BH. The SPVS had significantly (P<0.05) the highest digestibility coefficients of all nutrients followed by SPVH, while BH had the lowest values. The total digestible nutrients (TDN) and digestible energy (DE) values of SPVS as higher significantly (P<0.05) than those of BH and SPVH, while digestible crude protein (DCP) value of BH and SPVS was higher significantly (P<0.05) than that of SPVH. In the second experiment, the contents of organic matter (OM) and CF tended to decrease, but the contents of NFE, EE and ash tended to increase in SPVS and SPVH diets compared with commercial diet. While, CP tend to decrease in SPVH diets than that of commercial diet and SPVS diets. Rabbits fed 40% SPVS diet showed significantly (P<0.05) the highest digestibility coefficients of all nutrients and subsequently nutritive values and total volatile fatty acid (TVFA's) concentration. While, rabbits fed commercial diet recorded the highest pH value and ammonia nitrogen (NH3-N) concentration (P<0.05). Rabbits fed 40% SPVS diet showed significantly (P<0.05) the highest final body weight, total and daily weight gain, total and net revenue and improvement, slaughter weight, carcass weight, dressing percentage, meat weight and percentage. Rabbits fed commercial diet showed the highest average daily and total dry matter (DM) intake and amount of DM/kg gain, feed cost and feed cost/kg gain. Rabbits fed 20% BH + 20% SPVS diet showed significantly (P<0.05) the highest DM and ash contents, while those fed 40% SPVS diet had the highest CP and EE contents.
