Effects of dietary black cumin ( Nigella sativa L.) meal on performance, blood metabolites, and digestibility in a rice straw-based diet of fattening Garut lambs

Background and Aim: During black cumin oil production, black cumin meal (BCM) is produced as a by-product. This study investigated the potential use of BCM to partly replace concentrate in a rice straw-based diet of fattening Garut lambs. Materials and Methods: Twenty-eight heads of male Garut lambs aged approximately10 months with an average initial body weight of 20.7 kg/head (coefficient of variation 12.9%) were used. A completely randomized design was used to compare four different levels (0% [control], 5% [BCM-5], 10% [BCM-10], and 15% [BCM-15]) of BCM in rice straw- and concentrate-based diets on the performance of Garut lambs during 35- and 70-day feeding trials using seven replicates (n = 7). Blood metabolites and nutrient digestibility were also measured after the performance study. Results: BCM was rich in crude protein (36.8%) and tannins (21.6%). The BCM-10 and BCM-15 treatments increased (p < 0.05) average daily gain and feed efficiency compared with the control treatment in the 35-day feeding trial. All BCM treatments had greater dry matter (DM) intake compared with the Control at 70 days (p < 0.05). Furthermore, BCM-10 and BCM-15 had greater (p < 0.05) total protein, DM, and organic matter (OM) digestibility. BCM-15 had the highest (p < 0.01) blood triglyceride while BCM-10 tended to have higher (p < 0.1) blood glucose concentrations among the other treatments. Conclusion: BCM supplementation can partly replace concentrate and improve the overall quality of rice straw and concentrate-based diets, resulting in improved performance of fattening Garut lambs due to increased DM and OM digestibility, as well as protein and energy absorption. Approximately 10% of the BCM supplementation is suggested as the optimum level.