When biochar meets Tribulus terrestris: a natural approach to improving meat quality of rabbit (Oryctolagus cuniculus)

Rabbit meat is widely recognized as a nutritionally valuable and relatively sustainable source of animal protein, characterized by a high protein content, a low-fat level, and a favorable fatty acid profile. Growing consumer awareness of animal welfare, environmental sustainability, and health-related dietary choices has renewed interest in rabbit production systems and natural feed additives. Biochar (BC) and plant-derived bioactive compounds may influence nutrient utilization, growth performance, and meat characteristics; however, the effects of biochar and Tribulus terrestris (TT), particularly when used in combination, have not been sufficiently characterized in rabbits. Therefore, this study evaluated the effects of these dietary supplements on rabbit production performance, nutrient digestibility, carcass traits, and meat quality. Eighty New Zealand White rabbits were assigned to four dietary groups of 20 animals each, with 10 males and 10 females per group. The control group received a basal diet without additives, while the experimental diets were supplemented with 0.25% biochar (E1), 0.25% biochar and 0.1% Tribulus terrestris extract (E2), or 0.1% Tribulus terrestris extract (E3). The trial continued until 120 days of age. Six rabbits per group, comprising three males and three females, were selected for slaughter and carcass and meat-quality analyses. Growth performance, apparent nutrient digestibility, carcass parameters, muscle chemical composition, collagen characteristics, colour, pH, water-holding capacity, texture, and muscle fibre characteristics were evaluated. Dietary supplementation with biochar (BC) and Tribulus terrestris (TT) affected growth performance and selected meat quality traits in rabbits. The combined BC + TT diet resulted in numerically higher apparent digestibility coefficients for most nutrients; however, differences among dietary groups were not statistically significant ( p ≥ 0.057). Growth responses varied according to age and dietary treatment. At 56 and 70 days of age, rabbits receiving TT alone or in combination with BC had lower body weights than those in the control and BC groups ( p = 0.001). At 90 days, however, all supplemented groups had higher body weights and cumulative daily gains than the control group ( p = 0.033 and p = 0.036, respectively), while feed conversion ratio remained unaffected ( p = 0.658). Dressing percentage was not affected by dietary treatment ( p ≥ 0.900). Dietary supplementation modified muscle chemical composition, collagen characteristics, meat colour, water-holding capacity, and texture. The BC + TT group had the highest protein content and the lowest intramuscular fat content in the hind leg ( p = 0.023 and p = 0.047, respectively), while the TT group had the lowest hind-leg collagen content ( p < 0.001). Supplemented rabbits also showed higher loin cooking loss than control rabbits ( p = 0.001). In cooked meat, loin shear force was higher in the BC and BC + TT groups than in the control and TT groups, while hind-leg shear force was highest in the BC + TT group ( p < 0.001). The results show that dietary supplementation with biochar and Tribulus terrestris , applied individually or in combination, influenced growth performance and selected meat quality traits in rabbits. Dietary supplementation produced time-dependent effects on rabbit growth. Biochar administered alone showed the most consistent positive growth response, whereas the effects of TT, alone or combined with BC, varied across the rearing period. None of the treatments improved feed conversion ratio. The dietary treatments also induced measurable changes in muscle composition, collagen characteristics, meat colour, water-holding capacity, and textural properties. The combined use of BC and TT produced the most pronounced changes, including higher protein and lower intramuscular fat content in the hind leg, but was also associated with increased shear force and cooking losses in selected muscles. These findings suggest that biochar and Tribulus terrestris may represent promising natural feed additives in commercial rabbit production; however, their effects on meat technological and sensory properties require further evaluation.