Influence of probiotic supplementation and rabbit line on growth performance, carcass yield, blood biochemistry and immune response under hot weather

An experiment was conducted to investigate the beneficial effect of probiotic supplementation via drinking water on growth performance, carcass yield, blood parameters, and immunity of two rabbit lines during the summer season. In a 6-week probiotic supplementation trial, a total of 90 healthy growing rabbits having a similar weight (590.3±16 g) representing two lines (V-Line and Alexandria) were randomly allocated into three equal groups. Three levels of probiotics (0, 6.67 × 109 CFU/L and 13.35 × 109 CFU/L of Bacillus licheniformis) were administered through drinking water as non-supplemented, low, and high levels. A linearly increased body weight at 5 and 6 weeks of the experiment (p=0.01 and p<0.01, respectively) were noticed with the probiotic supplementation at high level. The same trend was noticed for the overall body weight gain (p=0.05). Probiotic supplementation did not affect carcass traits, except for heart and lungs, where the rabbits that received the high level recorded higher weights (p=0.01 and p<0.01, respectively). Probiotic supplementation showed a linearly effect (p=0.02) on the cell-mediated index after 24 h of PHA-P injection. Lower triglyceride concentration (p=0.04) was observed in the high group compared to the other groups. Concerning the line rabbit, although the Alexandria rabbits (Alex) recorded lighter body weight, they exhibited a better gain-to-feed ratio (p=0.05) compared to the V-line ones. Also, an increase in heart weight and spleen index (p<0.01) was found in V-Line rabbits compared to the Alex ones. Contrary, the Alex rabbits recorded a higher kidney weight (p<0.01) than that of V-Line. Overall, no difference was recorded between the rabbit lines in immune response. The beneficial effects of probiotic supplementation via drinking water on rabbit performance under hot weather were identified as improved growth performance, an enhanced lipid profile, and an early increase in cell-mediated immunity in both rabbit lines that received a high level of the probiotics.