A comparative study of growth performance and antioxidant status of rabbits when fed with or without chestnut tannins under high ambient temperature

The study was conducted to determine the effects of the inclusion of a natural extract of chestnut wood (Silvafeed ENC), rich in tannins, in the diet on growth performance and antioxidant status in growing rabbits under high ambient temperature (35 °C). A total of 120 New Zealand male rabbits (average body weight 1123 ± 13.5 g, 40 d old) were divided into three groups (40 rabbits per group) and fed a basal diet or the basal diet with 5 or 10 g of ENC/kg of diet (C, ENC5 and ENC10, respectively). Rabbits had free access to diets and water in an environmentally controlled room at 35 °C and 55% relative humidity during the entire period (21 d). On d 7, 14 and 21 of the trial, body weight and feed intake were measured and blood samples collected for assay of antioxidant indices. Liver tissue samples were collected on d 21 for assay of antioxidant indices. Results showed that ENC supplementation increased (P<0.05) average daily gain (ADG) in the first week of the trial. Compared with the control group, the ENC5 reduced (P<0.05) feed conversion ratio (FCR) and the ENC10 increased (P<0.05) average daily feed intake (ADFI). From d 8 to 14 of the trial, the ENC5 increased (P<0.05) ADG and reduced (P<0.05) FCR. In the last week, the ENC10 group showed a higher (P<0.05) ADG and lower (P<0.05) FCR than the control group. Compared with the control group, ADFI was reduced (P<0.01) by ENC5 treatment. For the overall period, ENC supplementation had a positive effect (P<0.05) on ADG and FCR. The final body weight of the ENC5 group was higher (P<0.05) than the control group. Furthermore, on d 7, the inclusion of ENC increased (P<0.05) superoxide dismutase (SOD) and reduced (P<0.01) malondialdehyde (MDA). The rabbits fed ENC5 had significantly (P<0.05) lower cortisol and higher (P<0.05) total antioxidant capacity (T-AOC) and glutathione peroxidase (GSH-Px) than the control group. On d 14, addition of ENC increased T-AOC (P<0.01) and reduced MDA (P<0.01). The ENC5 group showed lower (P<0.05) cortisol and higher (P<0.05) GSH-Px than the control group. On d 21, the rabbits in ENC-treated groups had higher (P<0.01) GSH-Px activities than rabbits in the control group. The rabbits fed with the ENC10 diet had higher (P<0.05) SOD compared with the control rabbits. In contrast, the opposite was true for cortisol (P<0.05) and MDA (P<0.05). On d 21, MDA was lower (P<0.01) with dietary ENC than without ENC in liver tissue. Hepatic GSH-Px activity of rabbits fed with the ENC10 diet was higher (P<0.05) than that of the control group. ENC supplementation seemed to have a positive influence on the growth performance and antioxidant status of growing rabbits under high ambient temperature.