Feasible feeding strategies for sustainable management of serve heat stress conditions: Effect of Milk Thistle extract on growth performance and health status of newly weaned rabbits

Abstract

The trail aimed to explore the effect of dietary supplementation of Milk Thistle (MT) extract on growth performance and health status of growing rabbits exposed to serve heat stress condition, considering the economic efficiency of supplementation. A total of 96 weaned male rabbits were divided into 4 groups (24 rabbits/group). The first group received the basal diet without any supplementation and served as a control (MT0), while 2nd, 3rd and 4th groups supplemented with MT at levels of 5 (MT5), 10 (MT10) and 15 (MT15) g/kg diet, respectively, for 10 consecutive weeks. Both of growth performance and feed utilisation were significantly enhanced by the dietary treatment, the optimum dose of MT was 12 g/kg diet for average daily gain, specific growth rate and performance index. However, it was 13 g/kg diet for feed conversation ratio. The polynomial regression analysis showed that the lowest values of rectal temperature and respiration rate were observed at doses of 11 and 13 g/kg diet respectively. The dressing percentage and the relative weights of liver and total edible giblets were significantly improved by the treatment (p = 0.0416, 0.0112 and 0.0032, respectively), maximising in the MT10 group. The MT10 and MT15 groups showed higher erythrocytes and leucocytes counts and lower levels of urea, creatinine and total cholesterol compared to the control (p < 0.05). Liver functions significantly enhanced in aforementioned two treated groups, the liver ultrastructure represented normal cytoplasmic organelles, and nucleus and mitochondria in MT10 group, while the MT15 group showed hepatocytes with dilated nucleus with most cytoplasmic organelles appeared well organised and normal except few small cytoplasms vacuolated. The levels glutathione, superoxide dismutase, catalase and total antioxidant capacity as well as immunoglobulin M, and immunoglobulin G significant improved in the MT-Treated groups compared to the control (p < 0.05). Economically, MT supplemented diets improved the net revenue of fattened rabbits during the summer season. In conclusion, the supplementation of MT extract at levels of 10 or 15 g/kg diet enhanced growth performance, feed utilisation, dressing percentage, hemato-biochemical attributes, immunity and redox balance of heat stressed growing rabbits during the hot season.

Keywords: Milk Thistle; blood metabolites; feed utilisation; growth; heat stress; rabbit.