Abstract
Twenty Crossbred (Baladi× Brown-Swiss) male growing-calves, 6 to 8 months old, weighing an average of 115 to 125 kg were subjected for evaluating ZADO supplementary effects on blood biochemical parameters, antioxidant status, thyroid activity, and growth efficiency of calves under semi-arid conditions. The experimental units were pinned equally in two groups. The control (G1) fed the basal ration, and the 2nd, treatment group (G2) fed the basal ration + a daily supplement of 10 g ZADO (exogenous enzymes) calf(- 1) day(- 1) in a powder form mixed well with ration. The results showed that ZADO treatment reduced (P < 0.001) each of respiration rate (RR), rectal temperature (RT), serum malondialdehyde (MDA), urea, creatinine, and cortisol. Also, caused a marked decline in oxidized glutathione (GSSG) and alanine aminotransferase (ALT) activities. However, supplemented ZADO to growing calves diets improved antioxidant status including reduced glutathione (GSH) and superoxide dismutase (SOD) activities, total antioxidant capacity, serum total protein, albumin, and globulin, as well as IgG and IgM besides. ZADO enhanced (P < 0.01) thyroid activity, and feed efficacy parameters. Finally, supplementing growing calves with ZADO under semi-arid circumstances alleviates the heat stress effect, and leads to an improvement in calves' growth performance.