ABSTRACT
The ameliorative effect of ascorbic acid supplementation and drinking chilled water on heat stress was studied on ram lambs. Twenty male ram lambs were randomly divided into four equal groups of five animals each and nearly similar in age and weight. The 1st group served as control (CTR), the 2nd group was given cold water (10-15 °C) without adding vitamin C (G1), the 3rd group was supplemented with ascorbic acid at rate 2.5 g/h/d (G2), the 4th group was supplemented with ascorbic acid in addition to the cold water (G3). All animals exposed to the same managerial and climatic condition during the complete experimental period. Body weight (BW) recorded at the beginning, then at biweekly intervals until end of the experiment. Feed intake, feed conversion efficiency, water intake per unit body gain and water intake per unit feed intake were calculated for each lamb. Rectal and ear temperatures, respiratory and pulse rates were measured. Blood plasma samples were analyzed for some blood constituents (total protein, albumin, globulin, glucose, total cholesterol, ALT, AST, calcium (Ca++) and potassium (K+)). Total protein, albumin, globulin, glucose, cholesterol and calcium concentrations were significantly higher (P≤0.001), however liver enzymes AST and ALT were significantly lower (P≤0.001) in the blood plasma of treated lambs (G1, G2 and G3) than those in control group. Cumulative feed intake, body weight gain, and cumulative water intake were significantly higher (P≤0.01) in G3 than other three groups. Rectal temperature (P≤0.05), respiration rate and pulse rate (P≤0.01) increased significantly, while ear temperature was not significantly affected by treatment. In conclusion, ascorbic acid supplementation ameliorates the adverse effect of heat stress during summer season. The body temperature, respiration and pulse rates have decreased as a result of the use of cold water or supply of ascorbic acid. Therefore, availability of cold water is paramount to prevent heat stress in sheep, especially during periods of extended hot and humidity.