The effect of ascorbic acid and L-histidine therapy on acute mammary inflammation in dairy cattle.

Ascorbic acid and L-histidine were investigated as antioxidant therapies for acute mammary inflammation. Mastitis was induced in eight nonpregnant Holstein cows by intramammary infusion of endotoxin. Treatments were administered in a 4 x 4 Latin square crossover design with 1-wk periods between challenges with endotoxin. Four individual treatments, control, ascorbic acid only, L-histidine only, and ascorbic acid plus L-histidine, were applied. Two doses of 25 g of ascorbic acid administered intravenously at 3- and 5-h postendotoxin challenge increased milk production recovery (9% higher, P < 0.02) and tended to reduce the extent of rumen stasis. Two doses of 25 g of L-histidine similarly administered decreased plasma antioxidant activities 5.5% (P < 0.05). However, ascorbic acid and L-histidine had no effects on rectal temperature, heart rate, respiratory rate, and dry matter intake. The data suggested that ascorbic acid provided some potential benefit for recovery from acute mammary inflammation in dairy cattle.