The effects of rumen-protected ascorbate and salicylate on performance and blood parameters of fresh Holstein dairy cows under heat stress conditions

To study the effects of feeding rumen-protected ascorbic acid and salicylic acid on performance of dairy cows under heat stress conditions, forty four lactating dairy cows in early lactation were allocated in a completely randomized design with 4 treatments and 11 animals in each treatment for 30 days. Experimental treatments were: 1) control (diet without coated ascorbic acid and salicylic acid), 2) diet contained 30 g/d coated ascorbic acid, 3) diet contained 10 g/d coated salicylic acid and 4) diet contained 30 g/d coated ascorbic acid + 10 g/d coated salicylic acid. Cows were fed with salicylic acid supplement had a higher daily milk yield (51.47 kg/day) compared to other experimental groups (P<0.05). Feeding of coated ascorbic acid increased milk fat percent, glucose, BHBA, NEFA concentration and decreased somatic cell count compared to other treatments (P<0.05). Total milk's solids, energy and fat corrected milk and milk urea nitrogen were increased in coated ascorbic acid group compared to control (P<0.05). Blood urea concentration in coated ascorbic acid and salicylic acid group were less than control group (P<0.05). The results showed that feeding coated ascorbic acid and salicylic acid could improve performance of Holstein dairy cows in early lactating phase under heat stress conditions.