• Journal of Animal Science and Technology
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• v.50 no.5
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• pp.705-712
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• 2008

Sixteen multiparous lactating Holstein cows were used to compare effects of supplementing 1)no additive(Control), 2)1.2% sodium bicarbonate(NaHCO3); 3)niacin(80g/d), 4)vitamin A+E (140,000IU+1000IU) on feed intake, milk production, milk composition and somatic cell counts during the summer months. Insofar as possible, treatment groups were balanced for lactation number and days in milk. Cows were fed a diet of 9.1kg DM of concentrate and 10.2kg DM of corn silage. Daily maximum air temperature in free stall barn was 35℃ for 3 days of the pretreatment periods and decreased gradually up to 27℃ during the treatment periods of 15days. Dry matter intake of corn silage was higher(p<0.05) for cows consuming NaHCO3 than those not consuming NaHCO3. Daily milk production for niacin and vitamin A+E supplementations resulted in significant(p<0.001) increase in milk production from 3 day of trials than control and NaHCO3. Milk fat percentage tended(p=0.09) to increase and milk lactose percentage was increased significantly(p<0.001) for cows supplemented with NaHCO3, niacin and vitamin A+E. Milk protein percentages was higher significantly(p<0.05) with supplemental niacin and somatic cell counts was higher significantly(p<0.001) with supplemental vitamin A+E. These data strongly suggest that supplementation of NaHCO3, niacin or vitamin A+E should be increased for improving milk production and mammary gland health of dairy cows under heat stress.