Effect of High-Nitrate Consumption on Lactation and Vitamin A Nutrition of Dairy Cows

Abstract

Groups of dairy cows obtaining about one-half of their total digestible nutrients (TDN) from high nitrate corn silage 0.78% KNO~, dry basis) or from regular corn silage (0.40% KNO~, dry basis) with either 1.25% or 0.75% KNQ added to their diet dry matter continued to produce normal outputs of milk with normal fat, protein, and vitamin A content during a nine-wk period. There was no demonstrable effect of nitrate supplementation on hemoglobin, on plasma carotene and vitamin A, or on liver carotene and vitamin A. Cows of different milking levels secreted in milk 1% to 2% of the two to more than three million I. U. of vitamin A consumed as carotene with no demonstrable effect of the nitrate levels being consumed. The 24 cows were quite consistent in having 55 I. U. to 65 I. U. of vitamin A per gram of milk fat produced. There was no observed effect of the nitrate feeding on the reproductive performance of the cows. Milk cows fed good rations showed no evidence of adverse effects to sublethal nitrate intakes even early in the experiment.