Effect of Source of Supplemental Nitrogen and Level of Nitrate on Feedlot Performance and Vitamin A Metabolism of Fattening Beef Calves

Abstract

Experiments were conducted to study the effect of source of supplemental nitrogen (urea, corn gluten meal, soybean meal) and level of potassium nitrate (0, 1.0, 2.0% KNO3) on performance and vitamin A metabolism of fattening beef cattle. Source of supplemental nitrogen or the addition of nitrate to corn gluten meal and soybean meal supplemented rations did not affect performance. Adding potassium nitrate to urea supplemented rations resulted in lower (P<.05) daily gains and feed intake. However, under conditions of equal feed intake, adding nitrate tended to increase gains of urea-supplemented cattle. Ruminal ammonia values were highest (P<.001) in cattle fed the urea supplemented rations and lowest (P<.001) in cattle fed the corn gluten meal supplemented rations. Addition of nitrate to the rations did not affect ruminal ammonia levels. Nitrogen source did not consistently affect liver vitamin A or carotene levels. A trend toward lower plasma vitamin A levels and higher plasma carotene levels accompanied the feeding of KNO3.