Effect of source of nitrogen in liquid supplements on the utilizaton of roughage by growing beef calves

Abstract

Six experiments were conducted to evaluate natural protein and urea as sources of supplemental nitrogen in liquid supplements for growing beef cattle receiving either costal bermudagrass or sorghum-sundangrass hay. Factors evaluated included average daily gain, liquid supplement intake as affected by type of roughage, roughage intake as affected by liquid supplement, nutrient digestibility and nitrogen balance of different roughages. Individually fed steers offered ad libitum intake of liquid supplements containing low protein (SMM), high urea (SMU) or high natural protein (SMP) consumed (P<.05) greater quantities of the SMM supplement. Steers consumed .37% body weight of both SMU and SMP. Pen-fed heifers consumed .32% body weight of the supplements containing a high urea level as compared to .26% body weight of the supplement containing high natural protein. Steers grazing on pasture consumed 1.0% of their body weight of SMM compared to .54% and .42% for steers fed SMU or SMP, respectively. Although none of the treatment differences for consumption of the SMU and SMP was significant, the trend was for greater consumption of SMU. Type of hay affected (P<.05) liquid supplement intake. All liquid supplement (SMM, SMU, and SMP) intakes were higher for steers fed sorghum-sudangrass hay than for steers fed coastal bermudagrass hay. Consumption levels of all liquid supplements increased non-significantly as roughage was restricted to 50% of that fed to steers in the previous period. Performance of pen-fed heifers of two age groups fed coastal bermudagrass hay ad libitum and allowed ad libitum consumption of high urea-containing liquid supplement or a high natural protein-containing liquid supplement was considered poor..