The effects of performance, economy of gain and carcass quality of slaughter heifers fed three levels of crude protein using two sources of additional supplementation

The purpose of this experiment was to test the effects on performance, economy of gain and carcass quality of slaughter heifers when grown and fattened on a urea-limestone treated corn-silage ration in which the daily crude protein intake per head was 1=7 to 1,8, 1.9 to 2.0 and 2.1 to 2.2 lbs, and to test for any difference between cotton seed meal and urea as an additional supplemental source. In addition to corn silage ad libitum each animal received 6.0 lbs of concentrate per day during a 140-day roughage phase to provide three different levels of protein. Ration 1 consisted of only corn and provided 1.7 to 1.8 lbs. of crude protein per head per day. Rations 2 and 4 consisted of corn plus cottonseed meal and provided 1.9 to 2.0 and 2.1 to 2.2 lbs. of crude protein per head per day, respectively. Rations 3 and 5 consisted of corn plus urea and provided 1.9 to 2.0 and 2.1 to 2.2 lbs. of crude protein per head per day, respectively. After 140 days the heifers were full fed a concentrate ration of eight parts ground shelled corn to one part cottonseed meal. Animals were finished to a designated ultrasonically measured fat thickness of 10 or 8 mm. The results of this study showed no significant (P > .05) differences were produced in feedlot performance or carcass characteristics by these levels or sources of dietary nitrogen.