Purdue University Agricultural Experiment Station Lafayette, Indiana
Mimeo A. H. 225 April 25, 1958 (Final Report)
A COMPARISON OF SUPPLEMENT A (32$ PROTEIN) WITH A HIGH UREA SUPPLEMENT (58$ PROTEIN) FOR CATTLE WINTERED ON MATURE AND GREEN CORNSTALK SILAGE
T. W. Perry, Donald Webb, C. H. Nickel and W. M. Beeson (Conducted at Lynnwood Farm, Carmel, Indiana)
Many people have assumed that protein supplements for cattle should be evaluated on the basis of protein equivalent content. For example, it has been proposed that 1 lb, of a 48$ high urea supplement is equivalent in supplementary value to 2 lbs, of a 24$ or 32$ supplement. However, research has shown that there are other nutritional factors associated with a protein supplement besides protein per se. Also, research at Purdue (Mimeo A,H, 123) and at other experiment stations has repeatedly shown that not over 1/3 of the protein requirement of cattle should be supplied from a non-protein nitrogen source such as urea. Urea is an excellent substitute for protein when fed at the proper level and balanced with other essential nutrients. Even on high corn diets, replacing all of the protein with urea caused a depression in gain, decrease in feed efficiency, reduction in selling price and increased cost per unit of gain (Purdue A.H. Mimeo 144)•
This experiment was designed to determine:
(1)	The comparative value of Supplement A (32$ crude protein) with a high urea supplement (58$ protein) when fed on an equivalent protein and energy basis. In order to make the supplementation equivalent in protein and energy, it was necessary to feed 1.5 lb. of the high urea supplement plus 1.5 lb. of corn—a total of 3*0 lb,—to be equivalent to 3«0 lb, of Supplement A.
(2)	The relative feed value of mature and green cornstalk silage for wintering steer calves.
Experimental Plan
Eighty head of Shorthorn steer calves, that had been purchased from a ranch near Folsom, New Mexico, at an average cost of S;p28.65 per cwt., were sorted into 4 lots of 20 animals each. The steers were started on the experimental rations on December 12, 1957, at an average liveweight of 561 pounds.
The treatments were as follows:
Lot 1 - Mature cornstalk silage ad libitum plus 1.5 lb. high urea supplement, 1.5 lb. ground shelled corn and minerals free choice•
Lot 2 — Mature cornstalk silage ad libitum plus 3»0 lb0 Supplement A and minerals free choice.