Submitted to: Professional Animal Scientist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 6, 2010
Publication Date: September 29, 2010
Citation: Phillips, W.A., Coleman, S.W., Chase, C.C. 2010. The case study: Effect of limiting access to winter wheat pasture on performance of Angus, Brahman, Romosinuano, and Reciprocal cross calves. Professional Animal Scientist. 26:561-569. Interpretive Summary: The protein concentration of winter wheat pasture exceeds the daily protein requirement of beef stocker calves by more than 100% and over consumption of protein results in greater concentration of nitrogen excreted in the urine, total nitrogen losses via leaching and gaseous emissions. The objective of this experiment was to determine stocker calf performance on winter wheat pasture when wheat forage intake was limited by cycling stocker calves on and off wheat pasture at 28-h intervals. A low-protein, high-energy supplement plus hay was provided when calves were off of wheat pasture and was used to reduced dietary protein concentration. Limiting access to wheat pasture by 50% was effective in reducing wheat forage intake and the amount of nitrogen excreted in the urine and has the potential to reduce the amount of nitrogen that winter wheat pasture grazing enterprises emit into the atmosphere. However, the cost of gain was greater for the Limit-grazed treatment than the Control group and gross receipts were reduced. A less expensive source of supplemental feedstuffs must be developed if Limit-grazing management is to be employed.
Technical Abstract: The CP content of winter wheat pasture exceeds the daily CP requirement of beef stocker calves by more than 100% and over consumption of N results in greater concentration of urinary N and total N losses via leaching and gaseous emissions. The objective of this experiment was to determine stocker calf performance on winter wheat pasture when wheat forage DMI was limited. In each of three years, stocker calves (BW = 251± 3.8 kg) were assigned to graze wheat pasture continuously (Control) or to graze wheat pasture 3.5d/week (Limit-grazed) plus confinement in drylot 3.5d/week. A total of 12 pastures were used (4/year x 3 years). Calves in the Limit-grazed group were fed supplemental feed and had ad libitum access to hay when not on pasture. Forage allowance was 1,501± 201 kg DM/calf at the beginning of the winter grazing season. Limiting access to winter wheat pasture decreased (P =0.03) ADG by 0.06 kg during the 120-d winter grazing season (November to March). During the 50-d spring grazing season (March through early-May), steers in the Limit-grazed group gained BW more rapidly (P = 0.05) than steers in the Control group (1.19 vs. 1.10). As a result, overall ADG for the 170-d stocker phase was not different (p=0.33) between the two management treatments. Limiting access to winter wheat pasture to 3.5 d/week increased carrying capacity of the pasture and decreased the amount of N excreted in the urine.