In a follow up to our November issue that discussed wheat pasture grazing, many areas are still waiting on a rain. Here's some calculations to help calculate available forage.
This year dry weather during the fall delayed planting and emergence of wheat, which will delay turnout of calves. Research indicates that forage intake and animal performance is limited when pastures have below 850 to 1,000 of forage per acre. The most success in a small grain forage grazing system is achieved if the start of grazing is delayed until forage is ready and grazing management allows for adequate leaf area for forage regrowth. Overgrazing and starting too early will limit animal performance and reduce total overall production of these pastures. If pastures are below this level, turnout may need to be delayed until pastures are ready.
• Wheat forage grows at 3 to 3.5 pounds of forage dry matter per acre for each growing degree-day.
• A growing degree day equals the average daily temperature of 40° F.
• If in a given day, the high temperature is 65° F and the low temperature is 45° F the average daily temperature is 55° F, so there are 15 growing degree-days.
• Wheat would be expected to produce 45 to 52 pounds of forage dry matter that day.
• So, 10 extra days of growth would be needed to get a pasture from 400 pounds of forage/acre to 850 pounds of forage/acre if these temperatures persist.
Setting stocking rates on wheat pasture in the winter has large impacts on performance of growing calves and can have large influences on productivity of pastures during the spring. Forage production and steer performance from 10-years of experiments were used to determine the response of ADG to initial forage allowance (lb initial forage DM/lb initial BW) on ADG during the fall and winter. The maximum ADG of 2.7 lb/day could be expected at 5.0 lb forage DM/lb initial calf bodyweight and ADG of 2 lb/day could be expected at an initial forage allowance of approximately 2.4 lb forage DM/lb initial calf bodyweight.
An easy rule of thumb is for wheat pasture there is 150 to 250 pound of forage dry matter per inch of plant height. To make the math easy, I use about 200 pounds of forage dry matter per inch.
• Pastures that are 6 to 7 inches in height would have about 1,200 to 1,400 pounds of forage dry matter per acre.
• A 500 pound steer should have 2,500 pounds of forage dry matter available at turnout (500 x 5 lbs DM forage allowance).
• So, about 2 acres of this wheat pasture should be adequate to meet steer performance goals.
• When forage allowance fall below 2 pounds of forage per pound of steer bodyweight, supplementation should be considered.