| | A question often asked by producers is how many animals can run on a particular pasture. Planning before putting animals out is a great start in trying to set-up a successful grazing year and needs to be monitored, managed and adjusted as the season progresses.
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“Adjustments through the summer and fall may include: pulling some animals, adding more animals, or having a shorter or even a longer grazing season depending on your starting stocking rate, says Grant Lastiwka, Forage/Livestock Business specialist with Alberta Agriculture and Rural Development. “How many animals you can run is referred to as stocking rate. The other concern is the pasture carrying capacity. By asking yourself a few key questions and conducting a pasture walk, you can more wisely estimate the correct stocking rate and length of the grazing season to balance forage production and desired use. This is referred to as carrying capacity.
“Set yourself up for success. Knowing pasture carrying capacity is crucial when determining animal numbers for a given length of time. While this is just one part of a whole grazing plan that can have many twists and turns . . . it is possibly the most important element.”
Determining carrying capacity is easy if you have grazing records. Take the recorded grazing days multiplied by animal numbers and calculate carrying capacity. If there will be a similar animals this year, ask:
- is the pasture in good condition
- is moisture or fertility the same
- was previous cattle condition and gains satisfactory
- is the turnout date earlier or later
- do you want to graze longer
- what might be done differently
“If you do not have records, producers need to know the pasture size (360 acres), how long a pasture will be grazed (150 days), the size of the cows and what the calves are weighing (1450 lb. cows and 200 lb. calves),” Lastiwka gives as an example. “By fall, calves will probably be about 500 lb., so on average a calf weighs 350 lb. If you calculate this out, 1450 plus 350 equals 1800 lb. of animal consuming about 2.5 per cent of body weight requires 45 pounds of forage a day. Intake is variable and can make for a great discussion. On an overgrazed pasture, 1.0 per cent of body weight can be consumed. When moved to a new pasture with 6 to 10 inches of new growth for a short time up to 4.0 per cent of body weight can be consumed.”
If the pasture is not in as good condition as you would like, Lastiwka recommends running fewer cattle or grazing for fewer days to allow this pasture to recover. Carrying capacity should always be a conservative estimate.
Using 330 acres for this example, the producers needs to know what the estimated forage yield would be if baled, or what height would it grow to. While this is a challenge, by looking at it a few different ways, a reasonable guess can be made. If it is a mixed pasture in reasonably fair condition which if left to grow all year would probably be about 10 inches in height, then an educated guess would be 250 lb. of dry matter/acre/inch of height giving a yield of 2500 lb.
“In continuous grazing we aim for 40 per cent use of growth, says Lastiwka. “The rest gets trampled, wildlife eat some, some is not used, and some is grazed severely and repeatedly (overgrazed). If rotational grazing is used that is balanced to carrying capacity, following by planning, monitoring and adjusting to desired outcome as you go, use rates can be higher and potentially not be harmful to the future productivity of the pasture. A 1000 lb planned use over 330 acres is 330,000 lb of forage if all areas are grazed. This does not happen in continuous grazing as some areas are grazed repeatedly and more severely, and some less while some not at all. But for planning this is sound of thought.
“Add 30 acres of open treed area where I would guess 800 lb. growth. Using 320 lb./acre to be grazed, this adds an additional 9,600 lb. if all areas are grazed. The calculations from here break down accordingly: 330,000 plus 9,600 equals 339,600 lb/45 lb/cow-calf pair/day gives 7547 days of grazing for a cow-calf pair. This then calculates to, 7547 days of grazing/150 days, means that the stocking rate is 50 cow-calf pairs for the 150-day grazing season.”
This should only be the initial planning in advance, and producers then need to determine if this stocking rate is reasonable. As the grazing season occurs, monitor results as they unfold. There may be chances to pull some animals if running short of grass, or graze longer if the pasture gets ahead of you.
“Having a much stronger estimate of stocking rates could keep your pasture more sustainable from year to year,” says Lastiwka. “However, planned grazing that adequately rests pastures in the active growing season is the best way to have a highly productive and sustainable pasture for years to come.
“Also keep grazing records this year, and this fall evaluate pasture condition and grazing patterns and severity and lack of use along with calf gains and cow body condition score are acceptable. Then make revisions to your plans based on what changes you would like to occur to the pasture and the animals. If you do this,
you will be better prepared next year to easily make sound and accurate stocking rate changes with more predictable results. Grazing longer is a goal of most producers in the cow/calf business. Balancing stocking rates and grazing days to forage production will result in a more sustainable carrying capacity from year to year.”
Producers who would like to go over their grazing plans can take advantage of their local Forage or Applied Research Association, by calling the Agricultural Research and Extension Council of Alberta at 780-612-9712.
Contact:
Grant Lastiwka
403-556-4248
310-FARM (3276) |
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