13 April 2010

5 minute read

While there are no easy management answers, if we review some basic plant growth biology and grazing principles, they may suggest some management strategies. Warning: this article may disrupt some conventional thinking.

We know that as spring progresses, grass growth will speed up. Our cool season pasture grasses produce about 60 per cent of their total dry matter production by early July. If your farm has a stocking rate that is matched to summer pasture production there is no way your cattle will be able to consume enough pasture forage to keep up with the flush of grass growth that will occur in late April through May.

Coupled with this explosion in grass growth is a physiological response to the shorter nights and longer days that triggers seed head production generally starting at some point in May. So not only is there more forage than can be consumed, but now the quality is steadily declining as a seed head is produced. It is very hard to fight this biology. Fast grazing rotations where hopefully the cattle just top the grass, combined with clipping the pastures to keep seed heads off are some standard management practices that are tried. In reality, these are not great solutions because cattle are not grazing uniformly and are not just topping the grass. They are grazing some places harder than others and there will be selective grazing resulting in uneven growth. Clipping pastures to keep the seed heads off can be very time consuming, not to mention the fuel and machinery costs that are incurred.

Instead of fighting the biology of spring grass growth, work with it. If your stocking rate is matched for summer production all of the pasture paddocks are not needed during the spring and early summer period. Paddocks must be dropped out of the spring rotation, and doing so will make it easier to manage the spring flush of growth. Which paddocks should be dropped out? Obviously any paddocks that had trampling and pugging damage during the winter and early spring are good candidates. This will give them time to recover, and/or for some paddock renovation and reseeding to be done. Next, drop those paddocks where it is easiest to get a tractor over. The goal is really to use the pasture paddocks with the most slope where clipping would be difficult.

The end result might be as much as 50% of your grazing acres dropped out of the spring rotation. The next thing that should be done is to divide those remaining pastures in half if at all possible. This will change stocking density, but not stocking rate. Stocking density is defined as the number of animal units being grazed per unit of land over a short time period. The stocking rate is defined as the number of animal units that are carried on a given unit of land over a long time period, generally a year. So, when paddocks are dropped out of the rotation, there is now the opportunity to graze more animal units, more pounds of animal per acre. This will accomplish a couple of things.

First, with more animal pounds on a smaller paddock acreage, a faster rotation is necessary. This will help keep plants in a vegetative growth stage. There may still be some seedheads, but seeds are not maturing before the plant is grazed again and the grass still has good nutritive value for the cows. Second, when stocking at more pounds per acre, cattle tend to be much less selective. Paddocks are grazed more uniformly, reducing the need to clip. Pasture forage utilization is increased.

Keep practicing good grazing principles, do not graze below a 3 inch height, and do not enter a paddock with less than 8 inches of growth. Remember if you have to err on when to pull cattle out of a paddock, it is better to leave more residual growth as compared to grazing lower. When grass growth begins to slow down and you can no longer pull cattle out of a paddock with 3-4 inches of residual and move to a paddock with 8 inches of growth, it is time to begin adding some of those dropped paddocks back in to the rotation to maintain these grazing principles.

The question will come up about what to do with those paddocks that are dropped out of the spring rotation. Options include taking a hay crop from them, clip them before they are worked back into the rotation, or just let them grow. The advantage of taking a hay crop is that it might be used later as a management tool, and fed in the late summer to protect paddocks from being overgrazed, particularly if a drought situation develops. The disadvantage is that there is some significant nutrient removal associated with a hay crop.

Clipping is another expense, but does allow nutrients to be recycled back into the paddock and clipping will maintain the vegetative quality of the paddock. If the paddock is clipped try to time it so that the regrowth will be at that 8-10 inch stage when the cattle enter to graze.

Letting the paddocks grow and mature could be an option if a heavy stocking density can be maintained and more pasture divisions added. Under heavy stocking densities cattle will select the best growth and trample the stemmy material in to the soil. When combined with the uniform manure cover that accompanies a heavy stocking density, this results in a mulch layer over the soil that conserves soil moisture, provides a favorable environment for nutrient recycling, and allows good regrowth potential. If the stocking density is heavy enough there would not be any need to clip the paddock after the grazing pass. If the stocking density is light enough to allow selective grazing, then it may be necessary to clip the paddock after this grazing pass. The stocking density that would allow this system to work is probably in excess of 200,000 lbs/acre. Think fifty 1200 lbs cows in a one-quarter acre paddock and you get the idea. This requires quick paddock moves; basically strip grazing across a pasture paddock. It is not something that the typical cow/calf grazier is going to try, but it is an option.

Most cattle graziers struggle with the spring flush of growth, seedhead development, rapidly maturing grass and uneven, selective grazing. Expecting different results this year without a management change is wishful thinking. Management options are available. The bigger question is are you willing to change your management?