How much forage is enough?

Producers need to consider weight, class and breed of livestock in determining forage needs

VERMILION, Alta. — Grazing basics tell producers to balance livestock demand with available forage supply.

The concept seems simple enough, but that balancing act requires different plans depending on the plant community, geography and cattle behaviour.

“You need to graze in a sustainable way so you can come back and maintain that asset,” said Donna Lawrence, a range management specialist with Alberta Agriculture. “We want to be able to do that forever.”

The four principles of range management are:

  • Balance livestock demand with available forage supply.
  • Distribute livestock grazing pressure evenly.
  • Graze in the proper season.
  • Allow effective rest periods after grazing.

Stocking rates are designed to graze livestock and sustain pastures as well as leave material behind to hold moisture and build soil.

Carryover adds litter and is not a waste of forage, she said at a women’s grazing school held at Lakeland College in Vermilion.

“It is a tough sell sometimes.”

The rule of thumb is to graze half and leave half, but the formula changes in forested areas because shrubs and forbs do not regroup as fast as grasses.

“In forested pasture, to sustain-ably graze we plan on safely grazing 25 percent of the available forage production,” she said.

Healthy range is sustainable and competes with weeds, and the land should be able to withstand drought.

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Fertilizer is only effective in pasture rejuvenation if there are healthy plants to take it up. Otherwise, producers are just fertilizing dandelions, said Lawrence.

A better solution for overgrazed land is to provide more rest and change the times the plants are allowed to rest.

Grazing rates are based on animal unit months.

The standard animal unit is the amount of forage a 1,000 pound cow with or without an unweaned calf up to six months of age can eat in a month.

Older calves need to be treated as an animal unit because they are also grazing.

The standard animal unit must be adjusted to take into account different requirements for different kinds, sizes and classes of livestock.

“If you do not adjust the AUM for larger animals, then you are overgrazing,” she said.

The AUM calculation indicates the potential grazing between the fence posts, but that may not actually happen.

Also, it is important to remember that most modern beef cows weigh 1,200 to 1,400 lb. or more.

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Cows of this weight range can consume 31.2 to 36.4 lb. of dry matter, or 21.5 to 40 percent more than the a 1,000 lb. cow-calf pair.

Therefore, these larger cows would have a greater requirement compared with the standard animal unit if calculating these equivalencies based on amount of feed consumed.

Other types of stock, such as mature bulls and yearling steers, are assigned animal unit equivalents based on differences in size and consumption compared with the standard animal unit.

Grazing plans also need to be adjusted to account for accessibility to forage and livestock grazing preferences and habits. Cattle do not uniformly graze a pasture because there may be barriers such as a river, muskeg or invasive plants such as knapweed, which cattle won’t eat.

Cattle are creatures of habit and can be lazy. There are areas they prefer and areas they avoid so active management is needed to keep them moving and use the pasture more efficiently.

“We have to adjust for the lay of the land, their preferences and what we are going to do about it,” she said.

A manager should also consider consumption rates, trampling and spoilage effects when predicting the amount of required forage.

Alberta Agriculture offers updated grazing charts here.

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