Most cool-season perennials will reach peak forage quality soon, if they haven’t done so already. This downfall from the spring flush of fresh growth results in lower fiber digestibility and crude protein, which limits forage intake, especially for stocker calves grazing pastures and rangeland.

Supplementing stockers is one solution to combat the consequences of the summer slump. However, a supplementation program will generate different results from a performance perspective — as well as an economic one — depending on the forage system.

Paul Beck with Oklahoma State University Extension says that after fiber digestibility and crude protein of native species in the Sooner State skyrocket in the spring, forage quality peaks in May, and then it steadily declines. Introduced pasture forages like bermudagrass that are common in the South also demonstrate a drop in fiber digestibility over the growing season, but crude protein levels don’t fall as quickly.

Because of this, Beck notes stocker calves grazing native range can experience a 1-pound deficit in average daily gain from early summer to late summer as forage matures. The beef nutrition specialist suggests reduced crude protein is specifically to blame for this performance pitfall, so providing a high-protein supplement can help.

Oklahoma State University research shows that feeding stocker calves grazing native range 2 to 2.5 pounds of extruded distillers grain cubes per head per day — or feeding 5 to 6 pounds per head three days a week — can boost average daily gains up to 1 pound per day. This translates to about 2.5 to 3.5 pounds of supplement per pound of added gain, respectively.

The same approach to supplementation won’t be as effective for stockers grazing bermudagrass pastures, though, because bermudagrass can maintain crude protein levels up to 12% during the summer. When these calves were fed extruded distillers grain cubes at a rate of 2.5 pounds per head per day — or 5.8 pounds per head three days a week — average daily gain only improved by 0.5 to 0.7 pounds. That equals 5.3 and 3.5 pounds of supplement per pound of added gain.

“Because protein content of the forage is usually adequate for growing calves in the fertilized bermudagrass throughout the summer, steers don’t respond to added protein like they do on native range,” Beck states.

The stockers in the second group still gained weight because of the extra energy from extruded distillers grain cubes, which offset lower forage digestibility. However, the same supplements were not as effective or cost-efficient as when they were administered to the calves grazing native range.

Beck notes protein supplementation can still be highly profitable in either situation, and even in years with high input costs. However, he encourages producers to consider their primary forages and look at the big picture of production before drawing up a supplementation plan.

“The response by growing stocker calves may not be the same on different forages and pasture types, so the economics of the supplementation program need to be evaluated based on the types of pasture and supplement, the supplement cost, and the margins of the stocker cattle enterprise based on the current markets,” he asserts.