– Neighborly Advice –
Evolving nutritional needs
Adapting cattle supplementation to forage changes
By Josh Zeltwanger, Ph.D., ProTrition Ruminant Nutritionist
Spring through mid-summer is one of the most dynamic periods for grazing cattle in the Southeast. Cool-season perennial pastures change quickly from lush, highly digestible forage to more mature, fibrous feed. As these changes occur, the nutritional needs of grazing cattle shift. Understanding how pasture quality evolves during this period can help producers adjust supplementation strategies to maintain performance while maximizing homegrown forage.
During spring, cool-season grasses are typically in a vegetative stage. Leaf growth is rapid, digestibility is high, and crude protein concentrations can exceed the requirements of most beef cattle. At this stage, the rumen environment is supported by nitrogen and fermentable carbohydrates in the forage. In many situations, cattle grazing abundant spring pasture require little additional supplementation beyond a balanced free-choice mineral.
This period should offers opportunities to improve animal performance. Energy supplements that complement forage characteristics can increase average daily gains of growing cattle with little impact on cost of gains. When selecting energy supplements, producers need to be cautious. High-energy feeds often incorporate high-starch cereal grains or fats, which can impair fiber digestion, and should be fed at a lower rate — around 0.25 to 0.5% of body weight.
When offering free-choice supplements, such as tubs, manufacturers often rely on technologies that moderate intake, but producers should still monitor intakes relative to feeding directions on tags. Moderate energy supplements often rely on low-starch feedstuffs higher in digestible fiber. These are less likely to alter fiber digestion at higher intakes (1.0 to 1.5% of bodyweight) and can provide similar gains.
As the season progresses and grasses begin to mature, the nutritional profile of forage gradually shifts. Plants transition from leaf growth to stem production and seedhead formation. Fiber concentrations increase, lignin accumulates, and digestibility declines. This is why supplementation strategies often change as the grazing season advances, focusing more on protein supplements.
Producers have several options for feeding protein depending on labor availability and management style. Protein tubs remain popular because they allow cattle to self-regulate intake while providing a steady supply of nitrogen and energy sources such as molasses.
Protein plays a key role in maintaining forage intake and digestion, particularly when crude protein levels decline. Even when pasture still contains moderate protein levels, rumen microbes may benefit from additional nitrogen to fully utilize the fiber fraction of mature grasses.
Producers have several options for feeding protein depending on labor availability and management style. Protein tubs remain popular because they allow cattle to self-regulate intake while providing a steady supply of nitrogen and energy sources such as molasses. Tubs can be especially useful in larger pastures where frequent feeding is impractical.
In operations where performance is more closely managed — such as with stocker cattle — pellets or cubes are often preferred. These allow producers to deliver a more precise amount of protein and energy on a scheduled basis. Cubes and pellets also make it easier to incorporate ingredients like distillers’ grains, soybean meal, or other by-products, helping keep feed costs lower.
Regardless of supplement form, the goal remains the same: to complement nutrients supplied by pasture without interfering with rumen function. Matching supplement type and feeding rate to forage conditions helps ensure cattle continue to efficiently utilize grazing. While energy and protein often receive the most attention, mineral nutrition remains critical throughout the grazing season. Rapidly growing spring grasses can create mineral imbalances that increase the risk of grass tetany, making magnesium supplementation important early. As summer progresses, trace minerals such as copper, zinc, selenium, and manganese play essential roles in immune function, reproduction, and overall health during heat stress.
Ultimately, the key to successful supplementation during the grazing season is recognizing that pasture quality is constantly changing. Early in the season, high-quality forage does most of the nutritional work, and supplements offer an opportunity to improve performance. As plants mature and digestibility declines, producers should focus on supplements that support rumen microbes and improve forage utilization. By adjusting supplementation strategies to match forage conditions, producers can maintain cattle performance while making efficient use of forage resources.
For more information about effective supplemental feed programs, visit with your local Co-op feed specialist.