Reflecting on the 2023 growing season in relation to the forage supply in the Midwest, there’s one dominating theme: drought!

Lundy erika
Extension and Outreach Beef Specialist / Iowa State University
Reynolds beth
Program Specialist / Iowa Beef Center / Iowa State University

As the majority of the cow herds enter the late-gestation stage of production with rapidly increasing nutritional requirements, the lasting impacts of drought conditions become a priority and major influence on supplementation strategies.

Some of the first steps in formulating a third-trimester diet involves taking feed inventory, including quantity and quality of those forages and other feeds on hand. While counting bales and tons of silage can be straightforward, getting the quality right requires a forage analysis to account for unique growing conditions. For example, drought can cause alfalfa stem growth to be impacted more than leaf, increasing the leaf-to-stem ratio, improving quality. Grasses, on the other hand, tend to have root structures that are not as drought-resilient and pull on plant reserves for survival, accelerating lignification and resulting in a lower-quality feed that is higher fiber, less digestible and often lower in crude protein. For all plant species, rainfall timing and heat stress events can make plants not follow normal growing patterns.

Once you have that forage test in hand, the task of formulating late-gestation and calving season diets to optimize feedstuff use begins. For most, this involves a supplementation strategy that both bolsters diet quality to meet nutritional needs and/or stretches the existing forage supply.

Utilize the forage test results to determine what the most limiting nutrient is preventing the forage from meeting requirements. In most cases with low-quality forage, protein is the first limiting nutrient. In general, supplementation of a protein source generally meets the energy requirement; however, there are incidences where additional energy supplementation is needed. Feeding a protein supplementation (corn byproducts, soybean meal, etc.) results in more nitrogen to feed the rumen microbes, increasing forage digestibility and passage rate of the low-quality forage, ultimately increasing total intake. On the flip side, high-starch energy supplements (grains) tend to be a cheaper supplement source but can negatively impact forage digestion as the amount fed increases. In this scenario, the rumen pH and the microbe population shift to favor starch digestion, which tends to limit forage digestibility and decreases overall forage intake.


Low-quality forages are described as having high fiber, low crude protein and low digestibility. In drought years, increased feed waste is expected because of the generally lower-quality, less palatable forages. Therefore, limiting intake can be one of our most effective tools to reduce feedout waste. Unrestricted access to bales fed on the ground or in some feeders can result in waste as high as 40%. However, if only offering what cows will consume in one day, feed waste can be reduced to less than 10%.

This might include only unrolling partial bales or reducing the amount of hay rings that are filled at once. However, if feeding in feeders or rings, it might not be practical to only offer one day’s worth of feed at a time and still provide adequate head space per cow to ensure accessibility to timid cows, so aim for feeding less than three days’ worth of feed at a time. Another strategy to reduce waste utilizing bale feeders is to restrict the time cattle have access. A Purdue University study gave the cow herd access to hay in bale rings for four, eight, 12 or 24 hours a day and found restricting access to eight hours a day resulted in the best weight gain performance and reduced waste by nearly 20% compared to 24-hour access.

If supplemental feeds are being delivered separate from the main forage, the delivery method and frequency fed should also be considered. For mature cows, approximately 2 feet of bunk space per head is recommended when limit-feeding a supplement. If feeding a supplement on the ground or top-dressing unrolled bales, strive to reduce trampling. This can involve feeding in piles rather than in a line or utilizing a hot wire to create a fenceline to feed along. While sometimes impractical to deliver a supplement daily, there are still benefits of supplementation every second or third day to help meet protein requirements. This feeding strategy is most effective with low-starch feedstuffs like corn byproducts and soybean hulls but results in no reduction of forage intake. Protein tubs are a popular, low-labor option to boost protein content of the diet, but no forage displacement will occur and an increase in dry matter intake is likely. Compared to other feedstuffs, the protein in tubs tends to cost more per unit, but they do offer labor savings.

If the goal of supplementation is to offset forage consumption, the supplement needs to be fed at rates higher than 1% of bodyweight. Some data estimates that feeding at 1% of bodyweight would result in about 0.5 to 0.75 pound of forage displaced on a dry matter basis for each pound of dry matter supplemented. The displacement rate is variable depending on the fiber, starch and protein content of the specific feed due to interactions impacting rumen digestibility. For a 1,400-pound cow, 1% of her bodyweight would equate to 14 pounds on a dry matter basis, or 15.5 pounds as-fed if supplementing with soyhulls (90% DM). This supplement would be expected to displace approximately 7 to 10.5 pounds of forage on a daily basis.

Every feed and supplementation plan is unique, but each must be flexible. The majority of diets fed to bred cows rely on fiber dictating gut fill and when the cow feels full. These drought forages are higher in fiber, so will fill the cow earlier and ultimately reduce total calories consumed. A concentrated supplement is a useful tool to boost nutritive intake and keep herd performance satisfactory.