Good forage pays during last trimester

The health and body condition of cows during late pregnancy is critical to their overall health and that of their calves. The body condition of a cow during its last trimester also affects subsequent reproductive performance.

Weather conditions and poor feed quality may lead to less than desirable body condition scores (BCS) during winter. Ken Olson, a South Dakota State University extension beef specialist, explains that cows going into their last trimester in good condition will hold a healthy weight better than those with a BCS of 4 or lower. Once in late pregnancy or after calving, it becomes more difficult to improve body condition score.

“An important issue to consider is the energy demand of winter cold stress,” Olson says. “Two weeks of 20°F below zero will take off one body condition point if the diet isn’t adjusted for cold stress. This is especially true for cows that are already thin.”

After assessing the BCS of the cattle, consider your forage inventory and quality. According to Olson, a cow late in gestation requires an adequate supply of a 50% to 56% total digestible nutrient (TDN) diet. If adequate grass or hay are unavailable, a variety of by-product feeds can make up the difference.

The beef specialist also recommends supplementing protein when needed. He explains that cows in late gestation need a diet containing 7% to 9% protein. Low-quality forages provide only 3% to 5% protein and will require supplementation. High-quality hay generally has an adequate protein content.

“A mature cow on winter range during her last trimester without supplement will lose one body condition point in about 40 to 50 days,” Olson notes. “Both protein and energy are deficient in dormant standing forage.”

High-fiber energy sources provide best options when energy supplementation is needed. These include products such as soy hulls, sugar beet pulp, and corn gluten feed. If protein is needed, Olson recommends oilseeds, oilseed meals, and by-product feeds such as fishmeal and distillers grains. Be sure to consider palatability when feeding by-products.

“It is best to start managing your cows’ BCS in the fall because this is the easiest and cheapest time to increase body condition,” Olson says. “Strive to have your cows at a BCS of 5 or better in late pregnancy. However, if weather or other conditions cause BCS to be less than desired as they enter the last trimester of pregnancy, feed management to obtain a BCS of 5 or slightly better by the time they calve will be critical to calf health and cow fertility during the following breeding season,” he concludes.

Michaela King

Michaela King served as the 2019 Hay & Forage Grower summer editorial intern. She currently attends the University of Minnesota-Twin Cities and is majoring in professional journalism and photography. King grew up on a beef farm in Big Bend, Wis., where her 4-H experiences included showing both beef and dairy cattle.