Supplementing short pastures

You could say there was a perfect storm coming into this spring. The combination of wet weather, cool temperatures, and less growing degree days has led to slow pasture growth. Low hay stockpiles have compounded the problem.

Where reduced forage availability isn’t enough to support grazing cattle, supplementation is required. This prompts the question, “What is the most efficient supplementation approach?”

Jeff Lehmkuhler, extension beef cattle specialist at the University of Kentucky, addressed this question in the May 2018 Off The Hoof Kentucky Beef newsletter. He offers the following considerations:

Grazing isn’t “free.” The energy needed to graze is greater than what is required for other natural activities such as standing or walking. “A cow grazing an acre would expend more energy than walking that same distance,” says Lehmkuhler.

Low forage availability. When forage dry matter (DM) dips below 2,000 pounds per acre or about 6 inches in height with 90 percent ground cover, animal intake will decline, which hinders performance. Maintaining the pasture sward at 3 to 4 inches high or greater will ensure there is around 1,100 to 1,200 pounds of DM per acre available, which will maintain forage intake at about 90 percent of normal.

Limited forage? Provide free-choice supplements. Note the word limited and not low. Digestive and metabolic disorders from overconsumption could become an issue if free-choice supplements are provided with somewhat reduced forage availability. Use free-choice supplements only when forage availability is not severely limited

Hay is the preferred replacement. Low-quality hay may reduce intake because it is more unpalatable than fresh forages; this isn’t necessarily bad. An intake of 5 to 10 pounds of hay per day can replace 25 to 50 pounds of fresh forage intake. If needed, add liquid molasses to bales to entice higher hay intakes.

Nutrient needs versus gut fill. Limit-fed supplements supply needed nutrients to cattle but don’t necessarily hinder DM pasture intake

“A supplement of mostly soyhulls, wheat middlings, and some corn gluten feed would likely have 78 to 80 percent total digestible nutrients (TDN),” Lehmkuhler explains. “Lush, lowly lignified pasture will have 65 to 70 percent TDN. For every 1.15 pounds of pasture forage dry matter, 1 pound of supplement is needed,” he adds.

“The exchange becomes more significant as quality lessens,” says Lehmkuhler. “Consider a mature pasture that has 58 percent TDN. One pound of supplement would replace 1.34 pounds of pasture dry matter.”

Rumen fill sensors can tell a cow to graze more even though nutrient requirements were met with the supplement. Supplements can also provide the extra energy that is needed to compensate for elevated grazing activity.

Maintain body condition. Spring-calving cows with a body condition score (BCS) of 5 should not lose more than one BCS between calving and breeding. Ensure cows calving in at a BCS lower than 5 do not continue to decline as they will be more challenging to rebreed.

Consider cost. Sometimes you pay more for convenience than the actual supplement product.

“A cube that can be poured on the ground with minimal feed loss may cost $300 per ton, but a soyhull-corn gluten mix may only cost $200 per ton,” Lehmkuhler explains. “You could lose a third of the mix due to spoilage and still breakeven.”

As the weather improves, pasture forages will make a comeback. This may be a short-lived problem, but these same principles can be used later in the season when extreme heat and drought cause forage dormancy.

Kassidy Buse

Kassidy Buse is serving as the 2018 Hay & Forage Grower summer editorial intern. She is from Bridgewater, S.D., and recently graduated from Iowa State University with a degree in animal science. Buse will be attending the University of Nebraska-Lincoln to pursue a master’s degree in ruminant nutrition this fall.