Cow size, forage quality key winter feed needs
|By Kassidy Buse|
Winter is, or soon will be, upon us. For producers, this brings winter feeding needs to the forefront. According to Glenn Selk, emeritus extension animal scientist at Oklahoma State University, estimating the forage usage by cows is a key aspect in determining how much hay is needed to winter cattle.
In an article in OSU’s Cow/Calf Corner newsletter, Selk says that forage quality is an influential factor to consider. Not only does higher quality forage contain more nutrients, but it also leads to higher intake.
“Higher quality forages are fermented more rapidly in the rumen, leaving a void that the animal can refill with additional forage,” Selk explains. This combination of higher nutrient content and intake is valuable to both the animal and also the producer.
To put this in perspective, low-quality forages with about 6 percent crude protein (CP) will be eaten at about 1.5 percent of body weight on a dry matter (DM) basis each day. Higher quality forage with 8 percent CP will be consumed at approximately 2 percent of body weight. Even higher quality forage, such as alfalfa silages, will be consumed at around 2.5 percent of body weight.
From these estimates, producers can then calculate the approximate amount of hay needed for winter feeding.
Let’s say you have a 1,200-pound pregnant, spring-calving cow and a grass hay with 8 percent CP. The cow will voluntarily consume 2 percent of her body weight, or 24 pounds per day on a DM basis. Since grass hay typically has a DM content of 90 to 93 percent, the cow will consume around 26 pounds per day on an as-fed basis.
“Unfortunately, we also have to consider hay wastage when feeding big round bales,” Selk includes. He continues that hay wastage is difficult to estimate but is typically around 6 to 20 percent.
With the previous example, if we assume 15 percent hay wastage, approximately 30 pounds of hay per day will be needed.
Following calving and through early lactation, a cow may weigh 100 pounds less but can consume about 2.6 percent of her body weight in hay on a DM basis. Once again, with our 1,200-pound cow example, this equates to around 36 pounds of hay on an as-fed basis per day.
“Accurate knowledge of average cow size in your herd as well as the average weight of your big round bales becomes necessary to predict hay needs and hay feeding strategies,” Selk advises.
Big round bales vary in weight, which is affected by diameter and length of the bale, bale density, type of hay, and moisture content.
“Weighing a pickup or trailer with and without a bale may be the best method to estimate bale weights,” Selk offers.
Kassidy Buse was 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 is currently attending the University of Nebraska-Lincoln pursuing a master’s degree in ruminant nutrition.