Snowy weather has swept southward through the Great Plains, reminding cow/calf producers in the region that the time for winter hay feeding has come or soon will be.
Hay or standing forage intake must be estimated in order to calculate winter feed needs of cattle, said Glenn Selk, Oklahoma State University Cooperative Extension emeritus animal scientist and managing editor of the university’s "Cow-Calf Corner" newsletter.
“Forage quality will be a determining factor in the amount of forage consumed,” he said. “Higher-quality forages contain larger concentrations of important nutrients, so animals consuming these forages should be more likely to meet their nutrient needs from the forages, plus cows can consume a larger quantity of higher-quality forages.”
Higher-quality forages are fermented more rapidly in the rumen, leaving a void that cattle can refill with additional forage. Consequently, forage intake increases. For example, low-quality forages — less than about 6% crude protein — will be consumed at a rate of about 1.5% of bodyweight on a dry matter basis per day, Selk said. Higher-quality grass hays — 8% or more crude protein — may be consumed at about 2% of bodyweight.
“Excellent forages such as good alfalfa, silages or green pasture may be consumed at the rate of 2.5% dry matter of bodyweight per day,” Selk said. “The combination of increased nutrient content and increased forage intake makes high-quality forage very valuable to the animal, not to mention the producer’s wallet and management options. With these intake estimates, producers can calculate the estimated amounts of hay that need to be available.”
Selk went through the following example of 1,200 lb. pregnant spring-calving cows with access to good-quality grass hay that tested out at 8% crude protein. Cows will voluntarily consume about 2% of their bodyweight, or 24 lb. of dry matter per day. Grass hays often will be 7-10% moisture.
“If we assume the hay is 92% dry matter or 8% moisture, then the cows will consume about 26 lb. per day on an as-fed basis,” Selk said. “Unfortunately, it is also necessary to consider hay wastage when feeding big round bales. Hay wastage is difficult to estimate but generally has been found to range from 6% to 20% or more.”
For the above example, assume 15% hay wastage. This calculates to approximately 30 lb. of grass hay that must be hauled to the pasture each day for each cow that is expected to consume the hay as the primary ingredient in the herd’s diet.
“After calving and during early lactation, the cow may weigh 100 lb. less but will be able to consume about 2.6% of her bodyweight in hay, based on 100% dry matter,” Selk said. “This would translate into 36 lb. of as-fed hay per cow per day necessary to be hauled to the pasture. This, again, assumes 15% hay wastage.”
Accurate knowledge of average cow size in a producer’s specific herd, as well as the average weight of the operation’s big round bales, becomes necessary to predict hay needs and hay feeding strategies, Selk pointed out.
“Big round hay bales will vary in weight,” Selk said. “Diameter and length of the bale, density of the bale, the type of hay and moisture content will greatly influence a bale’s weight. Weighing a pickup or trailer with and without a bale may be the best method to estimate bale weights.”