COW/CALF producers calculating their likely winter feed costs need to take into account the importance of estimating forage usage by cows, according to Glenn Selk, Oklahoma State University Cooperative Extension emeritus livestock specialist.
Selk said hay or standing forage intake must be estimated in order to make the calculations, and forage quality will be a determining factor in the amount of forage consumed.
"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," he said. "Just remember, cows can consume a larger quantity of higher-quality forages."
Higher-quality forages are fermented more rapidly in the rumen, leaving a void the animal can refill with additional forage. Consequently, forage intake increases.
For example, low-quality forages — those below approximately 6% crude protein — will be consumed at about 1.5% of bodyweight on a dry matter basis per day. Higher-quality grass hays — those with more than approximately 8% crude protein — may be consumed at about 2% of bodyweight on a dry matter basis per day.
"Excellent forages — good alfalfa, silages or green pasture — may be consumed at the rate of 2.5% of bodyweight on a dry matter basis per day," Selk said. "The combination of improved nutrient content and increased forage intake makes high-quality forage very valuable to the animal and the producer."
With these intake estimates, producers can calculate the estimated amounts of hay that need to be available.
Selk used the example of providing 1,200 lb. pregnant spring-calving cows with grass hay of good quality that tested at 8% crude protein. The cows will voluntarily consume 2% of their bodyweight, or 24 lb. per day. However, the 24 lb. is based on 100% dry matter. Grass hays often will be 7-10% moisture.
"If we assume the hay is 92% dry matter or 8% moisture, the cows will consume about 26 lb. per day on an as-fed basis," Selk said.
Plus, a producer also must consider hay waste when feeding big round bales. Hay waste is difficult to estimate, but studies have generally shown it to be between 6% and 20%, although it can be more.
In the example provided, assume 15% hay waste. Selk said this means approximately 30 lb. of grass hay must be hauled to the pasture for each cow on each day for which hay is expected to be the primary ingredient in the animals' diet.