Supplementing a cow during the winter can give a big boost to the growing fetus, according to a University of Nebraska researcher. Beef Range Systems Specialist Aaron Stalker said cows can receive adequate nutrition through the winter months by grazing cornstalks or by grazing winter range with two pounds of supplement daily.
Stalker said a current project is underway in Nebraska that is fine-tuning how much protein supplement a cow needs. They are also evaluating if there is an interaction between the cow’s body condition and how much supplement they need.
Stalker said his research has shown that feeding a protein supplement during the winter has had little affect on pregnancy rates, but it has been shown to greatly improve the weaning weights on calves that are only fetuses at that time.
“Our data has shown that if we didn’t feed the cow protein supplement when she was pregnant, the calf was lighter at weaning,” Stalker shared.
The fetus is sensitive to what the cow is eating. Cows that receive protein supplement or are grazing cornstalks have changes occur to their endocrine system, which sends a message to the fetus that it is growing in a good nutritional environment so it can grow to its genetic potential, he explained. If the cow is not receiving a supplement or grazing cornstalks, the calf may not be receiving enough nutrition so it will compensate by being smaller in mature size and may not grow as fast.
Stalker said cows can meet the nutritional needs for themselves and their growing fetus by grazing winter range with two pounds of protein supplement, like distillers grain or alfalfa, per day. Stalker said different protein supplements are available, and ranchers should select a least cost supplement that is available in their area and is easy for them to feed.
Find a cornfield
A simpler way to meet the cow’s protein requirements through the winter is by grazing cornstalks. Stalker said the most important thing to consider when grazing cows on a cornfield is to use the correct stocking rate.
Based on a 1,200-pound cow and 175-bushel per acre corn, Stalker said 1.5 AUMs (animal unit months) per acre, or 45 grazing days per acre, on irrigated cornstalks should be sufficient.
Stalker said producers who are utilizing a cornfield that yielded differently or a smaller or larger cow can utilize the cornstalk grazing calculator at beef.unl.edu under “Learning Modules,” to determine the correct stocking rate. The cornstalk calculator is also capable of determining the total costs per head per day of grazing a cornfield so ranchers can easily compare it to other feeding methods.
At 1.5 AUMs per acre, Stalker said it isn’t necessary for ranchers to supplement their cattle on the cornfield.
“There is a big nutritional difference in nutrient content of the corn plant,” he explained. “The corn grain is the most nutritional part of the corn plant, which is why cows will go through a field and eat all the downed corn first. The husks are the next most nutritional part of the plant, followed by the leaves, the cobs and finally the stems.”
The husks are about 58 percent total digestible nutrients (TDN), Stalker said.
“You have to cut your meadow pretty early to get 58 percent TDN in grass hay,” he explained. “That is pretty good quality and about what they need to maintain their weight.”
The problem producers run into, Stalker continued, is grazing the cornfield too long.
“Cows selectively choose the higher quality parts of the plant first,” he said. “Only about 12 percent of a cornfield is husks. The leaves make up a third. What happens is, the cow starts out with a higher quality diet, and as time progresses, the quality of that diet decreases.”
“If you stock that cornfield even heavier, that decline will occur even faster. That is why stocking rate is so important,” he continued.
The amount of leaves and husks in a field is a function of corn grain yield. Stalker said about 16 pounds of leaf and husk will be produced per bushel of corn. From there, the cows will walk on some of the residue and defecate on some, so he figures the harvest efficiency for the cow at about 50 percent.
Since harvesting machinery has become more efficient, cattle have suffered fewer problems with acidosis from consuming too much corn, Stalker said. However, if more than eight bushels of corn per acre are left in the field, or there is spillage from the grain cart, producers may want to consider some type of intervention like cross-fencing or adding sodium bicarbonate to the water.
For more information about winter grazing, Stalker can be reached at 308-696-6707 or by email at email@example.com. Gayle Smith is a correspondent for the Wyoming Livestock Roundup. Send comments on this article to firstname.lastname@example.org.