CENTENNIAL, Colo. — Supplementing cows during winter is a risk-management tool for cattlemen.
“We are trying to manage the risk of reproduction failure of not getting the cow bred,” said Tryon Wickersham, associate professor at Texas A&M University.
“Information helps us reduce the risk-management costs because the more information you have about your cows and forage, the better off you are.”
The best reason to supplement is to sustain body weight or improve body condition score, Wickersham said during a webinar hosted by the National Cattlemen’s Beef Association.
“Another reason is to increase body weight for cows that are too thin after weaning to add additional weight before they go into the winter season,” he said.
Cattlemen should consider three things — what nutrients the forage contains, how much forage is available and how much of the forage the cows are willing to consume.
“Also keep in mind performance goals,” Wickersham said.
Forage testing is essential, Wickersham stressed.
“Crude protein tells you how much is contained in the forage, but it does not indicate the value of the protein,” he said.
“Total digestible nutrients are an indicator of energy,” he said. “You can look at historical data for your region because sometimes that’s the best you can do and it’s better than no information at all.”
Generally, Wickersham said, “if you’re meeting their TDN requirements, you’re probably doing a pretty good job of their protein requirements.”
The requirements are highest at calving and early lactation, they decrease until the calf is weaned, which is when the cows have the lowest requirements, and then the requirements start to increase during gestation.
“After weaning, think about building body condition score when energy requirements are lowest because you get fairly good response to supplementation,” Wickersham said.
“With energy supplementation, we have to be concerned with substitutions,” he said. “If we feed greater than 0.5% of bodyweight as an energy supplement, we’re going to reduce the amount of forage they are going to consume.”
If the cattle are fed high quality forage, Wickersham said, don’t feed supplemental protein.
“The substitution becomes 1-to-1, so for every pound of energy supplement, you’ll decrease forage intake by 1 pound,” he said.
“With low quality forage, protein supplementation can double the intake of energy by cows,” he said. “When supplementing protein, we want to be as close to the requirement as possible because if you go above, you’re spending unnecessary money.”
Total Digestible Nutrients
Grazing corn residue can provide a good source of TDN to cows, said Mary Drewnoski, beef systems specialist at the University of Nebraska-Lincoln, who also spoke during the webinar.
“The majority of what cows eat is the grain, husk and leaf,” Drewnoski said. “The husk is a very good source of TDN, and the leaf is also decent at 43% to 45% TDN.”
For protein content, the grain is the highest at about 9%, husk from 3% to 4% and the leaf around 6%, the beef specialist reported.
“As the cows go through the grazing period, the plant parts that are the most digestible and have the most energy are harder to find so then you need to start supplementing them,” she noted.
Grain yield of the corn is tied to the residue, Drewnoski said.
“For every 100 bushels of corn in the field, you can graze a cow for one month,” she said. “And bred heifers will have 10% to 15% greater requirement than cows.”
Losses can occur if supplements are fed on the ground in corn fields.
“With dried distillers grains we can see significant losses of 40% waste,” Drewnoski said. “It is less with wet distillers grains at about 16%.”