To ward off fresh cow problems, consider adding a modest amount of chopped straw to far-off dry-cow rations, suggests Mike Hutjens, University of Illinois extension dairy scientist.
“The idea is to back down on energy density in the ration,” Hutjens explains. “If you can fill the cow up quickly by feeding a bulkier ration, she won't be able to eat the richer, high-energy feeds that can cause her to gain weight during the dry period.”
Weight gain sets her up for low dry matter intake, sub-par milk production and metabolic problems after she freshens, he adds.
University of Illinois nutrition researcher Jim Drackley recently reported how rations with varying energy densities can affect cows after they calve.
One group of cows in his study was given free-choice access to a corn silage-alfalfa haylage TMR during the early dry period. This ration's energy density was about 0.72 Mcal NEL/lb — fairly typical for corn silage-alfalfa haylage diets on Midwestern dairy farms.
For another group in the study, chopped wheat straw was added to the TMR to limit energy density (0.59 Mcal NEL/lb).
Bottom line: Cows on the typical, moderate-energy diet consumed an average of 160% of the National Research Council (NRC) recommendations for energy during the far-off dry period. They had lower feed intakes after calving than the straw-fed group, and also experienced more problems with ketosis, fatty livers and displaced abomasums.
Among the factors you need to consider when feeding straw as part of far-off dry cow rations:
Cows need some time (usually a week to 10 days) to adjust to a bulky, high-forage diet. Total intake can fall off while cows are making the adjustment. For that reason, you don't want to wait to introduce large amounts of straw into rations until cows reach the close-up dry period.
“If you don't get cows on straw far enough ahead of freshening, you could end up doing more harm than good,” says Hutjens.
It takes a fair amount of straw to lower energy in a corn silage- or alfalfa-based diet. Figure on 20-30% of total ration dry matter or 5-10 lbs of straw/day.
Different types of straw might work. Illinois researchers used wheat straw. “But there's no research showing that barley or oat straw wouldn't work as long as it's clean, dry and free of mold,” says Hutjens.
“Wheat straw has several physical characteristics (including a hollow stem) that make it well-suited for promoting mat formation in the rumen.”
TMR sorting can be a problem. Hutjens recommends a particle length of 2” or less for straw added to a TMR. Many conventional TMR mixers will have trouble reducing straw to that length or handling large volumes of straw.
“Most producers are chopping the straw in a tub grinder or forage chopper before they dump it into the mixer,” he notes. “Others are using vertical mixers.”
Cost is negligible. For a ballpark, figure cost of straw at 4¢/lb ($80/ton).
“You can find cheaper ingredients than straw,” Hutjens says. For example, he calculates corn silage at 3.5¢/lb.
“But you'd only be gaining pennies. When you consider the dollars you might lose in milk production or to metabolic health problems, it's really not worth your time to push the pencil too hard on this one.”
There's more than one way to do it. Hutjens notes that some producers opt to replace straw with chopped grass hay once cows enter the close-up dry period. Others continue feeding straw all the way through the close-up period and also maintain 1 or 2 lbs of straw in the fresh cow ration.
“It's a matter of figuring out what works for you on your farm and with your feeding system and management style,” Hutjens says. “If you're already getting high production, experiencing few metabolic challenges and seeing good dry matter intake before and after calving, I sure wouldn't tinker with anything too much.”