Cows may separate long hay in TMRs No doubt about it: Dry hay delivered in a properly balanced total mixed ration (TMR) can be a dairy cow's best friend, promoting proper rumen function, proper chewing activity, saliva production and fiber mat formation.

But dairy producers and their nutritionists need to tread carefully. In a nutshell: If it's not handled properly, dry hay can accentuate feed sorting and potentially set the cow up for a variety of problems linked to subclinical acidosis, including displaced abomasums and milkfat depression.

"In a lot of cases we've lulled ourselves to sleep thinking that if we just put some dry hay into the ration, we'll be covered," says Rod Martin, nutritionist with VitaPlus Corp. "But if all a cow does is sort the hay out, we're anything but covered."

Martin recently completed on-farm studies of TMR feed sorting on five Midwestern dairies. Using a Penn State forage particle separator, he measured sorts at six-hour intervals over 24-hour periods.

"On these farms and many others where we've made observations over the years, we've seen the same general trends," Martin notes. "If you feed higher quality and less hay, reduce particle size and feed a wetter ration, you'll have less problems with sorting."

Especially noteworthy, says Martin, was a herd that he first visited in May 1999. At that time, the manager was feeding 3 lbs of hay per cow as part of the TMR and cows were eating just over 73% of the long forage particles (measured in the top box of the separator). When Martin returned eight months later, the manager had reduced the amount of dry hay in the ration to 1.5 lbs/cow, added processed corn silage and raised the moisture level. Net result: consumption of long particles improved to over 90%.

Martin's checklist for reducing sorting problems related to dry hay in the ration:

- Reduce the amount of hay.

"You see it all the time," he says. "When producers run into a subclinical acidosis problem, one of the first things they do is add more dry hay to the ration. That just leads to more sorting. It's a paradox. Bottom line: If cows are sorting hay out, having 10 lbs of hay in the ration may not be any better than having 4 lbs."

- Process hay before it goes into the TMR. Running hay through a tub grinder or auger-type TMR mixer will shorten particle size and help curb sorting.

"You don't need material that's 6 or 8" long," says Martin. "Cows are less likely to sort out the hay if it's 2 to 4" long."

- Wet down the TMR before feeding. The drier the ration, the more sorting that goes on. Adding water, molasses or wet brewers grain will help hold the TMR together after it's delivered to the feed bunk.

"Water is definitely the cheapest way to go," says Martin. "Molasses might add a little stickiness but I'd probably only use it if I were short on corn, needed a sugar source or if the economics were justified."

- Feed more often. Pushing up the TMR several times a day or feeding two or three times a day will help ensure that cows eat the effective fiber component of the ration.

"We're seeing more farms mix up a large batch and leave half of it in the mixer for a feeding later in the day," says Martin. "There's some concern about mold problems during the hot summer months. But you can use mold inhibitors. And when it comes right down to it, what's the difference if the feed is laying in front of the cows or laying in the mixer?"