Hank Mayland and Dwight Fisher tell dairy farmers to cut forages in late afternoon for highest milk production. Mike English and Dan Undersander say morning is best, while Ev Thomas doubts that it matters much.

These researchers all tested the theory that afternoon cutting captures the most quality, because that's when sugar, starch and carbohydrate levels are highest. Their results varied, they suspect because of geographic differences in climate. More trials are under way.

“We certainly need to find out where it does and doesn't work,” says Mayland, a USDA-ARS soil scientist at Kimberly, ID.

Interest in afternoon cutting began several years ago, when Dayoon Kim, a Utah State University researcher, found that dairy cows produced about 8% more milk when fed afternoon- vs. morning-cut hay. In both cases, the hay was fed as 40% of a total mixed ration.

Then Mayland sent Idaho hay to Fisher and Joe Burns, ARS plant physiologists in North Carolina, for animal preference studies. In those trials, beef cattle, sheep and goats ate up to 50% more alfalfa or tall fescue if it was cut in late afternoon.

At least one other university study also has shown a quality advantage for afternoon cutting. But studies last year in New Mexico, Wisconsin and New York raise questions about the broad application of those findings.

Mayland points out that plants accumulate soluble sugars during the day via photosynthesis, then lose some of them at night through respiration. Although the daytime gain is small, cattle can detect it and will eat more of the higher-energy hay, he says.

That's probably true, says English, superintendent of New Mexico State University's Ag Science Center at Los Lunas. But he suspects that plant sugar levels change in response to more factors than just sunlight.

“I think it's a complicated issue,” says English.

Last summer, New Mexico researchers cut a one-acre alfalfa field 12 times — once every two hours — at each of five cuttings. They found big differences in quality among cuttings. Relative feed value (RFV) ranged from a little over 100 in the third cutting to well over 200 in the fifth. And in four of the cuttings, RFV was highest at 10 a.m.

English hesitates to put much credence in one year's data. But he suspects that mid-morning is the best time to cut hay in New Mexico. He figures sunlight is more intense there than in Idaho, so plant sugar content peaks earlier.

“I think plants open more quickly, fix sugars more quickly and shut down more quickly here,” he says.

Undersander, University of Wisconsin extension forage specialist, recommends morning cutting, too, but for different reasons. Late afternoon cutting lengthens the drying period by about a half day because not much drying takes place the first night, he says. That increases the likelihood of rained-on hay.

Morning cutting works better from a labor standpoint, too. Farmers usually are busy chopping or baling in the afternoon, says Undersander.

“So there are some practical reasons we don't want to go that way (afternoon cutting), unless there are some pretty strong indications that it's really better,” he states. “And we don't see that at this point.”

On several Wisconsin farms last summer, alfalfa was cut in the morning and afternoon at various times during the season. Samples were tested at cutting and after three weeks in storage as hay or silage.

The results showed little advantage for afternoon cutting. Non-structural carbohydrate levels increased during the day about half the time, but in only one of seven cases did the increase remain after three weeks of storage.

“I think that's probably due to our cool, cloudy weather,” says Undersander.

It's the same in the Northeast, says Ev Thomas, vice president of ag programs at the Miner Institute, Chazy, NY.

“In the Eastern and North Central regions and much of the South, we don't have as much sunlight intensity because of smog, pollution, humidity and clouds,” says Thomas.

Also, he says much of the research on afternoon cutting has been done with dry hay, where the crop is laid in wide swaths for initial drying. In July last year, he tested the practice on windrowed alfalfa chopped for silage at 40% moisture.

Sections of two fields were mowed between 7 and 8 a.m. and between 3 and 4 p.m. Initial forage tests revealed slightly higher sugar, starch and non-structural carbohydrate levels in the afternoon-cut forage. But the differences disappeared by the time the windrows were dry enough to chop.

Thomas figures the additional nutrients in afternoon-cut hay were lost to respiration during windrow drying. To reduce that loss, he suggests that silage producers who cut in the afternoon dry the crop in wide swaths.

But he's not excited about the potential benefits of afternoon cutting in his region.

“It fits dry hay production in the Southwest, but may not fit silage production in the Northeast,” says Thomas.

Sunshine Guarantees Energy Gain

The quality of forage crops always increases during sunny days, says Dwight Fisher, USDA-ARS plant physiologist at Watkinsville, GA.

“It's a guaranteed thing,” he says. “If you cut in the afternoon of a sunny day, the composition will show you an increase in digestibility, and that has been in the scientific literature for 40 years.”

The change is so subtle that it's difficult to measure. But animals can detect it, says Fisher, who did animal preference studies on afternoon- vs. morning-cut hay when headquartered at Raleigh, NC, in the mid-90s.

“The most surprising thing is that, not only are animals able to detect the difference, they recognize the forage when it's offered again alongside one that looks identical,” he says. “That's probably because this was an important aspect of survival for wild ruminants prior to domestication.”

While his earlier studies were with alfalfa and tall fescue grown in Idaho, Fisher and his colleagues recently evaluated afternoon cutting of switchgrass and other Southeastern grasses.

“The effect of afternoon harvest is still there, but it can be masked by rain during haymaking,” he says. “That's why afternoon harvesting is more controversial in the humid East than in the West”
Neil Tietz