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New Mexico State University

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Los Lunas Study Suggests Local Alfalfa Best Harvested on Fall Mornings

LOS LUNAS - If New Mexico cows could order their favorite locally grown alfalfa, they would probably ask for hay harvested in October, preferably in the morning.


when the most nutritious and best-tasting hay was harvested in a preliminary study in the middle Rio Grande Valley conducted by NMSU's Agricultural Science Center at Los Lunas.

It's not a matter of finicky cows, but of alfalfa quality.

"The time of day and the time of year that farmers harvest alfalfa make a big difference in the nutritional quality of hay," said Mike English, superintendent of the Los Lunas center. "The amount of starches and sugar fixed in the alfalfa through photosynthesis changes as sunlight patterns change, so the amount of sugar in the plant is different in the morning and afternoon."

Increasing feed quality is important, both to improve its nutritional value and because cattle tend to eat much more if they are served high-protein, low-fiber alfalfa, English said.

The Los Lunas center initiated its study because research in Kansas and Pennsylvania showed that the highest-quality alfalfa in those states was harvested in the late afternoon or evening, after the sun had gone down.

"Since conditions here are very different from those areas, we decided to test what's best in New Mexico so that local producers have more practical information about the best times to cut their fields," English said.

The study took place on a one-acre field sown with WL 323, a popular alfalfa variety developed by Wisconsin-based WL Research Inc. Researchers harvested the field five times from May to October 2000. Each time, they took 12 cuttings--one every two hours.

A local lab tested the samples' relative feed value (RFV), a measurement that gives a high score for alfalfa rich in protein, sugar and starch and a lower score for hay laden with fiber.

"For the cow, the difference is like eating a cardboard box laced with a bit of protein versus eating a cardboard box filled to the brim with ham and cheese," English said.

The study demonstrated large differences in RFV between cuttings, with October producing the highest-quality hay and July the lowest. On average, the October samples had about twice the RFV, scoring 219 in lab tests as opposed to 110 in July, English said.

"By October, the temperature is much cooler so the hay tends to grow slower than in the hot summer months, and that leads to more starches, sugar and protein in the plant and less fiber," English said. October, May and September produced the highest-quality cuts, respectively, followed by June and July.

The study also showed that RFV generally improved if the hay is harvested in the morning, although the best time to cut got progressively earlier as the months rolled on because of longer days and increased direct sunlight.

More testing is needed to draw final conclusions because there's only one year of data, English said. In addition, more testing should be done in other parts of the state because local conditions vary widely, he said.