A new way to test alfalfa

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The California chapter of ARPAS, in conjunction with Sapienza Analytica LLC, presented results of a study proposing a new approach to measuring pure stand alfalfa hay quality at the American Dairy Science Association annual meeting this past July in Denver.

Currently, forage quality and marketing systems in California are fiber-based, a practice dating from the mid-19th century. Researchers are hoping to revamp this system to provide dairy farmers, hay brokers, alfalfa farmers and nutritionists with more information about alfalfa, including rate and extent of degradability.

"Our goal is to develop the methodology to better predict how hay will be utilized by the animal, and then price hay accordingly," says Carl Old, an independent nutritionist who is working on the study.

Alfalfa hay is currently bought and sold according to Total Digestible Nutrients (TDN). "Dairymen and hay growers use TDN and think they understand it. But the measurement doesn't tell you anything," says Old. It doesn't give any indication of how an animal is going to digest the feed or utilize the nutrients to make milk, he adds.

For example, hay harvested at the beginning of the season with a TDN of 57 doesn't perform in the rumen the same as hay with a TDN of 57 harvested later in the season, but the price for each is more or less the same. The different cuts of hay perform differently because the chemical nature is different, explains Old.

This is why the California Chapter of ARPAS is developing a model that uses near-infrared (NIR) spectrophotometry to predict alfalfa quality.

NIR looks at the chemical bonds of the material it's scanning and tells us about the chemistry of what it's looking at, says Old. The group plans to use NIR to predict digestibility and metabolizability of alfalfa.

Work has been under way at the U.S. Dairy Forage Research Center in Madison, Wis., where metabolizability studies have been conducted on nine lots of hay. These hays were chosen for their analytical diversity and range from the low 20s to more than 50 percent acid detergent fiber or ADF.

"Once we know the metabolizable energy of hay, we know how much milk a cow will produce," explains Old. The benefit to nutritionists is there will be less guesswork on their end. The group plans to release a transferable NIR technology that will be available to laboratories in the later part of 2011.

Read the paper presented at ADSA.

View the ARPAS Poster.



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