Lignin test a new venture

Ray Mueller
Now Media Group


With the introduction of low lignin trait alfalfa by three seed suppliers, Dairyland Laboratories has responded by devising a new wet chemistry test designed to determine the correlation between lignin and the amount of forage fiber that is typically not digested by dairy cows.

During the summer of 2016, samples of low lignin alfalfa being grown on the Randy Doro and Nick Van Wychen farms in Outagamie County will be tested for their portion of undigestible neutral detergent fiber and compared to existing data bases on digestibility, Dairyland's business development manager Dave Taysom told attendees at the county forage council's 2016 educational program and annual meeting.

Headquartered at Arcadia and founded in 1958, Dairyland Laboratories is equipped to perform well over 100 types of tests on soil, forages, feeds, manure, water, molds and mycotoxins, Taysom said. It has customers in 42 states, six provinces of Canada and 19 other countries.

Lignin fundamentals

Lignin is the natural element that provides the strength to a great variety of plants and enables them to stand, Taysom said. As the the second-most common organic compound on the Earth, it enables vegetation to capture carbon, trees to move water internally and plants to supply organic matter to the soil.

In the alfalfa, grasses and other forages fed to dairy cows, it is known that the fiber (lignin is a component of it) that is not digestible limits milk production, Taysom indicated. To address that phenomenon in alfalfa, plant breeders endeavored to introduce genetic traits which reduce the amount of lignin.

As a result, Pioneer, Alforex and Forage Genetics have begun to sell alfalfa varieties with reduced portions of lignin, he noted. The respective reductions in lignin for those varieties are 5, 7 to 10 and 15 percent.

With lignin normally accounting for only about 7 percent of the total fiber in alfalfa, it is very difficult to measure for the differences that a small percentage of lignin reduction would make, Taysom stated. He said that the lignin in the highly digestible brown mid-rib corn silage can be as low as 1.7 percent while that in mature grasses can be up to 10.2 percent.

Testing procedures

With its UNDF240 wet chemistry test, Dairyland's formula measures how much fiber is not digested in an in-vitro setting after 240 hours. Taysom acknowledged this is several multiples of how long it takes forage to move through a cow's digestive system but explained that the purpose is to check the correlation between lignin and undigested fiber.

It's well known that a dairy ration with a heavy portion of starch feeds by itself reduces the digestion of neutral detergent fiber because of the more rapid passage through the digestive system, he said. There is also some fiber that will never be digested.

The UNDF240 testing protocol can be applied uniformly to all feedstuffs and can therefore serve as a driver for dairy ration makeup. He said the wet chemistry test fares well on repeatability, is applicable for a wide range of testing and provides a very good correlation with the near infrared testing that was introduced in the 1980s.

Low lignin attractions

As a forage crop, log lignin alfalfa provides several other attractions for growers, Taysom said. Research on those varieties has consistently shown that the reduction in lignin allows for a longer cutting interval on alfalfa without sacrificing quality while also adding to the yield per cutting.

That extension on the cutting interval can be eight to 10 days, enabling growers the opportunity to harvest similar yields with no dire effect on quality with three cuttings rather than four per growing season. He noted that natural factors also affect the portion of lignin in alfalfa and other plants because cloudy days and cool temperatures reduce its production, while sunshine and warm temperatures increase it.