Writer: D'Lyn Ford
LAS CRUCES - No plant found in nature contains proteins balanced for all of the amino acids necessary to keep animals healthy. That's why dairy cows need supplements along with their alfalfa rations.
Scientists at New Mexico State University are working to develop a more nutritionally complete alfalfa that may someday replace the need for a costly supplement.
To be nutritionally balanced, plants would need to produce a full complement of proteins containing 10 amino acids essential for animal life.
"One of the problems with alfalfa in terms of nutrition is that its protein is not very rich in one particular amino acid called methionine," said John Kemp, a plant molecular geneticist with NMSU's Agricultural Experiment Station. "So our project has been to improve the quality of the protein in alfalfa by raising the amount of methionine."
Tammy May, an NMSU animal nutritionist collaborating with Kemp, said methionine is important for muscle growth, particularly for growing animals. Proteins are among the most costly nutritional supplements, she added.
To beef up alfalfa's nutritional quality, NMSU scientists have turned to corn, which contains proteins with high levels of methionine. Using genetic engineering techniques, they are moving genes from corn -- called zein genes -- into alfalfa.
"By doing that, hopefully the levels of that deficient amino acid methionine will increase to the point that alfalfa becomes nutritionally a high-quality protein for the animals' feed," Kemp said.
So far, the research looks promising, he added. "Initially, the goal was to simply learn how to transfer these genes into alfalfa and have them produce this high-quality protein," he said.
Nearly five years ago, Kemp and NMSU scientists Suman Bagga and Champa Sengupta-Gopalan were successful on this front.
Now, they are working to transfer as many as three zein genes at a time into alfalfa so enough methionine is present to make a difference in cow diets.
"We believe we can produce enough to make a significant change, but those studies are ongoing," Kemp said.
A second area that the researchers are concentrating on is making sure the zein protein is in a form that's actually useful to the cows, which are ruminant animals with four stomach compartments. May said microorganisms in the rumen basically get "first dibs" on any food cows eat.
"To be of value to the animals, the protein must pass through the rumen unmodified so that it can go into the gut of the animal and be available as a source of protein and amino acids there," Kemp said.
Preliminary results indicate that the protein is stable through the rumen and can be digested by normal enzymes in the cow gut, he said.
The researchers are getting close to having a genetically altered alfalfa variety ready for testing, Kemp said. "We'll then need to grow that alfalfa out in the field for a while and begin to feed it to animals and to analyze whether it's actually making a significant improvement in their nutrition," he said.
While the zein research has been focused on alfalfa, the same genetic engineering techniques could be used to improve other forage crops. "In fact, one of our goals for many years has been to make this strategy available for human nutrition, and I think there are some very good possibilities there for improving crop plants we use for human consumption," Kemp said.
NMSU scientists are collaborating on the zein research with two private companies, Mycogen Inc. and Forage Genetics.
© 2013 New Mexico State University Board of Regents
NMSU - All About Discovery!