Fatter Cows and Chickens from GM Crops

New methods of genome editing that make precise changes in the DNA of living organisms could have a significant impact on agricultural biotechnology. Earlier this month, Boston-area plant biotechnology company Agrivida said it will use genome editing to create varieties of crops that are easier for farm animals to digest, potentially increasing the productivity of farms raising such animals for food.

Agrivida will use a method of genome editing offered by Precision BioSciences, a biotechnology company based in Research Triangle Park, North Carolina. Precision BioSciences’s technology uses proteins called meganucleases that are engineered to glom onto specific DNA sequences and then cut the DNA nearby. Michael Raab, founder and president of Agrivida, says its effort will mainly involve altering plants so that farm animals such as cattle can extract more energy from them.

Raab, a 2006 MIT Technology Review Innovator Under 35, founded Agrivida in 2002 with a focus on engineering plants for use in biofuels. When that market was slow to take off, Raab says, Agrivida adapted its plant-modifying methods for animal feed.

One feed crop that Agrivida is developing is a strain of corn that produces an enzyme to help chickens extract more of the nutrient phosphorous from feed. Nearly all chickens in the U.S. are already given this enzyme as an additive to their diets. Those enzyme additives are typically harvested from microbes and added to animal feed. Agrivida is developing corn that produces the phosphorous-liberating enzyme within its own kernels, using a gene borrowed from a microbe.

Agrivida also wants to increase the amount of energy animals like cattle can get out of chewing leafy material or stalks, says Raab. Many cows in the United States are fed grains, which are energy dense but lack the fibrous materials that the animals need for their specialized digestive systems to be healthy. They need something to chew on, and ideally that fibrous material would offer nutrients as well, says William Weiss, an animal nutritionist at Ohio State University. “Corn stalk is very chewable, but there’s not much nutrition there. If we could improve the digestibility of that, then cows could chew it and also get energy from it,” he says.

To prevent the transgenic enzymes from damaging plants while they grow, Agrivida modifies its enzymes so they are dormant until they are activated by heat or changes in pH during processing.