A genetically modified organism (GMO) describes an organism that has had its genetic material (DNA that codes for different genes) altered. Genetic engineering results in the alteration of an organism’s DNA via mutations, insertions of genes or by deleting genes.
GMOs have played a very important role in science, such as GMO bacteria that can now produce insulin. GMOs have also played a significant role in the food system to improve productivity, such as tomatoes that were altered to delay ripening so they can be harvested and last long enough to get to the grocery stores.
Genetic modification is different from selective breeding, where we have sows that are selected to have more piglets, or cows that produce higher amounts of milk. GMO products are notoriously called “frankenfoods,” although research has suggested that these products are perfectly safe. As of 2017, the United States has 75 million hectares planted with GMOs, while Canada had 13.1 million hectares. These numbers increase every year.
Not only does genetic engineering affect the food chain for people, but also our feeds for our horses. Grains are typically genetically modified by the insertion of various genes that provide them with traits to increase productivity. For example, crops may be altered to increase the nutrient content of the plant, such as corn that has been modified to increase the amount of the essential amino acid lysine. Other crops may be modified to allow them to resist pests. Corn that is resistant to fungi and mould infections may have decreased production of mycotoxins that could cause equine leukoencephalomalacia, a deadly neurologic condition.
There are two main types of crop GMOs: Bt and Ht. The bacterium Bacillus thuringiensis (Bt) produces insecticidal proteins, and these genes have been added to corn and other crops to allow these plants to resist pests, therefore decreasing the need for insecticides. This is beneficial for the environment and decreases our horse’s (and our own) exposure to insecticides.
Some crops are genetically modified to be herbicide-resistant or herbicide-tolerant (Ht) so that specific herbicides can be added to crops such as corn, sugar beets and soybeans to kill off invading species and allow the desired crop to grow more efficiently. Specifically, glyphosphate resistance is a common gene added, which allows the crops to be treated with glyphosphate-containing herbicides such as Roundup®. Therefore, it is possible for crops to have residual glyphosphate on them. However, traditionally Roundup or similar products are used to clear a field before seeding, or early in crop growth, and therefore by the time a crop is harvested for feed, any herbicide should have been washed away into the environment.
While not common, some crops may be retreated closer to harvest in a process called “desiccating,” perhaps increasing leftover residue on the final crop. Oats and wheat are not genetically modified, but may still be treated with glyphosphate products prior to harvest.
Grasses produced for hay production including timothy, orchardgrass, etc., are not genetically modified. However, the legume alfalfa is genetically modified to be herbicide-tolerant. For several years, Canada did not have GMO alfalfa and “organic alfalfa” was a niche market; however, since the introduction of GMO alfalfa and because it is a flowering plant and there is cross-pollination, it is possible that all alfalfa grown in North America will be genetically altered over time. A positive note with this genetically modified alfalfa is that farmers can prevent the toxic weed fiddleneck from growing. Fiddleneck is a plant toxic to horses that can cause liver failure and death.
So are these feeds safe? In 2016, the Food and Agriculture Organization of the United Nations came to a scientific consensus that foods and feeds derived from GM crops have no greater risk to health than the conventional crop. Therefore, it is unlikely that GM crops have a negative effect on equine health, although there have not been direct studies to date.
The aspect that is potentially worrisome is the exposure of the horse to feed ingredients with residual herbicides or to glyphosphates such as Roundup. Rutgers University, the State University of New Jersey, monitors the use of herbicides on horse pastures and reports that for non-lactating horses there are no grazing restrictions for any of the herbicides (except for Roundup), although waiting 1-3 days is advised. We could presume a similar timeline is warranted for treated grains prior to harvest for horses. For Roundup, horses should avoid a pasture for 14 days if it was a spot treatment, and for 56 days if the entire pasture was treated. Ultimately, some residue of herbicides on plants is relatively common, although likely not harmful.
If an owner wanted to offer their horse a GMO-free diet, they should focus on grass hay or pasture and oats. This type of diet will, however, be low in protein, and because soybean meal is the key source of protein for horses, an alternative protein choice should be selected (peas are a good alternative). Oats are also lower in calcium than desired, and a strict grass hay/oat diet might lack other vitamins and minerals, so the diet would need to be balanced with supplemental nutrients. Oil could be added to the diet, but not canola or corn oil. Rice and rice bran are also good alternatives for horses.
There are some GMO-free commercial grain mixes available that are balanced with protein, vitamins, and minerals already. Some of the bigger feed suppliers in the US carry “GMO-free” or organic varieties (Triple Crown’s Naturals, for example). There are some smaller feed companies in Canada that also offer these feeds.
Of course, any kind of GMO-free or “organic” products will likely come with a higher price tag, so is it worth it? According to published science, there are no health consequences from the GMO feeds themselves, and any leftover herbicide on products is hopefully gone. For humans, it is easy enough to consume a varied diet and avoid the “dirty dozen” (most pesticide-laden produce) to minimize any risks from residual herbicides. Our horses, however, eat the same thing day in and day out – hay/grain/hay/grain – so it could be possible that they might get higher exposure than humans would, particularly if the diet was high in corn, soybeans, and alfalfa. Deciding whether or not to go GMO-free might also depend on the horse itself; for a pregnant or lactating mare or a growing horse, or a very valuable animal, the price of a non-GMO diet might be worth it.
The discussion on the safety of GMOs, Roundup, and the niche market for GMO-free grain mixes is likely to continue for many years. Genetic engineering may be helpful to improve the efficacy of land use, nutrition of the product, and in some respects could be better for the environment (ie. decreasing pesticide use). However, there is worry about potentially increased used of herbicides, which is not the best for the environment or the horse.
If you do try to go GMO-free, be sure to discuss your feeding options with an equine nutritionist to help you balance your horse’s diet.