Fish Oil as an Omega-3 Source for Horses
Q: I understand that some people feed their horses fish oil or fish oil supplements for the omega-3 fatty acid benefits. I don’t understand why you would do that when horses are herbivores and don’t eat fish. Plus, I’ve read that some fish oils are high in environmental contaminants and that fish stocks are in decline, which doesn’t make it sound like a good idea. What am I missing?

A: Indeed, horses do not eat fish as part of their natural diet, although horses in Iceland are sometimes fed salted herrings in winter as a way of providing protein. Owners providing their horses fish oil, however, are not doing it for the protein, because the oil doesn’t contain protein. Rather they’re doing as a way of providing supplemental omega-3 fatty acids.

Long-chain poly-unsaturated fatty acids are essential fatty acids (EFAs), which horses require in their diets, and are often referred to as omega-3 and omega-6 fatty acids. In other species the commonly recognized EFA’s are linoleic acid (LA, 18:2, n-6) and linolenic acid (ALA, 18:3, n-3). The guidelines in the 2007 National Research Council’s (NRC) Nutrient Requirements of Horses for feeding horses suggests a dietary intake of LA of 0.5% of dry matter intake per day. However, the NRC makes no such recommendation for equine ALA intake. Fresh grass tends to provide a good source of plant-based ALA, often in amounts greater than LA.

Research shows that supplementing diets with plant-based omega-3 fatty acids alters the fatty acid composition of cell membranes, as well as decreases the synthesis of inflammatory mediators. Feeding a pound of flax seed (a rich sources of ALA) per day to horses suffering from sweet itch was associated with a significant decrease in reactivity to the Culicoides extract used during intradermal allergy testing.

If you can achieve these apparent benefits by feeding plant-based omega-3 fatty acids, why feed fish oil?

This comes down to the type of omega-3 fatty acid in plant versus marine sources. While plants provide ALA, ultimately, the horse, like other mammals, needs eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). Desaturase and chain elongation enzymes within cells convert the ALA provided by plants to EPA and DHA.

The efficiency with which this conversion occurs varies by species. Evidently, the conversion occurs in horses because EPA and DHA are found in their cell membranes even when no dietary EPA and DHA are provided. Some research has suggested greater cellular response to omega-3 fatty acids when horses consume EPA and DHA directly versus when fed ALA. This is where fish oil comes in, because fish oil provides a direct source of both EPA and DHA. By supplementing EPA and DHA directly you cut out the need for the conversion from ALA. DHA is also provided by some sources of algae and might be found in some equine supplements.

Should you be supplementing your horse with fish oil or algae?

It depends. If your horse is in good health, has access to fresh pasture, and has none of the clinical signs commonly associated with inadequate fatty acid consumption in other species (such as dry coat, flakey skin, and hair loss) then providing additional omega-3 fatty acids is likely unnecessary. If your horse is fed hay as a forage source adding a plant based omega-3 fatty acid source might have benefits, because omega fatty acids levels in hay are lower than in fresh pasture, especially in hay of lower nutritional quality. Providing EPA and DHA sources directly might benefit horses with inflammatory conditions where you are trying to support a healthy inflammatory response.

What about contaminant exposure and environmental impact of procuring fish oil?

Given the concerns about contamination of fish oils with polychlorinated biphenyl (PCBs, chemicals that pollute waterways and are found in fish) and heavy metals (such as mercury), plus concerns about declining fish stocks, how can you protect your horse and the environment should you decide to supplement fish oil? The fish oil industry does have standards that good suppliers should be following.

  1. First ask about the fish oil source. Some sources are more sustainable than others. Menhaden fish typically come from sustainable fisheries in the Atlantic and Gulf areas. These fish have the added benefit of being top feeders meaning that they are less likely to be consuming contaminants. Additionally, they typically only live for three or four years, so they have less lifetime in which to accumulate contaminants as compared to some longer lived fish species.
  2. Ask manufacturers if they are compliant with California Proposition 65, which is possibly the United States’ toughest regulation for monitoring food contamination. Fish oils in compliance with this proposition will have been tested for mercury, PCBs, and other potential hazards.
  3. Ask if the fish harvests are overseen by the National Oceanic and Atmospheric Administration (NOAA). This administration track renewability of fish stocks by monitoring the type and age of fish harvested. Another organization that monitors fishing are Friends of the Sea. This group looks at sustainability measuring by catch rates (the rate at which unwanted species are caught along with the desired catch). Both NOAA and Friends of the Sea go audit fishermen on boat and in the port.

But what about algae?

If you decide that you would rather seek algal DHA sources consider reaching out to manufacturers with similar questions, such as:

  1. How are they harvesting algae?
  2. Are they harvesting it from wild sources or growing it in controlled environments? How do they insure what species are in the products you are considering?

Finally, keep in mind that the research that shows promise of supplementing EPA and DHA directly was done supplementing gram quantities of these omega-3 fatty acids. Many supplements out there include EPA and DHA on their ingredient lists; however, the amounts provided are frequently less than 1 gram a day and, therefore, might have little impact except on your wallet.