Monday, December 19, 2016
Analyzing Nimo's Diet: Fats and Fatty Acids
Here is the next installment of my nutrition series. Today, I'm going to write about what Nutrient Requirements of Horses has to say about fats and fatty acids (see chapter 3).
To start out with, what are fats and fatty acids? I thought I knew, but to be honest, after I read this chapter, I'm not sure I understand what fats are anymore. The best I could glean is that fat may be a term used to describe a solid substance that acts as a carrier for fatty acids. (If the substance is liquid at room temperature and above, it is called an oil.) Fatty acids can be categorized in different ways, but the categories of monounsaturated, polyunsaturated, and saturated are the ones I am most familiar with.
Sources of fat (and fatty acids) can be animal or plant based, although Nutrient Requirements cites studies that show vegetable sources are more palatable - think corn, coconut, and soy rather than lard, beef tallow, and butter (see p. 44). Feed byproducts like rice bran, wheat germ, and copra (shredded and dehydrated coconut meal) are also sources of fat.
With all these sources of fat, I thought it would be nice to know not only which sources horses think taste the best, but also which ones are likely to be more bioavailable. Nutrient Requirements doesn't address that question, although it does cite studies that show that fat is better digested when it is added to hay and grain (like top-dressing) versus encased in a pellet (like in a commercial feed) (see p. 45). I think that is an interesting result given how frustrating it can be to deal with fat/oil supplementation. It turns out that it may be worth the extra aggravation to top-dress a horse's meals with a fat source rather than rely on a commercial feed.
But how much fat? This is another area that makes me want to throw my hands in the air and walk away from this whole series of posts. I have read that significantly increasing a horse's fat intake over what might be considered a "natural" rate (whatever that is) can offer benefits, particularly to the performance horse. This section of Nutrient Requirements does touch on those benefits when it states, "fat supplementation has other potential benefits, including improved energetic efficiency (Kronfeld, 1996), enhanced body conditioned, diminished excitability (Holland et al., 1996a), and metabolic adaptations that increase fat oxidation during exercise (Dunnett et al., 2002) (see p. 44). Great, so how much fat does my horse need to take advantage of those benefits?
Good question. It turns out that some studies seem to show benefits, others show no benefit, and some even show a negative result. Or the studies were poorly designed. Or they had a really small sample size (like 4 horses). And when it comes to performance horses, "the results of studies examining the effects of fat supplementation in horses on athletic performance are equivocal" (see p. 48).
As if that isn't frustrating enough, when it comes to recommendations on what to feed, Nutrient Requirements basically just summarizes some studies that have been done and the main result and leaves it to the reader to make a decision. The conclusion seems to be that yes, horses do need some level of fat in their diets if for no other reason than to be able to digest fat-soluble vitamins, and that level might be above 0.5% of the diet. And you can probably feed your horse rations with 12%, 14%, or even 16% fat for short periods of time without any adverse reactions. Supplementing with extra fat may or may not improve your horse's glycogen stores for performance and conflictingly (yes, I think I just made that word up due to my irritation with the lack of definitive research), it may or may not lead to glucose intolerance.
And how about those essential fatty acids (you may know them as Omega-3 and Omega-6)? No recommendation. They are essential, so we know horses need them, but in what ratio is a question left unanswered. I know I've seen supplement companies discuss the benefits of using products, particularly those with Omega-3 fatty acids, but Nutrient Requirements can't even hazard a guess on how much of these life-giving substances are necessary, much less optimal. So where do the supplement companies' recommendations come from? I'm not sure. Until I read this chapter, I was under the impression that a horse needed maybe a 3:1 ratio of Omega-3 to Omega-6 fatty acids (and what about Omega-9?). But now, I'm not so sure. I know studies have been done for people, and maybe there is an attempt to extrapolate the results to horses, but I'm not convinced that is a good idea, given the lack of any definitive answers for horses despite the many studies that have been done.
And one thing that was not addressed at all, which might even explain some of the conflicting results in the studies, is that all sources of fat are not created equal. Things like corn oil and soybean oil are typically made as byproducts from non-food industries (like ethanol and biodiesel). Oils may be chemically extracted and even "deodorized," which is a euphemism for removing the odor so you can't tell the oil is actually rancid. I think it is fairly general knowledge now that oils used for human food should be cold-pressed when possible and at least not chemically extracted, and I think the same concern should apply to oils used for horses. And that makes any kind of fat supplementation quite expensive. A gallon of really good coconut oil may run more than $100 and other niche-market oils like camelina and hemp are still about $85 per gallon. Olive oil may be a bit less expensive, but the olive oil you get in the store may not be pure olive oil due to the infiltration of some kind of scheme to cut the olive oil with lesser oils to skim profits (there have been a couple of books - here's one - and a few news articles written about the problem, but there are no indications that things have improved as a result).
I've actually researched fat options off and on for many years. I've fed ground flax seed, chia seeds, shredded coconut, stabilized rice bran, corn oil, coconut oil, camelina oil, and high fat commercial feeds as a way of adding fat to Nimo's diet. I've kind of settled on a combination of three of those right now. I feed about a quarter cup a day of chia seeds (mostly because they seem to be similar to flax seeds, but don't require the grinding), about a half a cup a day of shredded coconut, and 1 oz of camelina oil as a top-dressing to post-ride mashes. I would supplement with the camelina oil more, but it's too messy for me to add ahead of time to Nimo's feed bags and it isn't the best choice to ask barn staff to handle either. If I was feeding at my own barn, though, I would definitely be exploring its use a bit more because it stays liquid at cold temperatures and isn't as prone to rancidity as other oils like flax and rice bran oil are, but still seems to have many of the same benefits. I wrote a bit about the comparison between flax seeds and chia seeds in this post, and I covered my choice for shredded coconut in this post. I haven't written about camelina oil yet because I don't feed it every day and I'm still kind of wandering around in terms of why I'm feeding it and what benefits it might be offering.
So once again, this is an area that really does need more research and I think the information in this chapter does highlight the need to question claims about the benefits of fat supplementation. Obviously, if you are doing something that works for your horse, keep doing it, but I wouldn't necessarily recommend forcing the issue, either. If finding a good quality source of fat is expensive or feeding it is messy, it may be that your horse isn't missing out that much if you don't feed it.