Seminar Report – Heat Stress
|March 10, 2014||Posted by Melinda under Uncategorized|
Seminar was presented by nutritionist Marty Adams from Triple crown feeds.
For this and all the posts that contain seminar content summaries, the information presented is my best recollection based on my notes taken during the seminar. I try to be very clear where I am editorializing and deviating from strict reporting of what was said and presented. Any errors/differences from what was actually said are mine alone, with apologies to the presenter.
I got the best compliment during this seminar. Liz and fellow blogger told me that she had been able to follow his lecture and recognized all the concepts from reading my posts on this blog!!!!! This made me happy because:
1. Someone else besides me reads the long rambling physio posts
2. It was written well enough it was understood and RETAINED.
3. Looks like I got most of it right (very nice to have independent confirmation of the stuff I post here that I’ve researched on my own).
OK. Moving onto seminar content.
Sweat is most effective when evaporation is highest (evaporative cooling). Evaporation is highest when temperature is high…but humidity is low. This is the concept beyond the various heat indexes that try to combine temperature and humidity into a figure that gives you an accurate representation of how hard your horse is going to have to work to dissipate heat.
Evaluating potential heat stress
Adams presented the “EAT” which is an abbreviation and as close as I can tell is the addition of temperature and humidity…..
Under 150 is considered OK. 150-179 is considered a “caution zone”. Values that are 180 are higher suggest you should NOT ride.
To continue to generate sweat you must have water. Thus, much of managing heat stress in horses is making sure water intake remains high.
I’m not going to go into the specifics of how much water is being lost and the specific gallons of water a horse must consume to replace it. It’s information we have covered over and over here, and I feel like if I present too much repeat information you are going to start skimming these articles and thus miss a helpful, new detail. I feel like specific numbers relating to how much water is being lost are mostly for shock value – to emphasize that just because your horse drained a 2 gallon bucket of water does NOT mean he’s even close to replacing total losses at an endurance ride. Think in big “muck bucket” type quantities and you have a better idea of how much water your horse needs to drink.
Adams did mention that conditioning is a huge factor in how much water a horse will lose.
45-65 degrees F is the preferred water temperature of horses. Providing water in an insulated bucket in the shade will help. My thought: might be worth temping the water being provided for your horse at vet checks or the trailer.
Like we’ve discussed before thirst is driven by a loss of body fluid (hypovolemia) and an increase in the sodium concentration in the plasma (if you take away the water and have the same amount of sodium, or if you are losing sodium slower than water than sodium concentration will rise). Recall from my posts last year that horses lose more sodium in their salt than humans (humans are better about “filtering” out the sodium before that fluid we call “sweat” ends up on the skin) so even though lots of fluid is being lost, some sodium is being lost too, so it takes longer for the sodium concentration to rise in the blood – thus triggering thirst.
Time for a bit of editorializing: This presentation was the same as previous ones I’ve sat through, as well as my other research on electrolyte supplementation. We talk a LOT about the function and importance of electrolytes and how inadequate the thirst mechanism is in horses, and how much water/elytes are lost……and we can talk about what electrolyte formulas make sense to supplement with – but the details of how and when to supplement elytes in an endurance horse during a ride are up for debate. There is a major gap between what we know about the physiology of sweat/electrolytes/hypovolemia….and how to translate that practically to our endurance horses in terms of electrolyte supplementation. Adams gave electrolyte brand and composition recommendations and some “maintenance” type recommendations but stayed away from specific endurance ride protocols. As we will discuss later (in the seminar report from “current research in endurance horses”) even having blood work that tells you electrolyte levels doesn’t give you the recipe for how to supplement electrolytes during a ride. It’s your choice how big a leap of faith you want to take when designing your electrolyte protocol. Take what is listed here as yet more information to add your knowledge base.
When choosing an electrolyte evaluate the label. In general the label should contain the following electrolytes in this order:
Cl > Na > K > Mg, Ca.
Ideally sodium chloride is the first ingredient and potassium chloride is the second.
The recommended profile is:
Less than 10% sugar/dextrose.
Recommended brands were:
Perfect Balance electrolytes
Stress Dex was the only specific brand called out as being mostly sugar based and not recommended.
Other recommendations to support electrolyte concentrations in the gut was an every day diet that was composed of 1.5% BW in forage and no more than .5% concentrate (fat, grain). He comes back to discussing diet more in detail later so we will leave it at that for now.
Ideas for HOW to supplement electrolytes – IMO these ranged from the obvious and unhelpful to the downright dangerous.
– Mix beet pulp in a gallon sized bag with water and put electrolytes (look back at Dr. Susan Garlinghouse’s recommendations for feeding electrolytes for a much better overview on how to successfully do this).
– Syringe it orally. Recommended buffering mouth and gut to prevent potential ulceration, which I agree with – but he recommends “mixing electrolytes in corn oil to help coat and protect the mucous membrantes”. PLEASE DO NOT DO THIS. Under no circumstances should you EVER attempt to syringe oil into a horse (or other animal’s) mouth. Oil does NOT trigger the swallow reflex like other solids or liquids and the horse WILL INHALE THE OIL. And once that happens you are SCREWED. At the convention I asked a couple other vets what their opinion was and one hypothesized that by adding electrolytes to the oil you make it taste vile enough that they would swallow it instead of inhaling it – but I would NEVER take that risk. And I wouldn’t recommend that any of my clients take that risk. Not to mention someone hearing this advice might think that since syringing oil in this case was OK it would be acceptable to do it in other instances without the “vile tasting” electrolytes. The other confusing thing is that he recommended CORN oil. Which NO ONE recommends feeding any more because of it’s pro-inflammatory properties. In fact Adams himself later in the presentation when talking about oils specifically recommends other oils besides corn. I have no idea what his thought process was of corn oil was in this context beyond that it can be more palatable than other oils (when fed in the feed).
– Giving electrolytes through an NG (nasogastric) tube. Ummm…..folks don’t try this either. Not to mention I think this is ILLEGAL at endurance rides, can cause trauma, and you better make sure you have that tube in the STOMACH instead of the lungs once you start pumping water – my thought is your horse is in trouble if you have to start giving elytes through an NG tube and maybe you should just call your vet?
Adams recommends giving electrolytes whenever the horse is going to be cold or stressed. Stress increases adrenal gland function which increases urination. “Add an ounce or 2 of salt a day to the horses diet”. He said if you aren’t using plain salt, add double the amount of electrolytes in order to get the amount of salt you want. For example, give 2 oz of electrolyte if your intention is to give 1 oz of salt.
I’m not sure what my opinion is on this. Salt is needed in the diet and I give free access to loose salt and a block. I also will throw in an once or 2 of table salt or electrolytes in her mash on our ride days (a couple times a week. I tend to use salt when I’m working up to increasing amounts in food for palatability because it’s cheaper, and using electrolytes in the week leading up to a ride or trip so that there are no big changes on race day. I’m not sure that these sort of “maintenance” doses actually do anything to prevent impaction colics etc if the horse has access to salt in other ways – I’m doing it more so that they can handle the taste at rides.
Remember back last year in my electrolyte posts where I mentioned that the horse has a HUGE reserve of electrolytes in it’s gut? Adam corraborates that and said that horses on high fiber diets have 75% more water and 33% more electrolytes in their GI tract than horses on a low fiber diet. Yet another reason to make sure that our endurance horses have a diet full of hay and grass and forage! There’s also more blood flow to the GI during exercise with a belly full of fiber. Increased blood flow is critical for the absorption of water, elytes, and energy. Don’t have good blood flow, won’t be able to extract all the goodies. Good blood flow also supports good function and prevents colic.
The only down side to a high forage/fiber diet is that digesting the diet does generate more heat – but Adams said this was minor.
Speaking of diets and it’s link to managing heat….
The “heat increment” (or HI) describes the amount of heat released into the body due to chemical breakdown of feed in the horses’s body.
Feed that has a very low HI are fats and oils. Adams states that there are many advantages to feeding fats, but a decreased metabolic heat is one of them.
– Fat also shifts anaerobic threshold, and less lactate is produced.
– It was emphasized that the horse has to BE WORKING for this “fat metabolism” advantage to occur otherwise your horses are just getting fat as you feed fat…..
– Carbs have an intermediate HI, but the more grain you feed, the more risk of colic. Feeding fat actually allows you to increase the total amount of fiber you feed because fat is increased in calorie density – thus you can feed more bulk on the forage side, and still get the high calories into the horse without sacrificing the fiber/forage portion of the diet (which is so critical to avoiding many many health related problems).
Fiber and protein have the highest HI (which was one reason Adams was not a fan of straight alfalfa diets – I’m not either for a multitude of reasons).
For managing heat or cold stress, Adams suggested feeding diets that are lower HI in the hot weather (emphasize fats), and high HI in the cold winters (lots of high and high fiber).
Specific Heat related issue: Thumps
He briefly touched on thumps
Common in electrolyte depleted horses (however – my thoughts here – thumps can happen for a variety of reasons and sometimes it doesn’t make sense – like at the very beggining of a ride in the cool of the morning on a well conditioned horse. So like anything in medicine, what is often cited as black and white can be more shades of grey. Just keep that in mind) and depletions of Cl, Ca, Na, and Magnesium. Especially losses of Ca and Mg.
Excessive dietary Ca intake has an increased correlation to thumps because high amounts of dietary Ca tends to decrease calcitonin activity. Calcitonin is the “thing” that is responsible to mobilizing body Ca reserves when extra/more Ca is needed. If the diet is so high in Ca that calcitonin never needs to do anything……it tends to chill out and not do what it’s suppose to when it’s needed. In addition to it’s potentially high HI, this was the other reason that Adams doesn’t like straight alfalfa diets (and I agree).
CORRECTION: please see the comments for a discussion on Calcitonin/PTH and it’s link to Ca. It appears he misspoke and/or put the wrong thing on the slides (or perhaps I heard wrong, but I remember copying it from the slides….I’m going to see if I can find his email and email for a clarification). Calcitonin is on the wrong side of the “axis” and if the excessive Ca in alfalfa is inhibiting something it’s PTH (increased Ca would actually be increasing secretion of Calcitonin). Will let you know if I hear back from him. Thanks to the reader who caught this error.
He touched briefly on fatigue, but we have talked SO MUCH about fatigue and recovery in the last couple of posts that I’m not going to bother rewriting it. He spent just a couple of minutes on very basic concepts and ideas that we have discussed here in detail – dehydration, lack of energy, hyperthermia etc. If you remember back to last year during the body water/electrolyte posts, we briefly discussed factors of fatigue in endurance horses and it was discussed in Hinchcliff that perhaps the limiting factor in endurance horses was their ability to regulate their electrolytes and acid base balance. This is a concept that will come up again when we get to the “current research in endurance horses” seminar notes, so stay tuned. Needless to say hydration, heat, and electrolytes all play a big role in horse (and human) fatigue.
Unfortunately these aren’t going to be new to any of you here. Travelling or pasturing horses during the cooler hours of the day/night, increasing ventilation, providing cool water for drinking and bathing, and how to sponge/scrape horses.
The tried and the true. I was a little disappointed that he didn’t touch on the importance of heat conditioning horses since I feel like there is a sizable chunk of research on it since it’s been an issue at some international competitions.
What I would love to see is some one present on some of the more less traditional or harder-to-quantify ways of cooling horses.
– clipping over the jugular
– clipping various parts of the horse’s body
– using ice water versus cool water and scraping versus adding rubbing alcohol to the sponge water.
– Those “cooling” blankets
In summary, he touched on hydration, discussed electrolytes and what the composition should be in an electrolyte product, and explained some potential dietary contributors to generating metabolic heat (and it’s link to metabolic issues like thumps). All these factors play into the big picture of “fatigue”. The presentation was wrapped up with some practical time-tested cooling tips.
Next seminar report coming up: Groin and pectoral muscle pulls.