Wednesday, November 17, 2010

Feeding the boys: Part V

DISCLAIMER: I am not a vet or an equine nutritionist. This information is purely based on research I have done myself. Please do not mistake my research for actual advice on what to feed your horse. I'm just sharing my experiences so that other horse owners can have the information.

This is the fifth in a series on how I'm determining what to feed my two horses. For Part IV, visit here.

In the last installment, we figured out how much hay and concentrates, in pounds, I was actually feeding the boys. Here's the recap:
  • Saga was getting 15 lbs of forage and 9 lbs of concentrates (Purina Ultium), or a total of 24 lbs per day. That's within the range of 16.5 and 27.5 lbs that he's supposed to get, but it's an awful lot of concentrates. Plus, he still looked ribby, and his feet seemed to be increasingly sore on the Ultium.
  • Red was getting 15 lbs of forage and perhaps 1/2 lb of concentrates (Nutrena Lite Balance) daily. So he's well within the 13.5 to 22.5 lb range that we calculated for him, if a little on the low end. Red was in good weight, but he tied up after our last hunt. Is he selenium and/or vitamin E deficient, like the vet suggested?
Now it's time to get down-and-dirty with the math regarding how much vitamins and minerals the boys were actually getting, and how much they are supposed to be getting. Since there are a lot of nutrients in feed (my current count is 34), I'm going to concentrate on calculating some key values as examples.

Let's start with calculating non-structured carbohydrates, or NSCs. This is the combination of sugars and starches in a feed. Sugars, and therefore NSCs, are known triggers for laminitis -which is why you're not supposed to let horses graze on sugar-rich spring grasses. "Metabolic" horses, i.e. those with Cushings, are recommended to have no more than 12% NSCs in their diets (again, your mileage may vary depending on your source). Some non-horses appear to be more susceptible to increased amounts of sugars in their diet - for example, some barefoot horses can become "footy" within hours or days of having additional NSCs in their diets. Since Saga has been off-and-on footy, I was curious if the amount of NSCs in his diet might be causing some issues. However, I wasn't sure how much he was getting.

To calculate the total NSCs in your horse's diet, you need to add up all the NSC values for all the different concentrates and forages he's getting. Some feed companies post the NSC value of their feed right on their web site. Others you have to dig for online - and sometimes the numbers you find aren't consistent. If it's not on your feed bag label or on the company's web site, call the company and ask.

  • The reported NSC value for Purina Ultium is 16% (reference: COTH forum)
  • The average NSC value for Bermuda grass (coastal) hay is 13.2% (reference: equi-analytical). Ideally, I'd have my hay tested, but since I have not yet done so, we'll go with the average value.
To calculate the total NSCs your horse is getting, you first need to calculate how many pounds of NSCs your horse is getting for each feed source. Since NSCs are reported as percentages, to calculate pounds, you need to multiply the pounds of feed by the percentage of NSCs. Then you add the pounds of NSCs together and divide by the total amount of feed (in lbs) they're getting. Here are the calculations for Saga:

  • (9 lbs of Ultium) x (.16) = 1.44 lbs NSCs from Ultium

  • (15 lbs of Bermuda hay) x (.132) = 1.98 lbs NSCs from Bermuda hay

  • (1.44 lbs + 1.98 lbs) / 24 lbs = 14.25% total NSCs
So, Saga wasn't getting huge amounts of NSCs, but certainly there's room for improvement. In addition, I read the label on the Ultium bag carefully, and for a horse in moderate work (remember, Saga is in light work), he should be getting about 6.5 lbs of grain per day. I was over-feeding by 2.5 lbs per day, and he was still ribby. Eeek! I needed to cut back on the Ultium and change something else.

For Red, my main concern was that he might be Selenium and/or Vitamin E deficient, causing him to tie up. So, I needed to calculate the amount of these nutrients in his diet. Here are the calculations for Red:

  • Nutrena Lite Balance has 1 ppm (that's 1 part per million) of Selenium per pound of feed (reference: Nutrena web site).
  • Bermuda hay has no Selenium (reference: equi-analytical).
Since Red was getting approximately 1/2 lb of Lite Balance per day, that means he was getting .5 ppm of selenium per day.

Now the question is, how much Selenium does Red actually need? According to the book "Equine Nutrition and Feeding" by David Frape, a horse in light work needs 0.002 mg/kg BW/day. Let's decipher what this means:
  • milligrams (mg) = parts per million (ppm). So, 1 mg = 1 ppm
  • kg/BW/day is "kilograms of body weight per day". This means you need to convert the number of pounds your horse weighs to kilos. In Red's case, he weighs about 900 lbs, and 1 lb = .454 kg, so Red weighs 408.24 kg. I'll round up to 410 for easier math.
Now, we need to determine how much Selenium he needs based on his body weight by multiplying the number of mg by his body weight in kg:
  • 0.002 mg x 410 kg = 0.82 mg/selenium/day
We've already figured out that he's getting .5 mg (remember, ppm = mg, so .5 ppm = .5 mg) per day from his feed, so he's .32 mg/day short. That's nearly a third less Selenium than he needs!

Vitamin E
Now, let's do the same calculation for Vitamin E, since Vitamin E deficiency is another cause of tying up.

At 1/2 lb of Lite Balance per day, Red was getting 125 IU of Vitamin E per day.

How much Vitamin E should he be getting per day? Equine Nutrition and Feeding says 1.6 mg/kg BW/day. Doing the math, we get:
  • 410 kg x 1.6 mg = 656 mg Vitamin E per day
But wait, our units are off again! We need to convert IU to mg.

IU are "international units," or the measure of effect of a substance (reference: Wikipedia [yeah, Wikipedia, I know. Shoot me later.]) . The conversion factor for IU to mg is different for each type of vitamin. For Vitamin E, you divide the number of IU by 1.10* to get the number of mg. So Red was getting:
  • (125 IU/day) / 1.10 = 113.6 mg/day
YIKES! He's supposed to be getting 656 mg/day, so he's WAY low!

Since Red was low on both Vitamin E and Selenium, the vet's recommendation to add a supplement to his feed was probably a good one. If only I'd done the math beforehand, I'd have known this was a problem!

Feeding recommendations
One thing I realized as I started to read feed tags is that I was not feeding either concentrate within the recommended feeding levels. Nutrena recommends feeding Lite Balance at a rate of 0.25 to 0.5 lb (kg) per 100 lb. body weight (reference: Nutrena). If I had been feeding Red in the recommended quantities (2.25 to 5 lbs per day for a 900 lb horse), he would have had no problem getting the amount of Vitamin E and Selenium he needed.

HOWEVER, it's important to note that even when you feed in the recommended doses, your horse may be getting too much or not enough of something. For example, Saga needs 1 ppm of selenium/day (0.002 mg x 500 kg). If he had gotten the recommended 6.5 lbs of Ultium per day, he would have gotten 3.25 ppm of Selenium/day (Ultium has 0.5 ppm MINIMUM per pound of feed). I was feeding 9 lbs of Ultium per day, which is 4.5 ppm/day. Either dose is way too much! In fact, a little research on selenium toxicity in horses shows that the maximum a horse should ingest per day is 3 mg, and more than 5 mg/day can result in a horse that is "lame, loses weight easily and has a dull coat." HOLY CRAP! Saga was definitely footy on the Ultium, and he wasn't gaining weight. Maybe this was due to getting too much Selenium instead of getting too much NSCs? Since I didn't do a blood test, I'll never know, and he's no longer getting Ultium. Even so, it's a scary thought.

Now let me be clear - I am not disparaging either feed. It is my own fault for not reading the feed labels and following them. It is my own fault for not doing the math and understanding the possible consequences of feeding too much or too little to my horses. This is why being educated about feeds is so very important.

Next steps
I realize that my over-analytical self has probably gone overboard on all the math for feeds, and we only calculated a few key nutrients for our horses! There are lots of other things to looks at - fat, protein, calcium, phosphorous, iron, copper, manganese... and the list goes on. Since this post has already gotten so long, I'll wait till next time to discuss other nutrients I was concerned about, including protein, fat, calcium, and phosphorous. I'll also be posting the list of nutrients that I've accumulated along with the recommended doses for each nutrient from several different sources. That way you can do your own calculations for all these details.

And then... I have to figure out what to feed the boys!

* Ok, kidding, it's not that simple. It depends on if it's natural Vitamin E or synthetic, and what type of Vitamin E it is. See this page for more info. The ingredient list for Lite Balance says "Vitamin E supplement," so I don't know what kind of Vitamin E it is, but I guessed that it was d-alpha-Tocopherol. If someone else has better information, please let me know.


  1. When I was younger and living in Michigan, I remember selenium deficiencies being a big deal. We were using selenium supplements. It is interesting that Saga was getting way too much, and just from grain it sounds like.

    Again, I'll be stealing your calculations to see how much each of my horses is getting. :)

    I wonder if it's close or way off?

  2. in2paints, steal away! The calculations are meant to be shared... but please, double-check my sources (and your own!) and don't take what I've said for the absolute truth. It's entirely possible and eminently likely that I've made a mistake somewhere.

    I can't wait to see what your calculations say. Let me know when you have them!