Issues with Selenium

In the last 4 months or so Cash has really started to have a notable problem in one of his front feet with the hoof wall just deteriorating around the nails whenever the farrier tries to set a shoe.  This was surprising and concerning to me as when I first got him I instantly put him on a ration balancer to provide a balanced mineral supply to his diet.  The product I choose was Ranch-Way's Defiance Vital Edge Pelleted Mineral.  I'd used this product before with good results (or so I thought) and it was a better price than the other option in my area (Enrich 32) plus I liked that it had Biotin in it (yay! no extra hoof supplement needed).  In general, I expected it to help him out overall, with visible improvements in his coat, hair, physical appearance, and hoof growth.

Well, I did see a difference in his coat and (for the most part) his hair.  When Cash shed out in the spring I was very pleased with how his coat looked, it quite literally would blind you:

Physically he was gaining weight and muscle.  His feet were looking good, and we were making progress with correcting some poor angles he had.  But the new horn growth coming in didn't look any better than it had before.  I brushed it off as a result of the incredibly hot and dry summer we were having.

In September I took Cash off the Vital Edge, not really because I wanted to but because I was starting to pinch pennies for my upcoming maternity leave and unfortunately extra fancy grain for the horse was not a luxury I could afford--after all, horses have survived thousands of years without special supplements.  His weight was good and he was on a really nice, rich hay so I wasn't worried.  In hind sight, I am really really glad I did this, as if I hadn't taken him off it I might not have made the important connection that I will now explain.

Right about this time the horn growth that started way back in February when I started Cash on the Vital Edge was reaching the ground and being actively engaged by the farrier and thus shoes. This is when the issues with the flaky and shelly feet started.  My farrier noticed the difference right away and made an offhand comment wondering if he had a mineral deficiency.  I said I didn't think so and we left it at that.  However it got the wheels to turning in my head.

Fast forward to December.  Looking at his feet you can see that the lower 3/4 of the foot is this weak, cracking mess, the upper 1/4 (post Vital Edge) that is growing in is stronger looking, less cracks, and in general, healthier.  I pondered this, why would horn growth look better without a mineral supplement than with.  So, I sat down yesterday with the feed tag from the Vital Edge and did some research into mineral requirements for each ingredient listed.  As I went down the list and did my research one article pointed out that Selenium is a mineral that is often over dosed and that very little can create toxicity in horses.  I found a couple great articles from Kentucky Equine Research.  The first, Selenium - How Important Is It? told me that the minimum requirement is 0.1 mg/kg of diet per day, which for a horse consuming 10kg (2% of body weight) equals 1 mg per day.  Toxicity can start around 2mg/kg.  Another article, The Many Phases of Selenium stated that toxicity levels start at 5 to 40 ppm in horses (ppm is equal to mg/kg).  This wide range is dependent on the amount of exercise the horse is getting along with other minerals in their diet that can off-set the Selenium such as vitamin E, sulfer, and copper.  Well, the Selenium amount in the Vital Edge is 2.2 ppm.  Based on the first article, this is right at that threshold where toxicity can start.  A little more digging yielded that it is common for hay in Colorado to be naturally high in selenium (Merek Veterinary Handbook, Selenium in the Equine Diet), and hay alone can cause toxicity without additional supplementation.  Uh oh.  I learned too that the first signs of selenium toxicity is loss of hair in the mane and tail along with weak, cracking hooves.  Essentially what happens in the horn wall is that the excess Selenium replaces the sulfer in the keratin bonds, this weakens the hoof wall and will result in weak, flakey, and soft feet.  If the Selenium toxicity is high enough it can even cause the entire hoof to slough off... YIKES.  On the flip side, selenium deficiency can cause white muscle disease, myositis, and Exertional Rhabdomyolisis or "tying-up".

Based upon that research, and what I was seeing (which included a mysterious loss of hair around the dock of his tail--which at the time I had assumed was again, due to the dry conditions and I guessed he was rubbing his tail to relieve the itchiness) I have determined that Cash was suffering from a mild Selenium toxicity.  It is safe to say that I will never feed the Vital Edge again, bummer, because aside from the Selenium it really provided a wonderful balanced mineral supplement. 

So, now I'm on damage control until the compromised portion of Cash's feet grow out.  I've ordered some Keratex Hoof Hardener which is a product that chemically alters the molecular bonds of the hoof structure, resulting in a physically stronger hoof wall.  This is fantastic for helping a horse that has currently weak feet and needs help now and can't wait the 6-12 months for a new foot to grow out.  The reviews on it are great, plus it is a Horse Journal editor's choice.  I'm excited to try it!

Secondly, as soon as I start getting paychecks again I will be getting Cash on a hoof supplement so that he can get that Biotin back in his diet, which, without the excess Selenium, should be able to actually do it's job.  Research has shown that while a horse really only needs 1-2mg/day of Biotin, when supplemented between 15 and 20 mg/day it will therapeutically help to improve the quality of horn growth.  So, while you do see those hoof supplements that boast 30, even 40 mg/serving of Biotin, it's really a waste of money, you just don't need that much, it's excessive.  I compared ingredients and selected Grand Hoof Pellets.  It has great levels of Biotin, Methionine, Lysine, and Zinc--all of which are vital to hoof growth (though the methionine is kinda a moot point, it's an amino acid that is created when protein is broken down, so really if the horse is getting an adequate amount of protein already this isn't truly needed... but I digress).  The other thing I like about it is that it contains 5,000mg of MSM which helps with joint issues.  I was wanting to get Cash on a supportive joint supplement anyway so this works until I can actually add in a real joint supplement. 

Well, so I guess that is that.  I feel better now that I've located the issue and can actively proceed with fixing it.  I've gained a whole new respect for carefully analyzing the feed tags that come with your grain.  I obviously cannot feed a grain high in Selenium, and will thus be very picky about what goes into my horse's diet from now on.