Nutrient deficiencies in hay and pasture

This post has been brewing for a while, and I will still have more to add to it in the future as I get results back from our own hay. 

Several months ago, as I looked at a picture of Griffin tied to my horse trailer...

Griffin - 5 years old, spring 2012

I passingly thought his mane sure seems shorter and frizzier than it used to be when we first got him from the BLM pens.

Griffin - 2 years old, summer 2009

Then the other day I was in the pasture brushing Chico's mane, and I though the same thing. 

Chico - 8 years old, fall 2012

His  mane just seemed thinner and shorter than it was when he lived in Idaho.

Chico - 3 years old, spring 2007 - primarily looks thicker here, rather than longer.

And I looked through old pictures of Kachina, and though more subtle, I think it holds true for her her.  Longer when she first came to us, and shorter now.

Kachina - 6 years old, spring 2012

Kachina - 3 years old, summer 2009

I haven't really noticed it as much with Catlow or Cody...though I do feel like Catlow's mane is thinner, though still as long, so the difference doesn't show in pictures.  Don't horses generally get longer manes as they get older, not shorter?

This is a very odd subtle difference.  I also never thought that there might be an issue because their springtime coats come in so luxurious and dappled.  They never used to have dapples in Idaho.

But then, I started thinking about how Cody is now developing a crack at the toe of one front hoof anytime I let her hooves grow out a half inch longer than her soles...which is long, but it's not THAT long.  She never used to get cracks and this crack is not bad...it never extends longer than an inch from the ground, and I can trim all but about 1/8 inch of it off when I trim her hooves up usually.  And it doesn't make her lame or anything.  The first time she developed a crack was the summer of 2010 - that was about a year a half after I brought them here to Wisconsin from Idaho.  Since it can take up to a year for a hoof to grow from coronet band to the end of the toe, I started thinking....

Are my horses missing some vital mineral that affects both hoof and hair growth leading to brittle hooves and brittle hairs that break and make the mane shorter?  These signs are extremely subtle - I only have one tiny cracked hoof out of 20 hooves.  All the rest seem normal.

And my horses have always had access to a trace mineral block, a mineral block with selenium, and a plain white salt block.  Plus they have all the lush pasture they can eat, and good quality hay (grass with just a tad of alfalfa mixed in) during the winter.  They are fat and happy.

But am I missing something?

That question set me off on a long obsessive search.  I compiled information about the nutrient requirements for a typical 1100 lb horse living primarily on pasture - my horses don't even qualify as having "light" exercise. 

Then I found a forage testing laboratory (Dairyland Laboratories, Inc) that is near my area that also tests forages from around here.  I was delighted to discover that they report averages of all their test results for various classes of forages.  I found the information for grass hay.  I figured they would have data that was representative of my pastures and hay fields.

I then compared the needs of an 1100lb horse at maintenance to what that horse would consume in 22 lbs of average grass hay (according to Dairyland Laboratories).  I was immediately satisfied that my horses were getting way more than they needed for daily energy, and protein (but I did not examine individual amino acids), so I focused on vitamins and minerals.  Now, many of the vitamins (like Vitamin A and Vitamin E) are present and more than adequate in green pasture, but they are pretty much absent in hay.  Horses likely sythesize adequate amounts of Vitamin D in their skin when exposed to sunlight, but may not during certain times of year and if they are kept indoors.  And the B vitamins are a bit confusing...many of them are synthesized adequately in a horse's hindgut by their specialized microbes as long as they have adequate microminerals like cobalt.  Thiamine and Riboflavin are required in the diet, but were not measured in the forages I used.  They may be adequate (or not).  I decided not to focus on the B vitamins either.

Dairyland Laboratories reported data for: Calcium, Phosphorus, Magnesium, Potassium, Sulfur, Copper, Manganese, Zinc and Iron and Sodium.  They did not report information about Iodine, Cobalt and Selenium, which are all considered micronutrients needed in very tiny amounts and not likely to be in forages in our area (we live in a low Selenium part of the US).  And it is well known that forages are too low in Sodium for herbivores' needs and salt must always be provided extra.

I wanted to know: Are my horses getting adequate minerals? 

The answer:  The average grass hay forage in our area is deficient in Zinc.

And it doesn't seem to be just a little deficient.  It's a lot deficient.

My next question was:  Do the mineral blocks I have supply adequate micronutrients (Cobalt, Selenium, and Iodine), in addition to satisfying the need for Zinc?

The answer: No!  It does not meet the needs for Zinc!  It supples some, but not enough!  But, at the rate that my horses should consume the blocks according to their salt needs, the blocks do supply adequate Cobalt and Selenium.  My particular blocks didn't have enough Iodine either, though plain iodized white salt does have enough Iodine.

Would a zinc deficiency cause what I'm seeing?  Well, I don't think the subtleties that I've seen have been reported, but absolute Zinc deficiency does affect hair and hoof growth, in addition to a whole host of other issues.  I think my horses are getting some Zinc, just not enough.  My conclusion is that what I am seeing makes sense with a marginal Zinc deficiency.

What have I done to solve this?  Well, I looked into many different supplements and minerals.  Most do seem to meet the needs of the average horse, but I need a supplement/mineral that I can offer free choice.  I am not home to feed my horses every day.  We need a low maintenance option!

I found a free choice mineral at our local feed co-op called Kent Equestrian's Choice Equine Mineral.  It is meant to be fed free choice.  It contains about 25% salt, which is what drives the intake of the mineral at the appropriate amounts.  It does also have a little bit of molasses formulated with it to increase palatability, but I tasted it and it really is not very sweet...mostly salty.  Horses should consume 2-4oz of this mix daily.  It is affordable, and most importantly it meets all the minimum needs for the minerals missing in average forage (Zn, Se, Co) with the exception of Iodine.  It actually has enough of these components that the mix can be diluted 1:1 with iodized salt, and then it will still meet the minimum requirements when consumed at 2-4 oz of salt/mineral mix per day and then it also meets the needs for Iodine.

The Kent Mineral also has Vitamin's A, D and E.  It has adequate amounts to meet deficiencies in winter hay for Vitamins A and D, though is deficient in Vitamin E.  Now, Vitamin E is very costly to add to feed and is the one Vitamin that I've found is consistently not present in adequate amounts in supplements.  This Kent mineral does do a pretty good job of supplying more than many other supplements though.

This Kent mineral is meant to be fed without offering another source of salt, unless the weather is hot or your horse has more than a light amount of exercise.  Then salt will need to be added to it.  I'm pretty happy with it, since I can meet all the mineral needs of my horses with the one supplement plus some iodized salt.  And all without having to feed daily.  So far, I've been putting out 2-4 oz X 7 days X 5 horses (so about 5-8 lbs) of the full strength mineral every weekend split into 5 separate buckets in the barn, while still offering their salt blocks, and every weekend, I've come home and they've consumed it all.  I'm glad they like it, and I'm glad to know that they are getting their needs met now, and probably working hard to get that deficiency gone!

In case you are wondering about some of the other supplements and how they measure up.  Equishine pellets when fed at the rate of 2 oz per horse per day (you must also supplement salt) does meet all mineral needs (except for Iodine, but an iodized salt block will supply this), but it is deficient in Vitamin D and Vitamin E, though probably not a deal breaker for me...both of these vitamins are probably adequate in the summertime.  And Equishine does also have B-vitamins, though less than the recommended daily amount for Riboflavin and Thiamin, which may not be important since I'm not sure how much is present in forage - this will be a future point of research for me), and the rest of the B-vitamins may be made in the gut.  If fed at the higher rate of 4 oz per day, Vitamin E would still not quite meet minimum winter requirements, though it would then meet requirements for Vitamin D.

Another supplement I was asked to compare is called HS-35.  It has a ton of things in it (B-vitamins, amino acids...) but when I did the analysis, this supplement combined with good forage is deficient in Zinc, Selenium, Cobalt, Iodine, Vitamin A, Vitamin D and Vitamin E.  I would NOT choose this one unless you also offer a good mineral supplement.  You would be choosing HS-35 simply for all the bling ingredients which are B-vitamins and amino acids.

Purina Enrich 32 compared very well.  When fed at the rate of 1 lb per horse per day, it was only deficient in Vitamin D, and was actually pretty close to meeting the needs, thus when fed at 2 lbs per day, all the needs are met (except Iodine...just doesn't quite have enough).  This supplement fed at the lower feeding rate does actually meets the winter requirements for Vitamin E, which is rare in supplements.  The only thing I would have a concern with this supplement is that the Selenium content was just barely able to meet the minimum requirements of 1mg when fed at 1 lb/day.  This is actually true for Equishine too.  Research has shown that in comparison to only 1mg/day, when mares recieved 3-4mg/day, their colostrum had more antibodies in it that were transferred to their foals - so better immune responses.  If you are in a low selenium area like I am, I'd recommend maybe still feeding a selenium salt block with this, keeping in mind that you will likely boost the total selenium intake to about 3-5mg /day.  The maximum tolerated Selenium dose is about 22 mg/day and toxicity is seen at 50 mg/day (in a 1100 horse), so just keep that in mind when combining supplements that contain Selenium, especially if your forage might have some in it too.  Purina Enrich 32 also has added protein and fat.  I would choose this supplement if I had time to feed daily.

Purina also makes a compressed supplement block for horses called Purina 12:12 block.  This is another free choice option.  This block contains adquate amounts of all minerals (except Iodine is low), and does contain some, though not enough, of Vitamins A, D, and E.  But like I said before, these are all likely to be adequate in summer time.  Salt also needs to be fed in addition to this block, as this block contains very little salt.

Keep in mind that I only evaluated the trace mineral block brand that is in my local feed store.  Other brands may contain different amounts of trace minerals and may or may not meet requirements.  I have yet to investigate that, but I probably will just to know for future's sake.

Also keep in mind, that as a horse increases the amount of work that they do (or if they are pregnant or lactating), they needed increases in some of these nutrients.  Specifically Calcium, Phosphorus, Magnesium, Vitamin A, Vitamin E, Thiamine, Riboflavin, Potassium and Salt.  Though thankfully, most of these nutrients are present in more than adequate amounts in average forage, with the exception of Salt (and Vitamin A and E in dried hay) and of course Zinc if your forage happens to be deficient in that too.

And I have also learned that Zinc can be present in drinking water too, but sometimes, if other nutrients like Iron or Copper are present in high amounts in the diet, it can impair absorbtion from the gut of other minerals present in lower amounts.  So, I do not yet know how much Zinc might be in our water, but I'm going to find out. 

The nutritionist from our feed co-op is coming out tomorrow to take hay and water samples to be analzyed for all these nutrients, so that I can know for SURE that MY horses are getting what they need!

I spent days figuring out these analyses.  I'm sure there are websites that can do it too for less work than I went through.  But I learned a ton about nutrition while I did it. 

And I'm extending this offer to you.  If you want me to evaluate a certain supplement with the average grass hay data I have.  Just let me know...  :)


Update to this post:  This is a map I found from the USGS that shows levels of some minerals in soils across the US.  Very interesting to look at Zinc.  White means less and dark blue means more.  If you are interested, click on the link and you can see that there are similar maps for many other minerals available.  Keep in mind, I'm not sure how these relates to mineral deficiencies in forage, but I'd imagine that if the mineral just isn't there (or very small amounts) then plants can't take it up and offer it to our herbivores.

http://tin.er.usgs.gov/geochem/doc/averages/countydata.htm

Also remember that these maps do not reflect how much mineral a horse needs...just content in the soil.  Horses need very low amounts of some of the minerals, like Selenium, and even Copper and Zinc.  To illustrate that point, see the Sodium map.  You can see that there are some areas of the country where Sodium is relatively higher than other areas of the country.  However, in ALL parts of the country, Sodium content is not adequate in forage and herbivores must be supplemented (or they are wild, they will find a mineral "lick" where they can obtain higher amounts of salt than they can get from forage.