Thursday, January 01, 1998

Calcium, Phosphorus & Rice Bran - Susan Garlinghouse wrote:

> The science I`ve read is European feedlot science--they`ve gone from using anabolic steroids to Clenbuterol to gamma oryzanol as the laws have changed over there. I`m not a bran fan for another reason: coats the gut and prevents absorption of some nutrients.

I`m not a bran fan either and about for the same reasons. I`d much prefer feeding gamma oryzanol in a purified form for its anabolic benefits than rice bran. See below for full-blown ranting.

> Anabolism takes place in response to stressors that must be overcome. Certainly these stressors are different from endurance animals to racehorses, but an endurance horse that starts losing flesh and appetite instead of coming on with exercise preparation is equally in need of nutritional support.

I`ll agree with you there 100%. But I also agree with your own #1 rule: "do no harm". If at all possible, I`d much rather provide nutritional support for one system in a way that did not decrease integrity in another system.

> When you have time, please write a short review of the phosphorus question. I`m relatively unaware here.

Short? Me? HA! See below.

>> I guarentee that I can provide just as much Mcal of energy with a better nutrient balance---lacking only the gamma oryzanol---for a whole lot less money than you can get by feeding rice bran.

>So can I, but gamma oryzanol is about the only worthwhile component in rice bran

Agreed, agreed, and agreed.

> and it is gamma oryzanol that is producing the results that people notice and want to keep paying for.

So you`ll be marketing purified gamma oryzanol soon, yes? :-)

OK, here`s the deal on phosphorus. Tom, I know you already know 99% of this, intuitively if not otherwise, forgive me for covering all the bases for anyone else on the list that doesn`t know.

As you know, alot of minerals have some sort of interactions with other vitamins or minerals---copper and zinc, calcium and Vit. D, Vit E and selenium. One of these interactions is between calcium and phosphorus. The saying in animal science, who are a not-very-poetic and pathetically easy to amuse bunch, is "As goes phosphorus, so goes calcium". What they mean is that for every gram of phosphorus ingested in the diet, the body must match that P gram with another gram of calcium before the phosphorus can be absorbed through the intestinal wall. However, if the required gram of calcium is not available from the diet, the phosphorus remains the controlling factor and the body will STILL dig out that gram of calcium from wherever it can---like from its storage depot in the bones. It doesn`t take a rocket scientist to figure out that in any performance horse that`s putting alot of stress on its bones, not to mention remodeling bone in response to training, you do NOT want calcium being pulled out and lowering the bone integrity.

This is where the whole idea of calcium-phosphorus ratios comes from. The whole point is to make sure that for every gram of phosphorus you`re feeding, you`re feeding AT LEAST an equal amount of calcium (a 1:1 ratio or better), so that calcium isn`t being continually mobilized from bones. Most nutritionist advise that the ideal levels are somewhere between 1.2-2 parts calcium to 1 part phosphorus, but the main thing is just that more calcium is being fed than phosphorus.

The problem is that most grass hays contain only low to moderate levels of both calcium and phosphorus, while the majority of cereal grains are deficient in calcium and high in phosphorus. So in a horse being fed alot of grain and grass hay as roughage, it would be very easy to have an inverted ca-p ratio (less ca than p). A horse eating 14 pounds of grass hay plus 4 pounds of barley/corn is going to have a ca-p ratio of .96 to 1, which means that every day, 40 mgs of calcium is being removed from the bones. OK, this isn`t great but 40 mgs isn`t all THAT much, over an entire year about 15 grams of calcium. But still, if you`re going to pay all that attention to making sure every little detail is just right in fine-tuning an athlete, making sure the bone integrity is also anabolic instead of catabolic should be somewhere in the equation, too.

Just to make another example, say the same horse is still eating 14 pounds of oat hay, but now he`s getting six pounds of barley/corn. Now his ca-p ratio is .86 to 1 and now he`s catabolizing (losing) about 240 mgs a day, or about 88 grams a year. 88 grams is equivalent in weight (not volume) to about a half cup of water.

I honestly don`t mean to make this sound scary or melodramatic. Horses have ALOT of calcium stored away, so it`s not like an inverted ca-p ratio is going to make their legs shatter next week. On the other hand, catabolism is catabolism and it`s just not that tough to fix an inverted ca-p ratio.

So here`s partially where rice bran starts to come in. Lots of people see the nifty ads about rice bran containing 15-20% fat and so assume this is a great thing to feed to horses. (Actually, fat content or not, rice bran has less energy than wheat bran, corn, oats or barley, but that`s beside the point. Sorta.) So they go get a bag and feed it at the recommended amounts, which is what? A pound or two? OK, fine. What the pretty bag DOESN`t tell you is that rice bran has a higher phosphorus content than anything other feed, right around 1.57%. Wheat bran is number two at 1.13% Add that to the above horse`s ration and now he`s got a ca-p ratio of .55 to 1. That`s 650 mgs a day being pulled from bone, or 237 grams a year, equivalent in weight to more than a cup of water. That`s alot of calcium for a performance horse that has better things to do with it. Granted, it`s not all coming specifically from the cannon bones, but still...from bone.

Not to scare the dickens out of anyone, but a few years ago when I was hanging around the local equine hospital, a client brought in a lovely imported warmblood breeding stallion for x-rays because he always seemed to be progressively lame, even though he was only being ridden dressage. They took the horse`s history and radiographs, but on the way back to his trailer, the stallion got frisky, got away from his handler and went galloping merrily down the street. At the intersection, he stumbled and went down and totally shattered a cannon bone and pastern joint, which seemed a bit extreme under the circumstances - it wasn`t all THAT bad a crash. The damage was too great to fix and the very valuable horse was put down. Later, after they developed the original radiographs (now a moot point) the bones had so little calcium deposition, they looked like something was wrong with the equipment`s contrast. It turns out the horse got colicky on alfalfa and was a hard keeper to boot, so he`d been living for all his life on oat hay and ALOT of grain and bran. However, this was a really extreme example, so don`t take this as the Voice of Doom predicting that everyone`s legs will turn to dust by nightfall.

OK, so much for inverted calcium-phosphorus ratios. Most everyone knows that good-quality alfalfa is a dandy source of calcium, so all you have to do to balance an inverted calcium-phosphorus ratio is add more calcium in the form of alfalfa, right? Well, that`s true. Adding five pounds of alfalfa to the above ration will balance the ratio back to 1.2 to 1. Most people after hearing my patented Horrors of the Inverted Ratios tend to want to REALLY make sure their ratios aren`t inverted, so that feed a pretty fair amount of alfalfa, 50/50 or better. After all, the NRC even says that horses can tolerate calcium levels up to 7 to 1 without ill effect. This is one area where I will definitely agree with you, Tom, that the NRC should definitely not be taken as the last word.

I read the study that the NRC based these conclusions on and the only "ill effects" they were looking for were signs of toxicity, like you`d see with wildly excessive selenium or sulfur. If the horses did not actually drop down and froth at the mouth, NRC says that`s good to go.

There is one syndrome of an inverted ca-p ratio (that is, too much phosphorus, not enough calcium) that can be seen visually, called miller`s disease in the UK and bighead disease elsewhere. What happens is that the calcium being removed from the bone is replaced by connective tissue--an attempt by the body to create stability and support when bone isn`t available. Although it`s going on throughout the body, it will show up on the head, with an enlargement along the jawbones, especially the upper mandible. It makes the whole face look swollen and hence "bighead disease". However, this symptom may not show up unless the inverted ratio is a severe one, and sometimes not even then.

So here`s the problem I have with rice bran and subsequently high calcium levels. People feed rice bran for whatever reason---gamma oryzanol, fat content, whatever. If they haven`t heard about ca-p ratios, the odds are higher that they might have an inverted ratio if the primary source of hay is a grass hay. If they have heard about ca-p ratios, then they predictably add a whole bunch of alfalfa to "balance" the ratio back to where it`s supposed to be.

However, just because the ratio is 1:1 or better doesn`t mean minerals are being fed at the optimum levels, and here`s where we diverge a little in racehorse management vs. endurance horse management. Let`s say you`re feeding a horse 9 pounds of alfalfa, 5 pounds of oat hay, 2 pounds of rice bran and three pounds each of corn and barley. Lots and lots of horses get this ration every day. The ca-p ratio is 1.72 to 1, which most books, including NRC will tell you is within the ideal range. Peachy. However, if you keep crunching the numbers, you`ll find out that you`re providing approximately 61 grams of calcium, 36 grams of phosphorus and 28 grams of magnesium (according to NRC data), which is roughly four times as much calcium, 3.5 times as much phosphorus and 4.5 times as much magnesium as is actually required for maintenance. For that matter, if the source of the alfalfa was California, then in reality the magnesium content is probably considerably higher. Alfalfa plants have the ability to concentrate magnesium and so when grown in alkaline soil (like in California), the Mg content can be as much as seven times higher than alfalfa grown elsewhere. (And NRC doesn`t tell you that either, by the way). So in California, the above ration is probably providing more like around 80-90 grams of magnesium, about 13 times as much as is required.

So what, right? That`s what kidneys are for. Well, here`s the problem and there are two biggies. One is the one that Tom pointed out, that excessive phosphorus suppresses the absorption of other minerals. Yes, it does, who knows how much. Frankly, as of the last 1989 edition, NRC still didn`t have a clue exactly what got suppressed and by how much, they just know it does when fed to excess (like with rice bran). One of the problems with excess calcium is that it tends to get the calcium-mobilizing hormones lazy---there`s always plenty of calcium laying around, so no reason to have a high concentration of the hormones that move it out of the bone and into the bloodstream. Calcium is used as a regulatory factor in alot of physiological functions, not the least of which is muscular contraction. An endurance horse that has used up all his readily available plasma stores of calcium and can`t mobilize enough additional calcium from his bones (because the parathyroid hormones got caught with their pants down) is going to go into an electrolyte imbalance and potentially, thumps. (There are other factors to thumps as well). Whether this would be a problem in racehorses as well I couldn`t say---maybe Tom knows.

On to the other problem. One of the leading causes of colic in horses is enteroliths in the gut. The primary components that make up enteroliths are nitrogen, phosphorus and magnesium. Nitrogen comes from an excessive amount of protein, and nice, leafy alfalfa can be over 20% crude protein. That same alfalfa, as demonstrated above, is also contributing what can only be described as a sh**load of magnesium, and if you`re feeding grain and especially rice bran, guess where all that phosphorus is coming from. If you`re thinking this sounds like a recipe on How to Grow Really Big Rocks in Your Horse`s Gut, you`re right, it sure is. Here in So Cal, the majority of horses are still being fed straight California alfalfa, the greener and leafier, the better. It also just so happens that enteroliths are more common here than anywhere else in the country, wonder why?

So here`s the bottom line of why I am no fan of bran and specifically, rice bran:

1) Other than gamma oryzanol, it doesn`t provide anything that can`t be provided by other feeds better, cheaper and in better nutritional balance. I`d still like to know if gamma oryzanol is available in a purified form.

2) It`s sky-high in phosphorus, which increases the possibility of an inverted calcium-phosphorus ratio.

3) If the high phosphorus is "balanced" with alfalfa, then the high nitrogen and magnesium content of the alfalfa is contributing to a more alkaline condition in the hindgut and an increased chance of eventual enterolith formation.

I am all for nutritionally supporting performance horses of any discipline to keep them in an anabolic vs. catabolic state. Seems to me that if you`re going to go through all the trouble of conditioning the buggers, giving them the raw materials they need to build appropriate tissue is a fairly logical thing to do. But I also think that part of smart management is providing nutritional support without compromising any other part of the whole package. There are some supplements or feeds with a few disadvantages that I would be willing to ignore if it meant a big benefit in some area of performance. But, especially if gamma oryzanol is available elsewhere, I don`t think rice bran is worth it in the long run.

Just my two cents, of course. Your mileage may vary.

Sorry to make this, as usual, into the Great American Novel. Hoped it answered everyone`s questions (and then some) about why I start foaming at the mouth when people start talking about rice bran.

Susan Evans Garlinghouse

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