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Different types of magnesium - dose, RDI, bioavailability?

Horse Care
#1

In trying to find the best diet for my PSSM gelding I investigate each ingredient obsessively, so welcome to this week’s installment of “What’s Xan Fussing About Now? Magnesium!” :lol:

It came to my attention that not all magnesiums are created equal in terms of bioavailability (an imprecise measurement anyway) and elemental percentage. In fact each different salt is said to give different effects to humans and horses.

And, there appears to be little research into it all…

Undeterred by this, I used several types of Mg on my old, dearly departed OTTB and MagRestore at 4x the normal dose was nothing short of amazing, where all others failed to show a difference. “H’m, there is something to this…” I muttered at the time.

Anyway, to cut to the chase my current KWPN guy gets Magnesium Oxide which is not very bioavailable according to the interwebz, so I picked up a 1 week trial size of Mg Glycinate after some more unscientific research based on opinions from randos online.

The packet says that 1/2 tsp of Mg Glycinate weighing 2200mg has 401mg of Mg Glycinate in it, and according to the math in the first post on this page http://www.longecity.org/…/16932-bioavailability-elemental…/ that translates to 57.7mg of Magnesium, elemental.

  1. Is that math correct? Are the people on that site nuts?

  2. What is the RDI of elemental Mg for a 1400# horse? FeedXL indicates 12.7 g - is that right? I can’t find much else online giving an RDI.

3. Some sites say you cannot have too much Mg as excess is excreted  naturally. FeedXL says the upper safe level for magnesium is 102 g or  800% of his RDI. Comments? Is runny poo my sign or something more insidious to do with calcium, phosphorus and struvite stones?

Going to start ODing my horse on Mg Glycinate today because desperation. Thanks!

#2

I have no education or background in equine nutrition. BUT, what I have read on the ECIR group and Dr. Deb’s forum is that the bioavailability of various forms of magnesium is not the same for humans and horses. You can search those two groups for more info on equine bioavailability.

#3

Unfortunately there is not much research done on horses, so a lot of the information is extrapolated from studies on people and rats and other animals. I try not to get too vested in a position wrt nutrition because things tend to change as years go by. And btw, we just had this discussion a couple weeks ago, if you want to do a search.

#4

[QUOTE=Palm Beach;8645669]
Unfortunately there is not much research done on horses, so a lot of the information is extrapolated from studies on people and rats and other animals. I try not to get too vested in a position wrt nutrition because things tend to change as years go by. And btw, we just had this discussion a couple weeks ago, if you want to do a search.[/QUOTE]

Here’s the link…http://www.chronofhorse.com/forum/showthread.php?490324-Magnesium-concentration-vs-bioavailability&highlight=magnesium

In the case of your PSSM horse, is that high fat diets seem to affect the b-a of Mg in the diet. However, I could never find an interpretation of a “high fat” diet as well as at what point fat content begins to interfere.

#5

Thanks Brian.

Well it sounds like there’s no good data so I’ll throw and additional 57.7mg as Mag Glycinate at him for a week and see if he keels over dead. Or his muscles get nice and soft.

Hey maybe I should take some myself? :wink:

#6

Regarding Brian’s post, I seem to recall reading 20% fat as the ceiling. I can’t recall where I read that but it’s sticking in my head…

#7

[QUOTE=myleetlepony;8646155]
Regarding Brian’s post, I seem to recall reading 20% fat as the ceiling. I can’t recall where I read that but it’s sticking in my head…[/QUOTE]

I think you’re right.

Beth Valentine says “20% to 25% of total daily calories from fat” is a high fat diet. But Stephanie Valberg says

“Supplying fat at 6–10% by weight of the entire ration to PSSM Quarter Horses (unless a higher energy intake is required for exercise) is likely quite sufficient for managing PSSM, and further benefit from more fat has not been demonstrated in controlled trials. Note, how- ever, that none of these diets will result in clinical improvement of muscle stiffness and exercise tolerance in PSSM horses without changing the amount of daily exercise and access to turnout.”

and

“There is some evidence to suggest that detrimental effects may occur when feeding a very high dietary fat intake (25–30% of daily DE). Feeding unnecessarily high dietary fat may induce loose manure, decreased digestibility of other dietary components due to depression of activity by cellulolytic bacteria, decreased dry matter intake (which may propagate electrolyte and mineral deficiencies), and obesity.”

I also read on some sites that promote human high fat diets that Mg can be poorly absorbed, but they weren’t very scientific…

#8

[QUOTE=Xanthoria;8647063]
I think you’re right.

Beth Valentine says “20% to 25% of total daily calories from fat” is a high fat diet. But Stephanie Valberg says

“Supplying fat at 6–10% by weight of the entire ration to PSSM Quarter Horses (unless a higher energy intake is required for exercise) is likely quite sufficient for managing PSSM, and further benefit from more fat has not been demonstrated in controlled trials. Note, how- ever, that none of these diets will result in clinical improvement of muscle stiffness and exercise tolerance in PSSM horses without changing the amount of daily exercise and access to turnout.”

and

“There is some evidence to suggest that detrimental effects may occur when feeding a very high dietary fat intake (25–30% of daily DE). Feeding unnecessarily high dietary fat may induce loose manure, decreased digestibility of other dietary components due to depression of activity by cellulolytic bacteria, decreased dry matter intake (which may propagate electrolyte and mineral deficiencies), and obesity.”

I also read on some sites that promote human high fat diets that Mg can be poorly absorbed, but they weren’t very scientific…[/QUOTE]

In essence, both are almost saying the same thing…i.e. if calorie requirements are 32,000 calories, then 25% or 8,000 calories would need to come from a fat source, such as oil. Veg. oil is 4,000 calories per pound, so you’d need to feed 2 lbs of oil per day.

If the horse’s total diet was between 20 & 33 lbs per day, 2 lbs of oil would fall within the 6-10% of the total diet recommendation.

Iv’e always thought the 20% rule referred to the total diet. IOW, if the total daily intake was 30 lbs, you shouldn’t exceed more than 6 lbs of fat per day. That leaves a lot of room for variance. My suspicion is that the horse will “back off” the feed before you’d be able to get that much fat into them. Kind of like us eating those greasy french fries…they’re really good, but we can only eat so much.

So, I go back to my original question regarding fat interfering with Mg absorption. Is it at the 20-25% of calories or 6-10% of total diet or is it at the maximum level of 20% of the total diet or somewhere in between when interference takes place?

JMO

#9

[QUOTE=Xanthoria;8647063]
I think you’re right.

Beth Valentine says “20% to 25% of total daily calories from fat” is a high fat diet. But Stephanie Valberg says

"Supplying fat at 6–10% by weight of the entire ration to PSSM Quarter Horses (unless a higher energy intake is required for exercise) is likely quite sufficient for managing PSSM,

.[/QUOTE]

20-25% of calories and 6-10% by weight are not really comparable quantities, as written. It is conceivable that they are roughly equivalent.

#10

Wow I missed that key piece of information: %age of total DE vs %age of ration weight. Hm.

So my horse is getting 14% of his DE from 14oz, or not quite 2# of fat. So that’s not high fat by that measure.

His total intake is 26.6 lb (pasture intake an estimate so that’s annoyingly inaccurate) but 6-10% of that would be 1.6-2.6# of fat. So by the measure of %age of ration weight it is high fat.

Well feh.

#11

[QUOTE=Xanthoria;8647443]
Wow I missed that key piece of information: %age of total DE vs %age of ration weight. Hm.

So my horse is getting 14% of his DE from 14oz, or not quite 2# of fat. So that’s not high fat by that measure.

His total intake is 26.6 lb (pasture intake an estimate so that’s annoyingly inaccurate) but 6-10% of that would be 1.6-2.6# of fat. So by the measure of %age of ration weight it is high fat.

Well feh.[/QUOTE]

Sorry, I’m not following your math here…14 oz (assuming oil) would be 3.3% of total ration. How is that high fat?

How much of the 26. lbs is “estimated” pasture intake? Do you think 26.6 lbs of total intake sounds appropriate for a growing 1400 lb horse?

Are you calculating his caloric needs at 25,000 calories per day as well?

#12

I’m using FeedXL so there might be issues around that and how they estimate pasture intake and RDI based on his height, weight, age, workload etc… Also I forgot to add his Triple Crown Omega Max which is 32% fat: Here’s the DE breakdown with 1.5# TCOM added:

RDI: 26.3 MCal This diet: 26.7 MCal - 102% of his RDI.

36% Grass hay
11% canola oil (1.5 cups)
2% cod liver oil (2 oz)
9% Triple Crown Omega Max
16% beet shreds
11% alf pellets
13% pasture
1% supplement that is flax based

They recommend his total forage intake at 14# which I feel is very low, hence all the beet and alf I feed. His actual forage intake is 24.8# (give or take - they estimate 5.83#/day as the pasture is poor) - and he’s putting on weight.

So, I added up the 2 oils to get to 13% of the DE in his diet. In fact it’s higher due to the TCOM. If that’s 32% fat do I add 3% to the total DE from fat? Or is my math all wrong?

#13

I have not seen any of them posting on this thread, but there used to be a few posters who actually sold a special form of Mg, pimped it on every Mg thread, and of course had the secret formula to it working. So take any of that with a grain of salt.

#14

“14oz, or not quite 2# of fat.”

14 oz is not quite one pound.

#15

16 oz per pound. I have to look it up every time.

#16

[QUOTE=Xanthoria;8647607]
I’m using FeedXL so there might be issues around that and how they estimate pasture intake and RDI based on his height, weight, age, workload etc… Also I forgot to add his Triple Crown Omega Max which is 32% fat: Here’s the DE breakdown with 1.5# TCOM added:

RDI: 26.3 MCal This diet: 26.7 MCal - 102% of his RDI.

36% Grass hay
11% canola oil (1.5 cups)
2% cod liver oil (2 oz)
9% Triple Crown Omega Max
16% beet shreds
11% alf pellets
13% pasture
1% supplement that is flax based

They recommend his total forage intake at 14# which I feel is very low, hence all the beet and alf I feed. His actual forage intake is 24.8# (give or take - they estimate 5.83#/day as the pasture is poor) - and he’s putting on weight.

So, I added up the 2 oils to get to 13% of the DE in his diet. In fact it’s higher due to the TCOM. If that’s 32% fat do I add 3% to the total DE from fat? Or is my math all wrong?[/QUOTE]

Do you have the actual calorie #'s for the above list?

It took me a bit to understand how you arrived at adding 3% to total DE from fat, which might work for percentages. However the caloric value of TCOM would have to be equal to the oils to be accurate.

If it were me, I’d calculate total MCal from (canola oil+cod liver oil+TCOM)/RDI MCal=% DE from fat

How does FeedXL calculate intake & calories from pasture? Using the 13% of DE and intake of 5.83 lbs the caloric value comes out at just under 600 calories per pound. Which seems high for as fed and low for DM.

Considering the estimated calculated calories from pasture being <4000 calories a day, I’m not sure I’d even use pasture in the diet. I’d probably view pasture as bonus calories for purposes of weight gain or to offset variances in hay consumption.

#17

[QUOTE=Brian;8648394]
Do you have the actual calorie #'s for the above list?

It took me a bit to understand how you arrived at adding 3% to total DE from fat, which might work for percentages. However the caloric value of TCOM would have to be equal to the oils to be accurate.

If it were me, I’d calculate total MCal from (canola oil+cod liver oil+TCOM)/RDI MCal=% DE from fat[/QUOTE]

1.5 cups canola oil = 12.8 MJ
2oz cod liver oil = 2.1 MJ
1.5# TCOM = 10.6 MJ

Total: 14.5 MJ = 3.46 MCal
RDI MCal 26.3 MCal

3.46MCal is 13.16% of 26.3MCal

Is that what you meant?

I’m really wondering if I should get the grass tested - there’s so little and DE will change so much when it dries up - soon…

Here’s how they calculate:

Pasture intake is initially calculated based upon grazing hours, as follows:

  • An estimated pasture intake is calculated for your horse by taking the number of hours your horse has access to pasture and multiplying it by an estimated rate of pasture intake.
  • In the calculation we assume that a horse with more than 16 hours access to pasture can eat its total estimated daily intake of feed.
  • For example, a horse in light work is estimated to eat 2% of its bodyweight in feed per day, so if it had more than 16 hours access to pasture, it would be able to eat the full 2% of its bodyweight in pasture.
  • As the number of hours access a horse gets to pasture declines, so does the estimated pasture intake.
  • For example, a horse with up to 10 hours access to pasture is estimated to consume 65% of its estimated daily intake.
  • If your horse has access to drought stricken or overgrazed pasture, the estimated intake will only be 30% of the possible intake for your horse.
[B]What happens when you add other feeds?[/B]

Because a horse only has so much room in its gut for food, there is a limit to the amount of feed a horse is able to eat in a day. Therefore, if you add supplementary feeds in the form of hay or concentrates to the diet that takes the horse’s daily intake over and above the horse’s estimated daily intake, the estimated amount of pasture in your horses diet is reduced by the amount of feed you add.
For example:

  • If a 500 kg horse in light work has access to good quality Temperate Grass pasture for 16 to 24 hours per day, its estimated daily intake for that pasture will be 10 kg/day.
  • However, if you add 2 kg of alfalfa hay, and 1 kg of a concentrate feed to the diet, the estimated pasture intake will be reduced to 7 kg/day.

Yeah that’s how I see it - something to do between hay and buckets. He’s on it 24/7 but there’s so little I entered he was only on it 7-10 hours/day and quality=poor, overgrazed.

#18

Check your MJ calc. I think its 24.5 or 5.84 MCal. It’d be closer to 22% if my math is correct.

I wouldn’t worry about testing the pasture, especially if it’s going to dry up soon.

#19

I’m having seriously horrific flashbacks to high school chemistry…

#20

[QUOTE=Palm Beach;8649684]
I’m having seriously horrific flashbacks to high school chemistry…[/QUOTE]

sit down and focus on your breathing. It will pass…:smiley:

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