Feeding additional magnesium

[soloequestrian]

Following on from an earlier post, where I wasn't able to spell 'magnesium', I have got some magnesium to add to feed. The horse already gets a supplement that should give her 9g per day which is the NRC recommendation. She also in theory gets 25g per day from her grass intake (assuming 12.5kg grass per day) - this is from a forage analysis that is quite old now but I've never been able to find out how often they should be done. I want to give her more to see if it will help her be a little less determined to see predators behind every object. How much extra would be reasonable, at least as a starting point?

 

[ester]

It's not really the absolute amount as much as the ratio with calcium and phosphorous that matters.

 

[Sossigpoker]

Also different types of magnesium are absorbed better than other types. I think chelated is the most readily absorbed form.

 

[soloequestrian]

I've read that the ratio should be 3:2:1 Ca: Phos: Mg - are those the commonly used values?
I've also heard of people supplementing Mg up to 35g per day with no mention of increasing the Ca/Phos quantities.
Recommendations for reliable reading material welcome!