Dr. Getty: Hi, I'm a 3rd year vet student and have been learning about diet analysis (on my own, not in school unfortunately) and had a question. My horse's hay is very high in manganese (she gets about 2700mg per day). Do I need to bring the iron and zinc up to that level (to get the ratio of 4:4:4:1 for Manganese:Iron:Zinc:Copper)? It's still below the toxic levels that I read in nutrition books, but I worry about giving that much. I also read that Manganese can interfere with Phosphorus absorption, so maybe I should supplement that as well?

Where are you from? Auburn, AL

How did you locate this forum? online

Hi Audra,

First, let me commend you for taking it upon yourself to learn more about nutrition. It's true that nutrition is not a required course in most vet schools, and if it is, it is only one course. So, this is why I consider myself part of a "team" that all horse owners should have -- a qualified medical professional (your vet), an equine nutritionist with an advanced degree (preferably a Ph.D.), and a hoof specialist (preferably barefoot specialist).

Ok, now what I said all that, on to your question! If you are feeding 20 lbs of hay, for example, that translates in a 297 ppm level of manganese. According to the NRC, 400 ppm is the highest tolerable level. So you are in range. However, phosphorus can be a problem. So, I recommend that instead of fiddling with the iron, copper, and zinc levels, that you evaluate how much phosphorus and calcium is in the diet. You want twice the calcium level as phosphorus. If phosphorus is less than half of calcium, you can feed rice bran per day to add additional phosphorus. Rice bran offers 1.78% P on a DM basis and only .07% calcium.

All the best,

Dr. Getty
Author of Feed Your Horse Like A Horse

Audra Cook

Dr. Getty: Hi, I'm a 3rd year vet student and have been learning about diet analysis (on my own, not in school unfortunately) and had a question. My horse's hay is very high in manganese (she gets about 2700mg per day). Do I need to bring the iron and zinc up to that level (to get the ratio of 4:4:4:1 for Manganese:Iron inc:Copper)? It's still below the toxic levels that I read in nutrition books, but I worry about giving that much. I also read that Manganese can interfere with Phosphorus absorption, so maybe I should supplement that as well?

Where are you from? Bayfield, CO

Dr. Getty,
Thanks for your reply. The calcium and phosphorus are both above minimum levels and in the correct ratio range. Copper and zinc are both significantly deficient, however, so that's why I wanted to bring them up to the manganese level (in the correct ratio).

Where are you from? Auburn, AL

How did you locate this forum? online

Hi Audra,

Horses can tolerate high levels of manganese so I would be reluctant to suggest that you add more copper and zinc. But, since it reduces phosphorus absorption, I would recommend that you add some more phosphorus (and also calcium if needed.

All the best,

Dr. Getty [:-]
Author of Feed Your Horse Like a Horse


quote=Audra Cook]Dr. Getty,
Thanks for your reply. The calcium and phosphorus are both above minimum levels and in the correct ratio range. Copper and zinc are both significantly deficient, however, so that's why I wanted to bring them up to the manganese level (in the correct ratio).[/quote]

Where are you from? Bayfield, CO