Iron content in hay?

Asked July 20, 2017, 8:08 PM EDT

How much is too much iron in local grass hay (for horses). How does the weather (wet/ dry year) contribute to iron levels? What is the best way to decrease the iron content in the hay....lime, fertilizer, rain levels? Any insight & recommendations would be greatly appreciated. Sincerely, Sue Ingram

Clackamas County Oregon horses hay production

2 Responses

Hello Sue,
I will be at the Horse Center for the rest of today, but Monday I will check with my clinical nutrition and forage books to see what I can find on iron content and how it is influenced by weather and how to decrease it.
This is a very interesting question that I will need to dig deeper. I will be in contact with you on Monday.
Have a great weekend.
Dawn

Hello Sue,
I have done some research and hopefully the information I found can help answer your questions. The common range of iron in grass hay falls between 180-200 mg on a dry matter basis. On an as-fed basis these numbers would drop in accordance to the amount of moisture in the grass. Horse requirements range from 40-50 mg depending on their age and use. Toxic levels of iron are possible within the horse, but is not often seen unless an iron rich supplement is being used for a prolonged period of time. Toxicity is not common from forages, but not impossible. If toxicity is of question blood work should be done to determine iron levels.
Soil pH, rainfall and leaf:stem ratio seem to be the biggest influences on iron levels. High rainfall areas, such as in western Oregon, cause the soil to be acidic due to the dissolving of certain basic minerals and leaching. The more acidic the soil the more available iron is within the soil and thus the forage. Therefore, the application of lime to increase the pH and make the soil more basic should reduce the availability of iron. I have attached links to several OSU Extension publications in regard to lime application and soil pH manipulation.
If you haven't had the soil tested where the hay is being harvested that would be the first step. When you get the soil test results if the pH is less than 5.4 you should apply lime. The amounts are in the publications I attached.
The leaf to stem ratio also influences iron. Iron is stored in the leaf, so the higher the number of leaves the higher the iron. As the plant matures and the stem becomes more prominent the iron should reduce.
Links:
https://catalog.extension.oregonstate.edu/em9061
https://catalog.extension.oregonstate.edu/em9057
I hope this gives you are start. If you have any other questions please email me at the address below.
Dawn