I had never heard of this and knowing the general reputation of pet store employees (totally clueless) I thought I should check it out. Seems she was at least partially right.
Some hay, not just alfalfa, is treated with preservatives to prevent spoilage. Two types of preservative are commonly used: ammonia based organic acids and their salts, and microbial additives. The most common organic acids used are: propionic acid, a liquid, and anhydrous ammonia, a gas. It seems in using ammonia it´s very important not to exceed the application rate of 1% of dry weight because of the toxicity risk. I found this somewhat alarming:
Applying more than 1% ammonia to high quality forages can result in the formation of an unknown toxic compound. Animals consuming ammoniated high quality forage often exhibit hyperexcitability followed by death. The toxin is transferred into milk, so nursing calves and lambs also are susceptible to the toxin. HIGH QUALITY HAY MUST NOT BE TREATED WITH MORE THAN 1% AMMONIA (DRY MATTER BASIS).
More cause for concern:
Disadvantages of Using Hay Preservatives
1. Propionic acid is corrosive and can damage machines and injure workers.
2. Anhydrous ammonia is difficult to apply and is a hazardous chemical.
This information is from the Ohio State University Extension:
This leads me to wonder how much hay is treated with preservatives and whether this has any relation to some of the "mystery" ailments our pets suffer.
Apparently fresh cut alfalfa is sometimes treated with chemical "drying agents" too. Don´t know if I even want to go there.
Dawn says that they do not use any chemicals on their hay. However, she finds it somewhat ironic that we are worried about it, while some rabbit people are actually encouraging it! In her words: "they feel it will decrease any mycotoxin
problems." She goes on to say that properly dried and baled hay won´t have a mycotoxin problem even without the use of preservative chemicals.
Since I neglected to get permission to repost her email in its entirety publicly (I know, I´m sorry!) I probably shouldn´t. However, if anyone wants a copy of the email, I can forward it to you. (That´s allowed, right?)
We do not use any chemicals or preservatives in any of our hay. I am
aware that some producers do have access to this product and it is used
in areas of that receive a lot of moisture and they have problems with
getting hay "put up" in a timely fashion before it throughly dries.
It is ironic however because some rabbit owners are wanting to increase
the use of this product as they feel it will decrease any mycotoxin
problems. The bigger picture and concern is that you make sure that you
dry your hay throughly before it is baled and you will not have a
problem with spoilage, heating, or mycotoxins.
Be assured that our hay is not treated in any way with any chemicals or
preservatives. If you or anyone else has any questions please feel free
to call me or anyone else can email me as well.
Director of Nutrition and Product Development
Oxbow Pet Products
"Specializing in Herbivore Nutrition and Supportive Care"
The preservatives kill the molds and fungi, the chemical dessicants dry out the hay so the molds don´t form.