Question

Juju Bean is my middle-aged Trakehner mare that has a three-week-old filly at her side. She receives about 4 pounds of grain and 15 pounds of alfalfa hay per day, as well as free-choice salt and water. She does not have access to pasture. Since about day 220 of her pregnancy, she seems to be very itchy. This is her second foal, and nothing like this happened with the first one, though she was living in Florida when she carried and delivered that foal. I am perplexed. Can you help?

Answer

Watching an animal be irritated with itching can be exasperating. You should know, though, that feed allergies are not a common cause of pruritus (itching).

If the issue is related to feed, it would be caused by hypersensitivity to something in the diet.  Food allergies are actually rare but are caused by a reaction to proteins/allergens in the feeds and not a physiologic effect of the feed.

The most commonly incriminated feeds found in Juju Bean’s current diet are beet pulp, wheat, soy, and alfalfa. This is not to say that there couldn’t be any other food sensitivities than those I have listed.

Usually food allergies have an effect on the skin but can also affect the digestive and respiratory tracts.  Dermatological effects include generalized itchiness with or without skin bumps or welts.  Digestive tract involvement causes excessive gas and loose stools; respiratory tract involvement causes heaves or asthma.

There are allergy tests currently available that are used to identify possible allergens, but they are not without controversy. It would be useful to know what the mare was eating when she lived in Florida since she was not having problems then. Pinpointing what has changed in her diet, or if something in particular was added around day 220 of pregnancy, may help to determine a cause.

The most effective diagnosis is to do an elimination diet. This is done by eliminating all the current feeds/supplements and offering a hypoallergenic diet of oats and grass hay for 4-8 weeks. Then add the feed items previously used one at a time at one-week intervals.  If the itching returns, you will be able to identify the offending feedstuff.