OVC Student Veterinarians Share Externship Experience: Apparently all hay is not created equally

Each summer DVM students from the Ontario Veterinary College delve into practical experience at veterinary clinics across Ontario and additional locales. These blog posts are an opportunity to tag along with five of them this summer. This week student veterinarian Jodi took a pasture-to-plate approach to some hay samples. Check out all the student blogs at www.ovc.uoguelph.ca/externship

Working with Dr. Bob brings the unique opportunity to focus on some of his specialties like horse nutrition and toxic plants. Each week, we make our way into the fields to discover what is growing and where. I have already learnt a ton about the plants covering Southern Ontario pastures in early summer and have a better idea about the amount still left to learn.

This week, we also had the unique opportunity to take a ‘pasture-to-plate’ approach to our regular pasture walk. I got to consult with Dr. Bob on a hay sample analysis submitted by a curious client. The client wanted Dr. Bob’s comments on the hay composition as well as insight specifically on if the hay contained a toxic plant called hairy vetch (Vicia villosa).

Hairy vetch (Vicia villosa) was originally introduced from Europe and derives its name from its hairy stems and leaves. It is toxic to both horses and cows if it is consumed in large quantities (as a major portion of their diet) when the plant is reaching maturity. Typically, hairy vetch poisoning results in an immune system response that leads to skin issues, weight loss, diarrhea, and inflammation throughout the body. In large enough quantities, pregnant animals may abort their fetuses and mature animals may die suddenly. It is no wonder the client wanted to make sure we looked specifically for hairy vetch in the hay samples – it can be quite a nasty plant!

We set up our analysis station in front of the clinic and combed through the samples that were submitted. A passerby even commented that we “look like kids playing in a sandbox” – it was quite fun!

Above is a photograph of some of our plant findings within the hay samples. Each plant species contributes a different nutrient profile to the overall hay affecting its quality and suitability for different life stages like foals, adult horses, or pregnant mares. From left to right in the photograph: red clover (with flowers), tufted common vetch (upper), tufted common vetch seed pods (lower), tufted common vetch freshly-picked, alfalfa (with flowers), mature orchard grass, mature brome grass, timothy hay, and mature blue grass. Luckily, we did not find any hairy vetch in our searches and tufted common vetch does not have the same toxicity issues!

I had no idea how much complexity went into a bale of hay until I spent an afternoon ripping some apart and looking at them stem by stem. I realize now that I had little respect for the plethora of species that exist and make up what I previously referred to as “grass”. After a bit of time with the specialist though I have learnt that all hay is not created equally!

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