Those are not poisonous, but they should not be in the hay. Those things are just too prickly, and can stick to fur and bedding. They will get stuck on your clothing too. Very annoying!
I would filter through the hay, but if you find any more, I would prefer you just throw it out, and I will give you a store credit or refund. I am contacting the supplier to let them know and find out how it got in there. (It’s a nasty weed, and it looks like one was missed when they harvested). I am guessing it just got in one big bale, and even though it was divided into smaller mini bales, they look like something that wouldn’t shake out easily and get caught up even during the filter/separation process. . I will be going for a new hay run this week and I will be sure that they look through it thoroughly for these beforehand. If anyone else finds this in their Mature Oat hay, please email me directly through jenniferATbinkybunnyDOTcom.
Meow1 — I will emailing you directly regarding this as well.