What part of the Country are you in?
There are many plants that can cause reproductive Toxicity, loss of pregnancy, they do not normaly cause a cow to dry up, that sounds more like poor body condition due to poor nutrition. I would look at what their diet is and the availablity a good quality minerals, (loose mineral), not the salt blocks you get at the local feed store. It is easier to identify the plants to the location, but I do not think Onion type plants cuase any trouble, we are in central Texas, and there are wild garlic, onions etc. and they dont seem to have much effect on the cattle or horses, though they really don't eat them either, if yours are eating them, they need something in their diet.
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