I'm afraid vet bills are an essential and wholly expected part of keeping livestock, particularly breeding stock, entirely straying from the topic of "unexpected costs".
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You are both right in my opinion, yes Vet bills are part of keeping livestock. But most costs are predictable year on year so easier to budget for. I have kept horses for 30 years and hardly saw a vet other than for annual vaccines but with sheep & goats and the horses getting older this last year me and the Vet are getting to know each other better.
Unexpected costs? More like loss of earning from wasting spending too much time gazing and lambs and kids.