For us this is a tricky question that is evaluated on a case by case basis. My wife has a degree in Animal Science so is very knowledgeable about large animal anatomy. We keep syringes, needles, Pen, horse wormer, bandgages, etc. on hand all of the time and have used them, unfortunately, quite often this past year mostly on the horses. The last cow we had a problem with retained part of the placenta, after a week of pen shots she was doing better, but two weeks later she started going down hill again so she went down the road. We could have called the vet, spent tons of money, and still had a sick cow, but we cut our losses and sold her for cull. I must tip my had to our vets :cboy: because they are great for answering questions on the phone for us, letting us try a treatment, and then either we call them back or they will call us a couple of days later and see what the prognosis is. We use a large animal vet that is about 40 miles away for serious items and a vet that's only 10 miles away for smaller stuff. The farther vet we used exclusively, but then we moved and it got pretty expensive for them to drive 40 miles to give us health papers for a horse or cattle show.
Any way, back to the topic at hand. I guess it all comes down to your experience and what you are comfortable doing. We've successfully doctored horses with punctures in their sides, cows with abcesses in a hoof, and sick calves. There are two procedures that are automatic vet calls and that is to geld horses and to stitch up an animal. Gelding is a little more in depth than I like to get and we don't keep stitching supplies on hand, which we could I guess but don't need them very often. Ok I'm starting to ramble so I'm going to finish. If you have any questions or immediate concerns, call the vet.
One more thing. Make sure you know what course of action is comfortable for you before the vet gets to your place. Case in point, we had a young vet come out a couple of years ago because we had a mare that would conceive, but wouldn't stay bred after the first month or so. I had done some research, my wife was in school at the time and had talked to a professor about the mare, and we had come to our own conclusion about this mare's ailment. This newly graduated vet came out and he examined her and wanted to do this $250 evasive tissue testing that would prove the microbial...blah blah blah. I lost focus and only heard $$$$$$$. We told him no, that there had to be something less costly and equally effective and he came back with "There's a $50 uterine culture we could send to CSU." Yes, lets do that and if it's inconclusive then we can spend a little more money. Long story shortened, my wife and I were correct with our research, the mare ended getting sold to a little girl in Nebraska and we all are happy in the end.