Yes, LA .... also known as oxytetracycline, is one of the list of antibiotics that fall under the mandatory restrictions passed for the VFD rules several years ago and put into practice in several phases with the final phase in 2023. Any antibiotic that can be used in humans is strictly regulated now for animal use by the order of a veterinarian....
I was just thinking maybe you had some LA (oxytet) on hand and could use just a small squirt of it on her hooves.
Establishing a good relationship with a vet, and not overusing any drug, will get you to a point where most vets will sell/prescribe something and you will get a bottle of it to keep on hand for when you need to treat an animal without a visit from the vet every time.
Something as simple as "MultiMin" vitamins are also vet prescribed due to the amounts of stuff being "above" what is USDA approved... The selenium in it is above the normal recommended amount, so needs a vet approval to use it. Since we are in a selenium deficient area, it is well within what we normally need, but many people that think things like a little is good, a lot is better, get into trouble with overdosing on stuff... Sadly, it is "backyard farmers" that have this mindset that have gotten the different drugs a bad rap..... Overuse of any drug or even food additive like minerals, has given the animal industry a bad name. Some of it is warranted. But it has made it hard for those that have practiced animal care for years and know that there are times when something works off label.... and things you don't need to overdo either.
Most farmers do not automatically grab an antibiotic because of things like drug residue in the milk and meat now... sometimes using an antibiotic will do the job quickly and the animal does much better than dragging out all sorts of other treatments to have to result in the antibiotic in the end that has cost time and money on other stuff...
Foot baths for cattle are either copper sulfate or zinc sulfate... common on dairy farms that the cows are mostly in confinement... constantly on concrete and exposed to urine and manure... even in the farms that scrape the barns and keep them fairly clean... but cattle get hoof rot, and strawberry warts and such.
Sorry, this is probably a whole lot more than you wanted to know...