Colostrum management and disinfection are the first overriding prevention measures. In response to a recent post,  no one in Facebook land really knows why oral antibiotics might be used? I would say that for specific E.coli strains e.g. k99, before the vaccine kicks in and thats about it. Salmonells, its probably too late, but long term this is vaccination of the cow too. In other scour, if there calf is not sucking and there is signs of mucous membrane breakdown (blood and tissue in the scour) then injectible antibiotics could be a good idea. HOWEVER, rehydration and acidosis need to be addressed as a priority. Oral rehydration is the first treatment, not antibiotics, unless specifically prescribed by a Vet. Crypto is a different kettle of fish, as it is a protozoan and not a bacteria. Scour bugs (crypto, viruses etc) are additive, so disease increases with the number of different bugs and the sheer number of each bug also, so disinfection and vaccination keep those numbers down.