5cc sounds likes a large dose. Blackleg vacc's are usually standardized 2-3 mL, regardless of age of animal.
Find out from your vet if you live in a high risk Clostridial infection area. I do, so cows get vaccinated annually with Covexin Plus. Never used to, but a fellow in another town 8 years ago cleared 20 acres and let his cows out, after calving in the spring, onto the new ground. 34 cows and a bunch of calves dropped dead within a couple of days and bankrupted him. All were killed by Sordelli type Clostridium infection (just another strain of blackleg). Always been here, but plowing up new ground can really surprise a person.
I did use Ultrachoice 8, which I think Bez is referring to, but it didn't have the tetanus included in it, so I switched to Covexin Plus, which has everything Ultrachoice 8 has, plus tetanus, and is cheaper. :cowboy: