For last several years I have vacinated using Virashield 6+L5. I vacinate calves 30 days before weaning and again at weaning. I have always vacinated cows 2x a year. I realize manufacturer only says one booster a year is necessary so am going that way. Most of my cows are bred in June. It would be easier for me to vacinate in December than May. Do you think it would make that much diference what time of year I vacinate.
