Since a single dose may not be enough to produce an adequate level of herd immunity, North Dakota Extension veterinarian Charlie Stoltenow says giving a second dose is a kind of “insurance policy.” He emphasizes that two doses are especially important when administering killed vaccines because they don’t produce as strong an immune response as MLV vaccines.

Stoltenow advocates vaccinating calves against what he calls "the big four." These are: infectious bovine rhinotracheitis (IBR), bovine viral diarrhea (BVD), bovine respiratory syncytial virus (BRSV) and parainfluenza-3 virus (PI3).

"These vaccinations set it up so calves can better fend off other disease threats," he says. Additionally, he recommends producers consider vaccinating against clostridial diseases and Mannheimia.