I am not sure why I only had 2 heifers with snotty noses for one day this year , sold the feeders aff the cow, vaccinated my heifers I kept with Nasalgen PMH 3 as I have for the last 2-3 years . Last couple of years every time it warmed up they would get snotty noses. Did not bed them as much, not at all for awhile in fact. Usually vaccinate with Bovi Shield Gold one shot and Alpha 7 about 10-14 days post weaning, have not yet this year due to cows some of which some have never been vaccinated with a live vaccine are right next to them. Wish I knew why!