Breed of cattle, your location, what are they eating, type of pasture & minerals, current on de-worming, current on vaccinations, age of cattle, new arrivals or your present herd??? Sudden change of feed or hay type??
How many cattle and how long has this been going on? Do they have fevers? Could they have eaten something that would give them hardware disease? Pretty hard to say with such little info. Have you called a vet?
watch for pinkeye i had 16 with those symptoms and they came down with pinkeye and i am thinking ibr on my herd...but gladly i have gotten all but one back in pretty good shape but pink eye has hit my herd hard