Why there is no need of dental care in ruminants?

There probably is some need of dental care for ruminants but the number of ruminants that will live long enough to need dental care and are valuable enough to merit such care is very low. In general, when a ruminant's teeth are no longer working properly, the animal is either sent to slaughter or is humanely euthanized. The one major exception to this would be teeth extractions of molars due to severe infection - most large animal veterinarians will surgically remove the affected teeth and clean out the nidus of infection.