What they are:
Lamb horns are made from keratin, the same material as human fingernails and hair, and are a natural byproduct of lamb processing. 
For dogs:
They are a popular dog chew, particularly for those who enjoy a durable, long-lasting chew that can help with dental hygiene. 
Dental benefits:
Chewing on lamb horns can help to remove plaque and tartar buildup on a dog's teeth, promoting healthier gums and reducing the risk of periodontal disease, according to several pet product websites. 
Chewing satisfaction:
Lamb horns provide a satisfying chewing experience for dogs, helping to relieve boredom and reduce stress by releasing endorphins. 
Considerations:
While generally safe, it's recommended to supervise dogs while they're chewing on a lamb horn, especially strong chewers, as they can sometimes splinter. 
Low fat content:
Lamb horns are naturally low in fat, making them a good option for dogs on a low-fat diet or those with pancreatitis.