My friend has two horses confined to close quarters(on dirt not grass) that tend to chew planks into kindling also to bite owner. The had not had salt for an extended period of time and I'm not sure about mineral availability. Could you help identify the problem with a solution please? Tom
The chewing of the planks and the biting of the owner are not necessarily related. I will address each of your items individually.
1) chewing planks- this is actually a fairly normal behavior in horses that are confined and have nothing to do. With no grass to graze on, horses will often chew on other items in their environment. Providing them with hay to eat while turned out may help, or you can try different methods to deter them from the boards. These include running an electric wire at the top board, painting the boards with something that tastes bad (there are commercial products available) or putting angle iron on the boards so the horses have more difficulty chewing them.
2) Salt- The horses should have free choice access to salt and water. If the owner uses a salt/mineral block, then both issues can be addressed at once. If the horses are being fed a commercial mixed feed, it may already have the salt and minerals included in the feed.
3) Biting the owner- Horses bite out of aggression/self protection and lack of respect. Since you don't mention that the horses are charging him, or other things like that, we will go with lack of respect. The owner needs to handle the horses with a halter and lead rope, and correct them when they bite. I do not recommend striking the horse around the head, or on the muzzle, to discourage biting as you often then create a situation when the horse shies away from the raised hand. The horses need to learn to stay out of the owner;s space, which can be done most effectively by leading with a halter and lead rope, and a correction with the halter when the horse reaches into the owner's space.