Most people understand that constipation is stool that is drier and harder than normal with decreased frequency of bowel movements resulting in lack of or difficulty passing stools. In cases of constipation it is important to rule out things that may be obstructing the stool or causing pain when the pet is trying to pass feces.
Anal gland abscesses or back pain can cause an animal not to pass stool because it just hurts too much and this results in constipation. Sometimes with dogs in particular they will have eaten something they should not --like large amounts of cooked bone and they will end up with rock hard stool.
In the case of dogs, frequently they are not taking in sufficient water or they may have underlying kidney issues that are consuming lots of water and overall the dog is dehydrated. Poor nutrition ( such as feeding constant dry food), chronic illness, aging, or constitutional weakness can lead to deficiency of fluids.
Chinese medicine uses the analogy that with constipation the river has dried up and the boat will not float so the cure is to restore the river. So how do we do that?
Conventional treatments may include enemas, fluids either subcutaneously or IV, laxatives, motility drugs, higher fiber diets, or in severe cases in which the colon has stretched a lot a colonic reduction surgery.
Treatment principles from a holistic stand point are to moisten the intestines and tonify Qi ( which is life force or movement so the intestines have the ability to push the stool out) and Yin ( which is essentially fluid). Acupuncture , herbs, homeopathic remedies, fiber and food therapy work well to accomplish this.
Psyllium and flax seed can be used as fiber sources as can chickory root. Slippery Elm works well for constipation and diarrhea but you need the right formulation. Aloe, senna and cascara may help as well. Nux vomica, a homeopathic formula is great for cats.
Check with your holistic vet for a dose. For long standing constipation a Chinese herbal and acupuncture are needed. For cats that would be Ma Zi Ren Wan ( Hemp Seed Pill) teapills.