Responses to questions regarding bone eating tend to be rather negative, ranging from a simple, "I wouldn't recommend it," to the severe, "Feeding bone to your ferrets will kill them," and all points in between. Rarely are the benefits of bone eating discussed (exceptions include "Give Your Dog A Bone" and "Grow Your Pups With Bones" by Dr. Ian Billinghurst), although a growing number of veterinarians and scientists are turning away from the anti-bone tradition (can you call a history less than 50 years old a 'tradition"?) and embracing new studies. In an extended review such as this one, a discussion of benefits is more than appropriate. Most of these advantages have been more-or-less discussed during various rebuttals, but since their beneficial nature is so often overlooked, they are worth compilation within their own section. Benefits of bone eating can be divided into four basic categories: psychological, physiological, nutritional, and hygienic. Hygienic benefits include plaque removal and tooth polishing, as already discussed. The bone fragment stimulate the gums, improving circulation, and scrapes the tongue, helping to clean it. While the ferret chews, the salivary glands are stimulated, helping to wash particles out of the mouth and maintain proper oral pH. Salivary washing also helps maintain a proper oral ecology, helping to reduce the risk of the type of bacterial colonization that helps cause bad breath, gingivitis, and periodontal disease. Additionally, salivary washing helps reduce the pH within the esophagus and the stomach. Hygienic benefits also include a reduced risk of gastrointestinal blockage caused by hairballs. As bone travels down the digestive tract, hair tends to become entrapped in exposed trabeculae on large chunks of epiphyseal bone. If the bone's diaphysis was small enough to swallow, perhaps a mouse or rat femur, hair is commonly trapped within the hollow diaphysis and carried outside the body. Usually hyaline cartilage, the slick white material on the end of long bones, partially survives gastric digestion. When wet and semi-digested, fur tends to stick to it as it passes through the gastrointestinal tract. Overall, bone and associated particles of cartilage acts as a transport mechanism for fur, helping to move the slick material out of the stomach and intestines before it can ball up and cause trouble. It is an important part of nature's hairball remedy. Many of the nutritional aspects of bone eating have been covered. Bone is high in fat and protein, rich in essential fatty acids, vitamins, proteins, and minerals. The haemopoietic tissue found the red bone marrow is nearly a perfect food for mammalian carnivores. The mineral part of bone has a perfect calcium-phosphate ratio, and is easily absorbed. Carnivores are so well adapted to a diet that includes bone that those eating a "meat-only" diet will develop rickets, and such a diet during growth and development can cause other debilitating disease and even death. Bone is healthy for ferrets to eat, and for the most part it is harmless and safe for the animal to consume. [2-part post combined here] Physiological benefits of bone eating include supplying the body with chemical buffers that help maintain a constant body pH. Because bone provides the perfect ratio of mineral salts, it helps prevent or reduce the effect of osteoporosis, a potentially serious problem in de-sexed animals (spayed, neutered) especially those suffering from diseases that tend to leach calcium from the skeleton. Recent evidence suggests saliva produced by extended periods of chewing helps reduce stomach acids in the esophagus, preventing acid reflux and lower esophageal scarring. A hidden benefit for female polecats is the readily absorbable iron found in the red bone marrow; iron can be hard for the body to absorb if it isn't at a specific ionic arrangement. Bone marrow has iron in a perfect ionic configuration for absorption, helping female polecats offset the problems of prolonged estrus. Eating bone does not prevent the suppression of bone marrow due to hyperestrogenism, but, it does supply large amounts of iron and other nutrients in ratios perfect for making blood tissue, helping to offset the problem for as long as possible. This is not just a benefit for intact females, but it would be beneficial to ANY anemic ferret. Psychological benefits of bone eating are controversial because they are so difficult to prove. While it is well known that animals use specific behaviors to reduce psychological tension, it is unknown if chewing bone would reduce such stress in ferrets. However, a number of animal behavior studies suggest domesticated animals that are allowed to express behaviors found in their wild progenitors have lower corticosteriod levels in their blood. Corticosteriods (cortisol, cortisone, corticosterone) are glucocorticoid hormones produced in the cortex of the adrenal gland, and elevated levels have long been considered as a physiological index of stress. In other words, the more stress in a ferret's life, the higher the blood levels of corticosteriods. Stress can be caused by pain, inescapable aggression, extended confinement, overcrowding, boredom, disease, lack of strenuous exercise, inability to express natural behavior, and fear (among others). There are potential links in long-term elevated corticosteriod levels and various health problems, including depressed immune systems, tumor formation, irregularities within various hormonal systems, elevated heart rate and blood pressure (and associated heart and kidney disease), depression, and a suite of behavioral problems. NO research that I am aware of has linked these problems to elevated corticosteriod levels in ferrets, and I am unaware of ANY study looking at how corticosteriod levels in ferrets vary with various environmental factors (caging, diet, overcrowding, etc.). Nonetheless, while differences exist, the basic physiological rules that govern one species are applicable to others, and the veterinary community may underestimate the impact of stress on ferrets. For example, it is POSSIBLE stress may be a factor in adrenal disease, perhaps exacerbating the problems of early neutering and photoperiodism that are also implicated in the development of the disorder. Bones are chewed for two reasons: to obtain nutrients, and as a "downtime" activity. Downtime activities are essentially self-indulgent in nature, but are important stress relievers. Chewing has been shown to be important stress relievers in large cats, wolves, dogs, and other carnivores. The importance of chewing in dogs is so well known that selling things for dogs to chew is a multi-million dollar business. Chewing is also very important to ferrets, as those who have opened their wallets to pay veterinarians to look for fragments of rubber or other foreign objects lodged in the intestines of their pets can testify. Polecats are known to habitually chew bones, and fragments of partially consumed bones have been found within their dens and scats. This type of activity would constitute "free food" in that for very little energy--the cost of chewing--a polecat could obtain important energy and nutrients simply by chewing bones left behind from their last meal. For an animal with high-energy costs, this could be an extremely important source of nutrition that could spell the difference between eating just enough to survive until the spring, and death. I think ferrets have an inborn desire to gnaw bones, chewing them supplies stress-reducing satisfaction. Can I prove it? Just give me some time. Bob C [Posted in FML issue 4161]