EFFECT OF INCREASING DIETARY VITAMIN-A ON BONE-DENSITY IN ADULT DOGS

There has been an increase in vitamin A fortification of livestock fee ds resulting in increased residual vitamin A in organ meats, which are often used in canned dog foods. The effect on bone density of feeding various concentrations of vitamin A in a canned dog food product was investigated. Thirty-two random-source dogs were assigned to four trea tments in a randomized complete block design. The diets contained 15,0 00, 50,000, 116,000, or 225,000 IU vitamin A/1,000 kcal ME. Diets were fed tap to 1 yr. Computed tomography was used to determine bone densi ty of the right tibia at 0, 3, 6, 9, and 12 mo. Computed tomography is a more sensitive technique for determining bone density in vivo than conventional x-rays; There were no differences (P >.10) in tibia bone or marrow density in any of the dogs fed the various concentrations of vitamin A. There. was mw, interaction of time x diet on bone density (P > .05) or = bone marrow density (P > .05). In addition, there were no changes in serum alkaline phosphatase, calcium, or phosphorus. Thes e results indicate that concentrations of vitamin A three times the re commended maximum safe amount (71,429 IU/1,000 kcal ME) are not detrim ental to normal bone health in dogs. Therefore, these data support the hypothesis that canines are less sensitive to excess vitamin A in the diet than some other mammals.