Lack of effect of fluoride on reproductive performance and development in Shetland sheepdogs

A 10-y history of high rates of perinatal deaths and congenital anomalies in dogs in a Shetland Sheepdog kennel prompted investigations into the cause(s). Skeletal fluorosis (mottled teeth in pups, bony exostoses in adults) followed use of a commercial dog food later found to contain 460 ppm fluoride (F) from rock phosphate added as a mineral source. The effects of the water source and fluoride in dog food on female reproduction and teratogenicity were investigated in a 2-y, 2-way factorial study in the kennel. Twenty adult shelties of proven fertility were brought into the kennel and randomized into 4 treatment groups, each consisting of 4 females and 1 male. Treatments were: Group A, high F (460 ppm) dog food, well water; Group B, high F dog food, distilled water; Group C, low F (55ppm) dog food, well water; Group D, low F dog food, distilled water. Only Group C produced as many pups as expected. Overall the missed pregnancy rate (44%) in study bitches and perinatal death rate (50%) in 48 study pups paralleled the problems in shelties resident in the kennel. Higher rates for both variables in the high F and the distilled water groups seemed likely due to chance. The only major anomaly was in Group D; minor anomalies appeared in all groups. Although 460 ppm F in dog food did produce bony exostoses, we did not find convincing evidence that it adversely affected reproduction in shelties. The cause of the reproductive problems was apparently not the dog food, water, foliage, genetic factors, or infectious disease and currently remains undetermined.