Nuclear age needs for knowledge of the potential hazard to man from fallout on food—causing skeletal accumulations of strontium 90 (Sr⁹⁰)—are being served by the life-span experiments with 800 beagles underway at the School of Veterinary Medicine, Davis, under the sponsorship of the U. S. Atomic Energy Commission. These tests of low level radiation effects were started in 1957 and final data will not be available for 10 or more years. Some results to date include indications that pups can discriminate very little against Sr⁹⁰, assimilating almost 80% of the amount ingested in milk. Lactating dams discriminate against Sr⁹⁰ similar to adult dogs, and other species including man (about one-half of the ingested Sr⁹⁰ is assimilated). Observations of radiation-induced malignant tumors in beagles from ingested Sr⁹⁰ confirm results of experiments with smaller laboratory animals. Soft tissue cancers seem to occur at an earlier age than do bone tumors. Bone cancer in the beagle during the age of maturity has only been seen in those having high Sr⁹⁰ body burdens. The lowest cancer producing level of Sr⁹⁰ in the dog has yet to be determined. A wide range of incidental information on dog care is also being developed during the testing period. Modern cages have been designed and constructed that eliminate dog odor and offer solutions to many other kenneling problems. Whelping of several hundred litters of beagles indicates that the dam attains full maturity at three years of age. Records also show that about 20% of all pups die before weaning and that two-thirds of these are birth losses. Pups attain puberty between 10 to 12 months of age, which is a growth rate 10 times faster than man.

This is a progress report of the Radiobiology Project, School of Veterinary Medicine, University of California, Davis, sponsored by the U. S. Atomic Energy Commission under Contract AT(04–3) 472.