Beneficial effects of NTP-2000 diet on growth, survival, and kidney and heart diseases of Fischer 344 rats in chronic studies

Diet is one of the most important environmental factors influencing growth, survival, and appearance of age-associated diseases in rodents. NIH-07 ope n formula rodent diet was the selected diet for the National Toxicology Pro gram studies from 1980 to 1994. After a number of experimental diets were e valuated, a new one designated as NTP-2000 was selected for rodents in NTP studies beginning in 1994. This report summarizes the results of dosed feed and inhalation studies for differences in growth, survival, and severity o f kidney and heart lesions in Fischer 344 rats fed NTP-2000 or NIH-07 diets . In the dosed feed studies, male rats group housed and fed the NTP-2000 di et grew slightly slower, attained maximum body weight later, and lost less body weight by the end of the 2-year studies compared to the groups fed NIH -07. Female rats group housed and fed the NTP-2000 diet in dosed feed studi es had significantly slower growth, with lower maximum body weight compared to the groups fed the NIH-07 diet. In the inhalation studies, male rats in dividually housed and fed the NTP-2000 diet had slightly higher maximum bod y weight and significantly higher final body weight, with lower loss of wei ght when compared to similarly housed groups fed the NIH-07 diet. In inhala tion studies, female rats fed the NTP-2000 diet and individually housed had significantly slower growth. The NTP-2000 diet significantly increased the survival of male and female rats, with a dramatic increase in survival of males in inhalation studies. This diet also caused significant decreases in severity of nephropathy and cardiomyopathy, and the decrease was marked in males. These observations indicate that diets balanced for nutrients, such as the NTP-2000, could markedly improve the health and increase survival o f the rats used in chronic studies.