title: Effect of the AIN-93M purified diet and dietary restriction on survival in Sprague-Dawley rats: implications for chronic studies.
abstract: Survival, growth and dietary intake (DI) variables were monitored in a chronic 114-wk study in which male Sprague-Dawley rats [n = 120; National Center for Toxicological Research (NCTR) colony] consumed the AIN-93M purified diet ad libitum (AL), or an amount reduced by 31% of total AL intake inclusive of all macro- and micronutrients. The main objectives were to ascertain the survival characteristics of rats fed the AIN-93M diet and to determine whether dietary restriction (DR) increases longevity of rats fed this casein-based diet compared with the use of mixed-protein sources of the NIH-31 cereal-based diet in an earlier study. Body, liver, brain, the brain/body ratio, spleen, thymus and kidney weights, body length and body density were decreased (P < 0.05) by DR, whereas testis weight and skull length were not altered by DR. Significant age effects at 58 and 114 wk were found for body, brain, the brain/body ratio, liver and testis weights, and body density. Survival rates for the AL and 31% DR groups were 43.3 and 57.5%, respectively. Survival curves were not significantly different. The survival rate for AL rats fed the AIN-93M diet was not different from that of AL rats fed the NIH-31 diet (43.3 and 51.7%, respectively). However, the survival rate for 31% DR rats fed the AIN-93M diet was significantly lower than 25% DR rats fed the NIH-31 diet (57.5 and 87.5%, respectively) although both groups had similar body weights and energy intake at various ages. Nutritional components in the NIH-31 diet that are missing and/or reduced in the AIN-93M diet may interact with DR to increase 114-wk survival. Although the survivability, growth and anatomical results of this study suggest that the AIN-93M diet is suitable for chronic rodent studies, additional studies such as comprehensive histopathologic and physiologic investigations must be undertaken to complete the evaluation process.
authors.affiliation: Division of Genetic and Reproductive Toxicology, National Center for Toxicological Research, FDA, Jefferson, AR 72079, USA. pduffy@nctr.fda.gov
authors.forename: Peter H
authors.initials: PH
authors.lastname: Duffy
authors.forename: Sherry M
authors.initials: SM
authors.lastname: Lewis
authors.forename: Martha A
authors.initials: MA
authors.lastname: Mayhugh
authors.forename: Andy
authors.initials: A
authors.lastname: McCracken
authors.forename: Brett T
authors.initials: BT
authors.lastname: Thorn
authors.forename: Philip G
authors.initials: PG
authors.lastname: Reeves
authors.forename: Shirley A
authors.initials: SA
authors.lastname: Blakely
authors.forename: Daniel A
authors.initials: DA
authors.lastname: Casciano
authors.forename: Ritchie J
authors.initials: RJ
authors.lastname: Feuers
mesh_terms: D000375:Aging / Q000502:physiology*; D000821:Animal Feed; D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D004044:Dietary Proteins / Q000008:administration & dosage*; D004435:Eating / Q000502:physiology; D002149:Energy Intake / Q000502:physiology*; D005508:Food Deprivation / Q000502:physiology*; D006128:Growth / Q000502:physiology*; D008136:Longevity / Q000502:physiology; D008297:Male; D009929:Organ Size / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D016019:Survival Analysis
chemical_list: D004044:Dietary Proteins