title: Diet restriction in rat toxicity studies: automated gravimetric dispensing equipment for allocating daily rations of powdered rodent diet into pouches and 7-day feeders.
abstract: Survival of ad libitum-fed rats has declined in the 2-year carcinogenicity bioassay. Restriction of the number of calories, without compromise of the overall nutrition offered to animals including rats, results in increased lifespan of animals. Diet restriction in rats is best achieved through offering of rations of feed daily instead of weekly, as is routinely done in ad libitum studies. The objective of this project was to develop an accurate and precise method of dispensing daily rations of feed. A gravimetric vibratory-type dispenser was used to dispense target weights of 15 and 20 g of powdered certified rodent diet into either labeled pouches or seven-well carousel feeders. The tolerance of the dispenser was the target weight +/- 3%. The amount of food offered to the diet-restricted rats was approximately 25% lower than that consumed by rats offered diet ad libitum. After 2 years, male rats offered 20 g and female rats offered 15 g of powdered rodent diet daily had remarkably lower body weights than did animals offered the diet ad libitum. Generally, the rats ate the entire ration of food offered to them each day. Survival of the diet-restricted rats was 70% to 82% at the end of a 2-year study. This investigation demonstrates that modest reduction of food intake, resulting in increased survival of Sprague Dawley rats in 2-year carcinogenicity bioassays, can be achieved reliably and efficiently through use of an accurate and precise automated method of dispensing powdered diet for use in multiple rat studies. In addition, this method of food dispensing provides a practical way to administer test compound in the diet under the conditions of diet restriction.
authors.affiliation: Schering-Plough Research Institute, 144 Route 94, Lafayette, New Jersey 07848, USA.
authors.forename: J M
authors.initials: JM
authors.lastname: Petruska
authors.forename: T M
authors.initials: TM
authors.lastname: Haushalter
authors.forename: A
authors.initials: A
authors.lastname: Scott
authors.forename: T E
authors.initials: TE
authors.lastname: Davis
mesh_terms: D000821:Animal Feed; D000822:Animal Husbandry / Q000295:instrumentation*; D000818:Animals; D000830:Animals, Laboratory; D002273:Carcinogens / Q000633:toxicity*; D002940:Circadian Rhythm; D004435:Eating; D005260:Female; D005508:Food Deprivation; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley; D012727:Sex Characteristics; D015430:Weight Gain; D015431:Weight Loss
chemical_list: D002273:Carcinogens