The reduction potential of diet board feeding—survival and clinical chemistry of group-housed Sprague Dawley rats in a 24-month study

Although overeating is the root cause of many diseases and even premature death in laboratory animals, ad libitum feeding is still the prevailing practice in rodent husbandry. There is a need for practical methods of food restriction compatible with group housing. The diet board was developed as a mechanical solution to food restriction of group-housed rats. It tightly embeds food pellets in grooves cut into aspen boards, forcing the rats to gnaw wood to reach their food. In this two-year experiment, 146 nine-week-old outbred Hsd:Sprague Dawley ® rats were divided into four equal groups: diet board-fed males and females, and ad libitum-fed males and females. Blood samples for clinical chemistry were collected at regular intervals during the study, and times of spontaneous death or euthanasia were recorded. Triglyceride and cholesterol values were significantly lower in diet board males than ad libitum males. The restriction of food intake via a diet board significantly increased the 24-month survival rate for both female and male groups. The better observed survival rates amongst diet board-fed rats makes it possible to start long-term studies with far fewer rats than with ad libitum feeding. Thus, using a diet board appears to be a promising method for the reduction of animal numbers in long-term rat studies that is compatible with group housing.