Year: 2009
Type: dissertation
Abstract: Laboratory rodents are routinely fed ad libitum, i.e. food is available at all times in unlimited quantities. The practice of ad libitum feeding has been widely criticized. Concerns include the high incidence of morbidity and the low survival rates associated with ad libitum feeding. It has also been claimed to accentuate interindividual variability in research results. Dietary restriction, i.e. restricting caloric intake, has been proposed to resolve many of these problems. Dietary restriction does decrease morbidity and mortality and can also decrease result variation. However, the current methods of dietary restriction can also have negative impacts on both animal welfare and scientific integrity. Dietary restriction often subjects the animals to social isolation and to abnormal feeding schedules. As a consequence, the animals may suffer from unfulfilled behavioural needs and the interpretation of research results might suffer from the disrupted circadian rhythms. A novel method of dietary restriction, the diet board, was developed as a solution for feeding laboratory rats. The diet board is a wooden board into which food pellets are embedded. In order to obtain food, the rats have to gnaw at the wood, making it more difficult to eat. The diet board can be kept in the cage continuously. The diet board offers the possibility of combining dietary restriction with group-housing and unaltered circadian eating rhythms. In this dissertation, the diet board and its basic characteristics will be presented. The results are based on one experiment and some pilot studies preceding it. A total of 60 male Wistar rats were used. The rats were seven weeks old at the beginning of the ten week experiment. Half of the animals were fed exclusively with the diet board and the other half ad libitum, with the rats housed in groups of three. The diet board provided mild to moderate dietary restriction. The food intake was 85% of the ad libitum level and the diet board rats gained 15% less weight. The diet board rats had significantly less gonadal fat, but their skeletal growth was only minimally hindered. Serum albumin, alanine aminotransferase and protein levels were not altered by diet board feeding. Serum creatine kinase was slightly elevated in the diet board group. More differences were observed in variables related to energy metabolism. The diet board group had lower levels of serum triglycerides, free fatty acids and cholesterol; and a higher serum corticosterone. Surprisingly, serum ghrelin was significantly higher in the ad libitum rats. In serum leptin, adiponectin and insulin, no differences were detected. In variables related to stress reactions, the ad libitum rats had larger adrenal glands with a higher adrenaline and noradrenaline content, indicating elevated sympathetic tone compared to the diet board rats. In concordance with their elevated corticosterone levels, the diet board rats had a lower secretion rate of faecal immunoglobulin A. In conclusion, the diet board elicits milder, but qualitatively similar metabolic responses as those reported with other methods of dietary restriction. The variation in growth did not differ between the groups, indicating that the diet board did not result in uneven food accessibility or increased competition for food. The diet board was well suited for group-housing. The welfare implications are not conclusive, but there were no signs of stress-related pathology in the diet board group. The diet board seems a promising refinement alternative to the current methods of dietary restriction.
Source: Työväentutkimus Vuosikirja
Author: Iiris Kasanen
Language: English
Topic: Dietary Effects on Health
Subfield: Physiology (medical)
Field: Medicine
Domain: Health Sciences
Open Access status: green
OpenAlex ID: W2121699796