Food and water intake, growth, and adiposity of Sprague-Dawley rats with diet board for 24 months

Ad libitum (AL) feeding of rats leads to obesity and increased result variability, as well as premature morbidity and mortality. It may also alter metabolism and responses to foreign compounds. Moderate dietary restriction (DR) reduces these untoward effects without compromising the sensitivity of rodent bioassays. The diet board (DB) is a novel method for achieving moderate DR in group housing. Food pellets are firmly attached into grooves in an aspen board, and rats have to gnaw the wood in order to eat. Food is available continuously, but due to the effort involved rats eat less. This study simulated a chronic safety test to assess the long-term effects of DB feeding. A total of 146 male and female outbred Sprague-Dawley rats, nine weeks old at onset, were housed in groups of three and fed either AL or with DBs for two years. Food and water consumption were measured at six time points. The rats were weighed every one to two weeks. Body and tibial lengths and epididymal fat weight were measured at necropsy. Modified body mass index was calculated at five time points after one year of age. DB feeding reduced body weight and fat tissue moderately, more so in males. DB males ate less than AL males, but no differences were seen in the total food consumption in the females. There was no consistent difference in the within-group variations of the measured parameters. DB is a workable DR method, albeit some modification could enhance and standardize its DR effects, especially in female rats. </jats:p

Behaviour, stress and welfare of Sprague Dawley rats (Rattus norvegicus) on diet board feeding for 24 months

Abstract Diet board (DB) feeding aims to reduce the health hazards associated with ad libitum (AL) feeding. Rats have to gnaw wood to detach food from the DB, reducing their food consumption. We studied the welfare effects of DB by measuring faecal corticosterone metabolites (FCM), elevated plus-maze (EPM) behaviour and cage behaviour. In this two-year experiment, 147 group housed (n = 3) Hsd:Sprague Dawley® male and female rats were subjected to DB or AL feeding. DB feeding in females elevated FCMs and increased eating observations by 85%. The DB males were observed eating 30% more often and resting 4.2% less than their AL counterparts. The DB rats of both sexes had 19% increased cage exploration during daytime and 20% reduced grooming during night-time compared to the AL rats. The increased FCMs may indicate slight stress in DB females. The EPM results indicate there was no anxiety due to DB feeding at six months. The cage behaviour could point to mild chronic stress in DB rats, but the lack of effect on escape-related behaviour and agonism suggests that there were no substantial welfare problems. DB feeding did not seem to disturb the circadian rhythm. The smaller food requirements of DB females meant they had to sacrifice less time than males gnawing at the DB to satisfy their appetite