Foraging enrichment for laboratory rats

Abstract

Abstract The provision of foraging opportunities may be a simple way of improving an animal's welfare, but this approach has been neglected for laboratory rats ( Rattus norvegicus ). Standard housing contains little enrichment, and food is often provided ad libitum , which may result in inactivity and obesity, especially in mature males. Foraging enrichments may offer a way to correct these deficiencies. This study compared three potential enrichments — a limited-access hopper, gnawing sticks and a foraging device — to standard housing and feeding conditions, in order to examine their effects on rat body weight, food consumption, behaviour and preferences. The subjects were 12 mature male Wistar rats. Effects were assessed from daily weighing and from video records of the rats' behaviour over 24 h periods. The rats' preferences were determined using a four-way test system in which they could choose between a standard cage and cages offering the three potential enrichments. Compared to the standard housing and feeding, the limited-access hopper had a tendency to reduce food consumption, but the time spent feeding increased. The gnawing sticks provided the rats with the opportunity to gnaw, but did not affect other behaviours or body weight. The foraging device had the benefits of reducing aggression and allowing the rats to search for and manipulate food, but resulted in significant gains in body weight. Additionally, the foraging device was the preferred feeding source. Of the four possible feeding locations, the rats spent the least amount of time in the standard cage. The foraging device provided the most benefits but requires further modification to address problems of obesity.