How hungry is too hungry? Impaired learning leads to poorer payoffs in hungry broiler breeders.

Investigation into whether the degree of hunger of a broiler chicken, affects its ability to learn to use cues to identify more rewarding dietary options.

Year of Publication2010

Giving an animal what it wants can contribute to the animal‟s welfare. Choice tests are one way of identifying what an animal wants. However, stress may affect the cognitive capacities of the animal, which can lead to spurious results within choice test apparatus. Hunger can be seen as both a motivator and a stressor and is a serious welfare problem for chronically food deprived broiler breeder chickens. Conventionally feed restricted broiler breeders are expected to be highly motivated to obtain additional feed but does the degree of hunger affect their ability to learn to use cues to identify more rewarding dietary options? This was investigated by using a closed economy Y-maze task to determine the effects of feed restriction on broiler breeder ability to learn a food quantity discrimination task. The task was to associate black and white arms with large and small quantities of feed. Birds were reared to three different growth curves by means of severe (n=12), moderate (n=12) or very mild feed restriction (n=12). Absence of learning maintained the birds on their respective level of feed restriction. Learning the task and selecting the larger food option allowed birds to increase their feed intake. Time taken to traverse the Y-maze was also measured. Birds from all treatment groups traversed the Y-maze more quickly over time irrespective of group indicating that they had learnt that running down the Y-maze arms was associated with a rewarding outcome (food) (p<0.001). However, feed restriction had a significant negative affect on the birds‟ ability to learn to associate the black and white training cues with differences in food quantity (p=0.014). Consequently, both relative and absolute increases in average payoffs in terms of daily feed gains disproportionately accrued to the less feed restricted treatment groups. It is concluded that hunger affects the ability of broiler breeders to learn hunger-relevant environmental cues, perhaps by narrowing their attention such that they ignore potentially relevant contextual cues. However, low overall group success rates demonstrate that this task was difficult to learn even for less hunger-stressed birds. Therefore, Y-maze choice tests may not be the most appropriate method for determining hungry broiler breeder preferences between conventional and alternative diets (e.g. added fibre) designed to alleviate hunger.

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