The relation between preference and demand for litter substrates in the domestic hen

Abstract

Six hen's preferences between 5-min access to each of two litter substrates, sand and sawdust, were measured using dependent concurrent VI 60 s VI 60 s schedules of reinforcement. The obtained preferences were small and idiosyncratic. Demand functions were generated separately for each of the two substrates by requiring the hens to perform under increasing FR schedules. The demand functions were disorderly, some were linear, some were of mixed elasticity, and others curved upwards. No clear relation between the individual hens' preference and demand measures was found. The overall response rates, running response rates and average post-reinforcement pause durations were atypical compared to previous demand research, possibly due to low levels of reinforcer collection, but were similar for individual subjects in both demand conditions. During the demand assessment, dustbathing took place in a similar proportion of reinforcers for each substrate. During the preference assessment, a greater proportion of dustbathing took place during sand reinforcers. Individual hens did not consistently dustbathe more in their preferred substrate. It was argued that the inconclusive results were a product of the substrates used. The atypical demand functions, response rates and average PRP durations may have been due to behaviour that was not schedule related occurring during key time (i.e., the subjects may have been continuing a dustbathing bout). It is possible, that the two substrates were too similar, and thus the subjects did not have a clear preference for one over the other. In future research preference should be assessed prior to demand, to ensure a clear preference can be obtained, with reinforcers that are qualitatively more different than those used in the present experiment.