Ethics of feeding: the omnivore dilemma

The way in which animals are fed is an important aspect of their welfare. Not only does food provide the energy and nutrients vital for survival, but feeding is also associated with a number of other factors contributing to the well-being of animals. The feeding method can determine the animals' abilities to fulfil basic behavioural needs, such as foraging. The aim of this paper is to review and discuss the dilemma of choosing between ad libitum feeding (AL) and dietary restriction (DR). AL can produce obese individuals with severe health problems, though it does appear to be compatible with welfare-friendly management systems. On the other hand, DR is often associated with improved physical health and longevity but can leave animals suffering from hunger, frustration or aggression. The species discussed are the laboratory rat, pigs and poultry all of which are omnivores sharing many characteristics in their eating habits. The welfare implications of different feeding methods depend upon the definition of welfare used. Based on a definition of welfare in terms of functioning, DR could be considered the best way to feed animals, because it results in improved physical health and longevity. If welfare is defined in terms of natural living, it is also a requirement for the animal to be able to engage in natural foraging behaviours. From the feelings-based approach, DR can be viewed as preferable only in circumstances when animals are anticipated to live so long that they would otherwise suffer from the negative long-term consequences of AL. It is argued that incentives are needed to make farmers spend resources to ensure that farm animals are allowed to have their foraging-related needs fulfilled. Feeding of laboratory animals creates special dilemmas when it is important either to under- or over-nourish the animals for experimental purposes, in such instances there is a need for Refinement.