Food, water and malnutrition: perspectives on nutrient requirements for health and welfare in farm animals

Protecting farm animals from hunger and thirst is central to good welfare. However, there are a large number of situations where farm animals are exposed to nutrient restriction. Some of these, such as the effects of prenatal nutrition have received insufficient recognition as welfare issues. Generally it seems that there is a sufficient understanding of nutritional requirements for health in farm animals to form the basis for nutritional standards for health. However, our understanding of the impact of nutritional environments on psychological welfare and specifically hunger is much less well advanced. Science can make a major contribution to this area by developing a framework for interpretation of the impact of the nutritional environment on hunger. We present two frameworks that provide contrasting perspectives on welfare outcomes where nutrient restriction is achieved through qualitative restriction. We recommend that researchers should link their experimental work to a firmer theoretical construct of hunger to provide experimental tests of different frameworks. We see development of a robust framework to interpret the welfare effects of nutrient restriction as leading to improved measurements of hunger and to standards for nutritional welfare that could be accepted on a global scale.