ABSTRACT
There is increasing public demand in all countries for sustainable plant and animal production systems. A system or procedure is sustainable if it is acceptable now and if its expected future effects are acceptable, in particular in relation to resource availability, consequences of functioning and morality of action. When purchasing food, many people now consider efficiency of usage of world food resources, human welfare, animal welfare, biodiversity and conservation, genetic modification, fair trade and continuity of rural communities. The quality of the product is more and more frequently judged to be poor if the production method is unacceptable. All consumers have to consider whether or not they want a barren environment with little biodiversity and poor welfare of animals in order to get slightly cheaper food. In order to use resources efficiently, every person should eat more plant material than animal material and should not waste food. Where the killing of animals is a concern, there should be consideration of the many animals killed in the course of plant production, probably more than in production of some herbivorous animals. Animal production should focus on herbivorous animals that eat foods that humans cannot eat. Much of the earth can be used for herbivore production but is unsuitable for producing plants that humans can eat. Animal welfare is a major factor in the sustainability of food production systems and in food quality. The most important animal welfare problems all concern farmed animals: broiler chicken welfare, dairy cow welfare, laying hen welfare, pig welfare and the welfare of farmed fish. There is much scientific evidence about animal welfare and several other aspects of sustainability. New semi-intensive silvopastoral systems are being developed in tropical and sub-tropical countries in which pasture is combined with shrubs and trees with protein-rich edible leaves. Plant and animal production are greater than in pasture-only systems, biodiversity is much increased, animal disease is reduced and animal welfare improved.
