Background

The provision of fodder in early pastoral agriculture depended on the movement of flocks and herds to fresh pasture; at the same time this movement reduced the risks of ingestion of disease-producing organisms and (to a lesser extent) the spread of contagious diseases. The history of animal production since then demonstrates increasing pressure on pasture, as the numbers of people and animals grew and were crammed into the same area of country, with the cycle of use becoming ever more frequent. When migratory, pastoral agriculture gave place to a sedentary agriculture with enclosed fields the same process continued, as stocking rates increased to provide greater productivity; the culmination was the creation of crowded feed lots and intensive housing. With these developments the danger of disease increased; without veterinary help such changes could not have taken place at all. In parallel with increased veterinary understanding, however, have gone the findings of practical people, initiating subtle changes in management practices to avoid disease without a detailed understanding of its nature. Such practices as the frequent strawing-down of yards for the comfort of the animals and the aesthetic satisfaction of their owner also helped to control the ingestion of parasites of the alimentary tract, without a full knowledge of the identity and life history of the parasites. Similarly, rinderpest and bovine pleuropneumonia, periodic serious plagues of cattle in the United Kingdom in the nineteenth century, were both controlled by a veterinary-inspired slaughter and quarantine policy in advance of a full understanding of their aetiology; the former disease was last recorded in the U.K. in 1877 and the latter in 1898.