Animal husbandry in the British Agricultural Revolution of the 18th century, when livestock breeds like the Dishley Longhorn cattle and Lincoln Longwool sheep were rapidly improved by agriculturalists such as Robert Bakewell to yield more meat, milk, and wool. A wide range of other species such as horse, water buffalo, llama, rabbit and guinea pig are used as livestock in some parts of the world. Insect farming, as well as aquaculture of fish, molluscs, and crustaceans, is widespread. Modern animal husbandry relies on production systems adapted to the type of land available. Subsistence farming is being superseded by intensive animal farming in
Animal genetic resources for food and agriculture sustainability of a breed and therefore to the potential for successful conservation activities." The Pantaneiro cattle of Brazil are only one example of many at risk of extinction. Despite the importance of animal genetic resources, their diversity has been continually decreasing over time. "Factors as causes of genetic erosion: One of the greatest threats to livestock diversity is pressure from large-scale commercial production systems to maintain only high-output breeds. Recent molecular studies have revealed that the diversity of today's indigenous livestock populations greatly exceeds that found in their commercial counterparts. Climate change and its impact on livestock is being studied.