Agriculture is managed
exploitation of selected plants and animals to produce products of value to
humans. It is, and will probably continue to be, the major source of human food
and a significant contributor of other useful commodities. The actual number of
species exploited for cultivation or rearing is minute in comparison to the
multitude present throughout the world. Although there is some interest
currently on broadening the base through inclusion of additional wild or
semidomesticated strains, most human food originates from approximately
20 plant and about the same number of animal species.
Agriculture attempts to channel as much incoming solar radiation as possible into usable commodities through selection of appropriate varieties and provision of suitable environments. Plant or crop production provides the basis for any subsequent consumption by livestock or humans. In theory, humans in the position of primary consumers should produce the greatest efficiency, but the relationship is complex and not always rational. Most crops are grown primarily because some part of the plant can be consumed directly by people. Under many conditions, however, much of the plant material cannot be used because it is indigestible by humans. Ruminants (cattle, sheep, goats, buffaloes), other herbivorous animals (horses, camels) and some omnivores (pigs, ducks, geese) possess specially modified digestive systems that can extract substantial amounts of nutrients from plant material that is not suited for human food. These species have the digestive ability to satisfy much of their requirements for both maintenance and some production through grazing on marginal land and consumption of the considerable residues or by-products left over after extraction of plant components that can be used directly in human diets. However, faster growth or higher yields can be obtained whenever herbivores or omnivores receive "better quality" feeds such as cereal grains that might be suited for direct consumption by humans.
Critics of intensive livestock production allege that when consuming grains,
domesticated animals compete directly with humans and are responsible for
considerable malnutrition in lesser developed countries. Such simplistic
arguments are naive since almost all intensively managed animal units operate
in affluent, industrialized countries where cereal grains grow in surplus
rather than deficit amounts. Farmers often find they cannot dispose of surplus
cereals for even the cost of production so cycle these crops through animals to
obtain "value-added" products.
e.g.. hunter-gatherers, subsistence fishing, commercial fishing, sportsmen
Extensive: low input - low to moderate output
Examples of extensive practices are pastoralism, subsistence farming or most ranching operations.
Pastoralism - This form of animal agriculture is practiced by nomadic people with large, migratory herds and flocks grazing over communal lands. They limit inputs to regulating animal movement over large areas following natural feed supply with occasional vaccinations against the most serious diseases if these are government provided and enforced. Pastoralists are survival rather than market oriented. Natural cycles are followed so livestock product availability is limited to only certain seasons of the year.
Subsistence farming - Mixed farming with small numbers of pigs, poultry and small ruminants, usually scavenging or grazing on communal land. Livestock receive crop by-products, residues and kitchen wastes whenever these are available. Occasional vaccinations if this is part of a government sponsored, disease eradication program. Subsistence farmers, like pastoralists, follow natural cycles and are survival rather than market oriented. Their goal is to produce sufficient food to satisfy the needs of the immediate or extended family group. Occasional surpluses may be sold or bartered.
Ranching - Ranching involves large herds of cattle or sheep often grazing on communal land and following natural cycles for reproduction. Human labor input is minimal but provides occasional supplemental feed, disease treatment or prevention and predator control. Ranching is commercially oriented and generally entails a higher capital investment than simple pastoralism or subsistence farming. In contrast to the extensive grazing of cows and their calves or yearling animals on grasslands, a finishing stage in feedlots would be intensive.
Transitional (Intermediate) - everything between purely extensive and totally intensive
Intensive: "High input - high output farming." Characterized by:
In many regions, a substantial proportion of the population still relies on subsistence farming. Their major goal is production of sufficient produce to satisfy immediate needs of individual or extended family groups with occasional surpluses bartered or sold.
these situations, small ruminants, pigs and poultry are often kept but receive
no or very little purchased input and generally scavenge for all their feed.
Such livestock constitute a valuable waste disposal-recycling system,
contributing an occasional dietary supplement and providing a stable food
reserve. Large ruminants, if present, serve primarily as draft animals.
In contrast, the animal food
industry in affluent industrialized countries is a complicated sequence of
activities, beginning with plant converters and then incorporating animals as
primary and humans as secondary consumers. Integrated with specialized
producers are many input suppliers, transporters, processors and retailers,
creating a complex agri-food system conveying numerous commodities to final
human consumers. During the course of this
evolution, the rearing of farm animals progressed from a casual and often
secondary activity to an important life-style for many rural families, and
finally into a true business with profit as its major goal.
Livestock farms operate as value added enterprises with different strategies
to suit specific situations.
Forward to notes on "Factors Influencing Animal Production"
The National Agricultural Library, operated by the US Department of Agriculture, is an excellent source for agricultural and related information.