Animal Science and Production Technology - Adequate Food for All - page 348

Animal by-Products
Processing of meat, milk, and poultry for human consumption is associated with
many value-added products used in animal feeds (Chiba, 2005). Meat and bone
meal, whey, and feather meal are examples.
g r a z i n g P u b L i C r a n g e L a n D s a n D P a s t u r e s
Land grazed by ruminant livestock represents 26% of the total global land area and
nearly 70% of the world's land used for agriculture. Most grazed lands are too arid,
steep, rocky, infertile, or cold for arable crop production but do produce a variety of
grasses, shrubs, forbs, and other plants that are a potential source of feed for live-
stock. Most such plants are high in cellulose and lignin, which cannot be digested by
humans or by nonruminant animals such as pigs and chickens, but can be utilized
by ruminants, including cattle, sheep, goats, and buffalo, through microbial break-
down of the feed in their rumens. Therefore, grazing livestock permit the production
of food for humans on land that would otherwise produce little or no human food.
Because of the marginal character of most grazed lands, their productivity per unit
area is much lower than that of cropped land, but they contribute more than 20%
of global ruminant meat production and about 7% of global milk production. This
represents a significant part of the total food supply and is critical to the survival and
well-being of pastoral peoples.
Grazed lands have many functions apart from the production of animal source
foods. They harbor a substantial proportion of the world's biological diversity, they
are the site where much of the rainfall contributing to freshwater supply falls, and the
open space they represent is highly valued by an increasingly urbanized human pop-
ulation. Grazing represents an important tool for vegetation management. However,
improperly managed grazing can have negative effects on the environment and on
biodiversity.
grazing on Ranches in Arid Areas
Cattle, sheep, and goat ranching is widely practiced in North and South America,
Australia, New Zealand, and some other countries. In general, ranching occurs in
more arid areas and involves the maintenance of breeding herds for meat produc-
tion (milk production more commonly occurs on better land and in higher rainfall
areas). Offspring may be sent directly to slaughter at weaning, grazed in the same
area following weaning until they reach harvest weight, or sent at weaning or at some
later stage to feedlots for further feeding before harvest. Feedlots use forages, cereal
grains, and a wide variety of crop-processing by-products to increase the amount and
quality of meat, and their existence depends on a reliable source of “feeder” animals
raised on less-expensive land.
grazing on Improved Pastures in higher-Rainfall Areas
In Europe, in higher rainfall areas in the United States, and in other temperate parts
of the world, grazing more commonly occurs on improved pastures. The pastures
are often on steeper or potentially more erosive land or included as part of a crop