Recent concerns about the safety of the U.S. food supply and the
potential for bioterrorism, as well as incidents like mad cow disease
in Canada, have prompted a new look at livestock movements. The
potential for transmitting disease—whether due to bioterrorism
or a natural occurrence—increases when animals mix with other
animals at a variety of locations. An important early step toward
a cost-effective public strategy for managing such risks is to
understand livestock mobility. Why are animals shipped long distances,
and are livestock being moved more now than in the past?
Animals are often shipped long distances because doing so is frequently
cheaper than shipping the feed needed to reach slaughter weight
to the animals. Shipping livestock enables the efficient use of
feed and forage (grass or hay) supplies that vary by region and
season. This is most apparent when animals are moved from growing
areas to finishing areas (where livestock are fed to slaughter
weight) and then to slaughter plants.
Shipments of hogs, in particular, have increased dramatically—from
under 10 percent of total (December 1) inventory in 1990 to more
than 40 percent now. This increase reflects significant feeder
pig imports from Canada, and the development of the hog industry
in North Carolina and other States outside the Corn Belt. For example,
pigs born in grain-deficient North Carolina may be weaned and moved
to a growing/finishing facility in Iowa, where they consume corn,
soybean meal, and other feeds grown nearby. Then, they may be shipped
to slaughter plants often closer to major consumer markets in the
U.S. and to export locations.
In contrast, cattle and sheep shipments have remained fairly steady
at about 20 percent of inventories. Movements of cattle occur throughout
the country, but especially into (and within) the Northern and
Southern Plains. The top four cattle feeding States (Texas, Kansas,
Nebraska, and Colorado) account for 65 percent of the feeder cattle
supply and more than two-thirds of cattle slaughter. Sheep shipments
have declined sharply since the early 1990s as the U.S. inventory
continues its long-term decline. Colorado and California—two
major sheep feeding and slaughter States—account for almost
two-thirds of total interstate shipments.