Agriculture Reference
In-Depth Information
migrating birds can carry this disease and hot, dry periods favor the airborne spread to
other birds. While ducks and geese do not seem to be susceptible to Newcastle disease,
they are carriers and can infect other species. Although an effective vaccine exists for
Newcastle disease, most viral diseases are controlled by destroying infected flocks.
7.4.7 Marketing
The life span of a chicken can be as much as 10 to 15 years. A female chicken (hen) will
start laying eggs at about 6 months of age. The presence of a male in the flock has no
effect on number of eggs produced. Unfertilized eggs have a longer shelf life than fer-
tilized eggs, but some markets prefer fertilized eggs. In commercial flocks, layers are
kept for only 12 to 14 months of production. After this, egg production drops, and
the layers are sold for human consumption as stewing chickens. Chickens produced
specifically for meat (broilers or fryers) are usually sold when their weight reaches 1
to 1.8 kg. Under modern production conditions this weight is reached as early as
7 weeks after hatching.
Sale of chickens, ducks, and geese for meat depends on the presence of refrigerated
transport and storage. In developing countries where refrigeration is not widely avail-
able, birds are sold alive. They are harvested shortly before consumption. Frequently
middlemen purchase birds from individual farmers and market them at larger, whole-
sale markets in cities. In some cases birds may pass through five to six merchants before
arriving at the final consumer. The farmer typically receives 60 to 65 percent of the final
market price. In developed countries with reliable refrigeration, poultry is often har-
vested on, or near, the farm and only processed meat is marketed. This requires a well-
organized system of processing, grading, and packaging.
Eggs are a product widely consumed in many cultures. Eggs also require cooling to
maintain quality from the producer to the final consumer. This cooling may be by elec-
trical or mechanical means. Marketing of eggs in developing countries is often by
weight since grading and standardized sizes have not been adopted. There may also
be checks for quality by candling or flotation. Candling involves holding an egg in
front of a candle, or other light source, to judge the size of the air bubble in the
large end of the egg. An egg with a large air bubble will float in a bucket of water.
In either case, a large air bubble indicates an old egg and is usually rejected. Adoption
of size and weight standards for eggs usually accompanies sale by quantity. This is
common in most developed countries where eggs are sold by the graded dozen.
Feathers of both ducks and geese are an added source of income for farmers. Geese
are the source of down, used in jackets and bedding. Down feathers are the immature
breast feathers. These may be plucked from geese harvested for meat or plucked from
live geese. Growing geese undergo a process of molting (shedding) of feathers every
6 weeks. Careful timing permits plucking down feathers during molting to harvest
around 100 g of down from each goose.
In some European countries, fatty liver (foie gras) is an important product of geese.
To increase the size of the liver before harvest, the geese are force fed with wet maize
five to six times a day over a 2- to 3-week period. This causes the liver to nearly triple
in weight.
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