Agriculture Reference
In-Depth Information
increase in the number of pigs, and 40-50%
increases in the numbers of cattle, sheep and
goats. The global number of livestock animals
used in agricultural production has been esti-
mated to be 1.8 billion large ruminants, 2.4 million
small ruminants (sheep and goats), 20 billion
poultry and nearly 1 billion pigs (Niemann
et al ., 2011). This so-called 'livestock revolu-
tion' is being driven by the sharp rise in demand
for animal food products in many developing
countries, resulting in a pronounced reorien-
tation of agricultural production systems
(Delgado, 2003). The United Nations Food and
Agriculture Organization (FAO) predicts the
global population will rise to approximately
8 billion people by 2030, and will exceed 9 billion
people by 2050 (FAO, 2009). Accordingly, the
demand for animal protein is also expected to
grow as consumers in developing countries
become more affluent. When the year 2000 is
used as a base, projections indicate the need for a
68% and 57% increase in global meat and dairy
consumption by 2030, respectively (Steinfeld and
Gerber, 2010).
Although some may consider that the chal-
lenge of feeding the burgeoning world popula-
tion would best be met by reducing livestock
production and avoiding meat consumption, it
is unlikely that vegan diets will be acceptable
for many people. Although there are modest
decreases in meat consumption in some devel-
oped countries, there is a widespread and grow-
ing preference in developing nations for dietary
animal protein. Animal products contain con-
centrated sources of high quality protein that
complement those of cereal and other vegetable
protein. They also contribute dietary sources of
calcium, iron, zinc, and several B group vitamins.
There is evidence that increasing foods of ani-
mal origin in the diet of young children with an
initially low rate of consumption of these foods
leads to marked improvements in both physical
and mental development (Neumann et al .,
2007). Additionally, some livestock, particularly
ruminants, eat feedstuffs and graze marginal
lands that are not appropriate for the production
of plants that can be consumed by humans.
Livestock can also provide a variety of goods and
services that generate income and support the
livelihoods of millions of poor people in the
developing world. Their uses include livestock-
derived food and products, sale of these products
for income, use as assets for savings or trade,
draught power and transportation, manure for
soil fertility restoration, sale of livestock prod-
ucts for income, as a source of draught power and
transportation, in diversifying livelihood options
to reduce vulnerability, and their contribution to
the socio-cultural roles and obligations of their
owners (Rege et al ., 2011).
What is Animal Breeding?
Animal breeders use information (e.g. pro-
duction data, pedigree records) and technology
(e.g. DNA information) to select which animals
will become parents of the next generation. The
breeding value (BV) of an animal is defined as
the superiority of its offspring when compared
with the population mean. This value is esti-
mated based on the pedigree and performance
records of an animal and its relatives using
mixed-model equations first described by
Henderson (1953). Selection is based on the esti-
mated breeding value (EBV) of the animal as it
relates to the traits included in the breeding
objective (BO). The BO can be thought of as the
overall goal of the breeding programme. The role
of the animal breeder is to maximize the selec-
tion response towards the BO. Response is
defined as the difference in the mean phenotypic
value between the offspring of the selected par-
ents compared with that of the whole of the
parental generation before selection. The genetic
gain (DG t −1 ) per unit of time in animal breeding
programmes is directly proportional to the accu-
racy of selection (correlation between an ani-
mal's EBV and true BV), selection intensity (the
proportion of animals that are used as the par-
ents of the next generation), the genetic variabil-
ity (how much additive genetic variance there is
in the population), and is inversely proportional
to the generation interval (the time it takes to
replace a generation). Any technology that can
increase the selection response per unit of time
will accelerate genetic progress towards the BO.
Multiple-trait selection indexes can be
developed to optimize profit given a specific BO,
with different traits being assigned an economic
weight based upon their contribution to profit.
The index ranking of an animal is equivalent to
the term 'fitness' in wild populations, with the
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