Transcript Conservation and management of Farm Animal Genetic Resources

EVOLUTION OF DOMESTIC
PLANTS AND ANIMALS
Wilson Nandolo | Timothy Gondwe
Aim of this topic

Aim of the topic
To
equip students with
knowledge of evolution of
genetic diversity and
potential losses that occur
Objectives of the topic

By the end of the topic, you should be
able to
 Describe
origin of genetic diversity
 Describe the role of mutation, trade and
migration in genetic diversity creation
 Describe the Darwin Theory of Natural Selection
 Describe the process of livestock domestication as
component of genetic diversity
 Discuss causes of decline in numbers and diversity
Diversity from wild
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
Huge variety of animals and other species has arisen
from earliest, primitive form of life
Mutation has taken place on original genes due to
reaction to different environment, leading to creation
of new alleles ~ hence variation
This chance variation has occurred in size, shape and
functioning of animals, over the course of million years
And the variation has allowed animals to adapt to
particular environments or niches
Mutation, therefore, lead to creation of new genetic
variation
Creation of new breeds with domestication
and migration
The process of domestication began some 12 14 thousand years ago
 Both the process and the domesticated stock
produced by it have been carried by migrating
humans to most remote regions of the earth
 In each region and local area, domestic
populations adapted and evolved in response to
a great range of selection pressures

Creation of new breeds with domestication
and migration

In each case the primary factors
contributing to the final population were
complex and included
 founder
affects
 migration
 mutation
 natural selection and selection by man
Founder Group
The genetic make-up of each and every breed
or population is largely dependent upon the
genetic make-up of its founder group
 This foundation group was in turn dependent
upon the selection pressures it had previously
encountered

 and
upon the genetic make-up of its own founder
group

Thus, as tribes of people migrated across the
globe they took samples of their own livestock
with them to their new homes
Founder Group
In each location the people and their
livestock would adapt through selection
which is the survival of those individuals
genetically suited, or able to adapt to the
new environment
 A sample of this population would then be
taken with the next human migration to be
the founders of a new community in a
slightly different situation.

Spread of farming with domestication and
human migration
Source: FAO (2007): The SOW AnGR for Food and Agriculture, Rome, page 5
In-flow of genes


The migration of people and livestock has not
generally been in one continuous direction
In most regions there has been fairly constant trade in
livestock from one community to the next throughout
human history
When animals arose through mutation or trade
 that had better survival or production characteristics than
those found in the local population
 more of their adapted progeny would survive
 and the enhanced characteristics would soon become
common or even fixed within the group

In-flow of genes and AnGR diversity
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
Thus, other than geographically isolated situations, a
gradual inflow of genes has modified every
population that exists today
Thousands of years of
natural and human selection
 Genetic drift
 Inbreeding and crossbreeding


Have
Contributed to AnGR diversity
 And allowed livestock keeping to be practiced in variety of
environments and production systems

Natural selection ~ Darwin’s Theory

Natural selection is the term used to
describe all the environmental pressures
acting on an individual
 which
will result in it succeeding or failing to
survive and to reproduce

Only successful individuals will pass their
genes onto the next generation
Natural selection ~ Darwin’s Theory

The principal aspects of natural
selection are
nutrient
supply
Climate
parasites
and predators
and competition within the species
Natural selection ~ Darwin’s Theory


Darwin’s Theory of natural selection states that
species can change over time
And that their survival or success depends on how
well they fit their environment
 Termed

‘survival of the fittest’
The key to this process is variation between
individuals
 Which
has developed over years
 And allowed individuals to adapt to particular
environments or niches
Natural selection ~ Darwin’s Theory
Darwin’s work is usually linked to
evolution and natural selection of
wild animals
 But he also recognized changes in
domestic animals brought about by
artificial selection of early livestock
breeders

Domestication of animals

Domesticated animals are considered to be those
species
 that
are bred in captivity
 and modified from their wild ancestors

to make them more useful to humans
 who
control their
 reproduction
(breeding),
 care (shelter, protection against predators)
 And food supply

Domestication is different from taming wild-borne
animals
Domestication includes the following
steps
initial association with free breeding
 confinement
 confinement with breeding in captivity
 selective breeding and breed
improvement

Domestication included transition from
hunting and gathering to farming
Causes of domestication

During hunter – gathering periods, the
following occurred
 Unpredictable
climate
 Decline in big-game species
 Increased human occupation of available habitats
These led to risks of unpredictable variation in
food supply
 Domestication was a way to broaden human
diets

Discovery of domestication history

Archaeologists and animal geneticists use
various means
 to
unravel the history of domestication
including study of morphological changes to
the teeth, cranium and skeleton
 and the construction of demographic age and
sex curves which allow the identification of
patterns indicative of domestication

Livestock domestication process

Very few animal species have been successfully
domesticated

among the world’s 148 non-carnivorous species weighing
more than 45 kg
only 15 have been domesticated
 only six have become widespread on all continents (cattle, sheep,
goats, pigs, horses, and donkeys)





while the remaining nine (dromedaries, Bactrian camels, llamas,
alpacas, reindeer, water buffalo, yaks, Bali cattle, and mithun)
are important in more limited areas of the globe
Domestication was a complex and gradual process
which altered the behavior and morphological
characteristics of the ancestral animals
Some localized domesticated species
Livestock domestication process ~ Birds
Only ten species (chickens, domestic
ducks, Muscovy ducks, domestic
geese, guinea fowl, ostriches,
pigeons, quails, and turkeys)
 Are currently domesticated out of
around 10 000 avian species

Wild ancestors and relatives of livestock

With the exception of the wild boar (Sus scrofa)
 The
ancestors and wild relatives of major livestock
species are either extinct or highly endangered

As a result of
 hunting,
changes to their habitats, and in the case of the
wild red jungle fowl, intensive cross-breeding with the
domestic counterpart

This is unlike crop species that have their wild
ancestors found at their centres of origin
 And
hence, an important source of variation and
adaptive traits for future breeding programs
Essential elements for domestication to take
place

Important or essential characteristics for
successful domestication
 include
behavioral traits such as a lack of
aggression towards humans
 a strong gregarious instinct
 Including
“follow the leader” dominance
hierarchies which allow the possibility of a human
substitute as leader
a
tendency not to panic when disturbed
Comparison between domesticated wild animals
and their wild counterparts
Source: Diamond J (2002). Nature/Vol 418.
Major centres of livestock domestication
Source: FAO (2007): The SOW AnGR for Food and
Agriculture, Rome. Page 10
Origin and domestication of livestock
species (FAO (2007): The SOW AnGR for Food and Agriculture,
Rome. Page 7 - 8)
Origin and domestication of livestock
species (FAO (2007): The SOW AnGR for Food and Agriculture,
Rome. Page 7 - 8)
Origin and domestication of livestock
species (FAO (2007): The SOW AnGR for Food and Agriculture,
Rome. Page 7 - 8)
Origin and domestication of livestock
species (FAO (2007): The SOW AnGR for Food and Agriculture, Rome. Page
7 - 8)
Domestication took place at different time
period
Species
domesticated
Time frame (years ago)
Purposes
Dog
14000
Hunting and
watchdogs
Goats
10000
Sheep
8000 – 9000
Pigs
9000
Cattle
7000 – 9000
Chickens
5000 – 7000
Source: FAO (2007): The SOW AnGR for Food and
Agriculture, Rome. Page 11 - 14
Origin and migration of domestic cattle in
Africa
Source: FAO
(2007): The
SOW AnGR for
Food and
Agriculture,
Rome. Page 16
Essential elements for domestication
to take place
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the ability to breed in captivity
Physiological traits such as a diet that can easily be
supplied by humans
a rapid growth rate
Relatively short intervals between births
and large litter size
The rest of animal species do not have these
characteristics, hence fail to be domesticated
Transformation following domestication


Mutation, selective breeding, and adaptation have
shaped the diversity of livestock populations
The domestication process resulted in many changes
 some

are still ongoing
Particularly important have been morphological
changes
 However,
the world’s livestock diversity is currently
shrinking
 with rapid and uncontrolled loss of unique and often
uncharacterized AnGR.
Transformation following domestication
Transition from hunting and
gathering to farming resulted
into

More
work
Lower adult stature
Worse nutritional conditions
Heavier disease burdens
Evolutionary relationship of mammalian
species used for food and agriculture
FAO (2004)
FanGR :
Safeguardin
g national
assets … CD
Causes for declining numbers of livestock

Previous breed improvement programs
 Especially
crossbreeding with more
popular exotic breeds
Local breeds have been crossed with
exotics
 e.g. In Malawi

 BA
and LC
 Boar goat and Local
 Brahman and Zebu
Causes for declining numbers of livestock

Unfortunately such programs have gone with
unplanned and non-regulated breeding
strategies
And no record keeping
 Resulting in uncontrolled (non-systematic) random
mating
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With this, replacement of local breeds may
occur
And blood gets diluted
Causes for declining numbers of livestock
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Small herds or populations
Most animals are kept in small herds or flocks
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This creates difficulties in maintaining their genetic constitution
Resulting in high chances of inbreeding
Since in small populations, there is increased chances of mating between
related individuals
The smaller the number of animals used in breeding (N), the
greater the probability of inbreeding
1
Δ𝐹 =
2𝑁
ΔF is increase in inbreeding per generation
Small herds or populations


Where number of males and females are different, effective
population size (Ne) is used
This is the case for many species and breeds
4𝑁𝑚 ∗ 𝑁𝑓
𝑁𝑒 =
𝑁𝑚 + 𝑁𝑓



Where Nm, Nf are number of breeding males and females,
respectively
Increase in inbreeding is calculated as
1
Δ𝐹 =
𝑁𝑒
Optimal Ne is around 50
Causes for declining numbers of livestock
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Preference for fewer breeds to others
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Due to feeling of others being less productive
And concentrating on few breeds only
This results in others being neglected
And their numbers to decline
Boer Goat
Preferred to
Causes for declining numbers of livestock
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Genetic drift
This is a change in genetic constitution of breeds in a
population
This results in changes in gene frequency
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Possible loss of some alleles
Or fixation of others
Genetic drift is common in small populations
Leads to uniformity within and diversity between populations
Causes for declining numbers of livestock
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Direct replacement of local breeds by exotic popular breeds
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Local or indigenous breeds do not provide good returns
Owners develop little incentives to keep local breeds for commercial
purposes
They therefore replace with common breeds
This has been the case for many breeds in Malawi
However, the problem has been due to improper comparison
of the two breeds
Using conventional western methodologies
And without dual consideration for adaptation
Local pigs replaced by exotic
breeds for commercial purposes
Causes for declining numbers of livestock

Bottlenecks such as

Floods

Wars

Draughts

Theft cases

etc
Some Terminologies in AnGR
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Agro-biodiversity
Means agricultural biological diversity
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

This is a component of biodiversity that contributes to
food and agricultural production, and goods and services
Encompasses diversity of cultivated plants and domestic
animals
Includes



Within species diversity
Between species diversity
Ecosystem diversity
Some Terminologies

Biodiversity or Biological diversity


Means a variety of life of all forms, levels and
combinations
Encompasses

Genetic diversity


Species diversity
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
(Zebu, Brahman, Freisian etc)
(Chickens, ducks, pigeons etc)
Ecosystem diversity

(Upland, lowlands, high rainfall, semi-arid, desert etc)
Some Terminologies

Diversity

A set of two or more things that differ
•If one of the sets is removed, then there is
reduced or decline in diversity
•On the other hand, an addition of sets that
are different means an increase in diversity
Some Terminologies

Domestic or Farm Animal Diversity

A spectrum of genetic differences
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within each breed,
between breeds within each domestic animal species
Between species
Within diversity falls biological diversity
Within biological diversity falls animal diversity
Within animal diversity falls farm animal diversity (domestic
livestock)
All the different livestock are available for sustainable
intensification of food and agricultural production
Species and breed diversity
Which diversity can we claim to
identify with certainty here?
Breed diversity
Within breed diversity
Within breed diversity
Some Terminologies

Breed conservation
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

To maintain breeds of livestock for which numbers have greatly
declined and may continue to do so to the point of extinction if not
rescued
This may be for present or future use
Animal Genetic Resources Management


Sustainable utilisation of different species and breeds
within species for present use without jeopardising future
use
Includes aspects of conservation, improvement and
utilisation of breeds and species of livestock
Why Breed conservation?

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The world had different species and breeds of livestock,
including wild ancestors
That developed and adapted to different ecosystems
And providing a variety of uses, specific ecosystem and
cultural or tribal
Unfortunately many have become extinct
Some have declined in numbers, putting then in danger of
extinction
Why Breed conservation?

Current status
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There are about 40 + domestic livestock species
Only 14 % are used and contribute directly or indirectly
to food and agricultural production
These have been domestic and evolved into separate
and genetically unique breeds
These have adapted to their local environments and
community requirements
Some of these have declined


Currently about 6000 – 7000 breeds remain
And comprise the world’s animal genetic resources
important to food and agricultural production
Why Breed conservation?

Africa status
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
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Several livestock local breeds exist
Have remained undescribed and neglected
Have their numbers declining
The same applies to Malawi
The future of these breeds is very insecure if there
is no action to conserve them
Others are in danger of extinction if nothing is
done
Hence the need to conserve them
Role of animal production in agriculture
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Global livelihood for 1.96 billion people
 Over 50 % of these living in pastoralists and agro-pastoralists
Contributes to GDP and GNP of the country
 Malawi has 7 % of GDP; 2 % of GNP from livestock
Organic fertilisers
Draught power
Fibre for clothing, leather etc
Cultural significance
Employment for villagers
Cash reserves, moving savings bank
Contributes to risk management eg during hunger
Contributes to agricultural integration
Role of animal production in agriculture
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All these functions and uses can not be fulfilled by
one species
Having a broad range of animal species is
essential to meet all the functions
And for the many mixed farming systems
 That are more sustainable than in monoculture


Hence the need to conserve the species
Purpose for conservation of FAnGR
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To meet present and future needs
To meet future adverse conditions in case of diverse but changing
environment, climate, feeds, diseases, etc
To have a storehouse for genetic variation that is needed in breed
improvement programs eg. Selection
Keeping more and diversity spread risks among farmers
To meet the increasing and broad demand for locally and globally
livestock products
To maintain sustainable production based on diverse environment that
requires different genetic types
To maintain cultural affiliation as different breeds are integral part of
human heritage and are therefore to be nurtured for future generations
End of presentation