Transcript Adaptation in Beef Cattle

Adaptation in Beef Cattle
T. G. Jenkins
Meat Animal Research Center
Clay Center NE
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ADAPTABILITY
Frequently a focus of discussion
but are we all discussing the same
concept?
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Objectives:
1. What is meant by Adaptability
2. Evidence of Adaptability in beef cattle
3. Potential for application
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Terminology
Phenotype: the appearance of an
individual resulting from the
interaction of genotype and
environment
Genotype: total sum of all genetic
factors of an individual
Environment: all factors that
influence the expression
of
genes
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Types of Adaptability
Evolutionary: Trans-generational
Phenotypic: adjustments made by
individual within a lifetime
may be linked to biological
processes that are
evolutionary
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ADAPTABILITYEvolutionary Provides a species the ability for continued
existence (trans-generational)
adaptability could be
considered an optimization of a
phenotype to express fecundity
potential
What creates a need for the organism to change?
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Changes in conditions in which affects the
expression of the fecundity potential of
species
Environment
geographic location
food resources
climatic conditions
pathogens
etc
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What allows the species to change:
Genetic variability
Individuals exist within a population whose
genotype provides a selective advantage in the
altered environment allowing these individuals
to leave greater number of offspring
mutations
existing alleles
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Existing alleles (Mayr, 1970)
In manufacturing districts of England moth
change color from white to black because of
pollution. Predators were able to see white
moths so black had selective advantage
Mutation (Nature Biotech, Feb, 1999)
Specific strains of Salmonella have
become resistant to antibiotics
(Amoxicillin, Flofenicol, Streptomycin,
Tetracycline)
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Phenotypes vary because
genetic variation exists in
population that enable forces of
change (environment) to alter
genotypic frequencies
Selection
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Evidence for adaptation in beef cattle
Geographic location
Ngunni in Africa tsetse fly
Bonsmara Animals that suffer from hyperthermie
with
have an increased respiratory and pulse rate
concomitant metabolic, physiological and
endocrinological disturbances. Head shape
Breeds – foundation phase frequently
associated with geographic location, enhance
frequency of alleles of favored phenotypes
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Effecting genetic change may or may not lead
to alleviation of environmental constraint.
Failure
Composite population in Venezuela (all made using
50% Zebu and 50% unadapted Bos taurus breeds)
appeared to have failed to produce productive
cattle in spite of strong selection.
Success
Australian milking zebu (AMZ): Pakistani Sahiwal and
Red Sindhi dairy cattle were mated initially to highproducing Jersey cattle. Later, some infusion of Illawarra,
Guernsey and Holstein-Friesian bloodlines occurred.
Adaptation for heat tolerance and tick resistance in
“bred for milk production.
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Texas Longhorn
Why did this particular Creole type flourish in
hostile nutritionally sparse environment?
Resistant to tick fever
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Brisket Disease is caused
primarily by an oxygen shortage;
oxygen availability is 17% less at 5,000
feet than it is at sea level; 20% less at
6,000 feet, 26% less at 8,000 feet, and
31% less at 10,000 feet. Cause
excessive heart activity, eventually, the
heart wears out and stops beating.
The losses from the disease can vary
depending on the origin of the cattle. In
cattle born and raised at high
elevations, the losses tend to run from
.5% to 5%. In imported or lowland
cattle the losses can range from 30% to
40%.
There is test to identify animals that
are resistant, moderately heritable,
selection practiced to resolve
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Breeds reproduction at low Levels of Dry Matter
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Red Poll
Charolais
Angus
Pinzgauer
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Efficiency (g/kg DM)
Pinzgauer
Limousin
Simmental
Braunvieh
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Gelbvieh
Red Poll
20
Angus
Hereford
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Jenkins and Ferrell
.
1994. JAS 72:2787
Red Poll
Pinzgauer
Charolais
Angus
Gelbvieh
Limousin
Hereford
Braunvieh
Simmental
0
3000
4000
5000
6000
Dry Matter Intake (kg/yr)
7000
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Potential applications of Adaptability in Beef Cattle Production
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Forage selectivity
Parasite resistance
Endophyte resistance
Heat resistance
Water needs
Nutrient use
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What is required to implement “Adaptability” to
improve beef production
Recognition of novel phenotypes associated with economically important
traits
Determination if phenotype can be measured accurately
Assessment of variation associated with phenotype
Proportion of variation attributable to genetics
Programs to implement change
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