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Growth and Muscle
Production
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The goal of these lectures is to discuss
basic physiology associated with the
control of growth and muscle production.
The sections for this lecture are:
Animal growth and animal development
Muscle: structure, myogenesis, growth
Notes on whole-body growth
Notes on hormonal regulation of growth
Life is a series of chemical reactions occurring in
compartmentalized environments. The main purpose of life is to keep itself alive
Physiology, the study of how life works, is based on
the simultaneous occurrence of the following three
concepts:
levels of organization
structure / function relationship
homeostatic regulation
Growth & Muscle Development
Growth, general and normal expansion of
size as produced by accretion of tissues
similar in constitution to that of original
tissue or organ
Hypertrophy, cells increase in size
Hyperplasia, cells increase in number
Accretion, cells accumulate or secrete
1950 True growth, e.g. increase in muscle/bone
Fattening, accumulation of fat
Whole body growth, from cell changes up
Development, temporal collective changes
today Muscle Production involve homeostatic responses leading to a steady state that is
borderline to a pathological state (thus they are more susceptible to diseases).
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Human Growth & Development
Mother & son.
At 8-foot-4, Leonid
Stadnik, 33 years old, is
the tallest human being on
the planet (2005)
Arnold Schwarzenegger.
He won several world
bodybuilders competitions
and until recently was the
governor of California.
Average daily gain, or the daily increase in weight, is a direct reflection of the human
and farm animal’s ability to grow. Muscle growth, a main tissue that increased its
weight, does so by multiple reasons, ultimately affecting undifferentiated muscle cells.
Animal Growth & Development
Average daily gain, or the daily increase in weight, is a direct reflection of the human
and farm animal’s ability to grow. Muscle growth, a main tissue that increased its
weight, does so by multiple reasons, ultimately affecting undifferentiated muscle cells.
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Animal Growth & Development
Market Hog Performance
1950 today Average daily gain, or the daily increase in weight, is a direct reflection of the animal’s
ability to grow. By increasing it, producers can rise more livestock in a given amount
of time (compare increase efficiency or gain vs. fat / lean ratios vs. profitability).
Animal Growth & Development
The economic contribution of meat animal
production in the USA is significant (approx.
40% of total farm income). Therefore, …
1950 today Implementation of animal technologies that
may improve animal performance can mean
the difference between operational success
and failure. For example …
Paylean (ractopamine a ß agonist) is a
compound added to swine diets to improve
efficiency. It stimulates growth in some
tissues and blunt growth in others. Its use
require changes in type / amount of dietary
proteins provided to maximize the benefits.
Average daily gain, or the daily increase in weight, is a direct reflection of the animal’s
ability to grow. By increasing it, producers can rise more livestock in a given amount
of time (compare increase efficiency or gain vs. fat / lean ratios vs. profitability).
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Animal Growth & Development
how to get
from here
1950 to here.
today Average daily gain, or the daily increase in weight, is a direct reflection of the animal’s
ability to grow. By increasing it, producers can rise more livestock in a given amount
of time (compare increase efficiency or gain vs. fat / lean ratios vs. profitability).
Skeletal Muscle
Structure, Miogenesis, Growth
Muscle tissue has relatively large cells harnessed in a vast network of connective
tissue (epimysium, fasciculi, perimysium, primary bundle, scondary bundle, intramuscular fat or marbling, endomysium, sarcolemma).
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Skeletal Muscle
Structure, Miogenesis, Growth
Muscle tissue has relatively large cells harnessed in a vast network of connective
tissue (epimysium, fasciculi, perimysium, primary bundle, scondary bundle, intramuscular fat or marbling, endomysium, sarcolemma).
Skeletal Muscle
Structure, Miogenesis, Growth
Selected Myofibrillar and Other Cytoskeletal
Proteins Located in Muscle Fibers
Muscle tissue has relatively large cells harnessed in a vast network of connective
tissue (epimysium, fasciculi, perimysium, primary bundle, scondary bundle, intramuscular fat or marbling, endomysium, sarcolemma).
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Skeletal Muscle
Structure, Miogenesis, Growth
Approximate Composition of Mammalian
Skeletal Muscle (percent fresh weight basis).
Muscle tissue has relatively large cells harnessed in a vast network of connective
tissue (epimysium, fasciculi, perimysium, primary bundle, scondary bundle, intramuscular fat or marbling, endomysium, sarcolemma). DO YOU SEE A PROBLEM ?
Skeletal Muscle
Structure, Miogenesis, Growth
Multinucleated units like skeletal muscle cells are incapable of undergoing division.
Myoblasts or muscle cell precursors are responsible for increasing muscle mass. In
the G1-phase of the cell cycle, myoblast are sensitive to growth factors and steroids.
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Skeletal Muscle
Structure, Miogenesis, Growth
Multinucleated units like skeletal muscle cells are incapable of undergoing division.
Myoblasts or muscle cell precursors are responsible for increasing muscle mass. In
the G1-phase of the cell cycle, myoblast are sensitive to growth factors and steroids.
Skeletal Muscle
Structure, Miogenesis, Growth
Satellite cells are quiscent or dormants since they remain capable of re-entering the
proliferative cell cycle without dividing. They are the apparent target for growth
promotants used in adult animals, such as ßagonists, GH, IGF, steroids.
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Skeletal Muscle
Structure, Miogenesis, Growth
Satellite cells, located between the sarcolemma and the basal lamina, are activated to
proliferate and ultimately fuse with each other to form new muscle fibers. This rarely
occcurs normally in adults, but might be the site of action of some growth promotants.
Skeletal Muscle
Structure, Miogenesis, Growth
Satellite
Cells
Satellite cells, located between the sarcolemma and the basal lamina, are activated to
proliferate and ultimately fuse with each other to form new muscle fibers. This rarely
occcurs normally in adults, but might be the site of action of some growth promotants.
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Skeletal Muscle
Structure, Miogenesis, Growth
Satellite
Cells
quiscent
satellite
cell
activated
myoblasts
daugther cell
returning to
quiscence
proliferating
myoblasts
fusion with
pre-existent
microtubes
myoblasts
commited to
myogenic
linage
myoblasts
fusion
into new
myotubes
and new
myofibers
Satellite cells, located between the sarcolemma and the basal lamina, are activated to
proliferate and ultimately fuse with each other to form new muscle fibers. This rarely
occcurs normally in adults, but might be the site of action of some growth promotants.
Skeletal Muscle
Structure, Miogenesis, Growth
SC
quiescent
SC
SC
commited to
fusion
SC
SC
myogenic
into
activated proliferatingg
linage
myotubes
SC
maturation
into
myofibers
Satellite
Cell (SC)
Satellite cells, located between the sarcolemma and the basal lamina, are activated to
proliferate and ultimately fuse with each other to form new muscle fibers. This rarely
occcurs normally in adults, but might be the site of action of some growth promotants.
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Skeletal Muscle
Structure, Miogenesis, Growth
Factor
Satellite
Cells
Proliferation
Differentiation Migration
E2
increase
FGF
increase
decrease
Ghrelin
decrease
increase
HGF
increase
decrease
IGF-I
increase
increase
IGF-II
increase
increase
IL-6
increase
IL-15
increase
equivocal
increase
increase
Satellite cells, located between the sarcolemma and the basal lamina, are activated to
proliferate and ultimately fuse with each other to form new muscle fibers. This rarely
occcurs normally in adults, but might be the site of action of some growth promotants.
Skeletal Muscle
Structure, Miogenesis, Growth
Satellite
Cells
Factor
Proliferation
Differentiation Migration
Leptin
increase
decrease
LIF
increase
Myostatin
decrease
increase
PDGF
increase
T
increase
TGF-beta
equivocal
equivocal
TNF
equivocal
decrease
VEGF
increase
increase
decrease
increase
increase
increase
Satellite cells, located between the sarcolemma and the basal lamina, are activated to
proliferate and ultimately fuse with each other to form new muscle fibers. This rarely
occcurs normally in adults, but might be the site of action of some growth promotants.
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Skeletal Muscle
Structure, Miogenesis, Growth
control
fiber
#
feed restricted
Average daily gain, or the daily increase in weight, is a direct reflection of the animal’s
ability to grow. By increasing it, producers can rise more livestock in a given amount
of time (compare increase efficiency or gain vs. fat / lean ratios vs. profitability).
Skeletal Muscle
Structure, Miogenesis, Growth
Percentage (%)
Tissue weight
water
fat
muscle
fat
protein
bone
ash
Average daily gain, or the daily increase in weight, is a diret reflection of the animal’s
ability to grow. By increasing it, producers can rise more livestock in a given amount
of time (compare increase efficiency or gain vs. fat / lean ratios vs. profitability).
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Whole Body Animal Growth
Red of Muscle Fibers
White
Characteristics
in
Domestic Meat Animals and Birds
Average daily gain, or the daily increase in weight, is a direct reflection of the animal’s
ability to grow. By increasing it, producers can rise more livestock in a given amount
of time (compare increase efficiency or gain vs. fat / lean ratios vs. profitability).
Skeletal Muscle
Structure, Miogenesis, Growth
muscle fiber size
white
white
red
muscle fiber #
red
white
red
Average daily gain, or the daily increase in weight, is a direct reflection of the animal’s
ability to grow. By increasing it, producers can rise more livestock in a given amount
of time (compare increase efficiency or gain vs. fat / lean ratios vs. profitability).
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Whole Body Animal Growth
double muscled
normal
Average daily gain, or the daily increase in weight, is a direct reflection of the animal’s
ability to grow. By increasing it, producers can rise more livestock in a given amount
of time (compare increase efficiency or gain vs. fat / lean ratios vs. profitability).
Whole Body Animal Growth
Distribution of Body Components
During Growth and Development
Average daily gain, or the daily increase in weight, is a direct reflection of the animal’s
ability to grow. By increasing it, producers can rise more livestock in a given amount
of time (compare increase efficiency or gain vs. fat / lean ratios vs. profitability).
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Whole Body Animal Growth
Satellite cells respond to growth promotants
Average daily gain, or the daily increase in weight, is a direct reflection of the animal’s
ability to grow. By increasing it, producers can rise more livestock in a given amount
of time (compare increase efficiency or gain vs. fat / lean ratios vs. profitability).
Whole Body Animal Growth
Examples of growth promotants
Effect of
Exogenous GH on
Muscle Fiber Size
in Boars, Gilts and
Barrows.
Effect of betaAdrenergic
Agonists on
Muscle Fiber Size.
But what are they increasing ??
Average daily gain, or the daily increase in weight, is a direct reflection of the animal’s
ability to grow. By increasing it, producers can rise more livestock in a given amount
of time (compare increase efficiency or gain vs. fat / lean ratios vs. profitability).
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Whole Body Animal Growth
Effect of Major Genes on Histochemical Traits
of Valuable Muscles in Different Species
Data from
genetically
modified
animals
Data from
promotant
treated
animals
Relative Change (% control) in Amount of Type 1, 2A, 2Ax
& 2B Myosin Heavy Chain (MyHC) Isoform in Longissimus
Muscle of Pigs Feed PAYLEAN over a 6 week Period.
Average daily gain, or the daily increase in weight, is a direct reflection of the animal’s
ability to grow. By increasing it, producers can rise more livestock in a given amount
of time (compare increase efficiency or gain vs. fat / lean ratios vs. profitability).
Whole Body Animal Growth
Examples
of growth
promotants
Effect of Cimaterol on Muscle
Fiber Type Composition in
Young Friesian Bulls
Effect of Implants (RALGRO and SYNOVEX-S)
on Muscle Fiber Type Composition in Cattle
Average daily gain, or the daily increase in weight, is a direct reflection of the animal’s
ability to grow. By increasing it, producers can rise more livestock in a given amount
of time (compare increase efficiency or gain vs. fat / lean ratios vs. profitability).
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Hormonal Regulation of Growth
Performance and Carcass Characteristics of Implanted Cattle with
Estradiol (E2) and Trenbolane Acetate (TBA) Alone or in Combination
Average daily gain, or the daily increase in weight, is a direct reflection of the animal’s
ability to grow. By increasing it, producers can rise more livestock in a given amount
of time (compare increase efficiency or gain vs. fat / lean ratios vs. profitability).
Hormonal Regulation of Growth
Stress - related factors
Cas and others
Major Effects of GH
SS GHRH
GH
Average daily gain, or the daily increase in weight, is a direct reflection of the animal’s
ability to grow. By increasing it, producers can rise more livestock in a given amount
of time (compare increase efficiency or gain vs. fat / lean ratios vs. profitability).
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Hormonal Regulation of Growth
Stress - related factors
Cas and others
GH on Pig Growth and its Carcass
SS GHRH
GH
Average daily gain, or the daily increase in weight, is a direct reflection of the animal’s
ability to grow. By increasing it, producers can rise more livestock in a given amount
of time (compare increase efficiency or gain vs. fat / lean ratios vs. profitability).
Hormonal Regulation of Growth
Stress - related factors
Cas and others
hGRF on Lamb Growth and Carcass SS GHRH
GH
Average daily gain, or the daily increase in weight, is a direct reflection of the animal’s
ability to grow. By increasing it, producers can rise more livestock in a given amount
of time (compare increase efficiency or gain vs. fat / lean ratios vs. profitability).
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Hormonal Regulation of Growth
Adrenergic hormones
Response to Adrenal Medulla Stimulation
Average daily gain, or the daily increase in weight, is a direct reflection of the animal’s
ability to grow. By increasing it, producers can rise more livestock in a given amount
of time (compare increase efficiency or gain vs. fat / lean ratios vs. profitability).
Hormonal Regulation of Growth
Zilpaterol, Steers Growth and Carcass Performance Average daily gain, or the daily increase in weight, is a direct reflection of the animal’s
ability to grow. By increasing it, producers can rise more livestock in a given amount
of time (compare increase efficiency or gain vs. fat / lean ratios vs. profitability).
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Hormonal Regulation of Growth
Satellite cells respond to growth promotants
Average daily gain, or the daily increase in weight, is a direct reflection of the animal’s
ability to grow. By increasing it, producers can rise more livestock in a given amount
of time (compare increase efficiency or gain vs. fat / lean ratios vs. profitability).
Hormonal Regulation of Growth
Average daily gain, or the daily increase in weight, is a direct reflection of the animal’s
ability to grow. By increasing it, producers can rise more livestock in a given amount
of time (compare increase efficiency or gain vs. fat / lean ratios vs. profitability).
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Hormonal
Regulation
of Growth
A Chihuahua
walking with a
Great Dane
more than 50
times its mass.
Hormonal Regulation of Growth
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Hormonal Regulation of Growth
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