Transcript Animal Science

Animal Science
Breeding & Genetics
Original Power Point Created by Casey Osksa
Modified by Georgia Agricultural Education Curriculum Office
June 2002
August 2008
What is Flushing or
Conditioning?
• Feeding cows, ewes, & sows more
generously 2 to 3 weeks before breeding
• Feed grain or more lush pastures
• Grain:
– Cows 3-5#
– Ewes 1-2#
– Sows 2#
• After breeding, return to normal feed
August 2008
Why Flush?
• More eggs are produced
• Females come in heat more promptly
• More certain conception
– more uniform timing of birth
• 15- 30% increase in lamb and pig crops
• Exercise for fat cows, ewes, sows helps
August 2008
Genetics Terms
• Heterozygous = two different types of genes
(Bb)
• Homozygous = two similar genes (BB)
• Dominant Gene = trait overpowers others
• Recessive Gene = must be accompanied
with another recessive gene to express trait
• Incomplete Dominance = both traits express
themselves
August 2008
Punnet Square
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Shorthorn Cattle
R = Red
W = white
RW = roan
If a red bull (RR) is mated to a white cow
(WW), what color will the calves be?
August 2008
Punnet Square
R
August 2008
R
W
R
W
R
W
W
R
W
R
W
Punnet Square
• If a red bull (RR) is mated to a roan (RW)
cow, what color will the calves be?
August 2008
Punnet Square
R
R
r
August 2008
R
R
R
R
R
R
r
R
r
Punnet Square
• P = horned
• p = polled
• If a homozygous horned cow (PP) is
mated to a homozygous polled bull (pp),
what percent of the calves will be horned,
polled?
August 2008
Punnet Square
P
August 2008
p
P p
p
P p
P
P p
P p
Punnet Square
• If a homozygous horned cow (PP) is
mated to a heterozygous horned bull (Pp),
what percent of the calves will be polled?
August 2008
Punnet Square
P
August 2008
p
P p
p
P p
P
P p
P p
Punnet Square
• Mate an Angus bull that is homozygous
black and polled (BBPP) to a red
shorthorn cow which is homozygous red
and horned (bbpp).
• What is the probability that the offspring
will be black? Polled? Horned? Black and
Polled?
August 2008
Punnet Square
B P
bp
bp
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B bPp
B bPp
B P
B bPp
B bPp
Black = 100%
Polled = 100%
Horned = 0%
Black & Polled =
100%
Punnet Square
• Now mate two of the offspring which are
heterozygous for black/red and
polled/horned (BbPp)
• What is the probability that the offspring
will be black? Black Polled? Black
Horned? Red? Red Polled? Red Horned?
August 2008
Punnet Square
• How do you do a punnet square with
multiple genes?
• Use all possible gene combinations
• BbPp = could be BP, Bp, bP,bp
• 4 x 4 grid
August 2008
Punnet Square
August 2008
BP
Bp
bP
bp
BP
BBPP
BBPp
BbPP
BbPp
Bp
BBpP
BBpp
BbPp
Bbpp
bbPp
bP
BbPP
BbPp
bbPP
bp
BbPp
Bbpp
bbPp
bbpp
Punnet Square
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Black = 12 out of 16 or 75%
Black Polled = 9 out of 16 or 56.25%
Black Horned = 3 out of 16 or 18.75%
Red = 4 out of 16 or 25%
Red Polled = 3 out of 16 or 18.75%
Red Horned = 1 out of 16 or 6.25%
August 2008
Punnet Square
• Mate a heterozygous bull (BbPp) to a
homozygous cow (BBPP)
• What are the outcomes?
August 2008
Punnet Square
B P
B P
August 2008
B B PP
B p
B B Pp
bP
B bPP
bp
B bPp
Punnet Square
• Mate a (BbPp) bull to a (BBPp) cow
• what are the outcomes?
August 2008
Punnet Square
B P
B P
B p
August 2008
B B PP
B B Pp
B p
bP
bp
B B Pp
B bPP
B bPp
B B pp
B bPp
B bpp
Punnet Square
• What are the chances that a new offspring
will be a male (xy) or female (xx)
August 2008
Punnet Square
X
X
August 2008
XX
Y
Xy
Y
X
X B
X
August 2008
XX
XX
B
X BY
XY
Y
X B
X
X
August 2008
XX
B
XX
B
X Y
XY
Pregnancy Testing Advantages:
• Early warning of breeding troubles
(infertile, cystic ovaries)
• Rebreed nonpregnant females
• Grouping for proper nutrition
• More effective use of facilities (parturition)
• Guarantee pregnant females for sale
August 2008
Pregnancy Testing Cows
• Rectal Palpation
• 2 months after removing bull
August 2008
Pregnancy Testing Cows
August 2008
Pregnancy Testing Ewes
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Determine open ewes, after 60 days
Determine multiple lambs
Rectal Palpation (hollow plastic rod)
Ultrasonic scanning (light or sound if
fetus is present) can’t detect multiples
• Intrarectal Doppler (detects fetal
heartbeat (130-160)) can’t detect
multiples
August 2008
Pregnancy Testing Sows
• Ultrasonic detector
August 2008
Pregnancy Testing Mares
• Stop of Heat period- 18-20 days after last
ovulation
• Rectal Palpation - 45 days after mating
• Blood Tests : 20 -120 days after mating
• Ultrasonography: visual image of
reproductive tract, 10 days after mating
August 2008
Multiple Births
• Percent Twins:
– Beef .5%
– Dairy 2%
– Sheep 20-60%
– Horses 1.5%
• Twins not desirable in most other than
sheep, triplets undesirable in sheep
August 2008
Freemartin Heifers
• Sterile heifers that are born twin with a bull
• 85% of twin births with both sex
• Fetal circulations fuse, male hormone
circulates into female, interferes with
normal sex development
• Can examine vagina of heifer to determine
if freemartin (1/3 as long)
August 2008
Expected Progeny Difference
(EPD)
• Breed Specific (can’t compare epd’s of
different breeds)
• Expressed as + or • Birth Weight in pounds
• Weaning Weight in pounds at 205 days
• Yearling Weight in pounds at 365 days
• Maternal Influence (milking ability) pounds of
weaning weight produced by daughters
August 2008
Expected Progeny Difference
(EPD)
• Direct Calving Ease, size & shape of calf
• Maternal Calving Ease: size, internal
structure, uterine environment of female
• Gestation Length in days
• Yearling Height in inches
• Scrotal Circumference in centimeters
August 2008
Expected Progeny Difference
(EPD)
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Carcass weight in pounds
Marbling in USDA marbling degrees
Ribeye area in square inches
Fat Thickness in inches
August 2008
Expected Progeny Difference
(EPD)
Sire BW
WW
YW
Milk
A
4.9
12.2
13.2
-3.0
B
4
0.2
3.5
9.0
C
3
0
5
13.0
• Want to increase milk production?
• Want to reduce birthweight?
• Want to increase rate of growth?
August 2008
Crossbreeding
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mating of animals of different breeds
can increase productivity
produce animals with combination of traits
foundation stock for new breeds
introduce new genes quicker than in
purebreds
August 2008
Hybrid Vigor
• or Heterosis
• biological phenomenon which causes
crossbreeds to outproduce the average of
their parents
August 2008
Complementary
• the advantage of a cross where two or
more traits complement each other
• good quality of breed A and a different
good quality of breed B combine in the
offspring
• qualities complement each other
August 2008
Factors Affecting Crossbreeding
Advantages
• To achieve 15=-25% immediate increase
in yield per female, depends on:
• Making wide crosses =wider heterosis
• Select complementary breeds
• Use high performance stock
• Sound Crossbreeding Program: use
crossbred females
• Tap Purebreds: to renew hybrid vigor
August 2008
Two-Breed Cross
• Purebred Bulls X Purebred Cows of
another breed
• Angus X Hereford = Black Baldies
• 8-10% increase in weaning weight
• Does not use a crossbred cow
August 2008
Two-Breed Backcross
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or Crisscross
Breed A X Breed B = Crossbred calves
Crossbred X Breed A or B
Charlais Bull X Hereford Cow = Cross
Cross X Charlais
Yields 67% of maximum heterosis
August 2008
Three Breed Rotation Cross
• 3 Breeds (Hereford, Brahman, Charolais)
• Crossbred females bred to purebred bull of
breed A
• Resulting cross mated to purebred bull of
breed B
• Resulting cross mated to purebred bull of
breed C
• Repeat rotation
• 87% of maximum heterosis
August 2008
Three Breed Fixed Cross
• Crossbred cows mated to Purebred bull of
breed C
• All calves sold
• Purchase crossbred cows
• 100% of maximum heterosis
August 2008
Breeding Programs
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Selection of breeding stock is critical
Look at all traits, not just one or two
Purebred bulls
Be objective
August 2008
Heat Detection
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Producers miss 25-50% of heat periods
Delays calving by 30-40 days
Loss of income: $40 in dairy, $20 in beef
Chin-Ball Marker: marker attached to
bottom of a halter of a surgically altered
teaser bull (Gomer)
• Heat-Mount Detector: fabric with inkfilled capsule, pressure breaks capsule
August 2008
Heat Detection
• Pen-O-Block: plastic tube placed within
bull’s sheath, held by stainless steel pin
• Allows bull to mount cow, mechanically
impossible to breed
• Vasectomized Bull: can transmit disease
August 2008
Manipulating Estrous
• Artificial Lighting: ewes, mares, fowl
• Lengthen days, then shorten to simulate
natural breeding season
• Hormones:
• Progestagens: mimics pregnancy, feed,
inject, implant, for 14-20 days, when
removed, cows cycle 2-8 days later
• Prostaglandins: single dose injection, 90
hours later = estrous
August 2008
Induced Calving
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Artificially shortening gestation
Lower birth weight, less calving difficulty
Predict calving dates
Longer period from calving to breeding
After 269 days, cows injected with adrenal
steroid
• Calve 5-8 days earlier, 6-8 lb lighter calf
• Higher rate of retained placentas, lower
milk production
August 2008
Artificial Insemination
• Deposit spermatozoa in female artificially
• Legend: First done in 1322 by Arab (stole
semen from enemy stallion)
• First official: 1780 by Italion (dogs)
• In US for over 40 years
• 1988, 65% dairy cows AI’ed
August 2008
Advantages of AI
• Increases use of outstanding sires (cost)
• Alleviates danger and bother of keeping
a sire
• Can overcome physical handicaps of
mating: large bulls on heifers
• Sire that is no longer alive
• Reduce sire costs
• Reduces possibility of sterile sires
August 2008
Advantages of AI
• Helps control disease
• Possible to prove more sires (can
determine genetic worth easier)
• Creates large families of superior animals
• Increase pride in ownership of superiors
• Increase profits
August 2008
Limitations of AI
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Physiological Principles: timing of heat
Requires skilled technicians
Costly to start
Can accentuate damage of poor sires
May restrict sire market (avg or poor bulls)
May increase spread of disease (none to
date, but is possible)
• Abuse: mislabled semen
August 2008
AI Equipment
• Success = cleanliness of equipment
• Disinfect equipment
• Disposable equipment
August 2008
Collection and Handling
• Artificial Vagina - outer tube of plastic,
inner tube made of thin rubber, space
between filled with warm water & air, end
attached to a test tube
• Expose male to female in heat, then give
him a “dummy” to mount
• Some use a cow or steer in replacement
of dummy
August 2008
Collection and Handling
• Electrical Stimulation - limited use with
rams
• Electro-Ejaculator Apparatus - probe in
rectum gives a weak ac current
(530volts), series of stimulations applied
August 2008
Collection and Handling
• Rectal Massage of Ampullae - rectal
massage of the ampullae and collection of
semen in a funnel
– requires 2 people
– males must stand
• Collecting Semen from the Vagina - using
a sponge, pipette, spoon etc.
– semen is contaminated
August 2008
Semen Volume
Class
Bull
Ram
Boar
Stallion
August 2008
ml/ejaculate
5-6
1
200-300
50-150
Sperm Conc
800-1,200
800-4,000
25-1,000
30-800
No. Fem
300-500
40-100
15-25
8-12
Semen Extenders
• Add volume
• Preservative etc
• Antibiotics
August 2008
Semen Life
• Fresh - (room temp) use within 1-2 hours
• Fresh - (dilute & gradually cool to 35-40
deg F) 1 to 4 days
• Frozen - (liquid Nitrogen) -320 deg F
– store up to 30 yrs
August 2008
Packaging Semen
• Ampule - glass container (1 ml) transfer to
tube,
• Pellet - frozen pellets
– problems with ID, automation, sanitation
• Straws - plastic, 2-5 inch, 1/4 - 1/2 ml
– 95% of all frozen semen
• Shell-freezing - remove dead & abnormal
semen with a filter
• Lyophilization of semen - store in dry state at
low temp. (experimental)
August 2008
When to Breed
• Female is only fertile when an egg is
present which can be fertilized
• Eggs short lived
• Inseminate before egg is shed
• Cow doesn’t shed egg until 10 hours after
standing heat, lives 6-10 hours
• Cows in standing heat in morning are bred
in afternoon or evening
August 2008
Superovulation
• Injecting female with drugs which cause
the larger follicles to mature & release egg
(5-50 eggs)
• Normally 1 egg / 21 days
• Ovulation occurs over a period of time,
Repeated insemination needed
• 4-5 fertilized eggs average
August 2008
Embryo Transfer
Synchronize Heat Cycles of donor &
recipients
Inject drug to superovulate
Breed donor (natural or AI)
Collect eggs
Examine eggs (if fertilized)
Synchronize recipients ovulation
transfer eggs
August 2008
Embryo Transfer
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Advantages:
up to 50 calves / yr
speed rate of genetic improvement
import / export genetics
progeny test heifers earlier
beef calves from dairy cows
cows that can’t conceive but can produce
eggs don’t have to be sold
August 2008
Embryo Transfer
• Embryo Freezing - use as in AI
• Embryo Splitting (Cloning) - split at 7 days
then implanted = twins
• Embryo Sexing - 90% accuracy
August 2008