Transcript Animal_Genetics_Casey_Osksa

Animal Science
Breeding & Genetics
Original Power Point Created by Casey Osksa
Modified by Georgia Agricultural Education Curriculum Office
June 2002
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
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
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
Punnet Square
• 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?
Punnet Square
R
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?
Punnet Square
R
R
r
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?
Punnet Square
P
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?
Punnet Square
P
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?
Punnet Square
B P
bp
bp
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?
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
Punnet Square
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
• 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%
Punnet Square
• Mate a heterozygous bull (BbPp) to a
homozygous cow (BBPP)
• What are the outcomes?
Punnet Square
B P
B P
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?
Punnet Square
B P
B P
B p
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)
Punnet Square
X
X
XX
Y
Xy
Y
X
X B
X
XX
XX
B
X BY
XY
Y
X B
X
X
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
Pregnancy Testing Cows
• Rectal Palpation
• 2 months after removing bull
Pregnancy Testing Cows
Pregnancy Testing Ewes
• 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
Pregnancy Testing Sows
• Ultrasonic detector
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
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
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)
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
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
Expected Progeny Difference
(EPD)
• Carcass weight in pounds
• Marbling in USDA marbling degrees
• Ribeye area in square inches
• Fat Thickness in inches
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?
Crossbreeding
• 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
Hybrid Vigor
• or Heterosis
• biological phenomenon which causes
crossbreeds to outproduce the average
of their parents
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
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
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
Two-Breed Backcross
• 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
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
Three Breed Fixed Cross
• Crossbred cows mated to Purebred bull
of breed C
• All calves sold
• Purchase crossbred cows
• 100% of maximum heterosis
Breeding Programs
• Selection of breeding stock is critical
• Look at all traits, not just one or two
• Purebred bulls
• Be objective
Heat Detection
• 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
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
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
Induced Calving
• 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
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
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
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
Limitations of AI
• Physiological Principles: timing of heat
• Requires skilled techncians
• 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
AI Equipment
• Success = cleanliness of equipment
• Disinfect equipment
• Disposable equipment
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
Collection and Handling
• Electrical Stimulation - limited use with
rams
• Electro-Ejaculator Apparatus - probe in
rectum gives a weak ac current
(5-30volts), series of stimulations
applied
Collection and Handling
• Rectal Massage of Ampulae - 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
Semen Volume
Class
Bull
Ram
Boar
Stallion
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
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
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)
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
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
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
Embryo Transfer
• 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
Embryo Transfer
• Embryo Freezing - use as in AI
• Embryo Splitting (Cloning) - split at 7
days then implanted = twins
• Embryo Sexing - 90% accuracy