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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