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Sheep Selection

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Intermediate breeding season (late Aug to early winter) ... Common in black-face sheep. Due to inheritance and environment. Hot rations and lush pastures ... – PowerPoint PPT presentation

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Title: Sheep Selection


1
Sheep Selection Life Cycle
  • Chapter 31

2
Breeding Sheep
  • Reproduction
  • Seasonally polyestrus
  • Breed in the fall (most breeds)
  • Nonseasonally polyestrus
  • Breed in the fall and spring

3
Breeding Sheep
  • Reproduction
  • Long breeding season (estrus late summer to
    midwinter)
  • Rambouillet, Merino, Dorset
  • Intermediate breeding season (late Aug to early
    winter)
  • Suffolk, Hampshire, Columbia, Corriedale
  • Short breeding season (early fall to late fall)
  • Southdown, Cheviot, Shropshire

4
Breeding Sheep
  • Reproduction
  • Puberty is reached at 5 to 12 mo
  • Average estrus cycle is 16 d
  • Estrus is 30 h
  • Gestation is 147 d
  • Lambing rate varies within and between breeds
  • Keep replacements from ewes that have high
    lambing rates
  • Rams should have a breeding soundness exam
  • Motility, mobility, Mortality

5
Breeding Sheep
  • Reproduction
  • Other factors affecting lambing rate
  • Selection Crossbreeding
  • Crossbreed ewes are more likely to conceive
  • Age
  • Mature ewes are more likely to conceive
  • Environment
  • Light, temperature, and humidity affect
    reproduction in sheep
  • Respond to decreased daylight
  • More ewes in estrus higher conception rates
  • Sperm counts decrease in hot weather

6
Breeding Sheep
  • Reproduction
  • Other factors affecting lambing rate
  • Health
  • Disease, parasites, lack of feed, imbalanced
    ration
  • Sheep in moderate body condition are more likely
    to conceive than fat ewes
  • Estrus Synchronization and AI
  • Hormones can be used to synchronize or bring ewes
    into estrus
  • AI is used, but much more difficult than beef and
    swine
  • Estrogen in Feeds
  • High estrogen in feed low fertility

7
Breeding Sheep
  • Breeding Season
  • Handmated
  • Teaser rams are needed to detect ewes in heat
  • Pasture mated
  • Tagging Ewes (removing wool from dock and vulva)
  • Increases lamb percentages
  • Ewe should be checked 2x / d for heat
  • Usually ovulate at the end of the 30 h estrus
  • Detecting the sire
  • Paint on the breast of the ram
  • Paint color should change every 16 or 17 d
  • Goal breeding season to last 40 d

8
Ewe Production Cycle
Breed (Sept.-Nov.)
Spring Breeding???
5 mo. Gestation
Shearing ???
Cull (20-25)
Lambing (Jan. April)
9
Breeding Sheep
  • Purebred Breeder
  • Goal to make genetic changes in highly heritable
    and economically important traits

10
Breeding Sheep
  • Purebred Breeder
  • Highly heritable traits
  • Mature body size, yearling type score, face
    cover, skinfolds, clean fleece yield, yearling
    staple length, gestation length, ribeye area, fat
    weight, and retail cut weight

11
Breeding Sheep
  • Purebred Breeder
  • Moderately heritable traits
  • Birth weight, 90-d weight, rate of gain, neck
    folds, grease fleece weight, fleece grade,
    lambing date, milk production, carcass length,
    and bone weight

12
Breeding Sheep
  • Purebred Breeder
  • Low heritability traits
  • Weaning type score, weaning condition score,
    multiple births, number of lambs weaned, fat
    thickness over loin, carcass weight per day of
    age, carcass grades, and dressing percentage

13
Breeding Sheep
  • Commercial Breeder
  • Important when determining a breeding system
  • What are the available pasture and management
    resources?
  • What is the desired income percentage from the
    sale of lambs versus wool?
  • What are the potential benefits from heterosis?
  • How can breed differences best be utilized to
    meet the breeding and marketing goals of the
    flock?
  • What is the anticipated season of marketing?
  • How large is the flock?

14
Breeding Sheep
  • Terminal Crossing
  • Most market lambs are crossbred
  • Maximum heterosis
  • Combine meat and mother breeds
  • Three-breed Terminal Crossbreeding
  • Valuable when fine-wool is important
  • Australia- Merino wool

15
Inherited Abnormalities
  • Cryptorchidism
  • Single recessive
  • Cull rams that sire these lambs
  • Dont utilize cryptorchid rams
  • Dwarfism
  • Recessive and lethal
  • Cull ewes and rams that sire dwarf offspring
  • Entropion (turned-in eyelids)
  • Keep records
  • Inheritance is unknown

16
Inherited Abnormalities
  • Overshot or parrot mouth
  • Lower jaw is too short
  • Cull breeding stock
  • Undershot
  • Lower jaw is too long
  • Cull breeding stock
  • Rectal prolapse
  • Common in black-face sheep
  • Due to inheritance and environment
  • Hot rations and lush pastures
  • Do not keep for breeding stock

17
Inherited Abnormalities
  • Skinfolds, open-faced, closed-faced and wool
    blindness
  • Inherited
  • Select against traits
  • Spider Syndrome
  • Severe skeletal deformity in Suffolk
  • Outward bending of the forelimbs from the knees
  • Select against

18
Callipyge
  • Found in many breeds
  • Dorset, Solid Gold
  • Increased muscle mass
  • Leaner, higher dressing percents, heavier muscled
  • Meat
  • TOUGH!
  • Work to improve tenderness
  • Potential to increase profits for producer???

19
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20
Booroola Merino
  • Merino Breed
  • Higher production of offspring per birth
  • Fine wool
  • Offspring have poor performance

21
  • Chapter 31 Sheep Breeding
  • Understand how reproduction is different in sheep
    compared to other species.
  • What factors affect reproduction?
  • Know how heritable traits are (high, moderate,
    low).
  • What should be considered when designing a
    breeding program?
  • Know the different types of inherited
    abnormalities.
  • Understand callipyge.
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