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Animal Reproduction Animal Science

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Animal Reproduction Animal Science Definitions Purebred (straight breeding): the mating of animals from the same breed. Crossbreeding: the mating of animals from two ... – PowerPoint PPT presentation

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Title: Animal Reproduction Animal Science


1
Animal Reproduction Animal Science
2
Definitions
  • Purebred (straight breeding) the mating of
    animals from the same breed.
  • Crossbreeding the mating of animals from two or
    more different breeds.

3
Definitions
  • Homozygous-two parental genes calling for a
    specific characteristic that are identical
  • Heterozygous-two parental genes calling for a
    specific characteristic that are not identical.
    (The dominant gene will override the effect of
    the recessive gene.)

4
Purebred
  • Advantages
  • - Ancestry is known back to the start of the
    breed.
  • - genetically homozygous
  • - The foundation stock of crossbreeding.

5
Purebred
  • Disadvantages
  • - Undesirable traits are more concentrated
    because of the homozygous genes.
  • - Very expensive to start.
  • - Must market to get full value of animal.

6
Crossbred
  • Advantages of Crossbreeding
  • - Used to improve genetics.
  • - Dominant genes mask recessive genes.
  • - Hybrid vigor, or heterosis, occurs from the
    combination of genes.
  • - Cheaper to get started.

7
Crossbreed
  • Disadvantages of Crossbreeding
  • - Often lack superior genes of purebreds.
  • - Must settle for market value at sale barn.

8
BREEDING SCHEMES
  • Inbreeding Mating of related animals
  • - close breeding animals being mated are very
    closely related and can be traced back to more
    than 1common ancestor.
  • i.e. Father and daughter
  • - most intensive form
  • - high presence of undesirable traits

9
BREEDNG SCHEMES
  • Line breeding mating of animals that are more
    distantly related and can be traced back to one
    common ancestor.
  • i.e. Cousin, grandparent to grand offspring,
    half-brother to half-sister.

10
BREEDING SCHEMS
  • Out crossing the mating of animals of different
    families within the same breed.
  • Animals are not closely related
  • Purpose is to introduce new, desirable genes into
    the breeding program.
  • Reduces the changes of recessive genes appearing.
  • Most popular method of pure breeding.

11
BREEDING SCHEMES
  • Grading up the mating of a purebred sire to
    grade females.
  • Grade animal is any animal not eligible for
    registry.
  • Cheap method of improving the herd
  • Only one purebred sire is needed or artificial
    insemination can be done.
  • Improves the quality of the herd very quickly.

12
BREEDING SCHEMES
  • Two-breed rotation
  • Bulls from breed A are crossed with Cows from
    breed B.
  • The resulting heifers are bred to bulls from
    breed B for the duration of their productive
    life.
  • Replacement heifers chosen from these meetings
    are bred to bulls from to bulls from breed A.
  • Each succeeding generation of replacement heifers
    is bred to a bull from the opposite breed used to
    sire the replacement heifer.

13
BREEDING SCHEMES
  • Three-breed rotation
  • The pattern of breeding is the same as in a
    two-breed system, except that a bull from a third
    breed is used in the rotation of sires.
  • Four and Five-breed rotation
  • Used in large herds
  • A fourth of fifth bull is added to the system
  • Requires intense management practices.

14
Terminal Cross System
  • Cross is made that the offspring are undesirable
    for breeding.
  • Ex. Smut face lamb (Black faced male on white
    faced female.)
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