Animal Reproduction

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Animal Reproduction

• Animal Science II

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Estrus Cycle

• Time of day when a female will accept a male for
  breeding
• Length
• 21 day cycle
• Cow- 16-18 hours
• Sow- 2 days
• Best indicator is when the animal stand to be
  mounted

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Ovulation

• Release of the egg from the ovary
• Number of young born is an indicator of eggs
  released
• Sows 10 to 15
• Cow One
• Split eggs produce identical twins, triplets, etc.

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Methods of Reproduction

• Natural
• Artificial Insemination (AI)
• Embryo Transfer
• Cloning using Nuclear Transfer

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Artificial Insemination

• Steps
• Insert hand into the rectum and grasp cervix
• Insert insemination rod
• Deposit bull semen from the middle of the cervix
  to just into the uterus

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Artificial Insemination
Bovine Reproductive Tract Diagram
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Artificial Insemination
Sow Reproductive Tract Diagram
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Artificial Insemination
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Artificial Insemination
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Artificial Insemination
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Artificial Insemination

• Advantages
• Wider variety of superior bulls used
• Increase number of cows that can be bread to a
  superior bull
• Reduces disease
• Dont have to keep a bull on the farm

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Artificial Insemination
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Artificial Insemination

• Disadvantages
• Requires a trained inseminator
• Requires more time and herd supervision

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Embryo Transfer

• Procedures
• Superovulate donor
• AI
• Flush embryos (catheter)
• Isolate and classify embryos
• Store in liquid nitrogen
• Transfer to recipient
• Diagnose pregnancy 1 to 3 months later

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Embryo Transfer

• Advantage
• Genes of the female (dam) can be passed on faster
  than natural breeding

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Cloning

• Using Nuclear Transfer
• Procedures
• Flush (same as embryo transfer)
• Filter
• Remove genetic materials from recipient oocytes
• Nuclei is removed through microsurgery

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Cloning

• Procedures (continued)
• The nuclei are separated and each one is
  transferred to an unfertilized egg cell that has
  had its nucleus removed
• Plugs are placed in sheep for 5 to 6 days
  (develops to the 32 to 64 cell stage)
• Embryos are placed in surrogate, frozen or used
  to clone more animals

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Cloning

• Advantages
• Increase herd uniformity
• Increase herd quality
• Produce genetically identical animals

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Parturition Process

• Increased estrogen causes uterus muscles to
  contract
• Water bag appears and breaks
• The second water bag appears with the fetus

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Parturition Process

• Normal Presentation
• Front feet first
• Nose
• Head and shoulders
• Hips
• Rear legs
• Rear feet last
• Any presentation not in order could cause death
  of the baby and/or mother

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Parturition Process

• Several hours later the placenta and other
  membranes (afterbirth) are expelled
• A retained placenta is deadly

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Animal Genetics

• Genotype
• kinds of gene pairs the animal has

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Dominant Genes

• Genes in a pair that hides or dominates the
  effect of the other gene in the pair
• Indicated by upper-case letters
• Ppolled

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Recessive Genes

• Genes that are hidden or covered by the dominant
  gene in the pair
• Indicated by lower-case letters
• p horned

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Homozygous

• Homozygous gene pair carries two genes for the
  same trait
• PP polled and polled.

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Heterozygous

• Heterozygous gene pairs carries two different
  genes that affect a trait
• Pp polled, horned

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Sex Determination

• Half the sperm carries an X chromosome and one
  half carries a Y chromosome
• All the ova carry an X chromosome
• Male offspring in mammals
• XY
• Females
• XX
• In poultry the chromosome configuration is
  opposite of mammals

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Sex-Linked Characteristics

• Some traits are carried on only the X chromosome
  and some on only the Y chromosome
• Traits on the Y chromosome are transmitted only
  from fathers to sons
• Certain genes are expressed in only one sex
  although they are carried by both sexes
• milk production
• egg laying
• rooster tail feathers
• Sex-linked traits are often recessive and are
  covered by dominant genes

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Incomplete Dominance

• Takes place when one gene does not completely
  hide the effect of other gene
• The offspring has a mixture of the two traits
• Roan color is a mixture of red and white

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Linkage

• The tendency for certain traits to appear in
  groups in the offspring because the genes for
  those traits are located near each other on the
  chromosome and stay together to pass traits in
  groups

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Crossover

• Chromosomes cross over one another and split to
  form new chromosomes with different combinations
  of genes

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Crossover
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Mutation

• A new trait appears
• Did NOT exist in the genetics of either parent

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Punnett Square

• Used to predict the results of crossing animals
• Male gametes are shown across the top
• Female gametes are shown down the left side

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Punnett Square

• P Polled
• p horned
• Example
• Two polled cattle that are homozygous for the
  polled trait

Polled Sire
Polled Dam
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Punnett Square

• N Normal size
• n Dwarfism
• Example
• Normal size in cattle is dominant to dwarfism

Sire
Dam
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Punnett Square

• N Normal size
• n Dwarfism
• Example
• What if both parents are carriers for a trait or
  disorder?

Sire
Dam
What is the probability that a Homozygous dwarf
calf is born?