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Chapter Seven

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Cells in vaginal wall change in phases of cycle. ... together for the duration of their breeding life. ... can be devastating to a research project. – PowerPoint PPT presentation

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Title: Chapter Seven


1
Chapter Seven
  • Heredity and Breeding

2
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3
Breeding and Husbandry
  • Genetics deals with heredity.
  • why offspring resemble or differ from their
    parents
  • Similarities and differences
  • due to heredity
  • caused by environmental factors or mutations
  • Successful breeding of animals depends on
  • an understanding of basic genetics
  • breeding system that suits the needs of a
    particular protocol.

4
Genes Chromosomes
  • Physical characteristics of organisms are passed
    from one generation to next by genes.
  • an inherited characteristic such as fur or eye
    color, number of toes or the length of the
    intestine
  • Genes are on chromosomes made of DNA.
  • Chromosomes paired structures in cell nuclei.
  • Number of pairs differs for various species.
  • Normal members of a species have number of
    pairs.
  • Only ova sperm chromosomes are not paired.
  • When the ovum is fertilized by the sperm, the
    zygote forms paired chromosomes from the unpaired
    sets.
  • Half of each parents genes passed to next
    generation.

5
Expression Mutation
  • Expression is result of
  • interaction of paired genes.
  • Genes can be either dominant or recessive.
  • Recessive brown fur gene dominant black fur
    expression of dominant black gene (black fur).
  • Gene may mutate when passed parent to offspring.
  • Mutations may occur spontaneously or by chemical
    physical environmental factors.
  • Can be either harmful or beneficial.
  • Such animals have potential use as a model to
    help understand diseases or phenomena.

6
Reproduction
  • 1st step in sexual reproduction is production of
    sperm eggs.
  • Fertilization location/manner depend on species.
  • In most mammals fertilization occurs within s
    reproductive tract.
  • In other types of animals, it occurs outside the
    body.
  • Development site also depends on species.
  • In most mammals, zygote becomes implanted grows
    in the uterus.
  • In birds and reptiles, embryonic development
    usually occurs outside body, inside an egg.

7
(Image) Female Internal Reproductive Organs
8
Gestation Estrus
  • Time required for a zygote to develop into a
    fetus be born gestation period.
  • Natural end of gestation period called
    parturition.
  • Males produce sperm continually are ready to
    mate almost any time after reaching maturity.
  • Females mate only during specific times.
  • During estrous cycles, females eggs undergo
    changes which prepare them for fertilization.
  • During estrus the female allows mating.
  • Ovulation usually occurs at or near this time.
  • Cells in vaginal wall change in phases of cycle.
  • In some species samples can be collected from the
    vagina examined to determine phase of estrous
    cycle.

9
(Image) Embryonic Growth Phases
10
Breeding Schemes
  • Breeding schemes determine how similar or
    different parents are from offspring.
  • Scheme depends on animal requirements.
  • Inbreeding is used to produce animals with
    minimal genetic variation.
  • share characteristics are identified as
    specific strain
  • Strains are inbred after gt20 generations.
  • Rodents are the most frequently inbred animals.
  • C57BL, DBA/2, C3H, and BALB/c
  • A mating to an unrelated animal or a different
    strain contaminates the inbred line.
  • Escaped animal should not be returned to a cage.

11
Breeding Schemes II
  • Outbreeding is a scheme of breeding in which only
    unrelated animals of the same stock are mated.
  • Frequently used in rodent colony management.
  • Results in maximum genetic difference among
    animals.
  • Usually more vigorous animals larger litter
    size.
  • CF1, ICR, and Swiss
  • Other breeding schemes
  • usually involve mating for
  • desirable characteristics.
  • Animals share a common ancestor line breeding.
  • Cross breeding mating animals of different
    breeds.

12
Mating Systems
  • After determining genetic type required for a
    project selecting mating system appropriate to
    species being used, more than one mating system
    may be appropriate.
  • depends on management considerations
  • Monogamous mating 1 1 paired together
    for the duration of their breeding life.
  • Simplifies record keeping lends itself well to
    maintaining inbred or outbred colonies.
  • Gerbil is bred most successfully with monogamous
    pairs.

13
Harem Mating
  • Polygamous mating system 1 with gt 2 s
  • results in large of young from least of
    breeders
  • economical method of production
  • difficult to keep accurate records
  • s often share nursing responsibilities, causes
    uncertainty of which female gave birth to
    offspring.
  • for colonies when not critical to know which is
    the mother
  • Cage must be large enough for adults and young
    until offspring are weaned.
  • Separate housed are together for
    breeding.
  • Reduces of animals needed, permits accurate
    record keeping, but labor costs are high.
  • Used when s kill the young or are
    aggressive.

14
Other Breeding Concerns
  • Consideration should be given to selection of
    good breeding stock.
  • Animals should be healthy, young nonaggressive.
  • Females should exhibit good mothering
    characteristics adequate milk production.
  • The health of breeding animals must
  • be monitored and sign of illness or
  • disease should be reported immediately.

15
Maintenance of Breeding Animals
  • Rodents rabbits may desert, kill or cannibalize
    their young if disturbed.
  • Delay cage changes for a few days following
    birth.
  • Minimal handling of newborn animals is a general
    rule.
  • Wean 21 days of age in rats and mice.
  • Rodents build nests if provided soft paper,
    shredded wood fiber or cotton.
  • Rabbits require a nest box pull hair to line
    nest.
  • 1214 hours of light is best for
  • rodent breeding colonies.
  • The longer light period helps
  • establish consistent estrous cycles.

16
Record Keeping
  • The following are examples of information that
    could be kept for a breeding colony
  • Breed, strain and type of animal
  • Parentage or ancestry
  • Animal identification number
  • Sex
  • Date mated
  • Date of birth and number of offspring
  • Date weaned and number of offspring
  • Sex of young
  • Veterinary information

17
Animal Identification
  • Identify individual animals.
  • critical for determining parentage and lineage
  • Mixing animals in a cage or placing an animal in
    a different cage without proper identification
    can be devastating to a research project.
  • Cage cards are used to
  • identify each animal or
  • group of animals.
  • Card contains information about
  • history, genetic background,
  • IACUC , type of experiment contact.

18
Short-Term ID
  • Clipping or shaving various
  • locations or patterns
  • Nontoxic, waterproof dyes or markers
  • Markings, colors, sex, hair or breed
  • Collars for cats, dogs and nonhuman primates
  • Must be routinely checked as animal grows.
  • Loose-fitting collar could get snagged on cage.
  • Dogs and cats purchased from commercial suppliers
    have a USDA number on record.
  • USDA tag may be left on collared animals.
  • Collars may cause skin irritation strangulation
    interfere with neck bandages other apparatus.

19
Permanent Identification Methods
  • Implantable microchip transponders transmit ID.
  • Subcutaneous chip implanted
  • Recording device scans chip and reads
  • Ear notching holes at various positions
  • Notches holes a numbering code.
  • Easy to read and produces little trauma to
    animal.
  • Used in pigs rodents, not hamsters guinea
    pigs.
  • Holes or notches close over a period of time.
  • Sanitize punch tool between animals.
  • Toe clipping must have strong justification.
  • removal of 1st bone of certain toes a code
  • gttime, gtdifficult, gtstress than ear marking
  • Anesthesia is recommended.

20
Ear Wing Tags
  • Small metal clips are stamped with individual
    s.
  • Using special pliers, they are applied near the
    base of the ear or to the wing.
  • Procedure is quick and causes minimal pain.
  • Used on rodents, rabbits, sheep birds.
  • As with ear notching, the ID can be lost.
  • In birds a numbered leg band is an alternative to
    a wing tag.

21
Tattooing
  • 2 types of tattooing devices
  • Hand-operated instrument clamps onto ear so
    pointed tips pierce skin and ink dyes the
    underlying tissue.
  • Electrical pen-like tool has a reciprocating
    multi-point needle which marks the skin.
  • Ink is massaged into skin perforations.
  • Clean disinfect instruments between animals.
  • Ear tattoo ID in rabbits
  • Avoid damage to medial artery or marginal ear
    vein.
  • Use black ink on lighter colored breeds.
  • Green ink on dark-colored breeds
  • Tattoo may spread as animal grows, making the
    tattoo unreadable and tattoo may have to be
    redone.

22
Tattooing Continued
  • Ears - g. pigs, cats, dogs, monkeys ungulates
  • Dogs - ears, skin of flanks or oral cavity
  • Dogs anesthetized and tattoo area is clipped,
    washed dried.
  • Nonhuman primates - chest or inner thigh
  • Even individually housed animals should be
    tattooed a cage card posted w/ all other info.
  • Neonatal rats mice may be permanently IDd
  • by injecting tattoo ink subcutaneously
  • into ears, tail, hocks or toes, using
  • a series or pattern of dots.

23
Additional Reading
  • Nicholas, F.W. Veterinary Genetics. Iowa State
    University Press, Ames, IA. 1987.
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