Mating & Breeding Systems

Estrous Cycle

Full cycle influenced by hormones to include heat and gestation

Four stages:

• Proestrus - ova develops, non-receptive, aggression

• Estrus - ovulation, receptive

• Metestrus - non-receptive, preparation for pregnancy

• Diestrus - pregnancy

Monogamous mating

One female bred w/ One male

Long / Short term

Simple record keeping

Polygamous & Harem mating

Multiple females bred w/ One male

• Polygamous - females removed once pregnant

• Harem - females kept with group

Housing female mice together will normally synchronize their estrous cycles (Whitten Effect)

Normally used w/ transgenic mice (lower reproductive efficiency)

Downfalls

• Difficult record keeping

• Unable to differentiate offspring

• Cage size

Proestrus

Estrous stage

• Ova develop in the ovarian follicles

• Females may present signs of being receptive to the male, however, she will still refuse

• This stage can show aggression

• Increasing estrogen

Estrus “Heat”

Estrous stage

• Ovulation of the ova

• Female is receptive to the male

• Peak estrogen, LH surge triggers ovulation

Metestrus

Estrous stage

• Female will refuse the male

• Preparation for pregnancy

• Increasing progesterone, decreasing estrogen

Diestrus

Estrous stage

• Pregnancy

• High progesterone; low estrogen

Whitten Effect

Housing more females together will normally synchronize their estrous cycles (mice only)

Spontaneous Ovulation

Ovulation occurs cyclically, triggered by hormonal changes regardless of mating

• Rising estrogen → triggers LH surge → ovulation

examples: rodent, cow, horse, sheep

Induced Ovulation

Ovulation occurs in response to mating / copulatory stimuli

• Stimulation → hormonal signal → LH surge → ovulation

examples: cat, rabbit, ferret, camel, llama

Monoestrous

One or few estrous cycles per year

examples: dog, wolf, fox, bear

Polyestrous

Multiple estrous cycles per year

examples: rodent, cow, pig, cat

Intensive Breeding

Breeding system

• Male remains with the female and help raise the young

Advantages

• Maximum litters per female

• Postpartum estrus - females bred after parturition

• Less fighting

• Simple recordkeeping, less labor

Disadvantages

• Older litter must be weaned before new litter is born

• More cage space, males

Non-Intensive Breeding

Breeding system

• Male and Females housed separately, only together for breeding — remain separated until young are weaned

• Females should be brought to male's cage due to marking

Advantages

• Less fighting amongst female

• Newborns not killed by male

• More control on timing

Disadvantages

• No postpartum estrus

• Difficult recordkeeping, more labor

Timed Mating

Used to provide young at specific times for experiments

Vaginal plug confirm mating, not pregnancy

Ex. female introduced late afternoon, next morning shes checked for vaginal plug

Vaginal plug

Check to confirm mating, not pregnancy

Breeding Schemes

Plan for producing a colony with a specific genetic makeup

Four types

• Outbred

• Inbred

• Hybrid / Recombinant

• Coisogenic / Congenic

Outbred

Breeding animals are not related or are distantly related

Designed to maintain genetic diversity

Normally produces larger litter size and females are normally better mothers

Inbred

Minimal genetic diversity

Minimum of 20 generations of brother-sister matings

• Foundation colony: original animals w/ desired trait

• Expansion colony: ensures the desired trait isn’t lost

• Production colony: used for experiments

Foundation colony (founders)

Inbred colony of original animals with desired trait

Expansion colony

Inbred colony that ensures the desired genetic trait will not be lost if something happens to the founders

Production colony

Inbred colony of inbred animals used for experiments

Hybrid

Breeding of two different inbred strains

Used to transfer desired mutation from one strain to another

The original strains must be crossed to produce each generation (cannot be mated with each other F1xF1=F2)

Nomenclature always notes the female strain first

• C3D2F1: female (C3H/He), male (DBA/2)

Coisogenic

Spontaneous mutation occurs (at single gene loci) within an inbred strain

Needs to be bred to the same strain to be maintained

Ideal for studying gene effects

Congenic

Selectively mating an animal w/ specific mutation

F1 carriers are mated with the inbred strain for 10-12 cycles

Helpful to determine how genetics influences the expression of a gene