W8 LAB ANIMAL

Reproduction 

Breeding: the activity of keeping animals in order to produce animals that have particular qualities

Importance:

consistent animal supply -no over/under breeding 

optimized breeding programs -mating schedule, monitor estrus cycle, ensure high fertility rates

genetic integrity -genetic uniform

reproductive biology models -study fertility, pregnancy, development biology 

age standardized animals -reduce variability 

hormonal influence on research results -standardize conditions & interpret data accurately by understanding factors 

genetic modifications -generate transgenic model for advanced studies 

environmental adaptations -light cycle, temp, nutrition -well being & productivity 

welfare considerations -identify stressor, improve housing, handling, care

Altricial: immature - unable to care for themselves

Precocial: mobile & independent within hours/days following birth or hatch

Female reproductive system

Function:

produce ovum/ova

transport ova to site of fertilization

provide favorable environment for developing embryos

move offspring outside of body at appropriate time (birth)

produces female sex hormones

supplies nourishment for offspring after birth

Main Reproductive System of Female Rat:

Mammary glands

A pair of ovaries (connected to UH via oviducts) 

Uterine horns 

Cervix (two in rats; two in mouse)

Vagina 

Uterus (BIPARTITE UTERUS)

*vagina opening – Y shaped slit located directly 

                                  below the clitoris阴蒂

Vagina

Short muscular canal (from uterus to outside of the body)

Lined with mucous membrane which keep it protected and moist

Functions:

The birth canal

The orifice for the acceptance of sperm during mating

When born, females have vagina closure membrane/vagina plate ruptures on its own (6 w)

Rodents:

bicornuate uterus

oviducts

most Mullerian ducts remain unfused to form oviducts and uterine horns, with fused portion forming cervix and contributing to vagina

Humans:

ovaries, fallopian tubes, uterus, cervix, vagina

During fetal development, most Mullerian ducts fuse in midline and form uterus, cervix and contributing to vagina development 

Main Reproductive System of Female Rabbit:

Mammary glands

A pair of ovaries

Uterine horns 

Separate cervical canals

Vaginal canal

Mesovarium: a fold tissue that attaches the ovary to the broad ligament of uterus 

Mesosalpinx: surrounds and supports oviducts 

Mesometrium: largest fold supports uterus 

Main Reproductive System of Male Rat:

Testes in scrotal sac: produce sperm

Epididymus: collect and store sperm

Vas deferens: move sperm from epididymus to urethra

Urethra: carry sperm through penis to penis 

Penis: eject sperm out of the body 

OS penis (baculum): 

Baculum = bone found within penis – present in penises of some primates

Located at distal end of the penis, above urethra

Aid in sexual reproduction by maintaining sufficient stiffness during sexual penetration

Main Reproductive System of Male Rabbit:

Paired testes: produce sperm

Epididymis (caudal epididymis – store spermatozoa): collect and store sperm

Ductus deferens: tubes that move sperm from epididymus to urethra

Pelvic urethra: carry sperm through penis to penis 

Penis: eject sperm out of the body 

Menstrual cycle:

shed endometrium

sexual active anytime

hypothalamus produce gonadotropin releasing hormone

pituitary secretes FSH LH

ovary releases sex hormones estrogen & progesterone

Estrus cycle: heat

resorb endometrium

female sexually active during estrus phase

mating calls

Time of period in which female most willing to breed/mate

Controlled by hormone 

Determined by vaginal cytological changes by vaginal swab

Signs:

vibrating ear

lordosis -when touched

will be receptive to the advances of male rat

running in short fast bursts 

4-5 d

follicular phase high estrogen

luteal phase high progesterone

Proestrus 

follicles enlarge 

increased vascularity of female reproductive tract

redden vulva 

increase nucleated epithelial cells

increase estrogen 

Estrus 

most fertile -higher chance of successful impregnation

sexual receptivity -allow male to mount 

exhibit lordosis 

very high estrogen

LH surge 突然增长

ovulation occurs 24-48 h after surge

occurs spontaneously at night d3 

lasts 12-14 h

ovulation within 8-12 h after estrus onset

optimal sperm transport 

high uterus motility with contractions moving toward oviduct 

cervical mucus volumes increase

high cornified anucleated cells

Metestrus

corpus hemorrhagicum

uterus contractions subside

low estrogen

presence of mucus strand and sperm if mating occur

stop show estrus sign

presence of vagina plug at vulva or on pan

low anucleated cornified cells

high leucocytes & epithelial cells

Diestrus

corpus luteum

high progesterone

low FSH

LH maintain

may be pregnant, not come into estrus throughout gestation 

CL regress if no conception 

cycle starts all over again

high leucocytes & epithelial cells

Anestrus: sexual inactivity btwn 2 periods of estrus

no changes in vaginal cells

inactive 

no hormonal influence

not achieved puberty

Causes: pregnancy, lactation, age, puberty, lack nutrition, season, stress 

Vaginal plug

form from mixing of vesicular and coagulating gland secretions at time of ejaculation

next day after mating

may retain for 16-48 h

often fall out within hours after mating

on bedding or pan

visualized directly/otoscope

indicator of mating

not guarantee pregnancy 

firmly placed to vagino cervical junction 

permit large no of spermatozoa to reach uterus 

consist large qty of trapped spermatozoa inside a mass of coagulated proteins 

day 0 of gestation

Spontaneous ovulator

rodents

ovulate spontaneously during estrus 

Induced ovulator

rabbit

mate anytime

no specific estrus

only ovulate when mated

high % false pregnancies

palpation 14d after mating

small round movable balls

make nest 22d after mating

Pseudopregnancies 

sperm not fertile

CL not regress

high progesterone

doe look pregnant

show parturition behavior

will only deliver fluid during "parturition"

Pheromone 

urine, sweat, saliva, most body secretion

volatile 

sniff to sense

travel via vomeronasal organ (Jacobson) is the paired auxiliary olfactory (smell) sense organ in soft tissue of nasal septum, in nasal cavity above hard palate in various tetrapod 

to brain for identification & effect certain behavior

stimulate sexual arousal, desire, hormone levels, fertility 

Lee Boot effect

female grouped together in crowded areas will have estrus cycles suppressed

Whitten effect

female grouped together come into estrus spontaneously approx. 72h after expose to male urine

Bruce effect

pregnant female expose to new male will abort fetuses 

Parturition 

give birth

periodic stretch 

extend hind legs

make nest by gathering bedding and sitting in dark

rabbit bite out fur from abdomen

kindling at night

rodent stand in semi crouch position deliver pups (pinkish & close eye)

dams/does usually eat placenta

some share nursing of young, some kill newborn/other young (maternal instinct)

no handle pups in nursing/change bedding 1st week -cannibalistic

Weaning 

withdraw 

pups nursed by their/other moms in a colony

weaned after 3 w mice rats

female comes into estrus 72h after parturition

mom pregnant again, pups must weaned off b4 next litter born

prevent trampling, overcrowding

rats sexually mature 5-6 w

sexing done as early as a week

pups separated by sex when weaning occurs 

no housed alone 

Sexing

male greater anogenital distance