Animal Reproduction Flashcards
reproductive cyclicity
provides females with repeated opportunities to become pregnant
estrous cycle
physiological events that occur between periods of sexual receptivity (heat) and/or ovulations
the full cycle
estrus
period of sexual receptivity
anestrus
condition when females do not exhibit regular estrous cycle
polyestrous
uniform distribution of estrous cycles occurring regularly throughout the year (cow, sow)
seasonal polyestrous
“periods” of estrous cycles occurring only during certain seasons of the year (sheep, goats, deer, mare)
monoestrous
only one cycle per year, often lasting several days (dogs, wolves, fox, bear)
estrogen
Source— ovarian follicle and the placenta
Targets— uterus, hypothalamus, mammary tissue
Functions—mating behavior, uterine growth, secondary sex characteristics(why females look like females promotes GnRH —gonadotropin releasing hormone)
luteinizing hormone (LH)
Source— anterior pituitary
Targets— ovary (luteal cells in females), testis (interstitial cells in males)
Functions—ovulation, corpus luteum formation, progesterone production, testosterone production
follicle stimulating hormone (FSH)
source: anterior pituitary
targets: ovary (grandulosa cells) and testis (sertoli cells)
functions: follicular development, estrogen synthesis, sperm production
progesterone
source: corpus luteum (CL) and placenta
targets: uterus, mammary tissue, hypothalamus
functions: inhibits GnRH release, maintenance of pregnancy, mammary development
pregnancy hormone; pro gestation
testosterone
source: interstitial cells of testis
target: skeletal muscle, male reproductive tract
functions: anabolic growth, sperm production, secondary sex characteristics
gonadotropin releasing hormone (GnRH)
source: hypothalamus
target: anterior pituitary
functions: release LH and FSH
gestation
the period of fetal development, beginning wth fertilization and ending with parturition
fertilization takes place in the oviduct
the zygote migrates to the uterus
membranes form and attachment takes place between 20 and 30 days in cattle and horses, 14-21 in swine
cleavage
fertilization through zona pellucida (the thick transparent membrane surrounding a mammalian ovum before implantation) disintegration
differentiation
placentation
growth
shifts to fetus from embryo, ends in parturition
cow gestation length
285 days; 9 months
ewe gestation length
147 days; 5 months
mare gestation length
336 days; 11 months
sow gestation length
114 days; 3 months 3 weeks 3 days
stages of parturition
stage 1: preparatory stage involving cervical dilation and positioning of the fetus in the birth canal via myometrial contractions
stage 2: time of hard labor and expulsion of fetus
stage 3: expulsion of the placental membranes and subsequent uterine involution
initiation of parturition
initiated by the hormone cortisol released from the fetus; fetus under stress
dystocia
difficult birth, major cause of calf loss
relative dystocia
normal sized calf and small birth canal, often first time moms
absolute dystocia
abnormally large calf and a normal sized birth canal, most common cause of dystocia is from an oversized calf
hiplock
shoulders of the calf “lock” onto the bones of the pelvis during delivery, results in the calf getting stuck in the birth canal
artificial insemenation
advantages: genetic improvement through increased use of superior sires, disease control, improved record keeping, eliminates need for keeping bull
disadvantages: time required to detect estrus, percent of cows in estrus during the breeding, trained personnel required, overuse of inferior sires
artificial vagina
sire ejaculates into a man-made apparatus that mimics the feel of breeding a female by natural service
mimics by: temperature, pressure, lubrication, and position/angle
electroejaculation
an electrical probe is inserted into the rectum to stimulate ejaculation via slight electrical stimulus to the accessory sex glands
semen evaluation
after it is evaluated for volume, sperm concentration (hemacytometer or spectrophotometer), motility of sperm, morphology of sperm (abnormalities)
estrus detection
visual inspection: 30 minutes in the morning and evening, standing to be mounted (lordosis), mounting of other cows, swollen vulva, mucus
other tools: teaser animals, marker aids, heatwatch estrus detection system
rectocervical AI
manipulation of the cervix over the insemenation gun via the rectum (cows)
if cow is in heat in the morning, breed her in the evening
speculum
tube-like instrument that spans the vulva and posterior vagina allowing visual inspection of the cervix (deer and goats)
laparascopy
surgical introduction of semen directly into the uterine horns (sheep)
cervical
introduction of spirette with a counter clockwise rotation into the cervix
gilts- inseminate 12 hours after detection of estrus
sows- inseminate 24 hours after detection of estrus
vaginocervical
introduction of the insemenation gun into the cervix via the vagina (equine)
insemenation time is based on presence of a 35mm follicle, open cervix, and detection of estrus
dairy cattle AI
80-90% of the cows are bred artificially
21.2 million units of dairy semen sold domestically
beef cattle AI
about 13% of beef cows are inseminated, semen from angus and simmental bulls is most extensively, 1.3 million units of beef semen sold domestically
swine AI
about 80% of all pigs born in US are conceived via AI
horse AI
limited due to the rules of some breed associations, challenges associated with freezing equine semen
sheep and goat AI
limited because herds and flocks are dispersed over wide areas, cost per unit semen is high
estrous synchronization
a management technique that makes use of hormones to control or reschedule the estrous cycle: LH, FSH, Progesterone, Estrogen, Prostaglandin
advantages: decrease labor involved with heat detection, makes AI possible for extensive operations, may be economically advantages, may promote earlier conception, critical to embryo transfer programs
synchronization products
GnRH
PGF2a (prostaglandin-gets rid of CL/progesterone)
MGA (melengestrol acetate-progesterone, feed compund that keeps them out of heat until prostaglandin injection)
EAZI-BREED CIDR (progesterone based, similar to IUD?)
purpose of embryo transfer
increase productivity of genetically superior donors
maximize use of valuable semen
transport genetics across long distances
production of identical offspring by embryo splitting
embryo transfer
- synchronization of recipients with donor
- superovulation of donor female–produces many follicles
3.inseminate donor with semen from genetically superior bull - recovery and identification of viable embryos
- transfer of viable embryos into synchronized recipients
reproductive technologies
In vitro fertilization
nuclear transfer cloning
intra cytoplasmic sperm injection
gamete intrafollopian transfer
semen sexing
embryo sexing
preimplantation genetic diagnosis
in vitro fertilization
in vitro=in glass, in dish
involves placing sperm and matured oocyte together in a dish
keep embryo in vitro for up to 7 days- in vitro culture (IVC)
sperm sexing
works only because of the 3.5% difference in DNA quantity of X or Y bearing sperm
lasers are able to detect this 3.5% difference
selection method is called flow cytometry
some decrease in conception rates
sperm sexing
works only because of the 3.5% difference in DNA quantity of X or Y bearing sperm
lasers are able to detect this 3.5% difference
selection method is called flow cytometry
some decrease in conception rates
