Estrus =
In heat (noun)
Estrous =
The cycle (adj)
When does the estrous cycle begin in cows?
At puberty
Cattle have what kind of estrous cyclicality
Polyestrus
Cow estrous cycle length
21d
Cow estrous cycle duration
15h
Cow time from onset of estrus to ovulation
24-32h
4 stages of Estrous cycle
-Proestrus (d19 to estrus) -Estrus (d0) -Metestrus (d1-3) -Diestrus (d 4-18)
Follicular phase is made up of what two stages?
-Proestrus -Estrus
Luteal phase is made up of what two stages?
-Metestrus -Diestrus
Follicular growth and degeneration occurs throughout
Estrous cycle
Follicular dynamic: Cohort of small follicles begin to grow and secrete E2
Recruitment
Follicular dynamic:A group of growing follicles are selected
Selection
Follicular dynamic: Follicle becomes dominant; increasing amounts of E2 and inhibin secreted
Dominance
Follicular dynamic: Occurs continuously throughout folliculogenesis; it is the follicles that die off when a dominant one is chosen
Atresia
When does maternal recognition occur in bovine? What happens if theres no pregnancy?
-15-17d -No baby? PGF2 alpha
During recruitment, the hormone levels are: _____ FSH _____ LH ______ Inhibin
-High -Low-Low
During selection, the hormone levels are: _____ FSH _____ LH ______ Inhibin
-Low-Moderate-Low
During dominance, the hormone levels are: _____ FSH _____ LH ______ Inhibin
-Low-High -High
-Stimulate emergence of follicles (recruitment)
FSH
FSH is controlled by? Secreted by?
-E2 and Inhibin -Growing follicles
-Promote final growth and maturation -Stimulate ovulation
LH
LH is regulated by?
GnRH pulse frequency (Luteal phase by the tonic center: 6 pulses; Follicular phase by the surge center: 24)
What is a positive feedback on the surge center? Which then has what kind of feedback on FSH?
-Estrogen -Negative
Breeding Strategy: -Male exposed to cycling female -BUll does detecting -Beef industry
Natural service
Definitive sign of heat detection in cattle
Standing heat
What is the AM/PM rule?
-See animal standing in morning breed in evening -Breed that next morning
Pros to AI
-Genetics-Uniform -Calving ease for heifers
Equipment needed for AI
-NItrogen tank -Catch pen -Handling facilities-Time/labor -Meds
Secondary signs of Estrus
-Anxious -Vocalization -Restless (pedometer) -Vulva swelling -Mucous discharge-Chin resting -Head riding
Estrus detection system that records date, time, and duration of every mount
Heat watch system
How does a teaser bull work
-A bull that can not breed, but can leave a mark to show she's in heat -Can have lateral deviation of penis
Cows have an ___________ number of steps during estrus
Increased
Is fertility improved by control or synchronization?
NO-Can even be reduced
Pros of Synchronization of Estrus
-Reduce window of insemination -Reduce time spent in estrus detection -Enhance estrus detection -Allow scheduled breeding -Synchrony for embryo transfer
What are the opportunities to control the cycle?
-Control length of luteal phase-Control time of follicular wave emergence -Control LH surge and ovulation AI needs all 3
What does exogenous progesterone do?
-Alter LH pulse frequency -Prevents follicles from getting to pre-ovulatory size -Stops LH surgeno ovulation = no heat
You would use exogenous progesterone to extend what phase?
Luteal (trick cow into thinking it still has a CL)
Why would you want to extend the luteal phase?
If you give the progesterone (CIDR, MGA); then remove it and give luteolyse... the cycle will start and now you know day 0
-Orally active progestin -Used in feedlots -Suppresses ovulation and estrus signs-Synchronous estrus is following withdrawal -Causes poor fertility
MGA
Issues with MGA estrus synchronization
-Proper planning -Loss of synchrony
What can you use to shorten the Luteal Phase?
PF2alpha
When will PGF2 alpha work in the cycle
Day 6 post estrus
Pro of 2 shot of PF2alpha vs 1 in a herd
2 = more cows will come into heat
Issue with PGF2alpha
There is a variation in response(heifers faster response, brahman respond poorly, may be anestrus, may be pregnant)
Benefits of timed AI
-Synchronized emergence -Programmed luteolysis
What is more powerful than PGF alone programs
Wave emergency + luteal control with GnRH, CIDR, AND PG
How does Ovsynch (timed AI) work?
-Given GnRH -Give PGF2alpha -Give ANOTHER GnRH to push follicle -Breed 16-20h after that