Reproductive Cyclicity

Estrous

adjective describing the action "cycle"

Estrus

noun describing the event "standing heat"

20-22

What is the typical length of the estrous cycle?

18-24 hours

What is the typical length of estrus or heat?

Follicular Phase

follicles dominate the ovarian structure

-estrogen is dominant hormone

Luteal Phase

corpus luteum dominates follicular structure

-progesterone is the dominant hormone

Endometrial Lining

-increases during follicular phase alongside estrogen

-increases, levels off, and decreases with progesterone

Days 17-21

What days of their estrous cycle are cows in proestrus?

Proestrus

ovarian follicles are growing rapidly

-increase in estrogen secretion by growing follicles

-decrease in progesterone from CL

-mucosal layers of vagina and uterus multiply

to prepare the uterus for pregnancy

Why does the endometrium grow before ovulation?

"pro"-before estrus

What is a way to remember what proestrus is?

Day 1

What days of their estrous cycle are cows in estrus?

Estrus (Stage)

period of sexual receptivity (increased E2-more feminine behavior)

-also called standing heat

-Surges of FSH and LH from anterior pituitary gland

Sow, ewe, and mare

What species ovulate during estrus?

True

T/F: Mares have a large behavioral difference between estrus and other stages. They can be very aggressive to stallions and geldings outside of estrus.

increased E2 levels from proestrus have a positive feedback on GnRH and the gonadotropins

Why are there surges of lutenizing hormone and follicle stimulating hormone during estrus?

Days 2 to 4

What days of their estrous cycle are cows in metestrus?

Metestrus

-short transitional phase after ovulation

-decreasing estrogen and increasing progesterone concentrations

-recently ruptured follicle is reorganizing into the CL

-Cow ovulates during this phase

12h after showing signs of estrus

When should you artificially inseminate cows?

Day 5 to 16

What days of their estrous cycle are cows in diestrus?

Diestrus

-continuedd luteal phase after ovulation

-absent in animals with short cycles

-Corpus luteum is fully developed

-Progesterone exerts influence on female organs and HPA,

-CL regresses at the end of diestrus

13 days

How long does the corpus luteum remain functional in sheep?

15-17 days

How long does the corpus luteum remain functional in the sow, mare, and cow?

Anestrus

period between diestrus and proestrus in monestrous and seasonally polyestrous animals

-varies in length

-characterized by quiescence of reproductive tract

-ends when proestrus begins

Quiescence

term used to describe inactivity of the reproductive tract during anestrus

False

Anestrus is a stage of the estrus cycle.

The Menstrual Cycle

the events that occur between two successive menstrual period

-lasts 28 days

-similar to estrous cycle, but capped and ended by menses

Menses

sloughing of the endometrium to the exterior

False

Can cows or other livestock go through menses?

Differences Between Estrous and Menstrual Cycle

-there is no defined period of sexual receptivity

-there is a period of endometrial sloughing

-the timeline for description of cycle begins and ends with menses, not ovulation or estrus

Proliferative Phases

at beginning, menses occurs then endometrium begins to thicken in response to estrogen.

-occurs during the follicular phase of the estrous cycle

Secretory Phase

progesterone increases which causes endometrium to proliferate and thickens to maximum thickness in preparation for embryo

-occurs during luteal phase

Breeding Season

the time of year where producers intend reproduction to take place

-term used in the beef industry

-usually takes place in spring or fall

it is too hot

Why do producers tend to have their cows calve out in fall and spring rather than summer?

Voluntary Waiting Period

a term used in the dairy industry used to describe the 45-60 day recovery period before cows are bred back

45-90 days after partuition

What is considered a reasonable amount of time for a cow to conceive after parturition?

42-day breeding season

gives the last cows to calve two estrous cycles to undergo uterine involution and prepare for breeding

-gives more opportunity for recovery than 60 day breeding season

60-day breeding season

last cows to conceive only get one cycle before breeding

-gives less time for animal to recover and undergo uterine involution

Estrous Synchronization

essential to maintain a short (12-13 month) calving interval

Calving interval

12-12 months; a factor affecting the profitability of any cattle breeding enterprise

21 Days

How long is the estrous cycle in cattle, swine, horses, and goats?

1/3

How many of the cows will you (or the bull) catch in heat?

65-70%

What is the conception rate with artificial and natural insemination?

21%

After a week of breeding with natural habits, how many cows will be pregnant?

75-90%

What percentage of cows will display estrus within 5 days of a protocol?

50%

What percent of anestrous cows can be induced into fertile heat after an estrus synchronization protocol?

Hormones

-gonadotropin-releasing hormone (GnRH)

-luteinizing hormone (LH)

-follicle stimulating hormone (FSH)

-Estradiol (E2)

-Progesterone (P4)

-Prostaglandin F2-alpha (PGF2A)

GnRH

causes ovulation of dominant follicle (LH) or continued growth of immature follicles (FSH)

-responsible for releasing FSH and LH

-effect depends on where animal is in cycle

Cystorelin

GnRH analog used in estrus synchronization protocols

FSH

causes follicular development and estradiol synthesis

LH

stimulates ovulation, formation of CL and progesterone secretion

Follitropin-V

FSH/LH analog used in estrus synchronization protocols

it increases follicular growth

What happens when follitropin-V is given while there is no dominant follicle?

it causes ovulation

What happens when follitropin-V is given while there is a dominant folliicle?

Granulosal cells in follicles

What cells release estradiol?

Estradiol Effects

-stimulates sexual behavior and enhanced uterine mobility

-secretion of slippery mucous (helps sperm travel)

Progesterone

-maintenance of pregnancy

-inhibits GnRH release (inhibits follicle growth and ovulation)

-secretion of viscous mucous (blocks sperm)

Luteolysis

promotes uterine tone and contraction, ovulation

Lutalyse

PGF2A; causes luteolysis

-may not do anything if used in follicular phase.

ovulation will occur quickly after the injection

What will happen if lutalyse is given during the luteal phase while a follicular phase is occurring?

17 days

What is the length of the estrous cycle in the ewe?

28 days

What is the length of the estrous cycle in humans?

30 hours

What is the duration of estrus in cows and ewes?

24-30 hours

How long after the beginning of estrus does ovulation occur in cows and ewes?

5 days

How long after the beginning of estrus does ovulation occur in mares?

7 days

How long does estrus last in the mare?

50 hours

How long does estrus last in the sow?

36-44 hours

How long after the beginning of estrus does ovulation occur in sows?

Importance of Estrus Detection

-decrease days open

-improves herd conception

-fewer repeat breedings

-cows and heifers AI bred to your favorite bulls

-reduced number of called cows

Tail Chalk, Tail Paint

one-tone and two-tone

-check daily

-as cow is mounted paint can be rubbed off

-false positives-paint is wiped off while scratching on brush or fence

-short courses available

Kamar Patch

patch glued onto the tailhead

-red ink capsule

-ruptures when cows are mounted >3 seconds

-no mess

Kamar Patch False Positives

-cow can be ridden while trying to escape being ridden

-scratching

Heat Watch DDX

small radio transmitter attached to the tail head

-signal sent to a computer or pager

-expensive

-very hard to keep on the cow (falls off)

Pedometers

locomotion increase by 4x during estrus

-placed around rear leg and records number of steps

Behavior 6-10 hours before estrus

-vocal

-nervous and restless

-smells other cows

-attempts to ride other cows

-vulva moist, red, and slightly swollen

-will not stand to be ridden

Standing Estrus

lasts 6-24 hours

-stands to be ridden

-nervous and restless

-congregates

-vulva moist, red, and slightly swollen

-clear mucous discharge

Behavior up to 10h after Standing Estrus

-clear mucous discharge

-will not stand to be ridden

Behavior 1-3 days after standing estrus

-bloody mucous discharge

-will not stand to be ridden

3

How many estrous cycles are in a 60 day breeding period?

105-120 days

How many total days are in a recovery and breeding period?

45-60 days

How many days are in a recovery period?

Advantages of Estrus Synchronization

-groups females for parturition

-reduce time required for estrus detection

-shorter calving season or breeding season

-more uniform weaning weights (beef)

-labor saving tool for utilizing superior genetics

-eliminate estrus detection with timed insemination

Common Methods of Estrus Synchronization

-Ovsynch

-Cosynch

-Two-Shot PGF2a

-CIDR (beef, small ruminants)

Less Common Methods of Estrus Synchronization

-heat synch, presynch, selectsynch, MGA, MGA GnRH, etc.

Ov Synchronization Protocol

Day 0- GnRH injection

Day 7- PGF2a

Day 9- GnRH

-Timed AI 8-18 hours after GnRH injection

CoSynch Protocol

Day 0- GnRH

Day 7- PGF2a

Day 9- GnRH

-Timed AI at 2nd GnRH injection

Two-Shot PGF2a Protocol

Day 0- PGF2a

-heat check and breed day 0-7

Day 14- PGF2a

-heat detect and breed day 14-21

Two-shot PGF2a

Which protocol is common with producers who CIDR and is the most producer friendly?

CIDR

controlled internal drug release

-contains progesterone

-available for sheep, goats, deer, cattle

-most widely used in beef animals

July 2002

When were CIDRs approved by the FDA?

CIDR protocol

Day 0- GnRH injection (optional) and CIDR insertion

Day 6 or 7- Lutalyse

Day 7- Remove CIDR

next 3-5 days after removal

When should heat detection be used after CIDR removal?

48-64 hours after CIDR removal

When should fixed time AI occur after CIDR removal?

PreSync Timed AI Protocol

Day 0- PGF2a

Day 14- GnRH

Day 21- PGF2a

Day 23- GnRH (2-4 d after PGF2a administration)

-timed AI 8-18 hours after GnRH

Modified Targeted Breeding Protocol

Day 0-PGF2a

Day 14- GnRH

Day 21- PGF2A

-then heat check and AI

-timed AI 72-80 hours after PGF2a administration

Management Considerations of Estrus Synchronization

-have proper facilities to handle animals

-good reproductive records required

-have enough AI technicians to help (one technician/100 cows in not sufficient

-be sure cows are healthy, heifers are cycling

-use a good quality semen

30-50 cows per technician

What is a proper ration for cows per AI technician?

When Estrus Synch protocols are Started

-set up injection 50 days into milk

-initiate protocols into 65 days into milk

-1st breeding 75 days into milk

18-23 days post AI

When should producers check for return heat after AI?

False

Daylength is a consistent factor, but it cannot predict future environmental cues like seasonal changes.