Ruminant estrus cycle

Question 1

Normal cycle length of bovine

Answer 1

Normal cycle length- 21 days (range 18-24)

Estrus – 24 hours, behavior - 9 hours in notes
Estrous behavior - 7 hours in dairy cattle
- 12 – 18 hours beef cattle and heifers

Diestrus - 14 days (couple weeks) (80% of cycle)

Metestrus – 3 -4 days

Proestrus – 2 -3 days

Question 2

Cattle typically produce ___-____ follicle waves per cycle

Answer 2

2-3

Question 3

Standing behavior is produced by which hormone?

Answer 3

Estrogen
(bitch- estrogen to progesterone shift triggers)

Question 4

Proestrus starts after

Answer 4

Luteolysis

Question 5

Proestrus description

Answer 5

Starts after luteolysis
Development of dominate follicle that will ovulate.
Estrogen is the dominate hormone
Uterus starts to develop some TONE

Question 6

Estrus in the cow

Answer 6

LH peak occurs
Ovulation occurs ~27-30 hours after LH peak/surge
Estrogen dominate hormone
Uterus is toned – feels like a rope

Behavioral estrus

Question 7

Behavioral Estrus in bovine

Answer 7

Cardinal sign - Standing to be mounted

Secondary signs - restlessness, mounting other cows, increased activity (walking, calling), clear mucous discharge, drop in milk production

Question 8

Cardinal sign of estrus in bovine

Answer 8

Standing behavior

Question 9

Metestrus in bovine

Answer 9

Starts after ovulation

Uterus (early edema); softer

Ovary – cellophane ball, divot where follicle was -> Corpus hemorrhagicum

Progesterone begins to increase- remodeling occurring

Metestral bleeding – “Bleeding off”

Question 10

Diestrus in bovine

Answer 10

CH develops into CL

CL produces progesterone- Maximum production - Days 8-9

Day 16 - PGF from uterus will begin to lyse the CL (if not pregnant)

CL not responsive to PGF prior to Day 5

Question 11

The CL is not responsive to PGF prior to day…

Answer 11

5 of development

Question 12

Sheep and goats have what type of cycle?

Answer 12

Seasonally polyesterous
Short day breeders

Question 13

In seasonal breeders the onset and length of breeding period influenced by…

Answer 13

Photoperiod (#1)
Latitude and climate
Food availability
Breed (Temperate vs. Tropical)
Presence of a male
Breeding system
Physiological stage

Question 14

Short day breeders in the Northern hemisphere

Answer 14

Generally, August through March (breeding season)

Peak is October through December

Transition periods occur around the peak (Increased frequency at the begging and end of season)

Anestrous occurs in April to May

Question 15

Hormones In short day breeders, In long photoperiods (spring and summer)

Answer 15

Pineal gland releases inhibitory neurotransmitters to prevent/decrease the amount of melatonin being synthesized and released therefore decreasing the release of GnRH

Question 16

Large quantities of melatonin being released from pinealocytes in the pineal gland leads to…

Answer 16

Increased release of GnRH to allow for estrus cycle to take place

Question 17

In short day breeders, short photoperiods (fall and winter) lead to….

Answer 17

Inhibition on pinealocytes in the pineal gland is decreased and allows for larger production of melatonin. Melatonin stimulates the release of GnRH from the hypothalamus to initiate cyclicality

Question 18

The goat and sheep can have between __-__ waves of follicles during each estrus cycle

Answer 18

3-4 is the most common for both species
Goat: 2-6 waves
Sheep: 1-4 waves

Question 19

Signs of estrus in the ewe vs the doe

Answer 19

The ewe is more conspicuous
The doe is more obvious (tail flagging and mounting)

Question 20

Cycle length in the ewe

Answer 20

Cycle length: 14-19 days
estrus: 24-36hours

Question 21

Cycle length in the doe

Answer 21

Cycle: 18-22d
Estrus: 24-48h

Question 22

The goal in porcine breeding is…

Answer 22

> 2.2 litters/sow/year with
8-9 weaned piglets/sow/year

Question 23

Pig estrus cycle

Answer 23

18-24 (avg. 21) days
SINGLE wave of follicles

Gilts: estrus 36-48 h (1.5-2 days)
Sows: estrus 48-72 h (2-3 days)

Ovulation occurs 2/3 of the way through estrus (36 h average)

Ovulation occurs 24 h after LH peak

Multiple follicles rupture over a 1-4 h period

Question 24

Estrus signs in sows/gilts

Answer 24

Vulva swelling and redness
Vaginal discharge
Restlessness and vocalization
Actively seeking boar
“Pricking” of ears (standing up)
Lordosis response “back pressure test”