Stewart

Question 1

Polyestrus

Answer 1

peaks & troughs throughout year - cows & sows

x = Month, y = blood [E2]

Question 2

Seasonal Polyestrus

Answer 2

Long Day: Spring breeding season - Queen, mare

Short Days: autumn breeding season - ewe, doe

x = Month, y = blood [E2]

Question 3

Monoestrus

Answer 3

1-3 cycles per year; exhibit periods of estrus that last several days - bitch

-estrus lasts 5-9d on avg (may vary b/w 1-20d)

Interestrus interval (IEI) of bitch = b/w 4-12 months

x = Month, y = blood [E2]

Question 4

Describe the 2 major phases of the Estrous Cycle.

Answer 4

1. Follicular Phase: regression of CL to ovulation (20% of cycle). Proestrus + Estrus
- 1º ovarian structure = the growing dominant follicle.
- 1º hormone = estradiol

2. Luteal Phase: ovulation until the CL regression (80% of cycle). Metestrus + Diestrus
- 1º ovarian structure = CL.
- 1º hormone = progesterone

The Corpus luteum is a temporary endocrine gland that is produced by the reminiscence of the Graafian follicle after ovulation. It secretes large amounts of progesterone and also some amounts of estrogen and inhibin A. The progesterone secreted by the Corpus luteum helps in maintaining the endometrium for implantation and pregnancy.

In the absence of fertilisation, the corpus luteum degenerates and another menstrual cycle starts due to the disintegration of the endometrium.

Question 5

What triggers the start of Proestrus?

Answer 5

destruction of CL (luteolysis)

Question 6

What hormones are involved in the major endocrine transition phase, PROESTRUS, during the Follicular Phase?

Answer 6

Proestrus: period of transition from P4 -> E2 dominance

P4 = progesterone; E2 = Estradiol

Question 7

What behaviors characterize the Estrus phase?

Answer 7

Visible behavioral symptoms due to peak in E2 production
- sexual receptivity
- mating

e.g., male mounting; vocalization; increased locomotion

Question 8

What hormones are involved in the major endocrine transition phase, METESTRUS during the Luteal Phase?

Answer 8

Metestrus: decline in E2 and rise in P4

Metestrus: starts after ovulation

Question 9

Describe Diestrus

Answer 9

• longest stage of estrous cycle
• CH develops into fully functioning CL -> P4+++
• Ends when no MROP -> luteolysis (from P4’s positive feedback on prostaglandin)
• If pregnant, MROP will prevent luteolysis (neg. feedback on prostaglandin)

MROP = maternal recognition of pregnancy

Question 10

What species spontaneously ovulate?

Answer 10

doe, ewe, cow, mare, bitch
- ovulation automatically triggered from estrus; will always enter diestrus phase

Question 11

What species have induced ovulation?

Answer 11

QUEEN
- mating is required for ovulation & diestrus to occur (copulation induces GNRH & LH surge)

Question 12

What defines transition from luteal => follicular phase?

Answer 12

Luteolysis of CL

Question 13

Anestrus

Answer 13

Condition where female does NOT exhibit regular estrous cycles
- ovaries are inactive/do not develop ovulatory follicles or CH/CL

Question 14

What stages are distinctive in the Bitch (what are their avg. durations)?

Answer 14

1. Proestrus (avg. 9d)
2. Estrus (avg. 9d)

Question 15

What type of oocyte is ovulated in the Bitch?

Answer 15

Primary oocyte -> ova fertilized// 2º oocyte developed by 3d post ovulation

Question 16

What species has no MROP / has a persistent CL, regardless of pregnancy status?

Answer 16

Bitch

Question 17

Cat is crouching, has elevated hind quarters, increased vocalization & showing affectionate behavior. What phase is this cat in?

Answer 17

Estrus

Question 18

What species has their LH surge AFTER ovulation?

Answer 18

Mare

ovulation 1-2 days BEFORE end of estrus

Question 19

What is unique about camelids being induced ovulators?

Answer 19

require intro of seminal plasma to induce LH surge

Seminal plasma is the fluid portion of semen, secreted by both the epididymis as well as the accessory glands before and during ejaculation. Seminal plasma is a complex fluid, which serves as a vehicle for transporting ejaculated spermatozoa towards their journey from the testes to their target, the oocyte.

Question 20

ID stage of red- versus yellow-arrowed cow

Answer 20

COW
Red = Proestrus (incr. riding activity during proestrus)
Yellow = Estrus

Question 21

Signs of estrus in ewe/doe

Answer 21

Vocalization; tail-swishing; clear-to-cloudy cervical mucous

Question 22

What stage does the vulva swell in swine?

Answer 22

Proestrus

Question 23

Describe relationship b/w FSH & ovarian follicles

Answer 23

FSH stimulates growth of ovarian follicles -> once they get to a certain size, there is negative feedback on FSH

Question 24

Most follicles undergo __?__ , with only 1-2 being selected for __?__

Answer 24

Most follicles undergo __atresia__ , with only 1-2 being selected for __dominance__

Question 25

What causes Anestrus in pregnant versus non-pregnant small ruminant?

Answer 25

SR = short-day breeders
pregnancy: progesterone
non-pregnancy: photoperiod (april to may)

Anestrus = inactive ovaries; female ≠ exhibit regular estrous cycles

SR breeding peak = oct thru dec

Question 26

In cows, the CL is not responsive to prostaglandin (PGF) prior to day 5 because…?

Answer 26

b/c Metestrus just ended, so the CL is not fully formed/function yet (aka prior to day 5).
- Day 16: PGF from uterus will begin to lyse the CL (if no MROP)

Question 27

Small Ruminants are __?__ Polyestrous and onset/length of breeding mainly determined by __?__

Answer 27

Small Ruminants are __Seasonally__ Polyestrous and onset/length of breeding mainly determined by __Photoperiod__

Question 28

What months do small ruminants breed? What months are their peak?

Answer 28

Aug through Mar with peak Oct-Dec

Anestrous April-May

Question 29

Does have more __?__ signs than ewes during Estrus

Answer 29

Does have more __obvious__ signs than ewes during Estrus

Ewes mostly just vocalize + swish tail

Question 30

What is unique about ovarian follicles in swine?

Answer 30

Several follicles (10-20) ovulate over a 1-4h period

Sow- Female pig who has had at least one litter of piglets. Used for breeding. Gilt- A female pig that has not produced a litter of piglets yet or is being used to grow out and finish to butcher.