17.4.1: Introduction to farm animal reproduction

Question 1

True/false: you can tell about the cow’s cyclicity from her cervix.

Answer 1

False
Cervix tone is discussed in horses but not in cows

Question 2

Answer 2

Dominant follicle
* Contains oocyte
* Fluid filled (anechoic on ultrasound)
* Secretes oestradiol -> this drived oestrus

Question 3

Answer 3

Corpus luteum
* Highly vascularised transient endocrine gland
* Solid (homogenous, medium echogenicity)
* Produces progesterone

Question 4

1

Answer 4

Question 5

2

Answer 5

Question 6

3

Answer 6

Question 7

4

Answer 7

Question 8

5

Answer 8

Question 9

High levels of which hormone lead to an LH surge? What is the effect of the LH surge?

Answer 9

Oestradiol
Effect of LH surge = ovulation

Question 10

How long is the oestrus cycle in the cow?
How long is the luteal phase?
How long does standing oestrus last?

Answer 10

Question 11

You see a cow showing signs of oestrus. When should you AI?

Answer 11

Oestrus lasts ~ 1 day so ASAP!
In an ideal world, would AI 6hrs after the onset of oestrus; in practice, just AI as soon as you see oestrus.

Question 12

What will the ovaries feel like when a cow is on Day 1 of her cycle?

Answer 12

Day 1 = ovulation has just occurred
The ovaries will be small and it might be hard to palpate the tiny CL

Question 13

If you see a large CL and a large follicle present at the same time, which one is dominant?

Answer 13

The CL

Question 14

Which structures can you see on this ovary?

Answer 14

There is a small follicle (anechoic structure)

Question 15

Which structures can you see on this ovary? Which is likely to be dominant?

Answer 15

Question 16

What phase of her cycle is this cow in?

Answer 16

Follicular phase

Question 17

These two ovaries are from the same cow. What phase of her cycle is she in? Which structure will be dominant?

Answer 17

• She is mid-luteal phase
• She has a large follicle but the CL will dominate

Question 18

1

Answer 18

Question 19

2

Answer 19

Question 20

3

Answer 20

Question 21

True/false: the first oestrus after parturition is typically silent.

Answer 21

True

Question 22

How long after parturition should a dairy cow have had her first ovulation by?

Answer 22

3 weeks after parturition

Question 23

In which species do we see profound lactational anoestrus (in that while the young are there and suckling, she will not cycle)? What is the hormonal mechanism behind this?

Answer 23

Sow
Prolactin suppresses LH, thus there is no ovulation

Question 24

Why might we see anoestrus?

Answer 24

• Physiological reasons: gestation, lactation/presence of offspring (species differences), seasonality (long or short day breeders)
• Pathology: metabolic/ heat stress, ovarian pathology e.g. cystic ovarian disorders, inactive ovarian activity

Question 25

How soon after piglets are weaned would you expect a sow to ovulate?

Answer 25

* Weaning intiates oestrus and there should be an LH surge within 7 days * This may be affected by length of lactation, timing of weaning

Question 26

Answer 26

Cystic ovary

Question 27

**True/false:** GnRH will induce oestrus.

Answer 27

**False** * GnRH induces an LH surge and therefore ovulation (approx. 28hrs later) * If you give GnRH, AI the cow 6hrs later * It does not induce oestrus

Question 28

**True/false:** we can use GnRH to force ovulation/ luteinisation of cystic structures.

Answer 28

**True**

Question 29

Answer 29

Multiple growing follicles on both ovaries

Question 30

What is the effect of FSH and what are its clinical uses?

Answer 30

FSH stimulates antral follicle growth. There are few products that are FSH-specific; we can use eCG as this has mainly FSH-like activity. Clinical uses: * Superovulation: ovulation of more follicles than norma * Must administer early in the follicular wave for superovulation * Often requires repeated doses * Responses are varied

Question 31

What effect does LH have and how can we use it clinically?

Answer 31

We don't have an LH-specific product; we use hCG instead as this is LH-like in activity. This stimulates the final maturation of follicles, causes luteinisation and provides luteal support. Clinical uses (exact effect influenced by dose) * Induce ovulation when animals are in oestrus * To force ovulation when there has been repeated failure of conception in cattle * Treatment of cystic ovaries in cows and heifers

Question 32

What effect do progestogens have and what can we use them for clinically?

Answer 32

Progestogens -> negative feedback effect on the pituitary (mimics luteal phase) Clinical use: * Suppress the HPG axis * Used as a method of inducing/ synchronising oestrus by administration and withdrawal of the product * When we withdraw the product, cow will enter the follicular phase

Question 33

What is flugestone and what does it do?

Answer 33

* Progestogen vaginal sponge * Oestrus induction/ synchronisation upon withdrawal * Often used in combination with eCG

Question 34

What is a PRID/CIDR and what does it do?

Answer 34

* Vaginal device release progesterone * Oestrus induction/ synchronisation on removal * Often used in combination with GnRH

Question 35

What is altrenogest (a.k.a. Regumate) and what does it do?

Answer 35

Exogenous progestogen * Oral liquid * Used for oestrus suppression/ induction/ synchronisation in mares and sows

Question 36

How old does a CL need to be in the cow to respond to prostaglandin?

Answer 36

Must be over 6 days old to respond

Question 37

What must you ensure before giving PGF2a to an animal?

Answer 37

Ensure that she is not pregnant

Question 38

What physiological effects does PGF2a have?

Answer 38

* Lysis of the mature CL, causing progesterone to decline * Smooth muscle contraction (ecbolic effect on the uterus)

Question 39

What are the clinical uses of PGF2a?

Answer 39

* Termination of luteal phase to synchronise oestrus * Induction of abortion * Induction of parturition * Ecbolic efect: treatment of chronic metritis, treatment of pyometra is CL is present

Question 40

How soon after giving PGF2a to lyse a CL will a cow come into oestrus?

Answer 40

3-4 days after PGF2a

Question 41

Which protocol is pictured here?

Answer 41

P4 and PGF. This is followed by fixed time AI. This can be used in the cow or heifer.

Question 42

Which synchronisation protocol is pictured here and what animals is it used in?

Answer 42

OvSynch Used in cows

Question 43

Which synchronisation protocol is pictured here and what animals is it used in?

Answer 43

OvSynch with P4 Heifers

Question 44

**True/false:** melatonin can be used to induce cyclicity in sheep.

Answer 44

**True**

Question 45

**True/false:** it is common to use 2 doses of PGF2a in sow synchronisation protocols.

Answer 45

**False** * Unable to use 2 doses of PGF2a in the sow because CL only responds after day 11

Question 46

1-4

Answer 46

Question 47

1-5

Answer 47

Question 48

1-6

Answer 48