Reproductive Endocrinology in LAs

Question 1

What should be considered when treating a LA for reproductive conditions?

Answer 1

Ideally treatments should be reversible

Question 2

How can anoestrus be treated in the cow?

Answer 2

Correct underlying problems e.g.

• NEB
• Maternal bond
• Lameness
• Metritis

PRID or CIDR for 12 days.
+/- 500ui of eCG on removal.

Question 3

What external methods of inducing oestrus/ovulation in ewes is there?

Answer 3

Ewes are seasonal therefore manipulate photoperiod to increase melatonin (increased in dark hours) or give exogenous melatonin.

Ram effect - ewes will ovulate withi 3-4 days of having a ram loose with them.

Question 4

What needs to be done prior to eCG/PMSG administration to anoestrus ewes?

Answer 4

They need to be primed with progesterone 12 days prior to admin. (Or 3-4 days prior to introduction of a ram)

Question 5

How is puberty induced in gilts?

Answer 5

Give IM injection of PMSG+hCG (PG600). These have FSH/LH like activity.

Question 6

What are the methods of oestrus synchronisation?

Answer 6

1. PGF2a administration - shortens luteal phase (3-5 days later)
2. Ovsynch - GnRH to start follicle wave and then shorten luteal phase with PGF2a
3. Exogenous progesterone + PGF2a

Question 7

What is the disadvantage of using PGF2a alone to synchronise oestrus?

Answer 7

Heat detection is still necessary.

A single injection may not target a CL in the correct stage (i.e. when it is refractory to PGF)

Question 8

When should AI be performed when using PGF2a injections?

Answer 8

1. 2 dose PGF 11d apart + AI @72 and 96 hours

2. 2 dose PGF 11d apart + AI @ 84 hours

Question 9

Describe ovsynch.

Answer 9

….

Question 10

What is the reason for pregnancy compromise?

Answer 10

Insufficient progesterone possibly due to a defective CL.

Question 11

When is the best time to administer progesterone to support pregnancy?

Answer 11

<6 days after conception.

Question 12

Other than exogenous progesterone administration, what can be given to increase P levels?

Answer 12

GnRH 11d (cow) or d9 (ewe) after insemination.

Question 13

What factors contribute to COD?

Answer 13

Stress
Low oestradiol concentrations
low hypothalamic sensitivity to oestragen
Uterine disease
NEB

Question 14

What is the trigger for parturition with regards to maternal hormones?

Answer 14

Rising Oestragen:Progesterone Ratio

Question 15

What is used to superovulate animals?

Answer 15

FSH

Flushing: Lowers Oestradiol and promotes FSH

Question 16

What does immunising against androstenedione in the female animal achieve?

Answer 16

Removal of negative feedback on the hypothalamus/pituitary leading to increased FSH levels => super ovulation.

Question 17

What immunization against GnRH preparations are available?

Answer 17

Vaxtrate - bull
Equity - Stallion
Gonacon - White tailed deer
IMPROVAC - control boar taint

Question 18

How does spayvac work?

Answer 18

It has action against ZP proteins and it used in wild animals.