Artificial breeding of small ruminants

Question 1

List some reasons promoting the use of artificial breeding

Answer 1

Improve genetic merit of a flock

Improved disease control

Status symbol

Introduction of new breeds

Easier transport of male gametes

Insurance against death of a high quality ram

Question 2

What is the biggest factor which may induce shock of collected semen?

Answer 2

rapid T changes

Question 3

What methods can be used to collect semen?

Answer 3

Artificial vagina - rams require training

Electro-ejaculator - poorer semen quality

Question 4

What gross features should be looked at from a collected semen sample?

Answer 4

Colour

Volume

Wave motion (rapid waves)

Motility

Density (cream not milk)

Question 5

How should semen be handled for storage/transport following collection + examination?

Answer 5

`Dilution (1:4 - always add diluent to semen)

Cool to 4 deg C over 4-6hrs

± Freeze over CO2 then N2

Question 6

What BCS should ewes be at at the point of AI? What effect do variations from this value have on fertility?

Answer 6

BCS 2.5-3 ( + slowly rising)

• fat ewes = poor conception rates + dystocia
• ewes < CMW = no cycling

Question 7

What feed must be avoided in ewes which will be AI’d soon?

Answer 7

Oestrogenic pastures (clovers)

Lupins (common supp feed - max 2kg/hd/wk to prevent P4 metabolism in the liver)

Question 8

What methods can be used to synchronise oestrus in ewes? What hormone do these all work on?

Answer 8

Exogenous P4 admin:

• Progestagen vaginal implants (12-14d –> stim’s CL –> removal of implant triggers luteolysis)
• Sponges (Chronogest) = intravaginal progestagen tampons
• CIDRs = intravaginal progestagen implant

Question 9

What methods/hormones can be used to stimulate follicles/OV? why would this be done?

Answer 9

PMSG (pregnant mare serum gonadotrophin)

hCG > super-OV for ET programs

FSH > super-OV for ET programs

Question 10

What artificial breeding methods are available for ewes?

Answer 10

Synchronised mating: synch ewes then put rams in (>5%)

‘Shot in the dark’ (cervical AI): detect cycling ewes w teaser ram > daily AI of marked ewes

Laparoscopic AI: synch ewes > AI w frozen/chilled/fresh semen

Question 11

Protocol for managing ewes before laparoscopic AI

What analgesia is required for this method?

Skin prep site location?

Protocol for thawing frozen semen?

Aftercare?

Answer 11

Ax:

• Local = 0.5 mL at lap sites
• Sedation = xylazine (4-8mg IM)

Skin prep:

• 10cm anterior to teats on bare skin at the skin-wool jcn, inside the flank on both sides

Thawing semen:

• Thaw in 37deg water bath (20-30s)
• Hold in 30 deg C water bath for ≤30mins
• Check each batch for motility post thawing (wave motion)

Aftercare:

• suture any bleeders
• wound mgt
• minimal disturbances ≤3wks post op
• Back up ram in at 14d

Question 12

On laparoscopic AI, how is working space created?

Where is semen injected?

Answer 12

Space provided by inflating pelvic cavity w CO2 gas

Inject semen into greater curvature of both uterine horns

Question 13

Possible complications of laparascopic AI

Answer 13

Perforate bladder

Perforate rumen

Inflate omentum

Perforate vena cava

Question 14

Major steps in an embryo transfer program in ewes

Answer 14

1. Select donor ewes
2. Synchronise (sponge/CIDR)
3. Superovulate (PMSG/hCG/FSH)
4. Double AI (48 + 56hrs)
5. Embryo collection (5-7d post-AI)
   
   • Surgical laparotomy
   • Transcervical
   • Surgical transcervical
6. Embryo transfer (synchronise recipients to donors w/in 24hrs) → insert embryo into uterine horn on same side as ovary w CL