FASH6: Reproductive Management in Sheep

Question 1

What is the gestation period of sheep?

Answer 1

142-152 days

Question 2

What is the oestrus cycle length of sheep?

Answer 2

16-17 days

Question 3

what kind of breeders are sheep?

Answer 3

Short day breeders, signalled with melatonin increases

Question 4

What should the scrotal measurements be for a ram BSE?

Answer 4

Ram lamb - 32 cm

Shearling - 36 cm

Question 5

What is the ideal ewe lamb weight at tupping?

Answer 5

70% adult weight

Question 6

What do you look at when nutritional profiling?

Answer 6

GSHP-x: long-term selenium (low can results in embryonic loss)

Iodine: low associated with poor ewe fertility

VitB12: needed for gluconeogenesis

Albumin and Globulin

Question 7

What is the ideal ram to ewe ratio?

Answer 7

Adults: 1:40-60

Ram lamb: 1:30

Question 8

What are the different ways to manipulate breeding?

Answer 8

Synchronisation

• Ram or teaser effect
• Progestagen sponges

Advanced breeding season

• Melatonin implants

Question 9

What are the benefits of synchronization?

Answer 9

• Better labour management at lambing
• Easier flock health management
• Consistent lambs for sale
• AI use which can improve genetics

Question 10

What are the benefits of an advanced breeding season?

Answer 10

• Lambs ready for sale earlier
• Can enable 2 lambing periods

Question 11

Describe the ewe breeding season.

Answer 11

Anoestrum: dec-June

transition: June - Sept

Breeding: sept- dec

Question 12

What is the ram or teaser effect?

Answer 12

Can advance the breeding season by approx. 2 weeks and helps to synchronise the ewes

• You need to have no ram contact for over 4 weeks and then you introduce a vasectomised ram which induces ovulation
• Remove the teaser after 7 days and introduce a fertile ram 1 week later

Question 13

What is the ratio of vasectomised ram to ewe when doing the ram or teaser effect? What is the ratio of fertile ram to ewe?

Answer 13

V ram - 1:50-100

Ram: 1:25

Question 14

How do progestagen sponges work?

Answer 14

They synchronise ewes and can advance breeding season by 4-6 weeks

1. Day 0: insert sponge
2. Day 12-14: remove sponge ± PMSG injection
3. 36-40 hours later: introduce fertile tup
4. 48 hours later: remove ram
5. 16 days after sponge removal: put raddle rams out (1:10)

Question 15

How do melatonin implants work?

Answer 15

Melatonin can advance the breeding season by 2 months

• Day 1: (30 weeks before desire lambing) remove all rams, including ram lambs
• Day 7: implant ewes
• Day 42: (35 days after implant) introduce rams
• Day 60-70: peak mating activity
• Use raddles to monitor service

Question 16

What are the two methods of artificial inseminating lambs?

Answer 16

Laparscopic

• Requires GA
• Vet procedure
• Costly

Intra-vginal

• Convoluted cervix so thought to be ineffective

Question 17

Describe the general procedure for artificial insemination.

Answer 17

• Day 0 - insert progestogen sponges (or CIDRs)
• Day 12-14 - remove sponge and inject PMSG
• Introduce teasers after 24 hours
• Inject GnRH 30-36 hours later
• 48 hours later inseminate with fresh semen
• 53-58 hours later inseminate with frozen semen

Question 18

At what days gestation is it optimal to identify foetal numbers?

Answer 18

60-90 days

Question 19

How do you terminate pregnancy?

Answer 19

PGF2a

Question 20

How do you induce parturition?

Answer 20

Dexamethasone