Sheep Reproduction

Question 1

Describe the reproductive physiology of the sheep (seasonality)

Answer 1

Sheep are short day breeders.

As day length shortens increased melatonin production occurs (pineal gland), these stimulate kiss neurons to cause increased GnRH production, leading to cycling!

Question 2

What is the typical length of a sheep cycle?

Answer 2

16-18 days

Question 3

How long is the gestation period of sheep?

Answer 3

5 months

Question 4

What should a ram pre-breeding check include?

Answer 4

1. Toes - Check locomotion scores, arthritis, feet sores - will affect mounting!
2. Teeth - overshot, missing teeth - may be genetic, will affect nutrition and energy
3. Testicles - 30cm scrotal diameter,Firm and even, rigs,electroejaculator semen exam - genetic? poor fertility
4. Tone - BCS 3.5-4
5. Treat - Clostridia, pasteurellosis, louping ill vaccs, parasite control, shearing, lameness (footbath)
6. Other -
   
   1. Brisket sores - due to ill fitting harnesses

Question 5

Describe how electroejaculation is performed.

Answer 5

1. Ram is in lateral recumbency or standing
2. Probe (+lube) is inserted into rectum
3. Hold container for semen collection at the prepuce opening
4. Probe is on for 3-4 seconds
5. Repeat as necessary
6. Ejaculation (w/out erection) between stimuli

Question 6

When should semen collection on rams be performed?

Answer 6

DURING the breeding season (just prior to exposure to ewes), sperm quality is reduced significantly out of the breeding season.

Question 7

What indices are used when examining sperm samples?

Answer 7

1. Motility - wave motion (score 0.5) - place a drop of semen on slide and examine under microscope, KEEP WARM
2. Individual motility - x400 magnification of diluted sperm sample
3. Live vs Dead numbers - stained samples - abnormalities include detaatched head/ tail
4. Sperm numbers - needs to be greater that 250,000

Question 8

What can cause epidydimitis in the ram?

Answer 8

Bacteria: a. seminis, h. somni, h. ovis, brucella ovis

Caused by ascending urinary infection

Question 9

Why are rigs a problem for ram fertility?

Answer 9

Due to inappropriately high temperature of sperm within the retained testicle!

Question 10

What organism can cause scrotal mange in sheep?

Answer 10

Choriptes Bovis

Question 11

What is pizzle rot?

Answer 11

Ulcerative balanoposthitis

Caused by Cornyebacterium renali - risk factors include high protein diets leading to increased urea excretion.

Question 12

Describe pre-breeding nutrition of rams.

Answer 12

Want rams to be BCS 3.5-4 at the start of breeding season (high to account for weight loss)

Any problems should be addressed 6 weeks prior to breeding

Protein is very important for testicular growth - needs supplementing around late summer/ autumn (16% protein)

Question 13

What is the ideal ewe:ram ratio during the breeding season?

Answer 13

30:1 max

Question 14

How long should rams remain in with ewes?

Answer 14

35+ days, ie two cycles

Change raddle every 10-14 days

Question 15

Describe the “ram effect”

Answer 15

1. Isolate ewes from rams (6weeks)
2. Day 0 - Introduce teasers - pheramones in wool wax induce cycling in ewes
3. Day 2-3 - Silent heat 3 - rams will not mate
4. Day 14 - Remove teasers, introduce rams
5. Day 18 -20 - First ewes will cycle
6. Day 28 - Later ewes will cycle

Can induce cycling up to two weeks early

Question 16

How can Regulin ear implants affect seasonality?

Answer 16

Melatonin implants - stimulate early onset of repro activity

1. Day 0 - 30 weeks prior to lambing - isolate ewes from rams
2. Day 7 - Implant ewes
3. Day 42 - Introduce males - around 14-21 days later mating will occur

Question 17

What is flushing?

Answer 17

Increasing feeding of ewes 2 weeks prior to breeding to increase ovulation rates

Question 18

Describe the use of progestagen sponges to aid reproduction.

Answer 18

Inserted intra-vaginally for 12-14 days in order to synchronise ewe cycles

PMSG injection at removal stimulates cyclicing - ovulation 36-72 hours later