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Year 4 Livestock and One Health > Small Ruminants: Sheep Reproduction > Flashcards

Small Ruminants: Sheep Reproduction Flashcards

1
Q

What does it mean that sheep are ‘short day breeders’

A

Sheeps breeding season (conception) is from August- December when day length is shortest

Lambing season: December to May

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2
Q

Describe how seasonality works

A
  • Light comes into the eye (dependent on photoperiod)
  • Optic nerve to the hypothalamus to the super-cervical ganglion
  • To the pineal gland- the pineal gland either does or doesn’t produce melatonin
  • Light supresses melatonin
  • Increased melatonin in sheep from short days increases GnRH pulses
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3
Q

What controls seasonality?

A
  • Oestrogen negative feedback
  • Dopamine
  • Thyroid hormone
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4
Q
  1. How long do cycles last in sheep during the breeding season?
  2. How many follicle waves do they have?
A
  1. 16-18 days
  2. 2-5 waves 50% have 4
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5
Q

How long should rams remain with ewes?

A

At least 35 days
Allows ewes which did not convieve when first mated to be bred again

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6
Q

How can you identify a ram has mated a ewe?

A

Rams can be raddled to mark mated ewes

Allows accurate lambing

Allows accurate lambing

Allows identification of infertile rams and ewe and accurate lambing

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7
Q

How many ewes are needed per ram?

A

Recommended 1 ram for 30 ewes
Some farmers say 1 ram for 120 ewes

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8
Q

How is AI done in sheep?

A

Laparoscopically due to cervix

Pedigree or performance testing flocks only

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9
Q

How can reproduction be modified in sheep?

A
  • Genetics
  • Ram effect
  • Day length
  • Nutrition
  • Ram and day length
  • Day length in a bottle (melatonin)
  • Melatonin and genetics
  • Nutrition and day length
  • Pharmacological
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10
Q

How can breed and fecundity (genetics) modify reproduction in sheep?

A
  • Ideal numbers of lambs varies on farm- hill ewe 1 lamb
  • Number of lambs sold per ewe is key indicator
  • Many breeds/strains developed with higher fecundity
  • Genomic selection now identified- Bone morphometric protein signalling in ovary to determine follicle number

Examples:
FecB mutation of BMP receptor 1 in booroola sheep
Fecx1 mutations of BMP 15 in inverdale sheep
FecXg BMP 15 in belcare- 9 lambs or one

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11
Q

What is the ram effect?

A
  • Introduction of ‘novel’ male or after 2 weeks+ of male absence
  • Induce cyclicity earlier in the season
  • Can synchronise cycling sheep too some extent

Teaser animal can be used to synchronise and advance group for entire

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12
Q

What are the 2 peaks of oestrus activity after ‘ram effect’?

A
  • 1st ovulation silent
  • 19 days- non-silent oestrus
  • 25 days- second oestrus

Some have 1st ovulation on 19 and 2nd on 25

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13
Q

What is the average sheep gestation?

A

145 days
Varies with breeds

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14
Q

What happens to cyclicity and fertility after ram introduction after start of short days?

A
  • % of cycling increase
  • % fertile matings increase
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15
Q

How can seasonality be manipulated with light?

A
  • Exposing to articifically shortened or lengthened days
  • Animals become refractory to continuous signal
  • End when become refractory to long days
  • Can just treat males and then use the ‘ram effect’ to induce ewes
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16
Q

How can seasonality be manipulated with melatonin?

A

Give melatonin- regulin (ear implant)
* Breed affects time of usage
* Day 1 move ewes from sight, sound and smell of ram
* Day 7- implant ewes
* Day 42- introduce rams
* Delay of 14-21 days before mating allowing for cycle
* Use vasectomised rams for first 14 days for more compact lambing period

17
Q

What is flushing?

A

Altering nutrition to assist in conception
Static effect- ewes in better BCS have higher ovulation rate
Dynamic effect- increasing live weight gain gives higher ovulation rate
Increased more in lower BCS scores
Can give higher quality pasture/silage for week before

18
Q

Describe hormonal synchronisation with sponges in sheep

A
  • Chronogest- synthetic progesterone in a sponge
  • Intravaginal for 12-14 days to get into blood stream
  • Combine with PMSG (gonadotrophin- FSH) at removal to stimulate cyclicity out of season
  • Oestrus 36-72 hours after sponge removal
  • 1:10 ram:ewe, 1:5 out of season
  • Rams in 48 hours after sponges out
  • Lamb in 3 week period- most 7 days

Sponges get stuck, progesterone immune supressent- vaginitis

19
Q

How can prostoglandins be used for synchronisation in sheep?

A
  • Use prostoglandin to cause luteolysis and induce oestrus in cycling animals
  • Not authorised but half cattle dose has been used
  • Oestrus in 40 hours
  • can do 2 PG 7-11 days apart to induce 95% in 72 hours
20
Q

How and when can you induce lambing?

A

8ml dexamethasone (Dexafort) from day 140 after ram in
Lambing 40±7 hours later

Only if service date known

21
Q

What should be done and checked with sheep pre-breeding?

A
  • Cull out unproductive ewes- health, infertility, age
  • Introduce replacement ewes or ewe lambs
  • Check condition score and separate thin animals for additonal feeding- 3.5 optimal
  • Check rams and ensure 3.5 BCS
22
Q

How should ewes be fed for the following periods:
1. Conception to 42 days
2. 42- 90 days
3. 90- parturition

A
  1. Maintenance only (grass+/forage)
  2. Feed for maintenance + 2 MJ/day
  3. Good nutrition- 2x maintanence by lambing time- appetite reduced
23
Q

Why in days 42-90 days of pregnancy in sheep is nutrition very important?

A
  • Considerable placental development during this period
  • If restriction of nutrient intake will retard placental growth
  • And therefore foetal growth
24
Q

When can sheep be scanned?

A
  • 70-120 days ram in
  • 28 ram out

Count and spray

25
Q

What is done for a ram pre-breeding examination?

A
  • Physical examination- feet, brisket, caseous lympadenitis
  • Scrotal measurement- 30cm
  • Scrotal palpaiton- firm and even
  • Exteriorise and examine penis and vermiform appendage
  • Semen evaluation
  • Libido testing- mounting ability with ewes in oestrus
  • Mating dexterity- intromission
  • Serving capacity test- how many serves in a set time
26
Q
  1. Why is epididymitis a problem?
  2. How can it be diagnosed?
  3. What agents can cause it
A
  1. Sperm storage
  2. Palpable in scrotum and ultrasound
  3. Actinobacillus seminis, Haemophilus somnus, Histophilus ovis
27
Q

What is an inguinal hernia?

A

Bowel passes through enlarged inguinal canal

28
Q

What is a Rig ram?

A

Cryptorchidism

29
Q

What is the problem with cryptorchidism?

A
  • Testes need lower temperature for sperm to develop
  • Likely reduced fertility
30
Q

What determines wether a ram has testicular degeneration or hypoplasia?

A

Fertility history or previous examination
Degeneration if previous fertility success

31
Q

Would you pass a ram without a vermiform appendage?

A

No
* Why has it not got one?
* Likely urolithiasis and removed
* May still have stones

31
Q

Would you pass a ram without a vermiform appendage?

A

No
* Why has it not got one?
* Likely urolithiasis and removed
* May still have stones

32
Q

What can cause degeneration or hypoplasia?

A

Degeneration
* Small soft testes- produce low number of sperm
* Inflammation, extreme fatness, high environment temp
* Transport/stress
* Poor fertility in first year

Hypoplasia
* uni or bilateral- cryptochidism, hereditary

33
Q
  1. What causes scrotal mange?
  2. Why can it be problematic?
  3. How is it diagnosed and treated?
A
  1. Chorioptes bovis- crusty scabs
  2. If extensive then raises blood flow and testes temperature- degeneration
  3. Confirm by skin scrapes, doramectin- diazinon sheep dip
34
Q

What is pizzle rot?
(balanoposthitis)

How is it treated?

A

Penis infection
Rams and wethers
* Range from small ulcers and discharge to blockage
* Fly strike
* Corynebacterium renale, also associated with orf
* Produced ammonia from urea in unine
* High protein concentrated and lush grass risk factor
* Castration affects development of area so urinate inside prepuce

  • Tx- access to water, salt or ammonium chloride to acidify urine, isolate and clip wool
  • treat fly strike

Year 4 Livestock and One Health (58 decks)

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