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Module 22: Reproduction & Fertility > Ewe Fertility > Flashcards

Ewe Fertility Flashcards

1
Q

why does ewe fertility matter

A

Affects productivity of farms

Knowledge = power

  • Is there a problem
  • When is the problem occurring?

Only then you can do something about it

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2
Q

what are key things about sheep you need to consider when dealing with fertility

A

Seasonal breeders

UK peak fertility late autumn

17d cycle

First estrus (or two) of the season is silent (progesterone priming required)

Ovulation towards the end of estrus

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3
Q

when do you find out fertility has gone wrong

A

Breeding

Mid-pregnancy

Lambing

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4
Q

what % of ewes should be pregnant by the first 17d cycle

A

75-92%

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5
Q

what % of ewes should be pregnant by the second cylce

A

98%

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6
Q

at 45d scanning what % should be open/barren

A

2-3%

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7
Q

at lambing what % should be empty

A

5-6%

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8
Q

what are ewe realted fertility issues

A
  1. low ovulation rates
  2. lack of fertilization
  3. embryonic death
  4. abortion/mummification
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9
Q

what are individual ewe problems

A

Free-martins

  • Not as common as in cattle

Hermaphrodytes

  • Rare

Ovarian cysts

Persistent CLs

As for other species

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10
Q

what do low ovulation rates of ewes cause

A

Affects the maximal # of lambs to be born and therefore the productivity of the farm

During breeding:

  • Are the ewes cycling?
  • Are the ova healthy?
  • Number of ova per cycle
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11
Q

what affects the ovulation rates of ewes

A

Timing of the breeding season

Body condition and nutrition

Ewe breed

Age of ewes

Altitude and latitude

PMSG injection

Dietary photo-estrogens

Prolonged stress

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12
Q

how does timing of the breeding season affect ovulation rates

A

Ovulation rates highest mid-season

  • Receptiveness to the ram
  • Ram fertility
  • Both are highest in mid-season of breeding
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13
Q

what are the differences in hill breeds and low breeds and ovulation rates in the timing of breeding season

A

Hill breeds have later and shorter breeding seasons compared to lowland breeds

  • More susceptible to timing of breeding

Scottish blackface ewes cycle from late October to early January (over 2 months)

Texel or Suffolk have longer breeding seasons (Aug)

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14
Q

which breeds have a reduced seasonality of breeding

A

Dorset horn

  • June to February peak August to December

European breeds:

  • Spain, Greece, Finland

Equatorial:

  • Non-seasonal
  • Barbados hair sheep
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15
Q

what occurs when you breed out of season

A

Reduced # of lambs per ewe

Increased barren ewes

Longer lambing period

Increase in build up of infection

Unless hormonal or light manipulation is used

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16
Q

how does body condition score affect ovulation rates

A

Highest ovulation rates at optimal BCS

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17
Q

what is the optimal BCS for lowland, upland, hill breeds during breeding and scanning

A
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18
Q

what is flushing and its impact

A

Flushing:

Ewes in BCS 2.5-3 most impacted

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19
Q

what impact does the ewe breed have on ovulation

A

seasonality

prolifacy genes

breed variation in prolificacy

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20
Q

how does the age of ewes affect ovulation

A

Young ewes:

  • Need to be >60% of mature bodyweight
  • Cyclicity starts later and is shorter
  • Less active in seeking ram
  • Length of estrus behaviour (30mins-24 hours vs 12-36 hours)
  • Higher stress levels
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21
Q

how does latitude and altitude affect ovulation

A

Suitable for the breed of sheep

Variation in onset of estrus:

  • Low ground flocks further south = earlier
  • Hill flocks further north = later
22
Q

how do dietary phytoestrogens affect ovulation

A

Interfere with reproductive hormone cycle

Red clover is most common source in UK

Lucerne

Mycotoxins:

  • Not often seen in UK
  • Estrogenic effects or liver damage
23
Q

how does prolonged stress affect ovulation in ewes

A

Can delay onset of estrus activity

  • Prolonged wet weather
  • Stressful handling
  • Dog worrying
24
Q

what does embryonic death mean

A

Failure of implantation (day 19)

  • Delayed return to estrus

Embryo death post-implantation

  • Barren ewes if breeding period is limited

Resorption

Early fetal death

25
Q

what does higher ovulation rates correlate to

A

higher embryonic loss

26
Q

how long should you prevent stress to prevent abortion

A

esp during day 19 around implantation

first 42d

27
Q

what are causes of embryo death

A

prolonged stress

inflammatory/protein losing disease

selenium deficiency

iodine deficiency

nutrition

toxoplasma gondii infection

border disease virus (BDV) infection

28
Q

how is the duration of the stressor important in embryo death

A

Stressful handling

Gathering

Driving

Transport

Persistent rain

Dipping

29
Q

what are inflammatory/protein losing diseases that can cause embryo death

A

Sub-actue liver fluke

Sheep scab

Severe haemonchosis

30
Q

what elements are correlcted with litter size

A

selenium

iodine

copper

cobalt

manganese

iron

31
Q

when does selenium deficiency cause embryo mortality

A

3-4 weeks

increases barren rates

32
Q

how do you test for Se deficiency

A

Blood sample

Glutathione peroxidase — previous 2-3 month’s intake

Selenium — recent intake ($$$)

33
Q

when does iodine deficiency become apparent

A

first third of preg

less lambs per ewe

high perinatal lamb death + goitres

34
Q

what can cause iodine deficiency

A

pasture deficiency

brassica feeding

35
Q

how do you test for iodine deficiency

A

inorganic iodine levels

indication of iodine sufficiency

36
Q

how can over feeding cause embryo loss

A

suppresses progesterone concetrations

37
Q

what plants can have an effect on embryo loss

A

prolonged feeding of brassicas (kale, rape)

phytoestrogen containing plants (Red clover)

38
Q

what does toxoplasma gondii cause

A

Oocysts in cat feces in feed/environment

Abortion

High barren rates

39
Q

how is toxoplasma gondii tested for and prevented

A

Blood — seroconversion

Test barren and normal ewes

Min 6 of each

Vaccination

40
Q

what does border disease virus cause

A

Similar to BVD in cattle and can be transmitted to sheep

High barren rates

Abortion

Congenital deformaties

Persistently infected lambs (PI)

Immunosuppression in transient infection

41
Q

how is border disease virus tested

A

Blood sample

Antibody (6 barren, 6 pregnant)

Antigen if PI suspected

Infrequently diagnosed but probably could/should be tested for more frequently

42
Q

what drugs can affect embryo loss

A

Levamisole

corticosteroids

Prostaglandins

43
Q

what are history questions to investigate a fertility issue

A

Previous reproductive rates on farm

Sheep breed

Timing and length of mating

Ewe:ram ratio

Age spread of ewes

Ex young ewes with a young inexperienced ram

Age spread of rams

Type of fields used for breeding

Nutrition and supplementations

Body condition of ewes and rams

Potential stressors during/after mating

Records of saddle marks

44
Q

what are farm history questions

A

Nutrition and deficiencies diagnosed

Liver fluke

Sheep scab

Nematodes

Barren ewes

Abortions

Diagnoses

Investigations

Vaccination status

  • Toxoplasma
  • Enzootic abortion
45
Q

how is the flock clinically examined

A

Observe the group of ewes

  • Lameness
  • Breeding fields — topography and grass cover, red clover

Body condition scoring (min 10%)

46
Q

how are individuals clinically examined

A

Clinical examination

Body condition score

A selection of representative barren ewes (6-10)

All rams

47
Q

what are diagnostic tests for ewes

A

fecal samples (6-10)

abortion samples

skin scrapes

blood samples

  • trace elements
  • serology
  • metabolic profiles
48
Q

how can fecal samples help investigate fertility issues

A

Liver fluke

Nematodes

  • Young ewes?
49
Q

how can serology help investigate fertility issues

A

Toxoplasma and border disease

Enzootic abortion of ewes if abortion

50
Q

how can metabolic profiles help investigate fertility issues

A

Recent energy intake

Recent and long term protein status

51
Q

how does timing of investigation affect the diagnosis

A

Some investigations in subsequent breeding period:

  • Ram pre-breeding soundness investigation
  • Record paddle markings
  • Trace element blood samples
  • Trace element supplementation trial
  • Nutrition assessment

Module 22: Reproduction & Fertility (27 decks)

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