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Y4 Farm Reproduction > Managing fertility & manipulating the breeding season > Flashcards

Managing fertility & manipulating the breeding season Flashcards

1
Q

Aims of efficient reproductive management

A

Cattle: aim to produce 1 live calf once/year (dairy), aim to minimise variation in calf size at weaning (beef)

Sheep: aim to produce 1-2 live lambs each year

(Pigs: aim to produce >20 live piglets each year (≥ 2 litters))

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2
Q

Sources of reproductive failure

A
  • Failure to be bred
  • Failure to conceive
  • Pregnancy loss
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3
Q

The ewe year

A

Breeding (‘tupping’) - Autumn/winter
-> pregnant
Lambing - spring
-> lambs at foot
-> dry period (i.e. not pregnant and not lactating)

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4
Q

Reproductive targets sheep - breeding

A

Ewe:ram ratio
= number of ewes / number of rams
- target: <45-50 (dependent on age and type of ram)

Flock replacement rate
= (number of purchased ewes / number of ewes put to the ram) x 100
- target: <23%

Scanning percentage
= (number of lambs scanned / number of ewes bred) x100
- lowland target: 200%
- upland target: 170%
- hill target: 110%

Barren (non-pregnant) ewes
= (number of barren ewes / number of ewes bred) x100
- target: <2%

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5
Q

Reproductive targets sheep - lambing

A

Lambing percentage
= (number of lambs born / number of ewes bred) x100
- lowland target: 195%
- upland target: 170%
- hill target: 110%

Abortion
= (number of ewes aborted / number of ewes bred) x100
- target: <2%

Lambing intervention
= (number of ewes assisted / number of ewes lambed) x100
- target: <5%

Lamb rearing percentage
= (number of lambs reared to weaning / number of ewes bred) x100
- lowland target: 190%
- upland target: 165%
- hill target: 105%

Lamb losses from scanning to rearing
= [(number of lambs scanned - number of lambs reared)/number of lambs scanned] x100
- target <15-20%

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6
Q

Factors affecting reproductive performance in sheep - ewe factors

A

Failure to breed
- Body condition score
- General health
- Stage in annual cycle
- Season
- Anatomical/congenital abnormalities
- Errors in synch protocols
- Ram problems

Failure to conceive/maintain pregnancy
- Reproductive pathology
- Early embryonic death / abortion
- Errors in synch protocols

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7
Q

Factors affecting reproductive performance in sheep - ram factors

A

Failure to breed
- Low/absent libido
- Pathologies of the penis/prepuce affecting intromission
- Lameness
- Inexperience
- Too high ewe:ram ratio

Failure to conceive
- Pathologies causing orchitis/epididymitis
- Penile abnormalities
- Inadequate testicular circumference
- Sperm abnormalities

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8
Q

Reproductive targets beef cattle - breeding

A

Bulling period
= number of weeks bull in with females
- cow target = 9wks
- heifer target = 6wks

Calving interval
= time between 2 callings -> herd average
- target = 365d

Culling for infertility (barren cows)
= (number of non-pregnant cows / number of cows bred) x100
- target: <5%

Cow:bull ratio
= number of cows / number of bulls
- target: 30-50

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9
Q

Reproductive targets beef cattle - calving

A

Compact calving pattern
= (Number of cows calved in 1st 3 weeks* ÷ number of cows bred) x 100
*count all cows that calve from day 1st cow calves up to 3 weeks after expected start date (calculated as 285 days after date bull 1st joined cows)
- target:
– > 65% calved in 1st 3 weeks
– > 90% calving in 1st 9 weeks

Calves born per 100 cows put to bull
= Number of calves born ÷ number of cows in with bulls x 100
- target: ≥ 95%

Calves weaned per 100 cows put to bull
= Number of calves weaned ÷ number of cows in with bulls x 100
- target: ≥ 94%

Abortion
= Number of cows aborted ÷ number of cows bred x 100
- target: <5%

Calving intervention
= Number of cows assisted ÷ number of cows calved
- target: <5%

Calf mortality to weaning
= Number of calves died before weaning ÷ number of calves born x 100
- target: <5%

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10
Q

Reproductive targets dairy cattle – heifers

A

Age at first breeding
- target: 13.5 months

Weight at breeding
- target: 397kg

Height at withers
- target: 127cm

Age at first calving
- target: ≤ 24 months (not < 22 months)

Heifer submission rate
= Heifers bred ÷ heifers eligible to be bred x 100
- target: >80%

Heifer conception rate
= Heifers conceived ÷ heifers bred x 100
- target: >60%

Heifer fertility efficiency (also referred to as pregnancy rate)
= Heifer SR x heifer CR
- target: >55%

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11
Q

Reproductive targets adult dairy cattle (year round calving) - breeding

A

Conception rate
= Number of cows pregnant ÷ number of cows bred x 100
- target: >35%

Submission rate
= Number of cows bred ÷ number of cows eligible to be bred x 100
- target: >65%

Fertility efficiency (pregnancy rate)
= Conception rate x submission rate
- target: >25%

Calving interval
= Time between 2 calvings -> herd average
- target: 365d

Culling for infertility (barren cows)
= Number of non-pregnant cows ÷ number of cows bred x 100
- target: <5%

100 day in calf rate
= Number of bred cows in calf by 100DIM ÷ number of cows bred x 100
- target: ≥ 50%

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12
Q

Reproductive targets adult dairy cattle (year round calving) - calving

A

Abortion
= Number of cows aborted ÷ number of cows bred x 100
- target: <5%

Calf mortality to weaning
= Number of calves died before weaning ÷ number of calves born x 100
- target: <5%

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13
Q

Reproductive targets adult dairy cattle (block calving) - breeding

A

Conception rate
= Number of cows pregnant ÷ number of cows bred x 100
- target: >60%

Submission rate (1st 4 weeks)
= Number of cows bred ÷ number of cows eligible to be bred x 100
- target: >95%

Fertility efficiency (pregnancy rate)
= Conception rate x submission rate
- target: >55%

Calving interval
= Time between 2 calvings -> herd average
- target: 365d

6 week in-calf rate
= Number of cows in calf 6 weeks after breeding season starts ÷ Number of cows bred x 100
- target: >75%

Culling for infertility (barren cows)
= Number of non-pregnant cows ÷ number of cows bred x 100
- target: <8%

Age at first calving
= Herd average age cows calve for the first time
- target: ≤ 24 months (not < 22 months)

100 day in calf rate
= Number of bred cows in calf by 100DIM ÷ number of cows bred x 100
- target: ≥ 50%

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14
Q

Reproductive targets adult dairy cattle (block calving) - calving

A

Abortion
= Number of cows aborted ÷ number of cows bred x 100
- target: <5%

Calf mortality to weaning
= Number of calves died before weaning ÷ number of calves born x 100
- target: <5%

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15
Q

Factors affecting reproductive performance in cows - cow factors

A

Failure to breed
- Body condition score
- General health
- Milk yield (dairy)
- Anatomical/congenital abnormalities
- Errors in synch protocols
- Bull problems

Failure to conceive/maintain pregnancy
- Reproductive pathology
- Early embryonic death / abortion
- Errors in synch protocols
- AI errors -> AI commonly used in dairy herds

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16
Q

Factors affecting reproductive performance in cows - bull factors

A

Failure to breed
- Low/absent libido
- Pathologies of the penis/prepuce affecting intromission
- Lameness
- Inexperience
- Too high cow:bull ratio

Failure to conceive
- Pathologies causing orchitis/epididymitis
- Penile abnormalities
- Inadequate testicular circumference
- Sperm abnormalities
- AI errors -> AI commonly used in dairy herds

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17
Q

High yielding cows and fertility

A

Increasing yields over past 50 years associated with decreasing fertility -> global phenomenon
- Genetic selection
- Problems with postpartum resumption of cyclicity
- Reduced oestrus behaviour and length of oestrus
- Oocyte and embryo quality

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18
Q

High yielding cows and fertility - genetic selection

A
  • Possibly affecting fertility
  • Interaction with environment needs considering
  • Current evidence suggests some reversal
  • Improved through breeding decisions
    – Industry level -> changes in importance afforded to yield vs. other parameters (i.e. reducing genetic selection for yield a bit, and selecting more for longevity of animal e.g. fertility, lameness)
    – Herd level -> select progeny from cows with good reproductive performance
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19
Q

High yielding cows and fertility - Resumption of cyclicity and subsequent fertility

A

To achieve 365 calving interval cows need to start breeding before 58DIM and conceive by 84DIM (assuming 280d gestation)
- Assisted calving (slower resumption of cyclicality and subsequent fertility)
- Negative energy balance (negative effects on function of the ovary)
- Metabolic disorders (negative effects on function of the ovary)
- Uterine health (negative effects on function of the ovary)
- General health (especially lameness and mastitis)

Improved by identification and resolution of underlying issue -> use data to help

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20
Q

High yielding cows and fertility - NEB and fertility

A
  • Cows in NEB after calving -> adverse effects on resumption of cyclicity and embryo quality
    – Related to negative effects of NEB on circulating insulin like growth factors (IGF-1)
  • NEB also associated with increased risk of postpartum disease
    – Affects resumption of cyclicity
    – Affect uterine environment and health

Managed by ensuring adequate nutrition in the transition period (3 weeks before and 3 weeks after calving)

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21
Q

High yielding cows and fertility - oestrus behaviour

A
  • Oestrus detection fundamental for efficient reproduction
  • High yielding cows have shorter oestrus periods (~6hrs) and less standing time (~22s)
  • Lower oestradiol concentration
    – Increased metabolism in the liver, reduces the amount of time it is present to result in oestrus
    – Short-term decrease in production if stressed

Managed by focusing on improving oestrus detection

22
Q

Reasons for manipulating the breeding seasons

A

Cattle
- Aim for compact breeding season (if seasonal calving farm)
- Aim for consistency and 365 calving interval (if AYR calving farm)

Sheep
- Aim to breed as early as possible to maximise breeding opportunities and capitalise on higher lamb prices in Spring

23
Q

Basic principles of bovine cycle manipulation

A

Induce luteolysis -> shorten CL lifespan -> induce oestrus sooner
- Prostaglandin

Mimic luteal phase of cycle -> induce oestrus when withdrawn
- Progesterone releasing devices (CIDR/PRID)
- Prostaglandin usually also used to ensure no functional CL present

Synchronisation programmes typically combine both approaches

24
Q

Cows that are eligible for breeding

A
  • Those outwith the voluntary waiting period
  • Those that are not pregnant
25
Q

What does submission rate depend on?

A
  • effective identification of cows in oestrus
26
Q

How can cycle manipulation be used to maximise submission rates?

A
  • Synchronisation protocols and fixed time AI
    – Theoretically = SR of 100%
    – e.g. OvSynch, CIDR/PRID Synch
  • Synchronisation protocols and AI to observed oestrus
    – Still needs effective oestrus detection
27
Q

Advantages & disadvantages of the fixed time AI approach

A
  • Fixed time AI removes the need for oestrus detection
    – All eligible cows should be served if done right
    – Theoretically SR should be 100%
    – Can be used to ensure lots of cows are served at the same time (seasonal herd) or to compensate for suboptimal oestrus detection (AYR herds)
  • Maximises submission rate which usually offsets lower conceptions rate

But
- It doesn’t always work
- Lower conception rate than serving to observed oestrus or serving with bull

28
Q

Synchronisation protocols + serve to observed oestrus

A
  • PGF2α is the simplest -> injected animals expected to come into season 3-5days later
  • Progesterone devices also used
  • example protocol:
    – day 0 insert progesterone devise
    – day 6 inject PGF2a
    – day 7 remove progesterone device
    – oestrus occurs after 1-3d
    – serve 12h after 1st signs of oestrus
29
Q

Advantages and disadvantages of the serve to observed oestrus approach?

A
  • Oestrus detection is still needed -> not suitable on farms where this is suboptimal
  • Increased labour costs
  • Use of drugs to mimic part of the oestrus cycle means ovulation can be predicted with greater certainty
    – Can be used to ensure lots of cows are served at the same time (seasonal herd)
    or
    – to aid oestrus detection by allowing farmers to direct resources to oestrus detection for a defined window of time
  • Might be cheaper as fewer hormones involved overall, the progesterone releasing device is expensive
30
Q

How can manipulating the cycle shorten breeding season? (cattle)

A
  • Synchronise cows so more of them come into oestrus in the first 6 weeks
  • More time pressure -> select progesterone protocols if synched for FTAI (higher CR than OvSynch)
31
Q

Shortening calving pattern - options

A
  • CIDR/PRIDSynch -> as for dairy cows
  • Prostaglandin and natural service -> need to be meticulous with record keeping (so do not PG a pregnant animal)
  • CIDR/PRID and natural service
32
Q

Advantages and disadvantages of the options for shortening the calving period

A
  • Repeat injections are often less practical on beef farms than dairy farms
  • Can be used for fixed time AI or natural service (or AI to observed oestrus but difficult if cows in fields)
  • Suckling calves = reduced LH pulse
    – Most common cause of anoestrus in beef herds -> use CIDR/PRID-Synch if you believe this is the case
33
Q

Breeding sheep

A

Sheep are primarily a seasonally polyoestrous species
- Daylength is the main controlling factor
– Reduction in daylight hours -> melatonin production -> GnRH released
- Breed, geographic location and temperature have a lesser effect
- A few breeds can breed all year round, but fertility is still lower when there is longer photoperiod

This means we cannot breed sheep all year round (unlike cattle)

It also means that most lambs are born in the Spring

34
Q

Advancing the breeding season (sheep)

A
  • Productivity can be improved by breeding sheep earlier
    – Lambs are ready for slaughter earlier -> higher prices (Easter)
    – Can breed some breeds of sheep three times in two years
35
Q

Advancing the breeding season (sheep) - options

A
  • Ram effect
  • Melatonin implant
  • Progesterone (or synthetic progestogen) + equine Chorionic Gonadotrophin (eCG)
36
Q

Another term for eCG (historic term)

A

eCG used to be called PMSG (pregnant mare serum gonadotrophin) and this terminology is still commonly used in this context

37
Q

Advancing the breeding season (sheep) - ram effect

A
  • Advances breeding season by ~2wks
  • Entire or vasectomised ram presence -> stimulates ovulation
  • Need 2 vasectomised rams per 100 ewes
  • Usually left in for a week (although 2 days is sufficient)
  • Ewes and rams need to be at least 1 mile apart for at least 6 weeks prior to breeding
    – Consider neighbouring farms
  • Probably not enough if trying to capitalise on easter ram prices
38
Q

Advancing the breeding season (sheep) - melatonin implant

A
  • Advances breeding season by up to 2 months
  • Melatonin implant mimics effect of shortening photoperiod
    – GnRH is produced by hypothalamus at an earlier point in the year
  • Success can be variable
    – Some breeds (e.g. Suffolks and their crosses) respond better than others
    – Older, well-conditioned animals respond better than gimmers or ewes in poor condition
    – Melatonin is not effective in animals that are sexually immature (but these animals aren’t suitable for breeding anyway)
39
Q

Advancing the breeding season (sheep) - recommended approach to melatonin implant

A
  • Inject subcutaneously behind the ear
  • 30 weeks before intended breeding -> separate all male sheep and goats from ewes to be treated
    – Needs to be out of sight, sound and smell – the field next door will not be sufficient
  • One week later insert the implant
  • 30-40 days after inserting the implant introduce fertile rams to the ewes
    – Mating activity will commence 2-3 weeks after introducing rams
40
Q

Advancing the breeding season (sheep) - Progesterone/progestogen devices + eCG

A
  • Advances breeding season by 4 – 6 weeks
  • Also synchronises the flock
  • Intravaginal devices used +/- eCG injection
  • Suitable for cycling and non-cycling ewes
    – Non-cycling -> eCG is needed otherwise results are poor
  • Cycling -> eCG is optional but synchronisation is optimised if used
41
Q

Progesterone vs progestogen

A

Progesterone = hormone released by corpus luteum

Progestogen = any agent (synthetic or natural) that binds to progesterone receptors and acts similarly to progesterone

42
Q

Advancing the breeding season (sheep) - Progestogen sponges + eCG

A
  • Intravaginal devices (sponges) impregnated with a synthetic progesterone (Flugestone acetate)
    – Suppression of GnRH -> supresses ovulation (when sponge is in place)
  • Sponge left in place for 14 days
  • 200-400 IU eCG injection administered at time of sponge removed -> optimises synchronisation
    – If ewes are non-cycling inject 500 IU eCG
43
Q

Are heifers or 1+ parity cows more fertile, and therefore have a shorter bulling period?

A
  • heifers
44
Q

Benefit of a compact calving period for beef cattle?

A
  • all calves relatively similar size if short -> good for slaughter as can be sold at the same time
45
Q

Why are block calving targets higher than those for year round calving?

A
  • more time pressure (need to get it right that time)
46
Q

Why do poor BCS and health affect reproductive performance?

A
  • decrease expression of oestrus
  • decrease desire to be bred
47
Q

Which type of cows have a decreased expression of oestrus?

A
  • high yielding dairy cows
48
Q

What is the most common congenital abnormality that affects reproduction in cows?

A
  • Freemartinism
  • 2% Holstein freemartins still fertile
49
Q

OvSynch protocol

A

day 0
- US exam
- GNRH

day 7
- US exam
- PGF2a (given to luteinise CL)

day 9
- GnRH

day 10
- FTAI

between day 7-9 = 56h
between day 9-10 = 16-20h

50
Q

CIDR/PRID Synch protocol

A

day 0
- US exam
- GnRH
- insert device (progesterone)

day 7
- US exam
- PGF2a

day 8
- remove device

day 9
- GnRH (causes the dominant follicle to ovulate)

day 10
- FTAI

between day 7-9 = 56h
between day 9-10 = 16-20h

PGF2a & device removal not done at the same time - tying to synchronise the removal of the exogenous progesterone and any endogenous luteal structures - i.e. PGF2a doesn’t work instantly and so by the time the device is removed it has worked.

Y4 Farm Reproduction (11 decks)

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