Reproduction Flashcards
1
Q
What are some issues with pasture being the primary source of livestock nutrition?
A
- Under nutrition
- Trace Element deficiencies
- Internal parasites and soil bacteria
- Toxic plants
2
Q
When is under nutrition the biggest issue in pastoral livestock?
A
In winter when grass growth is low
- Animals are reliant on the pasture to get all of their minerals and trace elements
3
Q
Why can rotational and strip grazing become health challenges for livestock?
A
They have high stocking densities
- Potential rapid transmission of infectious diseases
4
Q
Why can large herd or flock sizes become a problem?
A
It is easy for individual sick animals or dead animals to go unnoticed by the farmers
5
Q
What farm events can predispose health problems in stock? e.g. pneumonia
A
Periods of acute severe stress
- Mustering
- Yarding
- Shearing
- Trucking
- Docking
- Weaning
- Drenching
- Dipping
- Dogs on farm
6
Q
What are the major health challenges facing NZ pastoral livestock?
A
- Pasture primary food source
- Management of grazing
- Large flocks/ herds
- Periods of acute stress
- Outside all year round
- Warm moist climate
- Fleece provides warm moist micro-climate
- Generally feed a monoculture
- Subject to wounds and abrasions which can predispose to disease
7
Q
What is the health issue created with farming outside all year round in NZ?
A
Animals are exposed to the extreme weather
- Mortality in calving/ lambing season
8
Q
What is the health challenge created by the warm moist climate in NZ?
A
Fungi thrive in pasture in warm moist climates
Rapid development and good survival of internal parasites
9
Q
What is the issue with sudden feed change in ruminants?
A
The rumen microflora need to adapt
- can cause stomach upsets
10
Q
What can cause wounds on farm that predisposes animals to infection?
A
- Deliberate wounds such as tail docking
- Accidental wounds caused by random objects such as wire
11
Q
What is important in regards to the health management of flocks and herds?
A
- Whole herd/ flock focus rather than individual focus
- Prevention of poor production and disease instead of treatment
- Subclinical and Clinical focus
- Integrate animal health and husbandry and farm business - Be Proactive!
12
Q
What are the steps in Investigating a herd/ flock problem as a veterinarian?
A
- Define the Problem
- Take History
- Environmental and Distance exam
- Individual clinical exam and Post-mortem exam
- Further logical and justifiable diagnostic tests
- Interpreting and decision making - effective communication
- Reporting back and future monitoring
13
Q
What is fundamental on a sheep farm to achieving high productivity and profits?
A
High Lambing Percentage
14
Q
What factors in regard to Lambing Percentage can we as Vets not influence?
A
- Weather
- Topography
15
Q
What about topography can we as vets influence?
A
- Where ewes are mated
- Where lambing occurs
- Fert application or not
16
Q
What does topography influence on a sheep farm?
A
- Ram tupping capacity
- Ewe feeding level (quantity and quality of pasture)
- Neonate survival
17
Q
What are factors important to lambing percentage that can be altered by good management?
A
- Oestrus
- Breeding season in ewes
- Ovulation rates
- Mating
- Fertilisation
- Embryo development and survival
- Foetal development and survival
- Birth
- Ewe Survival rates
- Perinatal survival
- Growth of lambs
18
Q
Describe Oestrus in sheep…
A
- 17 day cycle
- Ovarian follicular development occurs throughout the year
- Out of season follicles regress
- LH surge in breeding season
- Mature ewe oestrus: 12-36 hours
- 2ths 1-24 hours
19
Q
When are higher conception rates achieved in ewes?
A
Late March to Mid May
20
Q
On average when are the Rams put in with the Ewes in both North and South Island?
A
NI: 8th March
SI: 18 April
21
Q
What does high altitude do to the breeding season of ewes?
A
Significantly decreases the length
22
Q
If the North Island pushed back their average ram joining date what would be observed?
A
- Higher first cycle submission rate
- Less ewes returning
- Shorter mating period
- Shorter Lambing period
- Lambs born later when more grass for ewes
- Thus faster lamb growth rates
- Increased lamb survival
23
Q
Why does the North Island tend to have earlier ram joining dates?
A
- Premium prices for early lambs
- late lambs may have no food to eat if it dries out early (drought)
24
Q
What factors affect the ewes breeding season?
A
- Breed of sheep
- Latitude
- Altitude
- Age of ewe
- Ram effect (teasers)
- Photoperiod control
- Stress
- Hormonal induction of oestrus i.e. CIDRs
25
How does breed affect breeding season?
- Romneys have shorter breeding season than merinos
- Romneys have less cycles than merinos
- Poll Dorsets can breed almost all year round
26
What Questions would you ask a farmer that had an abnormally low lambing percentage?
- What was ram: ewe ratio?
- When was start of mating?
- When did mating finish?
- Were teasers used?
- Ewe BCS and weights pre mating?
- Level of nutrition, pre mating?
- Were ewes stressed prior to mating i.e. shearing, bad weather?
- Were rams harnessed? What was submission rates for the 1st, 2nd and 3rd cycles?
- Did you scan post mating?
- Do you have abortions on farm and do you vaccinate for these?
- What was lambing like? i.e. weather, dystocia etc.
- Are there any reasons that you can see as to why this may have occurred?
27
Why are young ewes difficult to get pregnant?
- Cycle later
- Shorter heats
- Less cycles with lower O.R
- Shy - don't seek out rams
- Lower conception rates
- Higher embryonic death rates
28
What should be done to increase young ewes conception rates?
- Mate separately to main mob of ewes
- Mate on easy rolling/ flat paddocks so rams can find them
- Use ram: ewe ratio of 1:50
- Use experienced rams
29
Why are Hoggets usually mated in May?
- They cycle later
- Increase weights
- Puberty
30
What is the best way to improve Hogget conception rates?
Use teaser rams to synchronise oestrus
31
When should vasectomies be performed?
At least 4 weeks prior to PSM
32
Why is it beneficial to synchronise ewe Hoggets?
- It gives 2 shots at mating in a single cycle
| - Allows a condensed lambing period
33
How do you synchronise Hoggets?
- No contact with rams for at least 3 weeks prior to PSM
- Flush on good quality feed >1250kgDM/ha
- Be mated in small flat paddocks
- Teasers out for 17 days prior to PSM is best
- Rams go out at day 17 at ratio of 1:50
34
What occurs after teaser effect?
- within 10 minutes, increase LH pulses (main one 27-36 hours after teasers in)
- Within 3 days most ewes have a silent ovulation
- 60% of these ewes develop a CL which maintains the cycle
- - repeat ovulation 18-20 days after initial teaser intro
- The other 40% of these ewes CL regresses 6-8 days later, they then have another silent heat 5 days later
Group 1: synchronised at day 18
Group 2: synchronised at day ~26
35
Describe how melatonin affects the ewes breeding season...
- Hormone responsible for photoperiod induced changes on hypothalamus and pituitary gland
- Released from Pineal gland 10 mins after darkness and stops 10 mins after sunrise
- Not very practical for increasing lambing percentage in a flock
36
How can bad weather affect O.R in ewes?
Can slow ORs down
| - especially if ewes have been shorn
37
Is shearing a stress to ewes?
Yes - its a major stressor
- especially if done 3 weeks either side of mating
- Must have plenty of feed and no bad weather
- Can increase O.R as the ewes increase intake (flushing)
38
What happens if shearing is done during mating?
All oestrus activity stops
39
How is hormonal induction of oestrus done?
1. Insert CIDR/ sponge into vagine for 12-14 days
2. Ewe injected with PMSG
3. Oestrus 24-72 hours later
40
What does O.R determine?
The maximum number of lambs that can be born
41
What factors affect O.R in ewes?
- Bodyweight and nutrition at mating
- Time of mating
- Ewe age
- Genetics
- Diet (phytooestrogens)
- Mycotoxins
- Level of feed when younger
- Pre-mate shearing
- Immunisation against ovarian steroids (androvax)
- Pre-mating parasite burdens
- Trace elements
42
How heavy should ewes be at mating?
55-60kg
43
Is there a correlation between O.R and Body weight?
Yes but only up to 65Kg
| - then O.R plateaus
44
What is the best way to manage different weights in ewes pre-mating?
Draft out lighter ewes and preferentially feed them
| - aim to make tail enders have a weight of 55kg to make average ewe weight 55+Kg
45
How does twinning rate increase with body weight?
As the live weight increases to 55-60Kg
| - for every 1Kg gain you get a 1.3% increase in LP%
46
What may be required in order to flush ewes well?
Supplements
- Silage/ summer crop
- No lucerne or red clover!
47
Why is it best to sell last seasons lambs before feb/ march?
They will begin to eat the food saved for flushing
| - may affect next years profits
48
What questions should you ask when investigating a low LP%?
- How many ewes mated?
- How did this 2th compare to MA ewes?
- Hogget mating? If so what was scanning %?
- How many rams used?
- Mating start date?
- When were rams removed?
- Were teasers used?
- Do lambs finish on time or is there a tail end?
- What are the lambs fed?
- What are live weights or MA ewes, 2th and hoggets prior to mating?
- Fed well prior to mating?
- Pasture cover pre-mating?
- Stocking rate different from last year?
- Pre-mating parasite control programme with the ewes?
- Used harnesses with rams?
49
What can happen if you have poorly grown Hoggets?
They become poorly grown 2ths and MA ewes
50
What should weight targets for ewes be at mating?
Hoggets: 42kg
2ths: 55kg
MA: 55-60kg
51
How does the age of the ewe affect O.R?
Older ewes have more ovulations than 2ths or hoggets
52
How does Genetics affect O.R?
Finnish Landrace ewes are very fecund
- often have 200% LP but this is poor for lamb survival
- Have more developing follicles and secrete more oestradiol
- Higher basal circulating rate of FSH and LH results in more ovulations per cycle
Finnish x are very successful
53
What are the two fecundity genes in sheep in NZ?
1. Booroola - merinos
| 2. Inverdale
54
What occurs in the ewes non-breeding season in terms of oestrus?
- The follicles develop but become atretic
| - Ovary releases constant low levels of oestradiol which has a negative effect on LH
55
What occurs in the ewes breeding season in terms of oestrus?
- Hypothalamus loses sensitivity to low dose oestradiol and releases GnRH
- GnRH stimulates pituitary to release FSH and LH
- FSH stimulates follicles to mature and release high levels of oestrogens starting oestrus
- High Oestradiol results in LH surge resulting in ovulation and development of luteal phase of cycle
- Progesterone in luteal phase has a negative feedback on LH release
- Progesterone declines after PGf2a is released from uterus at day 15 resulting in a pre-ovulatory rise in LH and a repeat cycle
56
Which hormone primes the ewes vaginal and behavioural responses to oestradiol for the next oestrus cycle?
Progesterone
57
What does lucerne contain that affects O.R?
Coumesterol
| - Oestrogenic compound
58
How does coumesterol affect lambing %?
It reduces it by 10-40% by decreasing ovulation rate
- due to -ve feedback that oestrogen has on pituitary and LH release
- tends to affect multiples, i.e. doesn't cause empty rates
59
Which clover varieties contain phyto-oestrogens?
- Mt Baker
- Tallarook
- Trifolium genus
- Pawera red clover
60
What are some other signs of phyto-oestrogen toxicity?
- Histological cervix damage
| - Udder development in young animals, empties and wethers
61
What affect do mycotoxins have on reproduction in ewes?
Depress reproduction
- pithomyces chartarum (facial eczema) in North Is
- Zearalenone on East Coast
62
What causes ovulation losses in ewes with facial eczema?
- Liver damage: lighter ewes, lose condition and may die
| - GGT increase of over 200IU over mating period
63
Why does a GGT increase of 200IU over the mating period cause ovulation losses?
- Direct -ve effect on ovulation by 4%
- Decrease in multiple ovulations by 3-6%
- Increase in empties by 3-5%
- Decrease twins by 3-5%
- Decreased lamb birthweight
- Delay in onset on breeding
- Decrease no. of oestrus cycles
- Can shorten breeding season by 20 days
64
How can FE be treated?
- Oral drenching with Zinc Oxide
- Time Capsule
- - Zinc Oxide slow release
- - Effective for 6 weeks
- - Give 2 weeks prior to risk
65
Describe Zearalenone...
- Most of NZ (espec East Coast)
- Fusarium fungus
- Saprophytic - lives in dead part of sward
- Late summer
- Ewes exposed prior to mating
- Decreases OR and fertilisation rates
66
What affect does Zearalenone have on Ewe breeding?
- Increased no. of dry-dry ewes
| - Less twins (lower scanning and LP%s)
67
How is Zearalenone toxicity diagnosed?
- Collect urine sample from pooled group of 15 ewes
| - Partially smoother ewes mouths to get urine
68
How do you immunise against ovarian steroids?
Use Androvax
| - An immunisation against the ovarian androgen androstenedione which is the precursor for oestrogens
69
What is Androvax?
- Tries to artificially increase the fecundity of vaccinated ewes by removing the low level oestradiol from the system so -ve feedback doesn't occur and LH levels are higher
- Low level antibodies to androstenedione affect LH rather than FSH which allows more LH to circulate
- More follicles ovulate in each oestrus = Increase LP%
70
Describe the androvax Programme in ewes...
- Unvaxed ewes require 2 doses before PSM
- - 1st dose 8 weeks prior to PSM
- - 2nd dose 4 weeks prior
- Annual boosters 4 weeks prior to PSM
71
Why can't ewes be vaccinated too close to PSM with androvax?
- Will get antibodies too high
- this results in complete anoestrus and barren ewes (due to all oestradiol coming from Androstenedione -> Ostreone -> Oestradiol)
72
What are the disadvantages of using androvax?
- Poor substitute for good management
- Can lead to problems with multiple births
- Must scan to know who multiples are
- Must have enough pasture at lambing
73
How many chances do ewes usually have of concieving?
2-3 chances per breeding season
74
What should the pregnancy target be after the end of the 2nd cycle?
95-98% in this 34-40 day period
75
Describe Ram Harnesses...
- Used to detect mating patterns within flock
- Allows submission rates to be seen and lambing dates predicted
- Change colour every 14 days
- Ensure crayon not too soft or too hard
- Wooly ewes harder to mark
- Not all marked ewes will lamb
76
Describe from fertilisation to day 30 pregnancy...
1-10 days: slow embryo growth
10+: embryo implants and rapidly grows
- Most EED occurs before day 18
- 20-30% fertilised eggs are lost
- If embryo lost before day 12 = no effect on cycle
- After day 12 the CL doesn't regress as fast which results in long cycles
77
When is early embryonic death a big problem?
When the EED occurs from the 2nd cycle or at the end of the mating period
78
Describe Placental Development...
- Starts 30 days after conception
- Completed by 90 days
- Size is determined by early nutrition of ewe
79
What are the factors involved in EED?
- Ewe age: young > old
- Genotype
- Nutrition: 1st 21 days important
- Se deficiency
- High temperature: 0-7 dasys before mating increases EED
- Stress: 20 days post mating
- Infectious causes
80
When is scanning performed in ewes?
40-90 days post mating
| - average is 45 days
81
What are the benefits of scanning?
- Ewes with multiples can be put in sheltered paddocks
- Ewes with singles tightened up if feed gets scarce
- Ewes with multiples get better lambing pasture cover for higher milk production and increased lamb growth
- Multiples preferentially fed to get in better condition for next season mating and improved O.Rs
82
When are there potential periods of loss on a sheep farm?
- Pre mating
- Mating
- Early, mid and late gestation
- Lambing
- Perinatal losses
- Post natal losses
83
What factors can affect an entire flock/ property that will reduce the no. of lambs born?
- Weather
- Nutrition
- Parasitism
- Trace elements
- Diseases
84
What is a good question rule to apply to any clinical problem on farm?
W5 H5 W5
85
What does W5 H5 W5 stand for?
- What is the problem?
- What are the signs?
- Where has these been seen?
- When has this happened?
- Why does owner think it's happened?
- How many animals affected?
- How often has this occurred?
- How have you managed these animals this year?
- How has this changed from previous years?
- How am I going to diagnose this?
- What did I diagnose?
- What am I going to do about it now?
- Where can farm client implement management changes to address these problems?
- When should he/she do these changes?
- Why should he/ she do these changes?
