Small ruminants medicine and production Flashcards
What is the role of the Veterinarian in the Australian sheep industry ?
The Veterinarians role
Rural practice
- make clinical diagnosis
- help create general flock management and preventative medicine plans
- biosecurity and animal welfare
- carrying out production improving plans (AI, ET)
- whole farm consultancy services
Departments of Primary Industries and fisheries
Animal health Australia
CSIRO
- field trials and research
- technical advice to sheep industry, and private Veterinarians
Veterinary schools
- research
- referrals (parasitology, pathology, virology)
- on farm disease investigation
Outline the steps involved in undertaking a flock or herd investigation ?
General principals of flock and herd investigations
- History
- Examination of the environment
- Examination of the animal
- Use of ancillary aids
- Data analysis and decision making
- Reporting and further monitoring
Deal with the problem at hand
+
Expand problem into whole farm approach
What factors would you consider when examining the History on farm ?
History
Define your problem
- characteristics of animals affected
- time line of events
- determine losses to date (morbidity / mortality rate)
- any prior treatment or control procedures
- history of animal management (tact, nutrition, reproduction etc)
Assess ability and experience of the farmer; separate owners observations from his her interpretation.
Property profile
- location
- size
- main soil type
- stocking rates, flock structure and sheep to cattle ratio
Any other available information.
What factors would you consider when examining the environment ?
Examination of the environment
Animals raised on pasture
- topography
- soil type
- feed availability / feed type
- water supply
Animals housed indoors
- hygiene
- ventilation
- overcrowding
What factors would you consider when assessing animals ?
When carrying out a clinical examination of a sheep what would be considered normal parameters ?
Normal parameters of a sheep
Temperature 39.5 * 0.5
Heart rate 70-90 / min
respiration rate 15-70/min
rumination rate 1-2 min
mucous membranes should be a pale pink
Hydration status - tent the upper eye lid
What dose it mean to utilize ancillary aids ?
Ancillary aides
- Parasitology tests
(faecal egg counts (FEC), larval culture and faecal egg counts reduction test - Haematology
- Biochemistry
- Histopathology
- Pasture and soil samples
Once you have collected all the information you need for a flock investigation what then ?
DATA ANALYSIS AND DECISION MAKING
- Tentative diagnosis, prognosis and therapy
Many production animals are multifactorial
- we need a whole farm approach
REPORTING BACK AND FURTHER MONITORING
- discuss the recommended actions with owner / manager
- report result of diagnostic tests
- schedule next visit and monitor the progress of your action
How would you go about assessing welfare of the animals ?
Welfare standards
Vets have it covered, vets get to judge
Australian animal welfare standards and guidelines for sheep
Initial regulations (minimum standard inputs, timing of procedures, appropriate feed and prophylaxis, yard and shed design.)
Welfare is based upon outcomes
- % lameness
- weight, BCS
- Fertility, lamb survival
- Nutrition, trace element status
Define the term marking rates ?
Lamb marking rates = the number of lambs marked per 100 ewes exposed to the rams
Facts
- Most Australian Merino flocks typical marking is 85% and first cross ewes 110% or higher
The critical lambing % for self replacement flocks is 60-65%
- marking results from fertility, fecundity and survival rate of lambs from birth to marking
- strong association between nutrition (stocking rate) and reproductive rate
How would you go about measuring reproductive performance ?
Measuring reproductive performance
Most commonly use lamb marking rates
- the number of lambs marked per 100 ewes exposed to the ram
This is used as getting the ewes pregnant isn’t usually a problem; the problem is keeping lambs alive
Define the terms ‘fertility’ and ‘fecundity’ ?
Fertility = percentage of ewes exposed to the rams that lamb each year usually around 95%
Fecundity = number of lambs produced per ewe each year
Describe the main economic drivers for sheep farmers ?
The main economic drivers of sheep farmers
Stocking rate (wool cut per Ha)
Net reproductive rate
SR and NRR tend to push against each other so its important to find the sweet spot
This is of less importance in merinos, but crucial in meat sheep. In meat sheep money relies heavily on lambing which is significantly affected by SR, where as wool is only a by product.
Nutrition drives both ST and NRR
What is the prime factor that determines lambing rates and lamb survival rates ?
Nutrition
How would you go about investigating reproductive loss ?
Investigating reproductive loss
Define the problem for infertility
1. At what stage is the issue occurring - conception rates, second half of pregnancy or perinatal.
2. Numbers + reliability of information.
3. Everything else - eg change of joining time, pastures, BCS, supp feed, new ram introductions etc
Define the three time periods in which reproductive losses occur ?
The time periods of reproductive loss
- Failure to get in lamb / early embryonic loss
- diagnosed at scanning - Second half pregnancy loss +/ - frank abortion
- Diagnosed, before lambing, often at marking. - Neonatal losses 1-5 days
- Diagnosed at marking
- Lamb survival (single 88%, twins 78%)
- most common period for lamb loss
For a normal production farm how many ewes do we expect to conceive ?
What factors could causes potential issues at conception ?
Metric = 95%
Expect 95% of ewes to get in lamb over a five week joining period (7 weeks on the shoulder of the season).
This will be diagnosed at scanning
Factors reducing the conception rate
- BCS < 2.5+
- clover
- new case of brucellosis (huge problem big losses)
- nutrition and seasonality
- rams, seasonality, oestrogenic infertility and some infectious diseases.
At what time point in the year should sheep be breed ?
Seasonality in the sheep
Sheep are short day breeders
- maximum activity occurs Feb to April/ May
- seriously reduced activity Jul to Nov
Merinos and Dorppers (less seasonal compared to European sheep breeds).
The further South the worst the seasonal differences in conception rate are.
How often is oestrus behaviour displayed in sheep over the breeding season ?
Oestrus behaviour in sheep
Short day breeders display oestrus about once every 16-17 days
In a mature ewe oestrus lasts for about 24 hours, but in a two tooth oestrus is displayed for a significantly shorter period of time.
Breed and age influences the season
- British breeds sharply defined season
- Merinos and Dorper’s less seasonal
- First cross ewes intermediate
Stress eg shearing and severe weather conditions can affect oestrus activity
What techniques could Veterinarians utilise to manipulate oestrus behaviour in sheep ?
Manipulation of the onset of oestrus behaviour in sheep
Ram effect
- peak oestrus between between days 18-26 after introduction of a ram
- works best in merinos/ Border Leicester NOV/ DEC joining
Intravaginal progestagen treatment + equine chorionic gonadotrophin (eCG) / pregnant mare serum gonadotrophin (PMSG)
- progestogen impregnated vaginal sponge
- sponge inserted into vagina for 12-14 days - high progesterone levels - when device removed - collapse of progesterone levels - gonadotropin hormones increase
- eCG /PMSG at time of sponge removal
oestrous occurs 25 -72 hours later
- manipulation of daylength increased
- melatonin implant (Regulin)
What issues could result from manipulating the timing of oestrus outside the breeding season ?
Manipulation of oestrus outside the breeding season
- lower conception rates
(40-50%) than for the normal breeding season - ewes who fail to conceive at the induced oestrus revert to anoestrus until the start of the normal breeding season.
Summary work with nature not against it
What factors could reduce ovulation rates ?
Ovulation
High ovulation rates are key to high lambing percentages (conception is an all or nothing event)
Ovulation rate influenced by
- time in breeding season (peak Feb-Mar)
- nutrition
- Breed (eg Merino and the Boorola gene)
- Age of ewes
prime lambs are joined at 7 months, merino lambs to be joined at 19 months (determined by age and weight)
- max ovulation rates achieved at 4-7 years of age
- plant toxicity
-
How can we manage ovulation through better nutrition ?
What should we aim for ?
Managing ovulation through nutrition ?
For each body condition score >1.5 to 4 you expect
1. 5% increase in conception rate (increase in ovulation)
2. Increase lamb birth weight and survivability (variable depending on starting point)
3. Increased lamb weaning weight
Rule of thumb - aim for CS3 at joining and all the way through pregnancy
What management practices can we implement to improve nutrition ?
How to obtain our goal
Aim; Have ewes in BCS 3 or a bit more at joining and all the way through pregnancy.
Manipulate
- change lambing time
- supplementation
- flushing
What is flushing ?
Flushing
Provide a nutritional spike in the lead up to mating.
Supposedly increases ovulation rate - called the dynamic effect.
- if you flush you also increase BCS
- flushing with lupins helps a great deal but extremely costly
- 500g/Hd/daily up-to two weeks prior to joining
What factors could influence fertilization rates in ewes ?
Rate of fertilization
Failure of fertilization is usually not a problem
Failure
- infertility of ewe or ram
- phyto-oestrogens
- ram percentage
- choice of mating paddock
- length of joining period
How do phyto-oestrogens effect fertility ?
Phyto- oestrogens “clover disease”
Temporary infertility
- when ewes are mated on green oestrogenic clover
- the cervical mucous increases in volume and becomes very watery - impairs sperm transport through the cervix
- fertility returns to normal within a few weeks of removal from the pasture
Permanent infertility can occur (rare)
- ewes grazing in high / moderate rainfall areas of Australia on Cultivars of subterranean clover
- T pratense
- Trifolium subterraneum
- grazed over consecutive years
- permenant changes to the epithelia of the cervix and uterus (cyctic glandular hyperplasia).
How would you diagnose Phyto-oestrogens in ewes ?
Phyto-oestrogens
Diagnosis
- history
- pasture inspection and identification of oestrogenic cultivars of sub clover (Trifolium subterraneum)
- examination of animals
- post mortem - histopathology of cervix uterus
The clinical signs
- may increase the incidence of dystocia
- increase in rates of pre lambing vaginal prolapse
- teat elongation and inapproprriate lactation
- urolithiasis in wethers (water belly)
- lambing typically lowered by 5-10%
What would you recommend to reduce phyto-oestrogens on property ?
Phyto-oestrogen recommendations
Prevention
- pasture renovation (expensive)
- Formonetin is maximal in green plant - so use cattle to graze the high risk paddocks
- cull sheep at a younger age when they are less susceptible to phyto-oestrogens
What factors could increase embryonic mortality ?
Embryonic mortality
Embryonic mortality is relatively high 20% within the first 18 days
Measure = increase in ewes lambing late (if there is time to return to oestrous)
Embryonic loss may be influenced by
- ovulation rate (higher multiple preg)
- nutrition
- age of ewe (higher in young sheep)
- high temperatures
- stress - shearing, treatments
- genotype
- Se deficiency
- infectious diseases (Toxoplasmosis, Border disease)
Describe the ewe factors that contribute to a poor scanning % ?
Ewe factors
- poor cycling, seasonality
- poor ovulation rates - usually nutritional but may be affected by some toxic plants
- failure of fertilization eg clover disease
- embryonic mortality (post 20 days) can be high, has many causes which are not easily managed (except reducing stressors)
Emphasise the importance of nutrition at all stages of pregnancy ?
The importance of nutrition at all stages of pregnancy
Conception
- poor nutrition leads to a lower ovulation rate
Placental development (D30-D90)
- poor nutrition can reduce cotyledons and size of the placenta. This causes a reduction in the nutrient supply to the foetus and lower birth weights.
When should scanning be carried out ?
Scanning
After 18-20 days
- beyond this point pregnancy is usually very robust
- scanning should track closely with the ewes that actually lamb
- total number of lambs born should closely reflect what was scanned.
If the number of ewes that do not lamb is > a few % less than those scanned THERE IS A PROBLEM.
What would you need to observe to consider abortion as a problem ?
Abortion is a problem
- Ewes scanned in lamb detected as likely not in lamb at pre-lambing treatments (crutching, drenching).
- these ewes will be obviously skinny, no udder development
- investigate seroly may indicate Camplobacta or Toxo - Frank abortions should not be more than 0.5% or a few lambs per mob.
- you should not see many - Wet / dry
- useful if there is not scanned and issue only noticed at marking
Dry
- not lactating (no udder development) lost before lambing
- lactating but no lamb; udder is involuting not much milk and it is watery - likely perinatal loss
- lastating; live lamb / lambs
Remember the metric 88% singles and 78% twins
What would you look for if wet / dry ewes at marking ?
How to wet dry ewes at marking
- not lactating (no udder development) lost lamb before lambing
- Lactating but no lamb; udder is involuting. Not much milk and it is watery - likely perinatal loss
- Lactating - live lambs/lambs
- Remember the metric should be 88% survival for singles and 78% for twins at marking.
What are the most common causes of abortion in ewes ?
Causes of abortion
Diagnosis in 57% of cases;
Camplobacter 32% (zoonotic)
Listeriosis 9%
Toxoplasmosis 26%
Less common causes of abortion in Australia
- Salmonellosis
- pestivirus ‘hairy shaker’
leptospirosis
- rRmulus (onion grass)
Describe the epidemiology and spread of Campylobacteriosis ?
Campylobacteriosis
Abortion storms 10-60% lamb loss (common Australian sheep)
- spread through direct contact with discharges from the vagina, aborted foetuses and placenta
- potential zoonosis - gastroenteritis
Factors increasing spread
- contaminated pastures where ewe aborted
- close contact facilitates spread (high SR, trail feeding, rotational grazing or confinement feeding.
- carrier animals
- crows and magpies may carry disease for several months and help its spread
Describe the Clinical signs of campylobacteriosis in the ewe ?
Pathology
Abortion occurs within three weeks of the ewe coming into contact with the bacteria
Aborting ewes will develop good immunity and are unlikely to abort again
- abortion mid-late pregnancy
- usually sporadic at first followed by an abortion storm 2-3 weeks later
- mainly maiden ewes
- still births
- birth or premature lambs and apparently normal but non viable lambs
ewes may remain placental membranes and develop metritus (rare)
Most aborting ewes show no sign of sickness
What would you observe in aborted foetuses from campylobacter ?
Campylobacter
Post mortem foetus
- gross lesions variable and non specific
- grey ‘rosette-like’ necrotic foci in foetal livers
Isolation of organisms
- aborted membranes, foetal stomache content
What could you do to prevent Campylobacteriosis ?
Prevention Campylobacteriosis
Ewe hoggets may be grazzed on infected paddocks in order to infect them while not pregnant, or aborted ewes with hoggets or lambs.
- vaccination (inactivated vaccine)
2 injection 2-3 weeks apart + yearly booster - recommended in high risk situations
Once an outbreak of campylobacteriosis has occurred what can we do?
Control Campylobacteriosis
Control
- hygiene (remove foetuses and membranes)
- spread sheep out if possible (reduce stocking rate)
- antibiotics
oxytetracyclines, erythromycin or tulathromycin
The earlier in pregnancy a diagnosis is made the better the out come
watch for
- lesions
- unvaccinated
- risk factors (crowding)
What is toxoplasmosis how does it spread ?
Toxoplasmosis
Protozoa in the intestine of cats
- final host cats
Sheep are infected through contaminated water or feed
- cat faeces containing toxoplasma oocyst
- very resistant in the environment
- cool wet climates
What are the clinical signs of Toxoplasmosis ?
Clinical signs
Ewes
- most outbreaks in maiden ewes
Clinical signs
- If infected when not pregnant - no clinical signs
- if infected in early pregnancy - no clinical signs / foetal death and reabsorption
- if infected in mid pregnancy (D60-120) birth of a still born or weak lambs, mummification, abortion (last 2 months)
- ewes no sign of sickness
Upto 40% abort
If infection in latter part of pregnancy (>120D0) - offspring normal (but infected and immune)
Describe the pathology of toxoplasmosis ?
Pathology Toxoplasmosis
Pathology ‘ necrotic, disgusting abortions’
- placental cotyledons bright to dark red with white foci of necrosis (strawberry)
- inter cotyledonary areas unaffected
- mummified foetus
Histopathology placental cotyledons, foetal brain, lung and liver
How would you go about diagnosing Toxoplasmosis ?
Describe Listeriosis and its spread ?
Listeriosis
Listeria monocytogenes (abortion, septicaemia in lambs and meningo-encephalitis)
Bacteria survive for long periods in soil and on decaying vegetation + can be present in the gut of healthy sheep.
- potential zoonosis
- disease common under wet muddy conditions
- outbreaks often associated with feeding poor quality silage (PH >5.5)
- occurrence is sporadic and unpredictable
- stressful conditions
Describe the pathology and clinical signs of Listeriosis ?
Listeriosis
Abortion occurs when a combination of stressful conditions are present - weakens ewes immunity - bacteraemia - bacteria in foetus and foetal membranes
Clinical signs
- abortion at any stage of pregnancy (usually late)
- rate 2-20%
- still births
- aborting ewes show generally no signs of ill health, occasionally development of reddish brown discharge after aborting (clears up with out treatment)
Post mortem foetus
- rapid autolysis (decomposition)
- multiple white foci
Describe the pathology and clinical signs of salmonella ?
Salmonella
zoonosis
S. typhimurium
Infection is transmitted by ingestion
Clinical signs
Abortion in addition to enteric signs of infection usually associated with stressful conditions
- mortalities, diarrhoea
- foetal death, abortions (last 6 weeks 60%)
- retained foetal membranes, septicaemia, high fever
How would you diagnose and control Salmonellosis ?
Salmonellosis
Diagnose
- Isolation of organism from foetal stomach and placenta
Treatment and control
- separate affected animals from unaffected animals
- reduce stocking rates
- avoid further stress
Possible antibiotics for affected animals and supportive therapy
- no vaccine in Australia
What is onion grass poisoning and what are the clinical signs ?
Onion grass (Romulea rosea var australis)
Primarily found in Victoria
Poisoning occurs through ingestion of the plant or fungus (Helminthosporium)
Clinical signs
Abortions, infertility and staggers
- ewes lose lambs early to mid pregnancy
- marking rate low 20% in affected herds, aborted foetuses usually not seen
Diagnosis is difficult as there is no specific pathological signs usually based on the composition of pasture.
Prevention = renovate the pasture.
Describe ovine pestivirus and how it is spread ?
Ovine pestivirus
Border disease - hairy shaker disease
(hypomyelinogenesis, congenital trembles)
Virus is transmitted by the mucous membranes
- close contact needed
- some sheep do not throw off the virus (carriers)
- ‘Hairy shaker’ lambs that survive are especially likely to become carriers
- virus can not survive on pasture more than a few days
What are the clinical signs of pestivirus ?
Pestivirus ‘hairy shaker syndrome’
If infected when not pregnant
- may develop a mild fever, but then develops immunity
Infection before day 50
- foetal death - reabsorption, abortion (most common at about 3 months)
- aborting ewes show no sign of sickness
Infection day 50-85 outcome is variable
- foetal death abortion
- birth of dead or live lambs (‘hairy shaker’)
Hairy shaker = hairy coats and varying degrees hypomyelinogenesis, cerebellar and cerebral dysgenesis, arthrogryposis
There is no detectable antibody in persistently infected animals
How would you diagnose, prevent and treat Ovine pestivirus ?
Ovine pestivirus
Diagnosis
- clinical signs / pathology
- virus isolation
- Histopathology foetal nervous system (myelin deficiency)
Prevention
- maintain a closed herd
- no effective vaccine in Australia
Control
- Identify and remove carrier animals
- slaughter this years lamb crop
(cull severely affected lambs and fatten lightly affected lambs for slaughter)
- buy in ewe replacements
- in endemically affected herds expose breeding animals early in life when not pregnant.
What is the cause and clinical signs of enzootic abortion of ewes ?
Chlamydia abortus - Enzootic abortion of ewes
Clinical signs
- abortion in the last three weeks of pregnancy
- stillborn lambs and weak lambs
- zoonosis
- can affect up-to 30% of ewes in previously uninfected flocks
- respiratory infection (flu like disease)
- pregnant woman abortion / still birth
How would you work to diagnose and control Enzootic abortion of ewes ?
Chlamydia abortus
Diagnosis
-History, post mortem (necrotic placentitis, thick, leathery intercotyledonary are, foetus appears normal.
- identification in stained smears
Control
- hygiene measures (isolate affected ewes and lambs), ewes usually immune after abortion
- vaccines are available overseas
- if entry into Australia quarantine with slaughter of infected animals
Describe the epidemiology of chlamydia abortus ?
Chlamydia abortus Epidemiology
Major source of infection is infected placenta and uterine discharges of aborting ewes
Transmission = ingestion or inhalation (dust or fluid droplets)
- introduced to the flock by purchase of infected animals
- ewe lambs can acquire latent infection and will abort during their first pregnancy
- aborting ewes remain chronically infected but do not abort again
- zoonotic
Describe Schmallenberg virus and its epidemiology ?
Schmallenberg virus (SBV)
New emerging disease in Europe
Genus Orthobunyavirus
not zoonotic
Epidemiology
- transmission of infection is by insect vectors (culicoides species) and vertically in utero
- incubation period 1-4 days
- short viraemic period (1-5 days) - low risk of introduction to Australia
Describe the clinical signs, diagnosis and treatment of Schmallenberg virus (SBV) ?
Clinical signs Schmallenberg virus (SBV)
Clinical signs
Adult sheep and goats
- no specific clinical signs
Foetal deformities, stillbirths or abortions (lambs, kids)
- brain and spinal cord damage and secondary muscles / skeletal abnormalities (arthrogryposis)
- spider lambs
Diagnosis
- serology (Elisa)
- Virus identification - PCR
Treatment and control
- no specific treatment available
- no commercial vaccines available
What is pregnancy toxaemia ?
Pregnancy toxaemia
Lambing sickness - twin lambing disease
- Occurs late in pregnancy when there is a very high energy requirement (foetal development, udder development and colostrum)
- these requirements often exceed what is available from feed - so the ewe utilises body reserves - normal to lose condition
Pregnancy toxaemia occurs when body tissues utilised very rapidly - metabolic overload
- often precipitated by stress which could cause a sudden restriction in food intake for 12-24 hours
Identify all risk factors which could predispose the ewes to pregnancy toxaemia (7)?
Risk factors for pregnancy toxaemia (7)
- Very fat ewes
(CS>4) interaction of energy requirements, fat mobilisation and appetite - Very thin ewes
Prolonged undernutrition / drought preg tox - Twins vrs singles
- Older ewes are more susceptible than maidens
- More common in British breeds and cross breeds than merinos
- Anything that decreases food intake
Foot abcess, cold weather, stress, yarding overnight, pink eye, teeth problems etc - Anything that may increase energy requirements
What are the clinical signs of pregnancy toxaemia ?
Pregnancy toxaemia (ketosis)
Clinical signs (progresses over a period of 2-7days)
- dullness, loss of appetite, lags behind the mob
- separation from the mob
- reduced response to approach
- stagger, stumble and fall down
Ewe will become recumbent, may stargaze, sink in a coma and die
- decreased birth weight and poor lamb growth
Flocks with pregnancy toxaemia have a significantly higher than normal mortality in neonatal lambs (mismothering, starvation and exposure deaths) and often a severe decrease in wool quality.
How would you go about diagnosing a case of pregnancy toxaemia ?
Diagnoses of pregnancy toxaemia
- History
- Clinical signs
- Clinical pathology
Hypoglycaemia (may progress to hyperglycaemia) low blood sugar
Ketonemie / Ketonurie
Glossy pale liver
What could you do to treat pregnancy toxaemia
Treatment is often unrewarding
If treating early vigorous treatment is necessary; no prospect of recovery once the ewe is down and unable to get up.
Provision of carbohydrate, stimulation of gluconeogenesis and the removal of foetuses
- increase energy intake and decrease output
If appetite is regained best prognosis
- glucose therapy/ fluid
- corticosteroids
- caesarean section
- allow easy access to water
- other calcium borogluconate
What management strategies would you implement to prevent pregnancy toxaemia ?
Management / prevention pregnancy toxaemia
Match energy requirements with feed availability
- assess quantity and quality of available pasture
- autumn possible poor quality feed before autumn break
- spring potential of low feed in late winter and cold climate
- monitor body weight and condition score
- supplementary feeding if required (grain)
- pregnancy test and give preferential feeding to ewes carrying twins/ multiples
Keep handling and holding of feed in late pregnancy to a minimum
What is hypocalcemia during late pregnancy in ewes, and any predisposing factors ?
Hypocalcemia
There is a high calcium requirement in late pregnancy and early lactation.
When calcium requirements are high, sheep will mobilise skeletal calcium reserves to maintain serum calcium level
Predisposing factors
- mature ewes during late pregnancy
- stress factors
- sudden reduction in calcium intake (change of feed, yarding)
- ewes on lush pasture or oat crops in late winter after a drought
- low dietary calcium intake and depeleted bone reserves from grain feeding during the preceding months
What are the clinical signs of Hypocalcemia ?
Clinical signs hypocalcaemia
Sudden onset (10s/100s)
- initially ewes become isolated and have a stiff gait with muscle tremors (rarely see this stage)
- ewes then become weak and remain recumbent, often sternal recumbency
- struggle when handled but unable to get up
- if not treated condition is fatal
- death may occur within a few hours upto two days after the start of CS
How would you diagnose and treat Hypocalcemia ?
Hypocalcemia
Diagnose
- History
-Clinical signs and a rapid response to treatment
- no typical features upon postmortem examination
Treatment
- Calcium borogluconate
- many sheep with hypocalcaemia also have low blood magnesium and low glucose levels
- so treat magnesium sulphate and glucose solutions
-
What management strategies could we implement to prevent Hypocalcemia in ewes during late pregnancy ?
Hypocalcaemia
Management
- avoid stress in late pregnancy or early lactation
- keep time in yards to a minimum
- add 1.5% limestone as a calcium supplement when feeding grain
- avoid access to plants containing high levels of oxalates
- always spike grain supps with Ca
Nutritional management risk factor
- avoid long term exposure to green grass dominant or cereal grain pasture
- movement from dry to cereal pastures
Compare preg tox and hypocalcaemia ?
What is Hypomagnesemia and its predisposing factors ?
Hypomagnesium
Grass tetany; occurs when cerebrospinal fluid Mg levels fall below normal
Predisposing factors
- high magnesium requirement during first few weeks of lactation (high milk producers greatest risk - older prime mothers)
- no stores of Mg; Mg requirements must be meet by the diet
- a sudden reduction of dietary intake eg yarding
- lush grass dominant pastures or rapidly growing fodder crops during late winter
Mg is actively absorbed through the rumen wall and can be affected by other factors
- acid soils (low in sodium, or high in potassium) may reduce Mg availability
What are the clinical signs of Hypomagnesemia ?
Grass tetany
Clinical signs
- Often found dead in the paddock
- ataxia, muscle tremors, tetanic signs
- collapse, convulsions with severe limb paddling, froth at the mouth
- death 4-6 hours
How could you prevent Hypomagnesemia ?
How could you diagnose or treat Hypomagnesemia ?
Hypomagnesemia
Diagnose
- history, clinical signs, rapid response to treatment
- Blood samples
- post mortem examination (low conc of Mg within the fluid of the eye + clostridial diseases)
Treatment
- ASAP
- magnesium and calcium causmag
- relapse possible, keep under farmer observation and retreat if necessary
What factors could increase perinatal lamb loss on farm ?
Perinatal lamb loss
Average loss across the sheep industry of about 15-20%
Risk factors
- predation
- lamb birth weight (optimal 4-6kg)
- litter size
- environmental conditions
- age of ewe
- nutrition of ewe (effect on placenta development, foetal growth and udder growth).
Nearly all perinatal lamb losses result of a failure to rapidly establish and maintain an adequate ewe-lamb relationship
How would you carry out an investigation into perinatal losses ?
Perinatal loses
- start estimation of loss numbers
- History of management
weather, nutrition, trace element supplementation (I, Se), lambing paddock, pre joining examination of ewes, breed and age of sheep.
To diagnose carry out lamb post mortem - do as many of these as possible
- dead / alive
- if born alive why did it subsequently die
- provide farmers with labels
Must know
- weight, sex
- external examination (walked, cleaned signs of predation, pressence of meconium staining and check naval).
- open lamb placed on its right side
( brown adipose tissue present around kidney and heart, milk in stomach?, lung aeration, hepatic rupture any abnormalities present).
What are the major causes of perinatal lamb loss ?
Define a primary exposure ?
Primary exposure
- extreme weather event
- normal viable lambs; breath, metabolised BAT, walked no significant CNS lesions
- yellow subcutaneous oedema of extremeties (indicating hypothermia).
What signs would you expect to indicate mismothering - exposure complex ?
What signs would you expect to see in a case of dystocia ?
Dystocia
Often high birth weight singletons
- breed effect texels
External examination
- meconium stains on birth coat
- subcutaneous oedema head and distal limbs
Abdominal cavity
- abdominal bleeding from liver trauma
Thoracic cavity
- petechia and ecchymoses of the pleura, thymus and heart
Brain and spinal cord lesions
- haemorrhage, congestion in and around the spinal meninges, presence of subdural clots
What would indicate predation ?
What is the difference between primary and secondary predation ?
Describe the clinical signs of watery mouth ?
What is watery mouth in lambs caused by ?
What element deficiencies could cause perinatal lamb mortality ?
The trace minerals
Selenium deficiency (weaner ill thrift)
- white muscle disease in lambs
- heart / skeletal muscle lesions
Copper deficiency (weaner ill thrift)
- sway back - enzootic ataxia
- hypomyelinogenesis of the CNS
Iodine deficiency
- Goitre
- subclinical iodine deficiency
What is the pathology of iodine deficiency, and its predisposing factors ?
Iodine deficiency
Iodine is essential for thyroid hormone production
The developing foetus has no stores of iodine; foetus synthesises its own thyroid hormones from maternal iodine
- necessary CNS development
- foetal growth
- thermoregulation after birth
Predisposing factors
- Goitogens deficient in iodine; Brassica, canola ,turnips and white clover
- high rainfall areas of the great dividing range and Tas are iodine deficient
What are the clinical signs of iodine deficiency ?
Iodine deficiency clinical signs
Subclinical iodine deficiency
- decreased metabolic rate
- impaired brain development, reduced lung development
- impaired suckling behaviour
- weak lambs very susceptible to cold stress
Iodine deficiency
- small woolless lambs which are weak and susceptible to cold stress
- high incidence still births
- Goitre - enlarged thyroid - may cause dystocia
- goats are more susceptible than sheep
What could we do to diagnose and treat lambs for iodine deficiency ?
Iodine deficiency
Diagnose
- compare thyroid weight
- histopathology of thyroid
- ewe serum iodine concentration
Treatment
- Lugols iodine to lambs
- shelter for lambs (protect cold stress)
- potassium iodide drench
- iodised salt blocks
- prevent pregnant ewes grazing crops containing goitrogens
What strategies could we employ to prevent / reduce neonatal lamb mortality ?
Preventing neonatal lamb mortality
- ewe BCS and nutrition
- scan (identify twin pregnancy provide better nutrition)
- select appropriate lambing paddocks
- predator control
- avoid disturbing lambs
- identify and kill poor mothers, or ewes with mastitis
- adjust time of lambing (influence of available feed and weather conditions)
- supplementing ewes with melatonin for lambs which experienced a compromised gestation (increase BAT)
Why carry out a breeding soundness examination ?
BSE
Identify those rams that are unsound for breeding (joining 1% of rams)
- usually carried out prior to joining
- generally check rams 10-12 weeks prior to the start of mating
- pre sale post purchase
- in response to a reproductive problem
What factors should we consider in a breeding soundness examination ?
Breeding soundness examination
History - breed, age, ID
5T TEST = toes, torso, teeth, testicle and tossle
Genitalia examination
- palpation scrotal skin wool cover, lesions
- palpation of scrotal contents (testis, epididymis)
- size, tone and lesions
- scrotal circumference (32cm 400ml)
- semen quality and quantity is closely correlated with scrotal circumference
- prepuce and penis
- semen collection and evaluation
What conditions may contribute to genital unsoundness in rams ?
Genital unsoundness in rams
- shearing damage
inability to fully extrude penis (congenital defect, adhesions) - hypospadias (birth defect urethra not located tip of penis).
- obstruction of urethra calculi (high feed concentrates
- pizzle rot (balano-posthitis)
- knob rot (balanitis)
- testes degeneration, testicular atrophy
- other diseases
What is pizzle rot and what agent causes it ?
Corynebacterium renale
Primarily a disease of wethers, grazing lush, clover dominant pastures (protein rich)
Pizzle rot may develop when bacteria are present + high concentration of urea in urine (protein rich diet)
bacteria produce ammonia - cytotoxic - damages pizzle membranes and external skin
What are the clinical signs of pizzle rot ?
Pizzle rot
necrotic ulcer on skin near the preputial opening; lesion often covered by scabs
- prepuce is typically swollen and oedematous
- ammoniac smell
- risk of secondary myiasis
- urolithiasis (kidney stone block)
How would you treat a case of pizzle rot ?
Pizzle rot
Rams do not usually develop severe internal lesions, most lesions are confined to the external prepuce
- isolate the infected animals
- acidify urine (restrict diet) ammonium chloride in water
- flushing pizzle with a mild antisepticum
-slitting of the pizzle in severe cases to allow drainage of urine and pus
How could we prevent pizzle rot ?
Prevention of pizzle rot
- ringing (castrate)
- restrict diet at certain times of the year
- testosterone injections (one treatment risk period spring)
Do not treat rams when close to joining
What is knob rot and its clinical signs ?
Cause unknown - Trueperella pyogenes
CS usually first observed during joining
- paraphimosis (prolonged retracted foreskin)
- necrosis and ulceration of penis
- extensive blood clots in the prepuce
- often concurrent vulvitis or vulvo vaginitis in ewe flock
How can we treat knob rot ?
Knob rot treatment
- remove rams from ewes
- antibiotic treatment
- antiseptic lavage of penis and prepuce
Some animals do not recover = euthanise
What factors could lead to testicular degeneration in rams ?
Testicular degeneration
Increased testicular temperature
- hot weather, any scrotal thickening, fever, septicaemia, over fatness, excessive wool over scrotum
Carry out a physical examination and semen examination
Treatment = shear ram, provide cool conditions (shade /airflow)
recovery may take months
What are the signs of a Brucellosis infection in the herd ?
Brucellosis ovis (rams)
- history
- extending lambing period (8 weeks)
- rams continue to work through joining period
- if joining period is short increase in the number of dry ewes
- More than 5% of rams with scrotal abnormalities
Clinical signs Rams
- soft swelling in the tail of the epididymis
- may develop into abscess - epididymis is enlarged and hard
- rams show no sign of sickness
- semen varies from normal to aspermia (lack of)
Can be present in a flock for many years without being detected
Describe the epidemiology and pathogenesis of Brucellosis ?
Brucellosis
Pathogenesis
The bacteria enter the body through any mucous membrane (preputial, penile, rectal, vaginal, nasal mucosal)
- local - lymph node - bacteraemia - epididymis (usually unilaterally in the tail) and accessory sex glands.
Transmission
Venereal disease from infected semen
- ewes vagina (infection not carried very long)
- homosexual activity (most important)
- intranasal infection
can also occur when infected ewes have recently lambed and are excreting organisms in the vaginal discharges
How can we diagnose brucellosis ovis ?
Diagnose Brucellosis ovis
- testicular palpation
- prevalence >5% is suggestive for brucellosis
- blood test serology
- complement fixation test CFT
- ELISA
- gel diffusion test (GDT)
- culture of semen / not routine / excretion is intermittent
- microscopic examination of semen Ziel-Neelson stain
- bacteriology PCR of genital tract
Often use a combination of tests to confirm brucellosis in rams
How can we control or eradicate Brucellosis ovis ?
Answer = B
What condition is caused by Actinobacillus and describe its epidemiology ?
Actinobacillus seminis / Histophilus somni
Cause
Gram negative bacterium
- occurs most commonly in young rams 6-15 months
- epidemiology and spread remains unclea
Many rams carry A.seminis/ H.somni without showing lesions (lower urethra or prepucial area); only a small number proportion of rams develops lesions epididymitis.
Describe the clinical signs and diagnosis of Actinobacillus seminis / Histophilus somni ?
Actinobacillus seminis / Histophilus somni
Clinical signs
- may have systemic symptoms in association with acute and severe epididymitis (isolate from flock, difficulty walking, may become recumbent).
- abscess epididymis
- atrophy testicle
- if located in accessory sex glands: no obvious CS but semen quality will be affected
- no signs of sickness in ewes
Diagnose = CS, serology, culture, PCR
Treatment = nil
Prevention = environmental hygiene and examination of rams prior to joining
Describe the development of immunity to GI parasites ?
Describe the clinical signs which result from GI parasites in sheep ?
Describe the timing of strategic drenching in the Victorian winter rainfall region ?
