Dystocia Flashcards
What is the most common cause of dystocia in cattle and sheep?
cattle - feto-maternal disproportion
sheep - malpresentations
What are the effects of dystocia?
- Reduced welfare
- Reduced production
- Cow = subsequent lactation
- Calf = 1st lactation
- Stillbirth
- Dam death
- Postpartum problems
- E.g. RFM, metritis, injuries
What are the options for management of dystocia?
- Manual correction and deliver per vaginum
- Caesarean section
- Foetotomy (foetus needs to be dead)
- Euthanasia of dam +/- foetus
When is manual correction and delivery successful?
If foeto-maternal disproportion NOT present
- Malpresentations
- Some soft tissue obstructions (e.g. vulval stenosis)
What are the indications for a caesarean section? When is it not suitable?
- foeto-maternal disproportion
- malpresentations that cannot be corrected
- breech calves
- elective (e.g. high value calves)
Not suitable if calf decomposing -> foetotomy
- Alternative approach needed if C-sec performed
What are the advantages and disadvantages of a C sec?
Advantages
* Increased chances of live birth
* Reduced risk of secondary complications such as nerve injury
* Can be quicker and less injurious to dam than prolonged difficult calving/lambing/kidding
* Survival rates for dam and offspring are favourable
* Can be quicker than a difficult per vaginum delivery
* The only method to deliver an oversized foetus intact
Disadvantages
* Inherent surgical and anaesthetic risks apply (as to all surgeries)
* But… may be increased risk of secondary infection (e.g. peritonitis) or adhesions
* Requires veterinary qualification and surgical competency
* Can be physically demanding in cattle, especially if the calf is large
What are the indications for foetotomy? What is the difference between partial and total foetotomies?
Indications Foetus is already dead
* Foeto-maternal disproportion
* Pathological foetal oversize
* Congenital foetal malformations
* Malpresentations that cannot be corrected
Partial = removal of part of the foetus only (e.g. head)
Total = division of the whole foetus into two or more sections
What are the advantages and disadvantages of foetotomies?
Advantages
* Reduction in foetal size allows easier delivery
* Can be quick (especially partial)
* Can be done without assistance (although assistance recommended if possible)
* Avoids C-sec
* Especially useful if C-sec contraindicated (emphysematous foetus)
* Better for dam in some circumstances
* Can be performed with minimal equipment if required
* Especially sheep
* Partial needs less equipment
Disadvantages
* Risk of iatrogenic injury
* Can be severe or even life-threatening
* Can take a long time (especially total)
* Exhaustion of dam and vet
* Requires training and technical competency
What are dropsical conditions? What are the 2 types?
‘Dropsy’ = accumulation of fluid
Hydrallantois
* Excess fluid accumulation in the allantois
* 85-90% of bovine cases
* Placental origin
* Foetus normal
* Sporadic occurrence
* Up to 10x expected volume of allantoic fluid
* Normal = 8-15 L
* Fluid accumulates after mid-gestation
* Failure in mechanisms of production and absorption
* Reduced number of placentomes
* Permanent alteration of endometrium
* Prognosis guarded to poor
* If survives, cull of cow recommended
Hydramnion
* Excess fluid accumulation in the amnion
* ~10% of bovine cases
* Foetal origin
* Foetal abnormalities present
* Related to foetal abnormalities
* Failure of swallowing or digestion of foetal fluids
* Future breeding prognosis of dam is reasonable
* Progressive abdominal enlargement in 3rd trimester
* Slower development than hydrallantois
* Uterus and abdomen accommodates extra fluid better
* Less sick cow
* Placentomes still palpable
* May go undiagnosed until parturition
* Large volume of thick, syrupy fluid
* Foetal abnormalities
Occasionally both occur together
What clinical signs are associated with hydroallantois?
- Bilateral abdominal distention
- Symmetrical
- Uncomfortable
- Inappetant
- Reduced/absent rumen function
- Due to compression
- Recumbency
- Tight uterine wall palpable per rectum
How would you treat hydroamnion/hydroallantois?
Induce/terminate pregnancy
* Prostaglandin / steroids
* Need to provide replacement fluids to cow
* Prevent hypovolaemia
* Correct electrolyte disturbances
Euthanasia
- Salvage slaughter if fit to travel
Trochar and drain fluid
* Rapidly re-accumulation of fluid occurs in hydrallantois
* Need to provide replacement fluids to cow
What is arthrogryposis? What are causes?
- Relatively common malformation
- Limb ankylosis
- Usually combined with other congenital malformations (e.g. cleft palate)
- Liveborn neonates unable to stand -> euthanasia
- Foetotomy or C-sec usually needed
Causes
* Genetic
* Autosomasal recessive in Charolais breed
* Viral infection in utero
* Schmallenberg virus
* Bluetongue virus
* Akabane virus
* Teratogenic plants
* Lupines (not all species)
What is schistosomus reflexus?
- Inside out’ foetuses
- Rare, fatal malformation
- Likely genetic
- Foetotomy or C-sec
- Be careful not to confuse with uterine rupture
What is congenital chondrodysplasia?
- ‘Bulldog’ calves
- Short legs
- Domed head
- Brachygnathia inferior (undershot jaw)
- Dexters, Holstein, Jerseys
- Likely genetic
- Other breeds reported
- Does not always = dystocia
What is hydrocephalus?
- Increase in CSF volume -> domed head
- Calves born alive may have neuro deficits
- Teratogenic viruses implicated
- BVDv
- BTV
- Akabane virus (not UK)
- May also form part of mixed congenital disorders
- Mild cases may calve unassisted
- Severe cases = C-sec
What is large offspring syndrome?
- Also termed ‘abnormal offspring syndrome’
- Varied congenital abnormalities reported
- Associated with assisted reproductive technologies
- Embryo transfer
- In vitro techniques
- Cloning
- Exact mechanisms unclear
- Very large neonates
- May be 2x average size
- Dystocia
- Macroglossia (enlarged tongue)
What are possible cranial defects?
- Ancephaly – no head (images 1a and 1b)
- Otocephaly – some head structures present but no skull (image 2)
- Bicephaly – two heads (image 3)
What are teratogens? How does the timing of exposure affect the influence they have?
Teratogen = agents causing foetal abnormalities or death
Zygote = affected by chromosomal or genetic abnormalities. Often result in embryonic death
Embryo = affected by environmental and infectious agents. Most high risk period for developing abnormalities
Foetus = more resistant to environmental teratogens but structures that develop late are still susceptible to being affected (e.g. palate)
What are common environmental teratogens? What effect do they have?
Hemlock
* Skeletal abnormalities if ingested between days 40-70 of gestation
* Abortion
* NB. is highly toxic to cattle and often causes death of dam
Nitrates/nitrites - Nitrate accumulating plants e.g. sugar beet, alfalfa or Nitrite based fertilisers
* Excess nitrate consumption exceeds rumen capacity for metabolism -> nitrate and nitrite absorbed into circulation -> interacts with haemoglobin -> oxidation to methaemoglobin
* This process can also occur in the placenta -> foetal death, weak calves
Ergotism - Mouldy feed
* Reduced size offspring
Lead
* Concentrates in CNS of foetus
* Neurological defects
* Reduced foetal size
What are examples of pharmacological teratogens? What effect do they have?
Benzimidazoles
* Sheep
* Abnormalities of the foetal skeleton, kidneys and vascular system
Tetracyclines
* All ruminants
* Dental discolouration
Steroids
* All ruminants
* Abortifacient
Prostaglandins
* All ruminants
* Abortifacient
Xylazine
* All ruminants
* Abortifacient in later stages of pregnancy
Why is early pregnancy in heifers not ideal?
- Remember puberty in cattle driven by weight, not age
- Puberty occurs at ~2/3 of adult bodyweight
- Well-grown heifers can therefore unexpectedly conceive to mis-mating
- Uncastrated youngstock
- Bulls running with herd
- Entire males escaping
- Poor heifer growth
- Increased risk of dystocia
What are the management options for early pregnancy?
Wait and see
* C-sec likely needed -> can be less optimal outcomes if performed in emergency
* Can be effective if farmer aware of mis-mating and requests vet assistance as soon as parturition starts
* Only addresses issue of dystocia
Elective caesarean
* Performed at/near end of gestation before parturition starts
* Need a idea of gestation duration à scan
* Only addresses dystocia
Induce parturition
* Aim to induce near/at term for viable but small foetus
* May still need C-sec if calf big
* Requires reliable insemination date -> scan
* Only addresses dystocia
Terminate pregnancy
* Prostaglandin
* Glucocorticoid steroids (dexamethasone)
* Reliability dependent on stage in gestation -> scan
* Early termination can mean limited effects of pregnancy on dam
Why is prostaglandin used in pregnancy termination? When is it best to use it?
- Lysis of CL -> pregnancy loss
- Progesterone needed to maintain pregnancy
- Stage of gestation is important factor in successful treatment
- < 100 days gestation = maximal chances (> 90%)
- 101-150 days gestation = moderate chances (~ 60%)
- > 150 days gestation = lower chances (≤ 40%)
- Because placenta also a source of progesterone between days 150-200
- > 270 days gestation to induce parturition -> live calf
- Abortion occurs within 7days if given < 100 days gestation
- > 100 days gestation timing and reliability of abortion reduced
Why are glucocorticoid steroids used in pregnancy termination?
- Reduces placental secretion of progesterone -> pregnancy loss
- Most effective in last month of gestation
- Can also be used after day 270 to induce parturition -> live calf
Dexamethasone
Give 20-30mg (for most products this is 10-15ml)
When would you give both prostaglandin and dexamethasone?
- For mid to late gestation (i.e. > 150 days) or if uncertain give both dexamethasone and prostaglandin
- Reduces progesterone from both placental and CL sources
- Increases likelihood of success
- Both drugs associated with increased likelihood of retained foetal membranes (covered this afternoon)
- No other adverse effects for the heifers reported
