Week 12 Flashcards
What are oxygen tensions in the foetus compared to a neonate?
Why conditions that affect blood supply have profound effect
What are the two major right-to-left shunts that by-pass the lungs in a foetus?
Where does the umbilical vein connect in the foetus? What does the aorta connect to in the foetus?
What happens at birth going from blood to air?
What happens when everything goes right with the lungs after birth?
What happens when everything goes wrong with the blood supply after birth?
What is the most important immunoglobulin in colostrum? How does a neonate absorb colostrum? Why is colostrum so important?
IgG.
* specialized enterocytes that absorb large molecules by pinocytosis (process becomes fairly inefficient relatively quickly; stopped after 24 hours)
** failure of passive transfer is associated with an increased risk of disease and mortality
When does a neonates own immunoglobulins become detectable?
* after 1-2 weeks of life, but do not reach significant levels for several months
* temporarily protected by the passive transfer
* half-life for equine maternal antibodies is approximately 20-30 days and most have gone by 6-months of age
Failure of passive transfer of antibodies can be a consequence of?
- Failure to ingest a sufficient quantity of colostrum: orphans, too weak to stand, unable to stand, unable or lack of desire to suckle (e.g. hypoxic-ischaemic encephalopathy)
- Ingested poor quality colostrum (low IgG content)- premature lactation (placentitis in mares), premature parturition (inadequate udder development), ingestion of grasses infected with specific endophytes (fescue associated agalactia in mares)
- Failure to absorb colostral components from gut lumen (seen in premature or dysmature neonates occasionally, delayed ingestion of colostrum)
How do you determine quality of colostrum?
* measure IgG e.g. > 800 mg/dL considered adequate for foals
* Assays or ELISA
Why is it important not to over feed or under feed the pregnant mare?
Over feeding increases foetal growth and can cause deposition of fat within the dam’s pelvic canal (increased risk of foeto-pelvic disproportion)
* poor nutrition in the final trimester of pregnancy leads to poor udder development and lactation
Why is low birth weight in a foetus a problem? Over feeding?
Neonates more likely to be susceptible to adverse environmental conditions- impaired heat conservation
* weak at birth–> impaired ability to consume colostrum and subsequently, adequate volumes of milk- immunity, starvation
* over-feeding increases foetal growth and causes deposition of fat within the pelvic canal–>increased risk of dystocia
What species is foetal-maternal disproportion a problem? Not a problem?
Cattle is more commonly a problem, not so much in horses
What are some common consequences when dystocia occurs?
* Hypoxic injury to neonate
* Neonates with hypoxic brain injury can be:
- slower to stand and nurse–> failure of passive transfer
- nurse poorly–> hypovolaemia/dehydration, hypoglycaemia, weak
* Neurologic signs are usually the most obvious consequence of hypoxia
- GI tract injury
- renal injury
What effect can decreasing ambient temp and inreasing precip have on neonates?
Greater relative surface area, evaporation of amniotic fluid, limited caloric reserve
* Newbown animals have stores of brown fat– stores rapidly depleted in cold weather if unable to consume enough milk
* compounded if dam’s milk production low
Discussion of pathogen load on neonates
* multifactorial in order to succumb to disease
* Inevitably exposed to organisms capable of causing disease
* Normal protective mechanisms can be overcome if environmental pathogen load very high
* Or a particuarly virulent pathogen is present
When can pathogen load become more of a problem? How can you reduce the risk?
* clean the mare’s perineum and udder before foal nurses
* removal of faecal material from foaling paddocks
High risk potential historical traits in a mare
High risk mare events during current pregnancy
High risk mare events during parturition
What is normal foal behavior (first 24 hours)?
Why do foals have dilute urine (except their first urine sample)?
Milk has a lot of water in it- (10% for a calf; 20-25% for a foal of bodyweight per day)
What are the reflexes you might look for in small animals?
When is the TB arbitrary birthday? SB?
When does mating season start?
What are the consequences of TB born later?
TB- 1st Aug
SB- 1st Sept
** Mating season starts 1st September– Melbourne foals may do better born August than July
** may be smaller than competitors at 2 yo (yearling)
* mare may be difficult to get pregnant early next season
