Lecture 23 - Alimentary 4 Flashcards
Briefly explain the mechanism of dehydration and shock in the ruminants:
- Fermentation of readily digestible carbohydrate causes increased osmotically active particles within the rumen
- Osmotic pull of water from ECF into the rumen
- Some material from rumen reaches large intestine
- Further fermentation results in osmotic diarrhoea
- The net result is hypovolaemic shock
- Bacteria and bacterial products (endotoxins) are then able to cross compromised ruminal wall
- This leads to endotoxic shock
What are the two different products of lactic acidosis in ruminants?
D-lactate (accumulation in rumen and blood)
L-lactate (used to host)
How does metabolic acidosis result in ruminal stasis?
Initially, it is by the direct effect of SCFAs (especially butyrate) - later on is due to damaged ruminal wall, hypovolaemia, metabolic acidosis and systemic toxaemia
How should rumen fluid collected appear normally and how will it appear in cases of ruminal acidosis?
Normally, protozoa keep particulate matter suspended in fluid - settling quickly occurs when the protozoa die .
What is the name of the bacteria that are shown below?
Gram positive Lactobacilli
What is the name of the condition that is shown below ‘star gazing cow’ relate this to ruminal acidosis ?
Ruminal acidos may lead to destruction of thiamine producing bacteria . This leads to a thiamine deficiency and polioencephalomalacia. The cow has opisthotonus and is showing a star gazing attitude
What are the two different types of bloat that are seen within cattle?
Free-gas bloat (fermentation is normal) - acute or chronic
Frothy (legume) bloat - feremntation is abnormal
What is the cause of failure of eructation (free gas bloat) and describe the appearance of the animal?
Free-gas bloat is associated with intermittant obstruction of the cardia - note the distended left paralumbar fossa
What is the pathophysiology of failure of eructation - frothy bloat?
Feeding of lush pasture that are high in chloroplast and in soluble protein results in the production of a stable foam that traps gas (stable foam resembles whipped egg white) and blocks the cardia and prevents eructation.
How do the clinical signs for frothy bloat differ to those seen in free gas bloat?
Signs similar to free gas bloat except absence of large asculatable ‘ping’ despite marked left flank distention
What are some sequale to frothy bloat?
Ruminal distention can rapidly lead to compression of the thorax, cardiopulmonary failure, recumbancy and death
What are primary cycle and secondary contraction cycles of the reticulum and the rumen?
Primary cycle - emptying and mixing contractions
Secondary cycle - contractions related to eruction of gas
What nerve controls forestomach motility?
The vagus nerve
Briefly describe how forestomach contractions are mediated:
The regulation is mainly via long vagovoagal reflexes. Sensory information from forestomach receptors is transmitted via vagus to integrating. The vagus nerve also conveys efferent signals from dorsal vagal nucleus back to the forestomach muscle
What are the four main abnormalities of motility (provide an example of each)?
- Depression of the gastric centrers in the centrla nervous system - anaesthesthics, drugs, pain, pyrexia
- Lack of excitatory reflex inputs via tension receptors in the forestomach (anorexia, vagus indigestion)
- Block of motor pathways (usually secondary to drugs such as atropine or to hypocalcaemia)
- Increased inhibitory reflexes inputs via epithelial receptors in forestomachs (ruminal distention, acids, abomasal or small intestine distention)
What is the name of the conditon shown below? Privde a potential cause:
Fibrinous pericarditis in a cow with TRP.
