Ruminant stomach pathology

What is this and its cause?

Bloat line, caused by bloat/ruminal tympany

Pathogenesis of frothy bloat (primary)

Cattle at pasture that eat a large amount of leguminous plants, containing lots of soluble proteins (clover, alfalfa, rich lush pasture)

Soluble proteins released from chloroplasts, degraded by microflora and raised to surface where it stabilises foam and is insoluble/denatured.

Trapped gas cannot be eructated

Seen in multiple cows dying following turnout to lush pasture

Pathogenesis of free gas bloat (secondary) and list causes (8)

Caused by physical or functional defect in gas eructation produced by normal fermentation

• oesophageal obstruction (tumour, stenosis)

• choke

• reticular adhesions

• vagus indigestion

• enlarged mediastinal lymph nodes (following pneumonia)

• tetanus

• milk fever

• lateral recumbency causing blockage of cardia

How can bloat cause death?

Combined physical and metabolic effects

Increased intra-abdominal pressure on diaphragm impacts respiratory and cardiac functions

= hypoxia

Compression of caudal vena cava decreases venous flow to the heart

Altered vagosympathetic reflexes

7 gross findings of bloat death in ruminant

Bloat (hard to assess post mortem)

Dark blood clots poorly = death from anoxia

Oedema, congestion and haemorrhage of cervical muscles

Pale hind limb muscles

Bloat line

Voluminous frothy content/physical causes of impaired eructation - depending on the cause

Gross and histological findings of ruminal acidosis and its pathogenesis.

Increased starch/sugar fermentation decreases pH

Gross:

• fermentative odour to rumen

• ruminal epithelium adhered to submucousa

• <5pH

• hyperaemic lamina propria

Histo:

• cytoplasmic vacuolation of epithelial cells

• Neutrophils in mucousa and submucousa

Diagnose this. What are the clinical signs (5), pathogenesis and diagnostic tests (3)

Traumatic reticulopericarditis

Wire or similar penetrates reticulum, causing inflammation and can lead to peritonitis and pericarditis

Signs:

• ruminal tympany

• pain on reticulorumen contraction

• pyrexia

• abdominal pain

• heart failure

Diagnosis:

• Withers pinch

• Pole test

• Eric Williams test (trachea should elicit grunt before ruminal contraction to indicate pain)

Pathophysiology and diagnosis of left displaced abomasum

Affects high producing cows within 6 weeks of calving

Poor management over transition - quick diet change, milk fever, retained foetal membrane

Diagnosis:

• pings over left flank

• reduced milk yield

• reduced appetite…

Pathophysiology and pathogenesis of right displaced abomasum and its diagnosis

Twisting causing abomasal torsion or volvulus

Can occur any time during lactation

• sick cow

• shock

• pain

Diagnosed = pings over right flank

What is this and what does it cause

Sarcinia bacteria. Cause of abomasitis in calves

What is this condition. Explain its pathogenesis and give risk factors (4).

Abomasitis

Affects dairy calves < 3 weeks old

Usually Clostridium (septicum) or Sarcinia bacteria - produce toxins and rapid fermentation

Bacteria enter digestive system by ingestion. They replicate and produce gas and toxins,

Toxins irritate mucousa = inflammation

Gas = bloat

Risk factors:

• overfeeding milk replacer

• insufficient colostrum

• rapid diet change

• environmental fomites

List causative agents of abomasitis (7)

Clostridium septicum - cause Braxy in sheep and calves. Linked to cold weather.

Sarcinia

Bovine viral diarrhoea virus - viral mutation to cytopathic form = cell damage and ulceration of GIT. Diagnosed with antigen/antibody testing

Zygomycetes - hyphal invasion = infarction

Haemonchus

Ostertagia

Coccidia

(toxins)

What is this abomasal parasite? How is it diagnosed (2)

Ostertagia ostertagia

Causes nodules on abomasal mucousa (especially in type II disease)

Diagnosis:

• abomasal wash

• FWEC

What are the three abomasal parasites of sheep?

Haemonchus contortus

Ostertagia circumcincta

Trichostrongylus axei

What is this parasite and its clinical signs? Diagnostic tests?

Haemonchus contortus

Pale mucous membranes/anaemia

Hypoproteinaemia

Damaged abomasal mucousa

Diagnosis:

• abomasal wash (count number of worms)

• FWEC - peanut agglutination test for H.contortus eggs

What is this condition?

Choke, caused by feed material obstructing oesophagus. Traumatic.