7.3 Pathology of Forestomach and Abomasum of Ruminants

What conditions can affect the forestomach and abomasum?

Rumenal tympany - bloat

Rumenal acidosis

Left and right displaced abomasum (LDA, RDA)

Tramatic reticuloperitonitis

Clostridial disease

What is frothy bloat?

Gas entrapment within froth in rumen

Legume feeding

What is free gas bloat?

Inability to eliminate free gas from rumen

Overproduction of free gas - carbohydrate overlaod

Failure to eructation - oesophageal obstruction, recumbency

Functional disruption to rumen - nerve dysfunction. hypocalcaemia

What are clinical signs of rumenal tympany (bloat)?

Abdominal distension

Rumenal hypo motility

Pain, discomfort and vocalisation

Tachypnoea

Recumbency and death

What is rumenal acidosis?

Normal rumen function - pH 6-7. buffered by saliva

Consistent diet

High levels of cellulose and hemicellulose

Slow passage of ingest through GIT

Need time to chew cud

What risk factors can cause rumenal acidosis?

Size of conc. feeds

Feeding frequency

Overall starch levels

Forage access

Ration sorting

Transition

Cow comfort

What can cause rumenal acidosis?

Acute rumenal acidosis - high quantity of CHO in short timeframe

Subacute rumenal acidosis (SARA) - chronic exposure to high starch levels. lack of physically effective NDF. herd level problem

What is the pathology (development) of rumenal acidosis?

Diarrhoea - osmotic draw from lactic acid. decreased gut transit time

Rumenitis - inflammation of rumen wall. liver abscessation. pulmonary thromboembolism

What are clinical signs of rumenal acidosis?

Acute rumenal acidosis - rumenal tympany and diarrhoea. tachypnoea. recumbency and death

SARA - decreased milk production, milk butterfat content, BCS, rumination. diarrhoea. undigested grains. faecal soiling. poor fertility

How can we diagnose SARA on farm observations?

Decrease/increase in faecal consistency and incomplete digestion

Poor cow cleanliness

Tail swishing

Decreased rumination and increase in dropped cuds

Ration assessment

How can we diagnose SARA?

Decreased herd performance

Decreased yields and bulk milk butterfat levels

Poor reproductive performance

Increased lameness and environmental mastitis

Rumenal pH monitoring boluses

What functional features can cause abomasal disorders?

Metabolic - hypocalcaemia. NEBAL. ketosis/fatty liver

Nutritional - concentrate to forage ration. physically effective fibre. rumen outflow

What physical features can cause abomasal disorders?

Reduced DMI and rumen fill

Pre-calving left shift

Post calving potential space

Genetics - abdominal contour

What is left displaced abomasum?

Most common form

Gas-distended abomasum displaced between left abdominal wall and rumen

Duodenum becomes compressed preventing outflow

Occasional intermittent/floating LDA

What are clinical signs of left displaced abomasum?

Selective anorexia - refuse concentrates

Decreased milk production

Decreased rumen fill and decreased faecal output

Extension of caudal part of ribcage

Ping on percussion - ventral half of abdomen between 9th and 12th intercostal space

What is right displaced abomasum (volvulus)?

Not most common form - 5% displacements

Abomasum floats up on RHS

Rotating over 90-180°

Volvulus/torsion

Obstruction of blood supply:

Sequestration of fluid and ions within lumen

Necrosis of abomasal mucosa and translocation of bacteria

Circulatory failure may superimpose metabolic acidosis due to hyper-lactatemaia

What clinical signs of right displaced abomasum are there?

Anorexia

Decreased milk production

Decreased rumen fill and motility

Extension of caudal part of ribcage

Ping on percussion on right flank - last 3 ribs and lumbar fossa

What is trauatic reticuloperitonitis (TRP)?

Ingestion of sharp penetrating object

Tyre wire syndrome

What is the pathogenesis of TRP?

Localised in reticulum

Trapped in honeycomb structure

Object penetrates reticulum wall due to luminal contractions

Peritonitis due to bacterial seeding - damage liver, heart, lungs

What are clinical signs of TRP?

Anorexia

Arched back/painful abdomen

Tachycardia

Pyrexia

Decreased GI stasis

Milk yield

How can we diagnose TRP?

Anterior abdominal pain tests

Auscultation

Diagnosis by exclusion

Abdominocentesis

Ultrasonography

Glutavac - fibrinogen test

What is abomasal ulceration?

Can occur in calves and adults

Caused by:

Stress

High starch/concentration ration

Concurrent disease

What is the pathogenesis of abomasal ulceration?

Ulcers on abomasal wall

Haemorrhage

Peritonitis

What are clinical signs of abomasal ulceration?

Foul smelling faeces

Melena

Anaemia

Tachycardia

Pale mucous membranes

What is clostridial disease?

Clostridium sordelli (abomasitis)- high milk intake in lambs 4-10 weeks. abomasal wall can be emphysematous, oedematous, hyperaemic

Clostridium septum (braxy) - abomasitis. ingestion of frosted forage. frosted feed damages mucosa of abomasum allowing bacteria to penetrate