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| − | ==Bloat/Tympany== | + | {{frontpage |
| | + | |pagetitle =Forestomach - Nutritional Pathology |
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| | + | |contenttitle =Content |
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| − | * When [[Eructation - Anatomy & Physiology|eructation]] fails, the [[The Rumen - Anatomy & Physiology|rumen]] becomes distended due to the accumulation of gas produced by the fermentation process. This distension is known as '''bloat''' or '''tympany'''.
| + | <categorytree mode=pages>Forestomach - Nutritional Pathology</categorytree> |
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| − | ===Clinical=== | + | </b></big> |
| | + | |logo =path-logo.png |
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| − | *The disease is acute and progressive and will result in death in a matter of hours.
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| − | ===Pathology===
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| − | * In severe bloating, that the [[The Rumen - Anatomy & Physiology|rumen]] almost fills the abdomen.
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| − | ** Diaphragm is displaced forwards, compressing the lungs.
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| − | ** Posterior vena cava (lying dorsally) is also compressed, reducing the venous return to the heart.
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| − | ** Respiration is depressed and animals die from anoxia.[[Image:oesophageal bloat line.jpg|thumb|right|150px|Oesophageal "bloat line" (Courtesy of Elspeth Milne)]]
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| − | *** Blood is dark (hypoxic) and clots poorly.
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| − | * The anterior parts of the body are often characteristically acutely congested.
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| − | ** Oedema and subcutaneous haemorrhage of head and neck tissues.
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| − | ** [[Oesophagus - Anatomy & Physiology|Oesophageal]] "bloat line" at thoracic inlet.
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| − | *** Congested and haemorrhagic cranially, pale caudally.
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| − |
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| − | ===Pathogenesis===
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| − | * There are two forms of bloat:
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| − | ** '''Frothy bloat/ Primary bloat'''
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| − | *** Occurs following ingestion of large amounts of succulent green plant material. This is highly fermentable and produces large amounts of gas.
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| − | *** Material contains high levels of soluble proteins. These act as foaming agents by reducing surface tension but increasing surface viscosity of rumenal liquids and a stable rumenal foam forms.
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| − | *** The [[Volatile Fatty Acids - Anatomy & Physioogy|volatile fatty acids]] of the plant material consumed lower pH, optimising conditions for formation of froth.
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| − | *** Gas present in bubble form is insufficient to trigger eructation, and so the [[The Rumen - Anatomy & Physiology|rumen]] becomes distended.
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| − | ** '''Free gas bloat/ Secondary bloat'''
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| − | *** May be:
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| − | **** '''Acute'''
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| − | *****Due to sudden [[Oesophagus - Anatomy & Physiology|oesophageal]] obstruction, for example by a solid foreign body (e.g. a piece of potato or turnip).
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| − | **** '''Chronic'''
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| − | ***** Results from partial [[Oesophagus - Anatomy & Physiology|oesophageal]] obstruction/ compression, or from interference with the normal eructation mechanism, e.g. with:
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| − | ****** partially obstructive foreign bodies
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| − | ****** actinobacillosis in the oesophagus or [[Oesophageal groove|oesophageal groove]]
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| − | ****** [[Oesophagus - Anatomy & Physiology|oesophagus]] or groove tumours
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| − | ****** chronic inflammatory or adhesive disease of the [[The Reticulum - Anatomy & Physiology|reticulum]]
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| − | ***** Some passage of gas is possible, so gas build-up and distenesion is more prolonged.
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| − | ***** Interference with cardiac and respiratory function is seldom life threatening.
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| − | ==Rumenal Acidosis==
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| − | * Like bloat, rumenal acidosis is associated with mismanagement of feeding and involves cessation or depression of [[Rumination - Anatomy & Physiology|rumenal movements]] with development of a degree of tympany.
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| − | * More common in cattle and goats than in sheep due to differences in diet.
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| − |
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| − | ===Clinical===
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| − |
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| − | * Animals display signs of abdominal discomfort, but usually recover if treated.
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| − | * Acute disease can result in death if acidosis is severe.
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| − |
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| − | ===Pathogenesis===
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| − | * Occurs following feeding of highly fermentable material, usually carbohydrate, in the form of concentrate or cereal
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| − | ** e.g. in barley beef feeding systems.
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| − | * An overgrowth of Gram positive bacteria results, breaking carbohydrate down very quickly.
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| − | ** Increased [[Volatile Fatty Acids - Anatomy & Physioogy|volatile fatty acid]] production decreases the [[The Rumen - Anatomy & Physiology|rumen]] pH to about 5.
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| − | *** [[The Rumen - Anatomy & Physiology|Rumen]] epithelium is damaged- ruminitis.
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| − | *** Osmotic effects of [[The Rumen - Anatomy & Physiology|rumen]] contents produce severe dehydration.
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| − | *** Death may ensue when the [[The Rumen - Anatomy & Physiology|rumen]] pH drops to 4.5 or below.
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| − | * Normal flora may invade the damaged wall of [[The Rumen - Anatomy & Physiology|rumen]] e.g. Fusiformis necrophorum.
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| − | ** Results in areas with mushy necrotic papillae.
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| − | ** Especially on pillars and ventral parts of [[The Rumen - Anatomy & Physiology|rumen]].
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| − | * Excess gas production may occur
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| − | ** Concentrate does not contain soluble proteins, therefore foam does not develop.
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| − | ** Only mild to moderate free gas bloat is likely- much of the rumenal distension which occurs with rumenal acidosis is due to fluid sequestration in the [[The Rumen - Anatomy & Physiology|rumen]].
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| − |
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| − | ===Pathology===
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| − | ====Gross====
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| − | * Gross PM findings may be non-specific.
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| − | * Ruminal stasis/bloat leads to rumen distension
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| − | * [[The Rumen - Anatomy & Physiology|Rumen]] contents are porridge-like.
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| − | * Rumenitis may be present
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| − | ** Normal flora invading wall of rumen may enter blood as thromboemboli and travel in the portal flow to [[Liver - Anatomy & Physiology|liver]]
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| − | ** Focal abscesses are produced, which heal with sunken star-shaped scars.
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| − | * Overgrowth of Clostridia may cause endotoxic shock with widespread petechial haemorrhages.
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| − | ====Histological====
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| − | * Microvesicles may be present in the epithelium of the [[The Rumen - Anatomy & Physiology|rumen]] papillae.
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| − | ** Contain mainly [[Neutrophils - WikiBlood|neutrophils]]
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| − | * May be focal erosions/ulceration.
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| − | ===Sequelae===
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| − | * Scarring- necrotised papillae are replaced by smooth epithelium closely adherent to sub mucosa.
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| − | * Has economic significance since many barley beef livers are condemned at meat inspection.
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| − | * More persistent organisms can invade [[The Rumen - Anatomy & Physiology|rumen]] wall producing chronic infection.
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| − | ** These are often fungi, e.g. Mucor (see [[Forestomach Inflammation - Pathology#Mucormycosis|Mucormycosis]]).
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| | [[Category:Forestomach - Pathology]] | | [[Category:Forestomach - Pathology]] |
