Difference between revisions of "Bloat"

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Also known as: '''''Ruminal tympany'''''
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==Bloat/Tympany==
  
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== Description  ==
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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'''.
  
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'''Bloat''' is the ruminal distension caused by excessive accumulation of gas produced by the fermentation process. Bloat can be categorised according to cause into '''Primary bloat''' (frothy bloat) and '''secondary bloat''' (free gas bloat). The condition progresses rapidly and can be fatal.
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===Clinical===
  
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=== Primary bloat  ===
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*The disease is acute and progressive and will result in death in a matter of hours.
  
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'''Primary bloat''', or frothy bloat is the most common type of bloat, and usually affects several animals in a group at once. The condition can occur in feedlot cattle but is most frequently associated with cattle grazing lush, leguminous pastures. It occurs following the ingestion of large amounts of succulent green plant material which is highly fermentable and produces large amounts of gas. The material also 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. The [[Volatile Fatty Acids|volatile fatty acids]] of the plant material consumed lower the rumenal pH and optimise conditions for the formation of froth. Gas present as foam is insufficient to trigger eructation, and so the [[Rumen - Anatomy & Physiology|rumen]] becomes distended.
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===Pathology===
  
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=== Secondary bloat ===
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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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Secondary bloat or free gas bloat results from any condition that interferes with eructation and includes physical or functional disroders of the oesophagus (e.g.oesophageal obstruction)or the forestomachs. Secondary bloat usually affects a single animal in a group and generally has a more sporadic occurrence.  
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===Pathogenesis===
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* There are two forms of bloat:
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It may be '''acute''' in the case of sudden oesophageal obstruction, caused by a foreign body such as a potato or turnip, or '''chronic''' resulting from partial oesophageal obstruction, compression, or from a forestomach motility disorder that interferes with normal eructation.  
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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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Causes of secondary bloat:  
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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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*Physical oesophageal obstruction
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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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*Lesions of the [[Oesophagus - Anatomy & Physiology|oesophagus]] or [[Oesophageal Groove|oesophageal groove]] such as tumours, abcessation or infection with [[Actinobacillus lignieresii|Actinobacillus lignieresii.]]  
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** '''Free gas bloat/ Secondary bloat'''
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*Prolonged lateral recumbency
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*** May be:
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*Excessive cereal ingestion
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**** '''Acute'''
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*Rumenal atony
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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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*Inability to eructate due to '''[[Tetanus]]''' or '''Milk fever'''
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**** '''Chronic'''
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*Chronic inflammatory or adhesive disease of the [[Reticulum - Anatomy & Physiology|reticulum]]
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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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== Signalment  ==
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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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Primary bloat can occur in feedlot cattle but is generally associated with pastures rich in leguminous plants. There is a particularly high prevalence in New Zealand due to the high level of clover. In the UK occurrence of the disease coincides with turnout to lush pasture, especially in spring and autumn.
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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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Secondary bloat due to oesophageal foreign bodies can occur in any animal fed feeds such as potatoes or turnips which may lodge in the oesophagus. Cattle with underlying conditions such as tetanus and milk fever are predisposed.
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***** Interference with cardiac and respiratory function is seldom life threatening.
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[[Category:Forestomach - Nutritional Pathology]][[Category:Cattle]]
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== Diagnosis  ==
 
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The diagnosis of bloat can usually be made based on the obvious distension of the left paralumbar fossa. When several animals are affected on lush pasture the cause is invariably primary bloat. If only one animal is affected, or there is doubt over the cause, the passage of a stomach tube or trochar will release large quantities of gas in the case of secondary bloat. A full clinical exam should then be carried out in order to determine the underlying cause.
 
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=== Clinical signs  ===
 
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*Visible distension of the left paralumbar fossa
 
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*Kicking ventral abdomen and bellowing in pain
 
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*Sudden death
 
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=== Pathology  ===
 
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In severe cases, the [[Rumen - Anatomy & Physiology|rumen]] almost fills the abdomen, the diaphragm is displaced forwards, compressing the lungs. The posterior vena cava is also compressed, reducing the venous return to the heart. Respiration is impaired and animals die from hypoxia
 
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=== Post mortem  ===
 
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Post mortem change resulting in rumen distention following other causes of death can complicate the diagnosis of bloat. If the post mortem exam is carried out shortly after death then bloat will be obvious due to distension at the left paralumbar fossa. Other post mortem changes consistent with bloat are:
 
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*Pale liver due to compression by the rumen
 
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*Rupture of the diaphragm
 
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*Inguinal and ventral perineal oedema
 
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*Oesophageal "bloat line" at the thoracic inlet.
 
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== Treatment  ==
 
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Primary, or frothy bloat is relieved by drenching with an antifoaming agent containing silicone or poloxalene, such as '''Bloat Guard''' or '''Birp''', or a '''vegetable oil''' mixed with '''detergent'''. Clinical signs should improve within one hour, if there is still no resolution after a second dose then alternative diagnoses should be considered.
 
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In peracute cases where the bloat is life threatening an emergency '''rumenotomy''' should be performed.
 
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Secondary bloat can be relieved by passage of a stomach tube in most cases. There will be instantaneous relief as the gas is released. In cases where the oesophagus is completely obstructed so that a stomach tube cannot be passed a 5mm diameter trochar and cannula should be passed into the rumen via the left paralumbar fossa.
 
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== Prognosis  ==
 
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If treatment is prompt prognosis is good, however the condition is rapidly fatal if left untreated.  
 
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== Literature Search  ==
 
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[[Image:CABI logo.jpg|left|90px]]
 
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<br> Use these links to find recent scientific publications via CAB Abstracts (log in required unless accessing from a subscribing organisation). <br><br><br> [http://www.cabdirect.org/search.html?q=%28title%3A%28bloat%29+OR+title%3A%28%22ruminal+tympany%22%29%29+AND+%28od%3A%28cattle%29+OR+od%3A%28sheep%29%29 Bloat/ruminal tympany in cattle and/or sheep publications]
 
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== References  ==
 
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*Andrews, A.H, Blowey, R.W, Boyd, H and Eddy, R.G. (2004) '''Bovine Medicine''' (Second edition), ''Blackwell Publishing''
 
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*Merck &amp; Co (2008) '''The Merck Veterinary Manual (Eighth Edition)''' ''Merial''
 
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{{review}}
 
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[[Category:Forestomach_-_Nutritional_Pathology]] [[Category:Gastric_Diseases_-_Cattle]] [[Category:Brian Aldridge reviewing]]
 

Revision as of 14:37, 28 May 2010

Bloat/Tympany

  • When eructation fails, the rumen becomes distended due to the accumulation of gas produced by the fermentation process. This distension is known as bloat or tympany.

Clinical

  • The disease is acute and progressive and will result in death in a matter of hours.

Pathology

  • In severe bloating, that the rumen almost fills the abdomen.
    • Diaphragm is displaced forwards, compressing the lungs.
    • Posterior vena cava (lying dorsally) is also compressed, reducing the venous return to the heart.
    • Respiration is depressed and animals die from anoxia.
      Oesophageal "bloat line" (Courtesy of Elspeth Milne)
      • Blood is dark (hypoxic) and clots poorly.
  • The anterior parts of the body are often characteristically acutely congested.
    • Oedema and subcutaneous haemorrhage of head and neck tissues.
    • Oesophageal "bloat line" at thoracic inlet.
      • Congested and haemorrhagic cranially, pale caudally.

Pathogenesis

  • There are two forms of bloat:
    • Frothy bloat/ Primary bloat
      • Occurs following ingestion of large amounts of succulent green plant material. This is highly fermentable and produces large amounts of gas.
      • 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.
      • The volatile fatty acids of the plant material consumed lower pH, optimising conditions for formation of froth.
      • Gas present in bubble form is insufficient to trigger eructation, and so the rumen becomes distended.
    • Free gas bloat/ Secondary bloat
      • May be:
        • Acute
          • Due to sudden oesophageal obstruction, for example by a solid foreign body (e.g. a piece of potato or turnip).
        • Chronic
          • Results from partial oesophageal obstruction/ compression, or from interference with the normal eructation mechanism, e.g. with:
          • Some passage of gas is possible, so gas build-up and distenesion is more prolonged.
          • Interference with cardiac and respiratory function is seldom life threatening.
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