Bovis ISSN 2398-2993

Ruminal bloat

Synonym(s): Free gas and frothy bloat

Contributor(s): Ash Phipps , John Tulloch

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Introduction

  • Ruminal tympany is also referred to as bloat.
  • Bloat is a non-infectious condition where there is over-distention of the rumenoreticulum from gas of ruminal fermentation or with stable foam.
  • Cause:
    • Primary ruminal tympany (pasture bloat, frothy bloat) is caused by excessive production and entrapment of rumen gas in stable and persistent foam.
    • Secondary ruminal bloat results from an inability to eliminate gas from the rumen by eructation secondary to another condition.
    • It should be noted that ruminal tympany may occur in association with other conditions such as hypocalcemia, anaphylaxis, and acute ruminal acidosis.
  • Signs: the primary sign of ruminal tympany is ruminal distension that results in the distension of the left paralumbar fossa.
  • Diagnosis: the diagnosis of ruminal tympany is based on clinical signs and history.
  • Treatment: will depend on the initial cause of ruminal tympany and the degree of clinical severity.
  • Prognosis: will be dependent on the initial cause of ruminal tympany and the form of intervention required to relieve the ruminal tympany.

Pathogenesis

Etiology

Primary ruminal tympany

  • An excessive production and entrapment of rumen gas (predominantly carbon dioxide and methane) in a stable and persistent foam.
  • Froth is generally associated with the feeding of immature, rapidly growing lush pasture, particularly legume pastures:
Pathogenesis of froth formation (pasture)
  • Succulent pastures promote less saliva production which results in an increase in rumen liquor viscosity.
  • Soluble proteins are released from ruminal microbial breakdown of chloroplasts in the pasture.
  • These soluble proteins rise to the surface of the rumen and become denatured and insoluble.
  • Combination of increased rumen liquor viscosity, insoluble proteins and normal mixing process of the rumen, allows for the formation of stable foam.
Pathogenesis of froth formation (feedlot bloat)
  • Low fiber and high concentrate diets results in a reduction in saliva production which results in an increase in rumen liquor viscosity as a result of a change in the microbial population of the rumen and microbial production of polysaccharides. Rumen microbes
  • Combination of increased rumen liquor viscosity from microbial production of polysaccharides, and normal mixing process of the rumen, allows for the formation of stable foam.
  • This results in prevention of eructation by the accumulation of froth and inhibition of the eructation reflex of the cardia.
  • With continued production of the stable foam through fermentation of the plant material, the rumen continues to distend.
  • In severe cases of ruminal tympany, there is increased pressure on the cardiovascular and respiratory systems which may result in asphyxiation or cardiac failure and death of the animal.

Secondary ruminal tympany

  • Inability to eliminate gas from the rumen by eructation secondary to another condition.
  • Usually involves physical obstruction of the esophagus that prevents eructation. Therefore, the clinical presentation would be similar to that of primary ruminal tympany.

Predisposing factors

Primary ruminal tympanic (feedlot bloat)

General
  • Primary ruminal tympany is usually associated with the feeding of lush, immature, rapidly growing legumes such as clover and Lucerne or finely ground grain (feedlot bloat).     
  • Can also occur in cattle grazing rapidly growing succulent ryegrass pasture in the pre-bloom stage.
Specific
  • Forage composition: high in protein, water, and soluble sugars but low in fiber will result in a high rate of gas production.
  • Both the rate of saliva production and composition play a significant role in influencing pasture bloat.
  • Bloat causing legumes are more readily digested by rumen microflora.
  • Rainfall and recent water application may influence the growth rates of the pastures.
Other factors associated with feedlot bloat
  • May be due to gas being trapped by the fine particles of the feed.
  • More commonly occurs when grain > 80% of diet or when Lucerne hay is used for roughage.

Secondary ruminal tympany

General
  • Inability to eliminate gas from the rumen by eructation secondary to another condition.
Specific
  • Acute form usually due to a physical esophageal obstruction choke or esophageal groove obstruction by afterbirth.
  • Chronic or intermittent bloat generally associated with lesions of the cardia, reticulum or esophageal groove commonly associated with actinobacillosis Actinobacillosis, fibropapillomas Papilloma, abscess associated with the reticulum, traumatic reticulo-peritonitis Wire, and vagus indigestion Vagal indigestion .
  • Less commonly lesions of the esophagus or compression of the esophagus due to lymphoma, diaphragmatic hernia, and enlarged mediastinal lymph nodes.
Other causes of secondary ruminal tympany include

Timecourse

  • Primary ruminal tympany: onset of disease is rapid within 1 hour of ingestion of specific pastures (especially in hungry cattle). Feedlot bloat is most common in cattle that have been on a grain diet for approximately 4–8 weeks.
  • Secondary ruminal tympany: the time course of the condition of secondary ruminal tympany is variable depending on the underlying condition. The condition may present acutely or chronically.

Epidemiology

  • The incidence of ruminal tympany is highest when the pastures are lush, young and growing, particularly in spring and autumn.
  • Ruminal bloat can occur in the individual or multiple animals if they gain sudden access to certain feed sources (for example: pasture or grain). 

Diagnosis

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Treatment

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Prevention

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Outcomes

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Further Reading

Publications

Refereed Papers

  • Recent references from PubMed and VetMedResource.
  • Lowe L B, Ball G J, Carruthers V R, Dobos R C, Lynch G A, Moate P J & Valentine S C (1991) Monensin controlledā€release intraruminal capsule for control of bloat in pastured dairy cows. Australian veterinary journal 68 (1), 17-20 PubMed.
  • Katz M P, Nagaraja T G & Fina L R (1986) Ruminal changes in monensin-and lasalocid-fed cattle grazing bloat-provocative alfalfa pasture. Journal of animal science 63 (4) 1246-1257 PubMed.
  • Bartley E E, Nagaraja T G, Pressman E S, Dayton A D, Katz M P & Fina L R (1983) Effects of lasalocid or monensin on legume or grain (feedlot) bloat. Journal of animal science 56 (6), 1400-1406 PubMed.
  • Howarth R E (1975) A review of bloat in cattle. The Canadian Veterinary Journal 16 (10), 281-294 PubMed.

Other sources of information

  • Parkinson T J, Vermunt J J & Malmo J (2010) Diseases of cattle in Australasia: a comprehensive textbook. New Zealand Veterinary Association Foundation for Continuing Education, Wellington, NZ.
  • Parkinson T J, Vermunt J J & Malmo J (2010) Diseases of cattle in Australasia: a comprehensive textbook. New Zealand Veterinary Association Foundation for Continuing Education. pp 87-88.
  • Radostits O M, Gay C C, Blood D C & Hinchliff K W (2006) Reference laboratory values veterinary medicine. In: Veterinary Medicine. A Textbook of the Diseases of Cattle, Sheep, Pigs, Goats and Horses. 7th edn. Saunders, China. pp: 325-336.


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