Also known as choke or ruminal tympany, bloat refers to gas distension of the fore-stomachs (rumen and reticulum) of the cow. This condition is a very common encounter among herds in Kenya and occurs in two forms, either in the form of a persistent foam mixed with the ruminal contents called primary or frothy bloat, or in the form of free-gas separated from the ingesta called secondary or free-gas bloat.
This form of bload is caused by the entrapment of the normal gases of fermentation in a stable foam. The coalescence of the small gas bubbles trapped in the igesta is inhibited and the pressure in the rumen increases because eructation does not occur. Certain plant substances such as Alfafa hay, legumes or vegetables (such as kale & turnips), and finely ground grain, have been shown to be primary foaming agents and initiate the process.
This kind of bloat is most common in animals grazing legume or legume-dominant pastures and it occurs when cattle are placed on lush pastures, particularly those dominated by rapidly growing leguminous plants in the vegetative and early bud stages, but can also be seen when high-quality hay is fed.
Free-gas/ Secondary bloat
This form of bload results from physical obstruction to eructation occuring from the esophageal region. Obstruction may be caused by a foreign body (eg, potatoe, avocado seed etc.), stenosis or pressure from an enlargement outside pressing on the oesophagus such as from tuberculous, lymphadenitis or bovine viral leukosis.
Other causes of free-gas bloat include: Obstruction of the cardia, interference with nerve functions/pathways involved in the eructation reflex such as vagus nerve, diaphragmatic hernia.
However, chronic ruminal tympany is relatively frequent in calves up to 6 months old without apparent cause; this form usually resolves on it’s own.
Signs of bloat
The following findings are seen on bloated cows:
- Depressed milk yield
- Sudden distension of rumen
- Distension of left paralumbar fossa and abdomen
- Discomfort and animal may lie or stand frequently
- Belly kicking and rolling
- Frequent urination and defecation
- Protrusion of tongue and mouth breathing
- Vomiting may occur
- Dyspnea and grunting
- Respiration rate increases up to 60/min
- Rumen movements decrease and stops in severe cases
- If severity continues, animal collapses and dies
- Increased frequency and strength of rumination
- Tympanic resonance
- Distension of rumen and left paralumbar fossa.
- Avoid feeding or grazing high-risk plants such as legumes or clovers. If feeding is necessary, ensure a slow transition and always ill cattle with a high dry matter feed such as straw prior to grazing. Do not overfeed inely ground grain or other highly fermentable carbohydrates.
- Continually administer an antifoaming agent during the risk period. This may be done by praying pastures with antifoaming agents – oils and fats or by adding antifoaming agent in feed or water.
- Avoid feeding apples, potatoes, or feedstufs that can lodge in the esophagus and block eructation.
- Prevent infections with bovine respiratory disease complex, bovine leukemia virus, and tuberculosis.