Bloat and flatulence

Erin Malone DVM PhD

55 Bloat and flatulence

Gas in the GI tract

Gas in the GI tract may be due to swallowed air (aerophagia), particularly in brachycephalic dogs (eg pugs, bull dogs) and dogs that eat very quickly. In most other animals, gas in the GI tract is mostly due to bacterial production of gas as they metabolize stuff. Gas is normally released as burps and farts (flatus). Bloat is generally due to gaseous distension.

Microbes produce more gas when they are happy and fermenting things. Microbes like

more stuff to eat
- fermentable feedstuffs eg corn
new stuff to eat
more time to eat
- slowed motility
- herbivores with elongated GI tract

Bloat happens when microbes are happy and gas is trapped and can’t be released. The gas may be trapped in either free gas form (air in a balloon) or as excessive foam with frothy bloat.

Simple stomached animals (dogs, cats)

Dogs and cats do have microflora. The amount of microflora is highest in the distal parts of the GI tract (colon). Some gas is usually evident in the colon. Radiographically we identify colonic gas by the “?” appearance and the path to the anus.

Some gas can be seen in the stomach, as well. You should normally see some gas in the stomach on radiographs (otherwise, there is too much fluid in the stomach):

Excessive gas in the stomach of a dog often indicates gastric dilation or volvulus, a life threatening condition. in these animals, the normal gas is trapped, creating severe pain and cardiovascular compromise. This is free gas bloat. These animals need emergency care.

Gastric dilatation and volvulus in dogs, abomasal displacements/torsions in cattle, and large colon displacements/torsions in horses all bear some similarities in terms of

who gets them – bigger or deep chested animals
clinical signs – distension, “pings”, respiratory and cardiovascular impairment
pathophysiology – blockage of gas relief
treatment options – decompression and tacking procedures (pexies)

Fermenters

Fermenters tend to have more bloat problems since they have more microbial activity. Foregut fermenters need to eructate or burp to remove the gas. Hindgut fermenters do more natural farting. Anything that increases the gas production or prevents it expulsion can be very dangerous to the animal involved.

Increased gas production happens with happy microbes : change in diet, change in motility, change in types of microbes

Inhibition of gas release occurs with physical or functional obstructions : blockage of the GI tract (esophagus for foregut fermenters, colon for hindgut fermenters), nerve or muscle dysfunction.

Examples of microbial dysfunction

RUMEN BLOAT

Ruminants can develop two types of bloat. Frothy and free gas bloat.

Frothy bloat develops when animals eat too much clover or alfalfa. The result of digestion is a stable froth that can’t be eructated. Treatment involves giving an agent that can break down the froth (mineral oil, poloxalene, dioctyl sodium sulfosuccinate ). This can be problematic if the whole herd if affected. Prevention is better.

Free gas bloat develops when

Microbes are happy – change in diet, change in motility, change in types of microbes(particularly as calves are developing into ruminants from the pre-ruminant stage
- As a juvenile switches from milk to other diets, the microbial environment becomes more important. Often there is a slight mismatch between the microbiome maturity and the diet
Muscle dysfunction – hypocalcemia or sedation leads to changes in eructation or motility
Nerve damage – changes in vagal function from pneumonia or traumatic reticuloperitonitis lead to loss of eructation or motility
Obstruction – esophageal obstruction prevents eructation, a plastic bag blocks omasal outflow

Free gas bloat is treated with passage of a stomach tube, trocharization and/or rumenostomy. The trocar and the rumenostomy provide a “relief valve” for calves with recurrent bloat.

If unrelieved, bloat can compress the venous return to the heart and prevent lung expansion. Both are bad.

FLATULENCE

Flatulence is normal and generally a good thing. Increased flatulence may be associated with changes in diet or exercise. If truly bothersome, pets can be put on charcoal, yucca or zinc acetate.

Prebiotics and probiotics for pets are becoming very popular but healthy animals probably don’t benefit much. Prebiotics are feed compounds that are generally believed to be good sources of food for the bacteria. Probiotics are replacement bacteria.

Pre/probiotic supplements may be most useful when an animal has been off feed or on antibiotics.

Key Takeaways

Microbes require very specific environments to thrive. In exchange, they provide immune support, inhibit the invasion of pathogenic microbes, supply essential B vitamins, and support intestinal cells
Prebiotics are “food” for the microbes while probiotics are microbes.
Flatulence is the result of microbial happiness and occurs with excessive feedstuffs, new feedstuffs and increased time to digest feedstuffs (slowed transit).
Bloat can be free gas (trapped air) or frothy (stable foam). Frothy bloat occurs with saponin digestion (legumes) and is treated with anti-foaming agents (oil in soapy water). Free gas bloat is treated by removing the air and removing any obstructions.