Heat Stress And Complications

About heat and how it might affect dogs’ metabolism and digestion.

Here are some interesting and partly related bits of information:

A healthy human may harbor typically 3 to 4 lbs of microorganisms.

In normal humans it is estimated that there may be as many microorganisms as there are human cells in the body. The average human cell is much bigger than a microbe.

Over 90% of these are in the gastrointestinal tract.

Approximately 50% or more of human fecal material consists of  remains of these microorganisms.

These microorganisms, fungi and bacteria, produce metabolites which are often beneficial to the host. In fact the larger animal host is often so
dependant on the action and products of the microbes that we could ask technically which is the host? This question would apply quite obviously to ruminants but also is valid for humans, dogs and possibly most or all other animals.

The major products of GI and many other common fermentations are short chain fatty acids or volatile fatty acids such as acetate, propionate, butyrate and lactate. In the gut these SCFAs are the principle source of energy for the cells lining lower tract. It has been determined in a typical human (on a typical diet at the time the study was done) that 5 to 10% of the total energy needs of humans are supplied by the SCFAs produced by microbial fermentation.

So the importance of probiotics and prebiotics etc.

Microbes are sensitive to heat and other changes in their environment. The may produce different metabolites as other enzymes are activated or when different substrates and nutrients are available or absent. In certain conditions the microorganisms will produce endotoxins and when certain microorganisms decompose they may also release endotoxins which can have major effects on the host.

In a study with dogs intended as models for human pathology it was found that endotoxic shock was a major contributor to heat stroke fatalities. When the dogs were pretreated to remove the GI inhabitants using enemas and antibiotics before exposure to extreme heat the survival rate went from 20% without to 80% with antimicrobial pretreatment.

Sterilizing the gut is not a good idea in practice, but this study is instructive to show where part of the problem lies. And it may be possible
knowing this to develop better treatment and prevention for heat injury or other stress related enteritis.


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