Why does my dog get diarrhea after changing his diet?

Choosing the Right Diet for Your Dog

Nutrition is arguably the most important component in maintaining your dog’s health. The health and optimal function of almost all organs in the body will ultimately depend on the diet your dog is eating, from puppyhood until they are adults. It’s therefore very important to choose the best and appropriate diet for your dog.

There is no one perfect diet for a dog. Their nutritional needs change as they go through different changes in their lives. Nutritional requirements are also dependent on the type and breed of the dog and the environment they’re in. Components in a dog’s diet such as protein and fat content should be carefully considered in choosing a diet for your dog, as these can greatly affect the dog’s health in the long run.

The requirements for these nutrients will change as the animal gets older. As such, there will be instances where you’ll need to change from one type of diet to another. However, changing a dog’s diet is not as simple as it seems. If not done correctly, a dog may develop adverse food reactions that lead to gastrointestinal signs like vomiting and diarrhea.

Symptoms of Adverse Food Reactions in Dogs

Adverse food reaction is a blanket term used to describe any detrimental health reactions a dog gets from food, from food poisoning, food allergies, or any food-borne gastrointestinal problem. It is often confused with food allergy, and although quite similar in presentation and manifestation, these are two entirely different things.

While both are characterized by the dog’s immune response towards their food, they differ in the sense that food allergy has a defined and documented cause while a general food adverse reaction can happen even if the dog is not allergic to any components of the food, such as during an abrupt transition from one type of dog food to another.

Digestion and absorption of ingested food highly depends on the enzymes the stomach and the intestines produce as well as the population of microbiome present in the latter part of the intestinal tract. The type of digestive enzymes and microbiome depends on the food being ingested by the dog and will change accordingly during diet changes.

For example, a puppy will have digestive enzymes that are more suited to digest milk proteins and will have indigestion and gastrointestinal issues if given a diet with minimal or no milk components. As they get older, their digestive enzymes change to be able to digest and process more complicated protein sources such as meat and meat-based products.

This is also true in adult dogs used to eating a certain type of diet. Their digestive enzymes and microbiome have adapted to the diet they’re used to eating. An abrupt change in the type of diet (change in brand or protein base) will cause an inflammatory response along the intestinal lining, leading to gastrointestinal signs such as vomiting and diarrhea. This is what happens in cases of adverse food reactions due to sudden diet changes.

My dog has diarrhea after changing her food. How is this treated?

Most cases of diarrhea due to sudden diet changes can easily be corrected by changing back to the diet the dog has been used to. As mentioned above, adverse food reaction during diet change happens when the digestive enzymes in the dog’s gastrointestinal system cannot fully process the components in the new diet, resulting in diarrhea and vomiting. Changing back to the old food where innate enzymes can easily digest will help control signs associated with the adverse food reaction.

In cases with severe symptoms, medical management such as antidiarrheals and anti-emetics may be needed to fully control the gastrointestinal disturbance. Severe cases can predispose the intestinal tract to secondary infection and the proliferation of pathogenic and opportunistic bacteria requiring antibacterial therapy to treat.

Most cases respond well to treatment and changing back to the previous diet, with signs resolving in 24-48 hours after the start of treatment. If left untreated, the continuous inflammation along the intestinal lining may lead to more serious health conditions.

How to Prevent Diarrhea When Changing Your Dog’s Food

It has been shown that as the dog goes through different changes in their life, diet change is necessary to meet changes in their nutritional requirements. It has also been discussed how diet change opens the risk of a dog getting adverse food reactions causing gastrointestinal signs like vomiting or diarrhea. How, then, are we supposed to meet changing nutritional requirements without risking gastrointestinal issues?

Most, if not all, vomiting and diarrhea cases due to diet change happen when the switch is done abruptly. Sudden change in the dog’s diet causes improper digestion. However, this can be easily avoided by transitioning from one diet to another gradually. The slow transition allows the gastrointestinal system to adjust and produce necessary enzymes suitable for digesting the newly-introduced diet. Proper change in diet is usually a week-long transition and follows this process:

Days 1-2: 25% new diet and 75% old diet

Days 3-4: 50% new diet and 50% old diet

Days 5-6: 75% new diet and 25% old diet

Day 7: 100% new diet (completely transitioned)

This week-long gradual diet transition is often enough to prevent vomiting and diarrhea from occurring. Some dogs that have a very sensitive stomach may require a longer transition, but the same principle applies. By gradually transitioning diets, especially at times when diet change is needed to make sure nutritional requirements are met, we significantly reduce the risk of adverse food reactions and prevent signs of diarrhea and vomiting in dogs.

Read more:

Gastrointestinal Diets for Dogs and Cats

What You Need to Know About Feeding Your Dog a Raw Diet

Can Dogs Get Sick From Drinking Too Much Water?

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