The most efficient alarm on the planet for dog owners is probably the sound of their dog retching. The immediate response is to jump out of bed, direct your dog to the nearest hard surface, and wait for whatever his stomach rejected to end up on the floor. Then it’s time for disinfectant, paper towels, and lots of water.
Is the vomit a foamy liquid with a yellow-green tint? This substance is known as bile, an alkaline produced in the liver that aids in digestion. Vomiting bile often happens on an empty stomach and is not the same as a dog regurgitating food. Some attempt to describe bilious vomiting as a response to bile irritating a dog’s stomach when it’s empty:
"Hunger pukes" are most common in raw fed dogs, since raw food is digested in approximately 4 hours as opposed to kibble fed dogs. Kibble takes approximately 8 hours to digest, which is why raw fed dogs tend to vomit in the morning before they get to eat breakfast.
The reason this happens is because the rate in which raw and kibble are digested are completely different. Once kibble is ingested, it turns into sludge and sits in your dog’s stomach for up to 6 hours while the body tries to break it down. So your dog gets a sensation of being full for a longer period of time. On raw, your dog’s body consumes protein within 2 hours… thus leaving your dog feeling hungry much quicker and the body reacts to this with hunger pukes.
While this hypothesis may seem sensible at first (and decreasing time between meals can stop bilious vomiting in many cases), it doesn’t address what causes the bile production in the first place. When we look at the source of the problem, bile production, we move away from treating the symptom and toward a real solution.
Bile Production: Where, When, and Why?
The liver produces bile to help intestines absorb fat and expel the body of waste. Bile travels from the liver, through various channels, and eventually empties into the gallbladder, where it can aid in the digestion.
Each time you feed your dog, its body responds by releasing bile. The exact timing is still up for debate. Does this occur just prior to the time you regularly feed your pet? When you open their food container? As you place their food bowl before them? As they take their first bite?
In medium-sized dogs, normal bile levels are 15mL. According to the Cornell University College of Veterinary Medicine (CUCVM), most animals have higher bile concentrations when eating than on an empty stomach; this makes sense. More food requires more help to break down fats, and that is bile’s main function.
Overproduction of Bile
Bile is clearly a necessary component of the canine digestive system. But is the presence of “too much” enough for the dog’s body to eject the liquid?
It could be. One research study at CUCVM found that up to 20% of dogs have higher concentrations of bile when “fasting” than when feeding. They list three reasons why this may happen: “a recent meal, gall bladder contraction during fasting, or delayed gastric emptying.”
Delayed gastric emptying is a condition in which dogs’ intestines move food along the GI tract too slowly. Since there is still technically food present in the digestive tract during this phenomenon, it may not explain why bilious vomiting occurs on an empty stomach (since these dogs ate recently).
Gall bladder contraction during fasting may occur because of disease or other unknown reasons. Research on fasted gallbladder contractions in canines is still sparse.
“A recent meal” could be interpreted a couple of ways:
Kibble takes more time to digest than raw food, so a “recent” meal of kibble could necessitate a longer duration of bile production.
The fat content of the food may be too high, triggering the gallbladder to produce more bile to help break down excessive fats.
Studies comparing specific canine diets, with special focus on bile production and release into the intestines, are not yet common. In other words, there is no consensus, and hardly enough data to form a solid hypothesis regarding why dogs vomit bile. Each dog has a unique diet, digestive environment, and dietary history, so pinning down a “normal” level of bile production, and what might induce vomiting, is no easy task.
What should I do if my dog vomits bile?
If your pup occasionally gets sick when he’s gone too long without a meal, you can feed more frequent meals to keep food in his stomach. Try it in the form of a bedtime snack, 2 meals per day versus 1, or a raw, meaty bone chew.
If this occurs extremely frequently, or despite your efforts to decrease time between meals, consult your veterinarian and consider the below.
If more regular feedings are our solution, we’ve done nothing to change the amount of bile produced, which is produced in response to what your dog eats.
If this phenomenon happens excessively, your dog simply having an “empty stomach” may not be the most comprehensive explanation.
Reconsider: a closer look at the source
The liver produces bile when fats need to be broken down. Do you know exactly how many fats you’re feeding your dog? And if it’s the “right” amount? Ultimately, you may be feeding a dog food much higher in fat calorie content than you realize, which could stimulate its body to produce too much bile.
NOTE: This is not to say that fats are bad for your dog! In fact, they’re an essential part of dogs’ daily diet. Dietary fats can help break down and use fat-soluble vitamins, provide essential fatty acids (EFA’s), which canines cannot produce on their own and help with building cell structure and function.
If an abundance of fat in your dog’s diet could affect bile production, but fats are also an essential part of his diet, how much should you feed?A diet of approximately 10-15% fat is considered healthy and essential for the majority of adult canines. Keep in mind this can vary depending on your dog’s age and activity level.
Bilious vomiting seems to occur in many dogs, but it shouldn’t necessarily be written off as normal, especially if it’s frequent. If not, reduce time between your dog’s meals or give him a “second dinner” late at night to keep food in his stomach. Keep an eye out for other symptoms (lethargy, loss of appetite, change in thirst, bloody stool/vomit, etc.), evaluate his food’s fat content, and consult your veterinarian to discuss other symptoms or fat intake.