Experienced and professional animal trainer provide their insights in answering this question :
A. If the dog did not eat anything dark, this is a real cause for concern. It could be blood which could mean an issue internally with the organs. The dog should be seen by a vet immediately.

How to Identify Common Pet Problems ?

Our sources include academic articles, blog posts, and personal essays from experienced pet care professionals :

If you are experiencing dark vomit it is important to seek medical attention immediately, as this may be a sign of a potentially life-threatening problem such as internal bleeding. Other symptoms that may accompany dark vomit include dizziness, chest pain, shortness of breath, or heart palpitations.
It might even resemble dark coffee grounds. Your vomit may appear black if the blood has been oxidized by the acids in your stomach. The iron in your blood turns from brown to black with time. Since the blood is no longer bright red, it means that the bleeding has either stopped or is only happening in a small amount.
Although a small streak of red blood could be caused by simple stomach irritation (often due to the vomiting itself), vomit that is uniformly bright red, black, dark red or dark brown, or vomit that looks like coffee grounds is an emergency. Seek veterinary care immediately.
A bright green- or teal-colored vomit suggests your dog ate mouse or rat poison, and you should seek immediate medical advice from your veterinarian or animal poison control center. Quantity: A dog who has gulped down a large bowl of water or dog food too quickly will regurgitate a large volume of material.
Dark red, dark brown, or black vomit, or vomit that looks like coffee grounds, suggests that your dog is vomiting blood that`s been digested. A dog whose vomit looks like this could have a stomach ulcer, an intestinal blockage, or another serious condition causing internal bleeding.
Coffee ground emesis (or vomitus) is vomit that looks like coffee grounds. It`s dark brown or black in color with a lumpy texture. The appearance comes from old and coagulated blood in your gastrointestinal tract. It`s a sign of internal bleeding.
Stomach acid, or gastric acid, is a watery, colorless fluid that`s produced by your stomach`s lining. It`s highly acidic and helps break down food for easier digestion. This helps your body absorb nutrients more easily as food moves through your digestive tract.
Black vomit can be due to your dog ingesting something of a similar color (such as farm animal poo or mud/dirt). However, black vomit can also indicate digested blood caused by eating toxins or bleeding within the gut. Black vomit shouldn`t be considered normal, and urgent veterinary advice should be sought.
Brown. Brown vomit usually indicates the regurgitation of food that was never properly digested. It usually occurs when a dog eats too fast or swallows too much air gulping down their food. In most cases, you should be able to see undigested kibble or wet food chunks in the vomit.
If your dog`s vomit is dark, red, or black, veterinarians recommend contacting your veterinarian as soon as possible. It`s always a good idea to check with your veterinarian if anything seems off, because a dog vomit color guide is just that—a guide and not a diagnosis.
Prompt attention from a veterinarian should be sought if your dog vomits multiple times in one day or for more than one day in a row. In addition, you should seek veterinary attention if your dog shows the following symptoms accompanied by vomiting: Loss of appetite. Change in frequency of urination.
In cases where the cause is thought to be dietary indiscretion, your veterinarian may advise you to withhold food for a short time, until vomiting appears controlled. After this time, you may be advised to feed your dog a bland, easily digested diet.
Most people fully recover from the most common types of food poisoning within 12 to 48 hours. Some types of food poisoning can cause serious complications. Death from food poisoning in people who are otherwise healthy is rare in the United States.
If your dog vomits green, brown, or yellow liquid, it`s usually harmless. But if your dog`s vomiting red liquid, or even black vomit with a coffee-grounds appearance, it can mean bleeding from your dog`s stomach or other parts of the GIT. This can be an emergency and you would need to contact your vet immediately.
One of the most common ways to help a dog that is recovering from vomiting is to feed them a bland diet (usually white rice, sweet potato, boiled chicken or white fish). If your dog has been treated by your vet then they may also give your dog a specially prescribed diet and some medication to help them feel less sick.
Bile is a greenish-yellow liquid made and released by the liver and stored in the gallbladder. It aids in the digestion of food and fluids by breaking down fats into fatty acids. Your body then takes up these acids into the digestive tract.
It may be fresh and bright red, or older, darker and coagulated, like coffee grounds. Hematemesis is a sign of internal bleeding from the upper portion of your digestive tract — the esophagus, stomach and first portion of your small intestine called the duodenum.
Vomiting that is very forceful or continues for a very long time may cause a tear in the small blood vessels of the throat. This may produce streaks of blood in the vomit. Swollen veins in the walls of the lower part of the esophagus, and sometimes the stomach, may begin to bleed.
The colors from yellow to red indicate an acidic solution, colours blue to violet indicate an alkaline solution and a green colour indicates that a solution is neutral.
It is possible for a dog to vomit blood and still appear normal, depending on the underlying cause of the bleeding. Some possible causes of vomiting blood in dogs that may not cause significant illness include mild gastrointestinal irritation or inflammation, foreign body ingestion, and tumors.
Some of the signs of parvovirus include lethargy; loss of appetite; abdominal pain and bloating; fever or low body temperature (hypothermia); vomiting; and severe, often bloody, diarrhea. Persistent vomiting and diarrhea can cause rapid dehydration, and damage to the intestines and immune system can cause septic shock.
Intestinal parasites, including hookworms and roundworms, have both been known to cause bloody vomit in dogs. In particular, hookworms can be particularly damaging to the lining of the intestinal tract.
It is important to note that many dogs may not show every clinical sign, but vomiting and diarrhea are the most common and consistent signs; vomiting usually begins first. Parvo may affect dogs of all ages but is most common in unvaccinated dogs less than one year of age.
Although vaccination is effective at preventing Parvo, even vaccinated dogs may occasionally be infected by Parvovirus and develop disease. The vaccine provides immunity against the virus, but it is not 100% effective.

Relevant Questions and Answers :

the most relevant questions and answers related to your specific issue

Q. Rescued a dog almost two weeks ago, and now that her kennel cough is gone her personality shines!! No previous training, how should I start?
ANSWER : A. POST FOUR:

After your dog is familiar with the behavior you lured from scratch, and taught to your dog, you can start to use the “no-reward marker” I talked about. What you do is ask the dog to perform the behavior, and if the dog does not perform the behavior, you simply say your no-reward marker (choose one: eh-eh, hey, uh-oh, oops) show them the treat, put it behind your back, and BRIEFLY ignore your dog. Just turn your back for a second or two, before turning back to your dog and saying, “let’s try that again.” When you’re ready to start over with your dog, make sure you move around. If you are repeating the same cue while in the same position, while your dog is in the same position, you are likely to receive the same results. The more you move around, and start fresh, the better your chances are of having your dog listen to your cue the second time around. BIG rewards when they dog it successfully! Lots of praise and treats.

My no-reward marker is “hey.” When my dog does something wrong I say, “hey” and she immediately understands that she needs to offer a different behavior. This is clear to her. I don’t have to say it in a mean way, I simply say, “hey” in a normal tone of voice and she understands what the word means.

Once you’ve built up that connection and communication with your new dog, you can work on all kinds of fun behaviors! I personally enjoy the more zen-like behaviors: https://www.youtube.com/watch?v=ruy9UMcuGh8

I like to teach my dog fun tricks that offer her a “job” to do of sorts like object retrieval: https://www.youtube.com/watch?v=I4iertZSva8

(object retrieval training completed; what it looks like: https://www.youtube.com/watch?v=jx0Dml28FGY)

Scent-games are fun too! Very confidence building. Hide a REALLY smelly treat in a box, and place that box in a line of boxes. Let your dog go in the room while saying something like “search!” or “find it!” and watch them hunt for that smelly treat! Lots of rewards when they find it!

Q. Whenever I take my dog on walks he always barks at people and others dogs in my neighborhood. What should I do to resolve the problem
ANSWER : A. The very first thing to do is to make sure your dog is getting sufficient physical and mental exercise every day. A tired dog is a good, happy dog and one who is less likely to bark from boredom or frustration. Depending on his breed, age, and health, your dog may require several long walks as well as a good game of chasing the ball and playing with some interactive toys.

Figure out what he gets out of barking and remove it. Don’t give your dog the opportunity to continue the barking behavior.

Ignore your dog’s barking for as long as it takes him to stop. That means don’t give him attention at all while he’s barking. Your attention only rewards him for being noisy. Don’t talk to, don’t touch, or even look at him. When he finally quiets, even to take a breath, reward him with a treat. To be successful with this method, you must wait as long as it takes for him to stop barking. Yelling at him is the equivalent of barking with him.

Get your dog accustomed to whatever causes him to bark. Start with whatever makes him bark at a distance. It must be far enough away that he doesn’t bark when he sees it. Feed him lots of good treats. Move the stimulus a little closer (perhaps as little as a few inches or a few feet to start) and feed treats. If the stimulus moves out of sight, stop giving your dog treats. You want your dog to learn that the appearance of the stimulus leads to good things.

Teach your dog the ‘quiet’ command. Oddly, the first step is to teach your dog to bark on command. Give your dog the command to “speak,” wait for him to bark two or three times, and then stick a tasty treat in front of his nose. When he stops barking to sniff the treat, praise him and give him the treat. Repeat until he starts barking as soon as you say “speak.” Once your dog can reliably bark on command, teach him the “quiet” command. In a calm environment with no distractions, tell him to “speak.” When he starts barking, say “quiet” and stick a treat in front of his nose. Praise him for being quiet and give him the treat.

As in all training, always end training on a good note, even if it is just for obeying something very simple, like the ‘sit’ command. If you dog regresses in training, go back to the last thing he did successfully and reinforce that before moving on again. Keep sessions short, 15-20 minutes max, and do this several times a day.

Q. Why does my dog eat grass?
ANSWER : A. As another user mentioned, dogs can eat grass when they want to vomit. Sometimes, when a dog has an upset tummy, they will eat grass. If you notice your dog eating grass frantically, you can assume vomiting will shortly follow. Grass does not digest and pass normally. If your dog eats too much grass, it can cause serious issues with pooping. Your dogs poop can end up all tangled inside of her, and it can need veterinary assistance to remove it. The same goes for celery, so avoid feeding celery to your dog.

The other day my boyfriend accidentally left the laundry room door open where we were keeping the trash that was filled with cooked chicken bones. She ate one of the chicken bones lightning fast. We had to induce vomiting by feeding her some hydrogen peroxide. After we had fed her the peroxide, she immediately began frantically eating grass because her tummy was upset.

If there is something lacking in your dogs diet, it could be that your dog is eating grass to make up for it. I am sure that my dogs diet is extremely well balanced (I do not only feed her an air-dried raw food-type diet (Ziwipeak), but a wide variety of safe, healthy foods), so when she eats grass, I know that it is because she has an upset tummy.

That is why I think it is important making sure your dog has a very well balanced diet. If your dog is on a low quality kibble, your dog may be trying to let you know by eating grass (or eating poop).

Q. How do I determine how much my overweight pet should weigh?
ANSWER : A. There are many tools to determine overweight and obesity levels in pets. A new tool, morphometric measurements and body fat index, are available to accurately determine a pet’s ideal weight; this will allow an accurate determination of the amount of food a pet should receive to achieve weight loss. Feeding the correct amount will lead to greater weight loss success.

There are many weight loss food options to help pets reach their ideal weight. Your veterinarian can help make a ideal weight recommendation. Here are some tips to help your dog lose weight in a healthy and safe way:

1. Diet: Providing a healthy and well balanced diet is essential to your pet’s overall health. Finding the right food for your dog can be a challenging process. For those overweight animals many commercial dog companies offer weight loss diets, but it is important to evaluate food labels for adequate nutritional content.

You want to ensure you are not missing other essential vitamin or mineral content. Volume of food is also important and the amount of food that works for one breed of dog may not be the same for another breed of dog. Portion control as opposed to free-choice feeding can help your dog to drop a few unnecessary pounds.

There are also prescription weight loss foods designed by veterinary nutritionists, such as Hill’s r/d (http://bit.ly/1AoENSd). Some pet owners find that home cooking is the best option for helping to provide a well-balanced and realistic diet plan. There are websites such as balanceit.com that offers recipes to fit your dog’s specific needs. Consulting with your veterinarian or a veterinary nutritionist to find the appropriate diet is a great way to help your dog be as healthy as possible.

2. Exercise: Another great tactic for weight loss for your dog is exercise. Whether this is through running, walking or playing with a favorite toy all of these are wonderful types of exercise to help keep your dog at a lean and healthy weight.

For those pet owners with busy schedules utilizing professional dog walking services or playtime through dog daycare services is another option. It has been shown that those pet owners that exercise regularly with their pets generally live a healthier lifestyle.

3. Physical therapy: As animals age pet owners offer encounter their favorite canine having more difficulty walking and have a dwindling desire to play with toys. Physical therapy, specifically hydrotherapy is a wonderful way to help older and arthritic animals gain more mobility and lose weight. Hydrotherapy has been proven to have several therapeutic effects on the body including, muscle strengthening, relief of swelling, decreased joint pain, less stiffness in limbs, improved circulation, weight loss, and increased tissue healing to name a few. For more information on the benefits of hydrotherapy:
http://bit.ly/1w1qqoy

4. Veterinary visit and blood work: Weight gain can also be related to underlying health concerns such as hypothyroidism or other endocrine disorders. Scheduling a veterinary evaluation and routine blood work can be another important component in increasing the longevity of your dog’s life. Conditions such as hypothyroidism that predispose dogs to gain weight can be treated with a daily medication to improve hormonal balance. If feel that your dog is unnecessarily overweight there can be an underlying health condition that needs to be addressed.

5. Healthy treats: Pet owners love the chance to reward their favorite canine companion with treats and most dogs jump at the chance to consume these delicious products. The problem is many treats, which can include commercial dog treats or table scrapes can add many unnecessary calories to your dog’s daily intake. Reading labels and making note of the calories in these treats is an important component of understanding your dog’s overall health. Treats should not exceed more than 10 percent of your pet’s daily calories. There are healthier treats that can be offered to your pet to keep calories lower yet provide a fuller sensation. A pet owner can add steamed or pureed vegetables, such as carrots, green beans or sweet potato to add more fiber and thus a fuller feeling for your dog.

Q. Which common foods are poisonous to pets?
ANSWER : A. That’s a great question. As responsible pet owners we need to be aware of food items that can be harmful to our canine or feline companions. Here are some of the most common foods proven to cause illness in our animals at home:

Chocolate: A favorite and irresistible treat amongst most humans, chocolate is considered toxic to dogs. In very small amounts it is usually not a huge issue, but with larger volumes and with darker chocolates pet owners should be concerned. Chocolate contains methylxanthine theobromine, which is similar to caffeine. Chocolate ingestion can cause vomiting, diarrhea, hyperactivity, issues with normal heartbeats, seizures, and in some severe cases, death. It is best to keep your favorite chocolate treats in a good hiding spot and out of reach of your dog or cat.

Grapes and raisins: Dogs should not consume grapes and raisins because of the risk of acute kidney failure. Most dogs experiencing grape or raisin toxicity will begin to have vomiting and/or diarrhea within 6-12 hours of ingestion. Other abnormal clinical signs include lethargy, abdominal pain, dehydration, and tremors. Kidney failure develops within 24-72 hours of the initial ingestion. There are some dogs that do not experience these devastating side effects. It is best to contact your veterinarian or veterinary emergency facility if you believe your pet has ingested grapes or raisins.

Garlic and onions: We often forget that our meals contain these two popular ingredients and will allow our furry companions a few bites or licks. Onion and garlic both can cause a type of poisoning that results in damage to red blood cells, making them more likely to rupture. They can also cause stomach upset and mouth irritation. Look for pale gums, increased breathing or drooling or any vomiting or diarrhea.

Bread dough: Unbaked bread dough is considered poisonous to our pets. The bread dough, when ingested, expands in the stomach because of the warm and moist environment. This can lead to a bloated or even twisted stomach. In addition yeast is often added to our baking products to help get bread to rise, and when this yeast is fermented it produces both carbon dioxide and alcohol. The alcohol produced can be absorbed into the bloodstream and causes dangerous drops in blood sugar, blood pressure and body temperature. Common clinical signs include vomiting or retching, distension of the stomach, weakness and collapse.

Macadamia nuts: Ingestion of these nuts are not proven to be fatal in dogs but can cause them to experience uncomfortable clinical sings, including fever, joint stiffness, vomiting, tremors and difficulty walking, especially in their hind legs. Often your pet will start to feel better after about 48 hours, but supportive veterinary care (such as pain medication) may help ease their discomfort.

Xylitol: The most common ingredient used in sugar-free gum is xylitol, which is a non-caloric sweetener. It is also found in some oral rinses, toothpastes and vitamins. Xylitol and dogs do not mix – it can cause a dangerous drop in blood sugars levels. Dogs will often display signs of disorientation, black tarry stool, tremors and seizures. If severe enough some dogs have developed liver failure. Keep your gum away from your canine companion.

Avocados: Avocados are not actually poisonous to dogs or cats but as many veterinarians can tell you the avocado pits can cause a foreign body obstruction. Avocados contain persin, which is actually toxic to the majority of pet birds. The abnormal clinical signs associated with avocado ingestion in birds include, respiratory distress, inability to perch, liver and kidney failure and sudden death.

Go forth and enjoy your favorite foods, but keep in mind which foods you should avoid sharing with your furry family members. Whenever in doubt, contact your veterinarian for healthy and safe food suggestions.

Q. Why do dogs eat grass?
ANSWER : A. Some pet parents get concerned when they see their favorite canine nibbling on grass in the yard. They wonder whether it is because hunger, boredom or an indication of an underlying illness. Often the consumption of grass will result in vomiting because it irritates the stomach and gastrointestinal tract. This is an extremely common problem for dog parents. There is no one reason for why dogs exhibit these behaviors and it is very much dependent on each dog. Here are some of the reasons why our dogs choose to eat grass:

1. Nutritional Issues

Historically speaking, dogs are considered omnivores, which mean they consume a variety of both meat and plant-based food. There is some indication that dogs with a low fiber diet may choose to scavenge in the grass to fulfill this nutritional deficiency. These dogs may also find that grass has an appealing flavor and consistency. If you feel that this may be the reason for your beloved canine consuming grass then consider discussing with your veterinarian on how to incorporate more fiber into your dog’s diet.

2. Boredom

Many dogs who are not receiving adequate exercise will be become bored and search out activities to occupy their time, including eating grass. Evaluate how much exercise your dog is getting on a daily basis and consider more walks or other fun activities, such as playing fetch or tug of war.

3. Upset Stomach

There is a belief that dogs with an upset or gassy stomach will self-medicate by consuming grass. Vomiting often follows this grass eating activity eliminating the contents of the stomach or changing the gas distension within the gastrointestinal tract. However, there is not much scientific evidence to back up this theory. If you are concerned about too much gastric acid in your dog’s stomach or any other underlying medical issue that could be the reason for their grass eating, consult with your veterinarian.

Overall, grass eating is usually not toxic to your dogs unless your lawn contains chemicals, including pesticides or herbicides. Monitor your dog’s behavior along with his diet and exercise to determine if there is a reason for the inappropriate grass snacking.

Q. What can I do to stop my dog from barking at people and front doors?
ANSWER : A. Ignore your dog’s barking for as long as it takes him to stop. This means don’t give him any attention at all while he’s barking. Your attention only rewards him for being noisy. Don’t talk to him, don’t touch him, and don’t even look at him. When he finally quiets down, even to take a breath, reward him with a treat. To be successful with this method, you must wait as long as it takes for him to stop barking. If he barks for an hour and you finally get so frustrated that you yell at him to be quiet, the next time he’ll probably bark for an hour and a half. Dogs learns that if they bark long enough you’ll give them attention.

Teach your dog the ‘quiet’ command. It may sound nonsensical, but the first step is to teach your dog to bark on command. Give your dog the command to “speak,” wait for him to bark two or three times, and then stick a tasty treat in front of his nose. When he stops barking to sniff the treat, praise him and give him the treat. Repeat until he starts barking as soon as you say “speak.” Once your dog can reliably bark on command, teach him the “quiet” command. In a calm environment with no distractions, tell him to “speak.” When he starts barking, say “quiet” and stick a treat in front of his nose. Praise him for being quiet and give him the treat.

When your dog starts barking, ask him to do something that’s incompatible with barking. Teach your dog to react to barking stimuli with something that inhibits him from barking, such as lying down in his bed.

Make sure your dog is getting sufficient physical and mental exercise every day. A tired dog is a good dog and one who is less likely to bark from boredom or frustration. Depending on his breed, age, and health, your dog may require several long walks as well as a good game of fetch and playing with interactive toys.

Q. How do I desensitize my dog to squirrels and stray cats in the neighborhood?
ANSWER : A. It depends on the goal that you have in mind. I am going to assume that you would prefer that your dog not chase squirrels or stray cats in the yard/street. In this case, your options include: (1) training your dog on a “Leave it ” cue using positive reinforcement methods, (2) training your dog not to pull on its leash when it sees a squirrel/stray cat, and (3) training your dog to perform a more desirable behavior when it sees a squirrel/cat.
Training your dog on a cued “leave it” command is useful because it will give you the ability to tell your dog to stay away from any number of undesirable objects on your command. Training your dog to perform a more desireable behavior when it sees a squirrel or cat will substitute a behavior you find acceptable (sitting, laying down, coming to the door, etc.) with a behavior you dislike. Your dog can still react, just in a positive way. If your dog pulls on the leash every time you see a squirrel/cat, training not to pull will make your walk safer and more pleasant.
The ideal training method to use with dogs, or any animal for that matter, is positive reinforcement training, particularly a method called “clicker- training.” The basic concept of positive reinforcement training is to pair a reward (reinforcement) with a behavior you want to increase in frequency. In other words, when your dog performs the behavior you desire, it receives an award, which reinforces the desired behavior so you get more of that behavior. There are many excellent books in stores or on-line that describe positive reinforcement training in detail and many give step-by-step instructions for training common commands like “leave it”. Look for books that specifically mention positive reinforcement training or clicker-training. You can also take dog training classes to learn the techniques, find a mentor who already uses clicker-training, or request a consult from one of the pet experts on this site to guide you.