Is your dog drinking enough - or too much?
Dogs need a continuous supply of water, especially in warm weather, and particularly after exercise. They need water for more than just their daily maintenance requirements; depending on how a dog is spending their time, their water requirements can go up and down dramatically.
There are four main areas where water is needed by dogs.
First, there is a continual low level of water needed to allow the normal metabolism to function. Water is needed all around the body, for the liver, kidneys, blood supply, and for many other reasons. A dog's body is made up of around 60|% water, and this needs to be topped up continually. The amount of water needed depends on the size of the animal, but typically it's around 30 - 50ml per kilogram body weight. This means that a small 5kg terrier might drink around 150 - 250ml (up to half a pint) every day, while a 30kg Labrador might drink between 900ml and 1.5 litres (up to 3 pints) daily.
Owners need to ensure that their dog has a continual supply of fresh water in their bowl. This is normally placed beside their food bowl, and topped up once or twice daily. The bowl should also be emptied, cleaned and refilled regularly; just as humans don't like drinking water that's been sitting there for over a week, neither do dogs.
It's good practice for owners to monitor how much their pet is drinking, perhaps measuring the precise amount every few months. If they are drinking significantly more than the amount I have mentioned, there could be an underlying disease issue. There are many conditions that can cause an increase in thirst, including diabetes, kidney disease and liver disease. If a pet suddenly starts drinking more water than normal, you should collect a urine sample, and go to the vet. Early diagnosis of illnesses allows prompt treatment, which is more likely to lead to a prompt and effective cure.
The second reason for dogs to need water is temperature control. Dogs cool down by panting; if they get too hot, they pant rapidly. When they pant, warm moist air evaporates from the surface of their tongue, taking heat out of the body. This is a water-intensive process: a panting dog might take 150 breaths a minute. If they lose 0.25ml (a twentieth of a teaspoonful) with every breath, that makes 37.5ml minute, or 2250ml (4 pints) an hour if they are continually panting. When you read these figures, it's obvious that it's essential that dogs have a plentiful supply of fresh water in hot weather.
The third reason why water is needed is exercise. When dogs run, as well as producing heat (which, as explained, needs water to allow cooling to take place), the body also produce toxins and metabolites, such as lactate and carbon dioxide, in the muscles. These need to be removed from the muscles by the blood stream, and then they're metabolised and excreted by the liver, lungs and kidneys. These processes all need water. A dog that is exercising heavily has a greater water requirement than a dog that's resting. This is why the first thing that dogs do after a walk is to take a deep drink of water.
The fourth reason why dogs need water is because of disease processes. The body has a natural inclination towards keeping a balance of hydration, and some diseases upset the balance. Examples include vomiting and diarrhoea, where fluid is lost from the front and back end of the dog. Other diseases that affect the water balance include diabetes (too much urine is produced, leading to water loss), womb infections (fluid accumulates inside the womb, taking the fluid out of the circulation) and there's a long list of other conditions too. The dog's body naturally wants to replace the lost fluid in such situations, and an increase in thirst is often the first sign to an owner that their pet is in the early stages of an illness.
Generally, if a dog is offered continual fresh water, they will drink enough to ensure that their body stays at the right level of hydration. There are some instances where a dog cannot drink enough to replace the missing fluids. The most obvious example is serious gastroenteritis with repeated bouts of vomiting and diarrhoea. In such cases, the dog cannot drink enough water to replace the fluids that are being lost. Severe dehydration follows, which can be life threatening. Affected animals need to be taken to the vet for intravenous fluids to correct their fluid balance.
Vets are adept at assessing animals' fluid balance. A simple physical examination can be enough (e.g. checking for sunken eyes and skin that "tents" when pinched, rather than flattening down immediately), but a blood test is the best way to carry out a detailed assessment. Oral fluids containing electrolytes can be enough to rehydrate mild cases, but a drip of intravenous fluids is often the fastest and safest way.
When I first heard about bottled water for dogs, I thought this was another fad. However, on reflection, the idea has strong merit. Dogs need to be encouraged to drink. A special, flavoured water (to encourage dogs to drink it), with a blend of electrolytes to help a dog's fluid balance?
Yes, I can see that this has a role to play, especially in a summer of hot weather, with thirsty dogs all around.