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November 2011
Jeff Grognet, DVM, BSc(Agr) & Louise Janes, BSc(Agr), DVM
Scalded grass due to dog urine
Grass Scalding
Urine. Some veterinarians call it “liquid gold” because it has incalculable value in determining a dog’s health status. However, puppy owners who have to clean it up call it a waste product. Likewise for people who take pride in their lawns. To them, dog urine is a force that wreaks havoc on their pristine green carpets.
Urine scalding of grass is so upsetting to some people that they won’t allow their dogs access to their beautifully manicured lawns. Others try to limit unsightly yellow urine stains by adding ingredients such as baking soda or apple cider vinegar to their dogs’ foods. These are seldom, if ever, effective.
To minimize urine damage to grass, it is important to understand the factors that affect it. The first is the makeup of the dog’s urine itself. The second is the natural resistance of the grass and soil to the effects of urine.
The sex of the dog also influences urine damage. Female dogs tend to urinate large amounts in one spot. Males urinate in little bits, and often not in the middle of the lawn. This makes urine scalding of lawns almost entirely a female dog problem.
Urine has three important characteristics – urine pH (acidity/alkalinity), nitrogen content, and salinity – that influence its effect on grass.
Urine pH is dictated by a dog’s metabolism. Typically, canine urine is slightly acidic, but diet affects it. For example, vinegar contains acid. Adding it to a dog’s food makes her body acidic. She responds by eliminating the excess acid in her urine, thereby lowering urine pH. Baking soda has the opposite effect. It is alkaline by nature so it raises urine pH. Tomato juice and vitamin C, other additives that supposedly ward off yellow spots, are mildly acidic.
Despite common beliefs, changing the pH of a dog’s urine has a very limited effect on lawn health. As well, after a short while on the supplement, the dog’s body adjusts and brings the pH back into the normal range.
Nitrogen content in the urine is the most significant factor that impacts grass health. The body excretes nitrogen in the form of urea which is then broken down into ammonia by soil bacteria. Ammonia at high concentrations is toxic to plants. It burns grass in the same way as excessive fertilizer.
Have you ever noticed how well grass grows around a urine-scalded spot? This is because the nitrogen eventually acts like natural fertilizer, promoting grass growth. When yellow spots are reseeded, they grow well the following season.
Urine salinity – the salt content – is the last factor. Concentrated urine has more salt (and more urea) than dilute urine. When the buffering ability of the soil can’t handle the amount of salt and nitrogen in the urine, the grass dies.
The negative effects of high nitrogen and salinity can be counteracted by diluting the urine with water. Thus, you can save your grass by following your dog around with a bucket of water and immediately splashing it over her urine spots. Alternatively, you can get your dog to drink more water to make her urine more dilute and less toxic.
However, the most effective way to combat lawn death from urine is to build up the soil’s natural buffers. This can be done by leaving grass clippings on your lawn or sprinkling compost, peat moss, or wood ashes on your grass. Under these conditions, the soil has a better ability to withstand a sudden dump of nitrogen, sparing the grass.
The last way to prevent urine scalding is to train your dog. Simply teach her to urinate in an area where scalding marks are of little consequence. This way, it won’t matter how often she urinates, whether her urine is acidic or alkaline, or whether it is too concentrated.
Urine Health
Have you ever noticed that your dog’s urine smells “stronger” if she has a bladder infection? And, if you have a lawn, the yellow spots on your lawn seem bigger? These are real changes and observant owners often wonder why they occur, but we can explain them if we look at what infections do.
Dogs with urinary tract infections have bacteria in their urine. And, many bacteria manufacture an enzyme (urease) that breaks down urea (a waste nitrogen product in the urine) to ammonia. Ammonia evaporates as a gas and is responsible for the unique (noxious) odor of “infected” urine.
Ammonia has another effect – it is toxic to grass. It kills lawn more aggressively than the urea in normal urine. If you suddenly see more dead, yellow spots on your lawn, your dog may be suffering from a urinary tract infection.
The conversion of urea to ammonia also makes urine more alkaline (has a higher pH). Veterinarians measure this on a urine test and use it for screening for infections.
Urine pH, in turn, influences what happens to minerals in the urine. Minerals that stay dissolved in normal urine (which is slightly acidic) can precipitate and form crystals (called struvite) in urine with a higher pH. In some dogs, these crystals readily coalesce into bladder stones. Thus, dogs with chronic bladder infections can develop stones.
The over-riding factor in treating and preventing stones is to keep infections under control but also maintain a dilute urine. Think of it this way – if you don’t drink enough, your urine becomes dark yellow. This concentrated urine contains lots of mineral. Obviously, this contributes to crystal, and possibly stone, formation.
If you drink a lot of fluid, your urine resembles water and contains very little dissolved minerals. Under these circumstances, crystals are less likely to form. Stones that are already present may even dissolve.
Urine concentration has a tremendous bearing on the occurrence of a second type of bladder stone – the oxalate stone. At one time, it was believed that acidic urine caused these stones to form, but we now know that oxalate stones can form in any pH. Also, cutting minerals in the diet has little effect. The best way to prevent oxalate stones is to stop the crystallization of minerals by ensuring the patient’s urine stays dilute.
To make your dog’s urine more dilute, her water intake must be increased. One way to do this is to feed canned food rather than dry food. Canned food is 75 percent water, so your dog takes in a lot more fluid while eating canned food compared to dry kibble.
Another way to promote water intake is to soak her dry food in water before feeding. If this is not enough (your veterinarian can do a simple urine test to see if the urine is sufficiently dilute), then dropping the dry food in the water bowl can help. She will lap water as she retrieves her food pieces.
Most bladder stones can be prevented by making your dog’s urine both colorless and odorless. The side benefit is that your dog will also be at a lower risk for urinary tract infections. She’ll produce a large volume of dilute urine that effectively flushes out the bladder regularly.
For more information contact Dr. Jeff Grognet or Dr. Louise Janes at
Mid-Isle Veterinary Hospital
5-161 Fern Road West
Qualicum Beach, BC
Tel (250) 752-8969
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