By Dr. Melissa Brookshire, DVM
Along with owning a dog come many benefits and sometimes a few drawbacks. One major drawback for homeowners is the grass staining that occurs in the yard. Grass staining is usually the result of the combination of 3 factors of the urine: urine concentration, basic or alkaline urine pH, and urine nitrogen content. Normal urine often burns the grass, particularly when dogs urinate in one spot. You might even notice that there is a ring of healthier, greener and taller grass around the burn spot. This is because the urea in the urine, when too concentrated will burn the lawn, but when diluted on the edges of the urine spot actually acts as fertilizer.
Concentrated urine has more solutes (particles which can affect grass health) than dilute urine. Female dogs’ urine may be more likely to cause more grass damage than the urine of male dogs because females typically squat and urinate in one spot, whereas males tend to urinate in smaller amounts as they wander from spot to spot or spray urine over a larger surface area. Making sure that your dog is well hydrated can help maintain a less concentrated urine, but this will not necessarily prevent the problem entirely.
Dogs typically have a fairly neutral urine pH, between 7 and 7.5. Diets that are very high in protein content will often lead to a lower (more acidic) urine pH. Some bacterial urinary tract infections can raise your dog’s urinary pH. In addition to infection, urinary pH is affected by many metabolic diseases and medications. Urinary pH below 6.0, while healthy for lawns, may not be so healthy for dogs, as it can lead to development of calcium oxalate crystals and stones in the urine. This is why diets for healthy dogs do not typically contain any ingredients to lower the urine pH.
Nitrogen metabolism is necessary for normal health. Nitrogen is an essential element present in all amino acids. It is derived from dietary protein intake, is necessary for protein synthesis and maintenance of muscle mass, and is excreted by the kidneys. Renal nitrogen excretion consists almost completely of urea and ammonia. Very high protein diets can increase the amount of both urea and ammonia in the urine.
There are a couple of other ways to deal with those burn marks. Simple tips such as hosing the lawn after your pet urinates can help prevent lawn damage. In addition, encourage your dog’s outdoor time to be when the lawn is at its peak moisture level, after precipitation, watering, or dew. Encourage your dog to utilize shaded areas of the lawn, as the soil will contain more water here to dilute the urine. One final tip is to take your dog to the edge of the grass , particularly if it is the first outing in the morning or after your dog has been indoors for a long time because the urine will be more concentrated at these times.
Changing the diet likely will not help much, if at all. Feeding a lower protein, higher carbohydrate diet may help raise the urine pH and lower the amount of urea in the urine, but may not be the right choice for a particularly active dog or a young dog.
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