The mentality that your pet should eat the same thing, meal after meal, day after day, for its entire life, is pretty silly to begin with; but that's what we're told to do. Nobody would ever do this with their child, nor would any pediatrician recommend such nonsense. But the pet food industry has convinced most pet owners that, while nobody has come anywhere near such a magic diet for humans, they have devised the perfect diet for your pet.
It's bad enough that pet owners have been told to feed their pet one thing their entire life, but the industry has also largely succeeded in convincing people that any other diet regimen is unhealthy. Could you imagine your doctor telling you that eating anything other than Total cereal (hey, it has all your vitamins and minerals) three times a day was bad for you?
Feeding the same diet, over and over again, is more likely to be the cause of disease, sickness, and poor health. People often object to the idea of diet rotation at first, saying that their pets do well on a certain food, but how many times do they eventually switch because they have to? Allergies, food intolerances, and lack of interest (most pets get tired of eating one food day after day, imagine that) from their pets cause most people to switch foods more than once. Unfortunately, they do this because circumstances force them to, not because they're intentionally maintaining variety in diet for optimum health.
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