During a diet trial for a cat, which type of product could invalidate the trial if given regularly?

• A. Hairball remedy
• B. Tuna-flavored treats allowed
• C. Regular dry kibble
• D. A flavored oral preventive

Answer: (D)

In a diet trial, the goal is to isolate the effect of the test diet on the cat’s GI signs, weight, and stool without introducing other variables. Giving a product regularly that isn’t part of the diet can confound the results. A flavored oral preventive is typically administered on a schedule and can influence appetite, digestion, or gut flora, and may even add calories or nutrients that distort how the diet alone would behave. This makes the trial’s outcomes harder to interpret. The other items are either components or allowable additions within a controlled plan, or are less likely to shift the GI or energy balance in a way that would completely invalidate the results.