Determining key protocol requirements for in-home cat food palatability testing

In-home palatability testing of cat foods has the benefit of producing outcomes that are highly representative for the target pet population. Here, we determined the minimal in-home cat food palatability study duration and sample size. Privately-owned cats participated in either a one-bowl acceptance test (14 female,18 male; 6.2±4.6 yr; 4.5±1.3 kg) or two-bowl preference test (13 female, 17 male; 5.9±3.3 yr; 4.3±1.1 kg) where they were provided two complete extruded dry foods. The two foods provided were formulated to contain either a high (food H HP and H LP ) or low contrast (food L HP and L LP ) in palatability. The one-bowl test was done in a cross-over design. Feeding periods for both tests were 10 days and food leftovers were weighed daily to assess test food intake. Food intake percentages (one-bowl) and ratios (two-bowl) were analyzed across days using repeated measures ANOVA with post hoc Tukey tests. Bootstrap sampling was used to assess the impact of increasing the number of test days and sample size on the precision of the food intake estimates. There were no significant differences across days in one-bowl food intakes nor two-bowl intake ratios regardless of foods indicating that one test day suffices. More test days did reduce variation in the food intake measurements, thus increasing precision, but decreased test accuracy as cats with low food intake became missing values when dropping out of the study population. Increases in sample size increased precision, and the required number of cats for reliable outcomes varied between foods, food intake measurements and chosen margin of error. When implementing a margin of error of 10%, sample sizes would range from 12 to 43 cats in one-bowl trials, depending on the food in the acceptance test, and 17 to 23 cats in two-bowl trials, depending on the contrast in palatability between the foods in the preference test. The development of protocols for in-home palatability testing of cat foods may progress further by identifying and controlling sources of variation in the cats’ food intakes as a means to increase the precision of measurements. • A one-day test provides reliable test outcomes for in-home acceptance and preference testing • Inclusion of more test days increases precision, but decreases accuracy • A sample size between 12-43 provides reliable test outcomes • The required sample size depends on the food, food contrast and accepted precision level