Design of digestibility trials for dogs and cats

The Association of American Feed Control Officials (AAFCO) have recently published recommendations for standard protocols for measuring the apparent di gestibility of diets for cats and dogs (AAFCO 1993). The protocol recommends a 5-d precollection or ad aptation period followed by a 5-d period of feces col lection for both species. The domestic cat is an obligate carnivore, whereas the dog has adapted to a more var ied diet, and it seems likely that the latter may be more adaptable to a varying diet. Previous studies have shown differences in the digestibilities of diets in cats and dogs (Kendall et al. 1982), although adaptation to the diet over time was not examined. The purpose of this experiment was to examine whether this protocol is suitable to measure apparent digestibility in both cats and dogs. Materials and methods. Experiment 1: Digesti bilities measured over different collection periods. A diet designed to meet the nutrient requirements of both cats and dogs (moisture 71.8, protein 11.4, fat 8.5, carbohydrate 6.1, ash 2.2 in g/100 g) was fed to four adult cats and six adult male beagles for 21 d. Feces were collected over three time periods: days 47, days 8-14 and days 15-21. Food and feces were analyzed for gross energy (bomb calorimetry), protein (Dumas method), fat (acid-ether extract), ash and moisture (thermogravimetric analysis) to determine apparent digestibilities. Experiment 2: Feces output of cats. Six groups of six cats each were fed one of six different diets (4 canned and 2 dry) for a total period of 21 d as above. Wet feces output over days 8-14 and 15-21 were re corded. For each diet wet feces output per 100 g dry matter eaten was calculated for each cat over each time period. Differences between the time periods were compared using Student's paired t test and Duncan's