Determining the protocol requirements of in-home dog food digestibility testing

Abstract

In-home pet food testing has the benefit of yielding data which is directly applicable to the pet population. Validated and standardised in-home test protocols need to be available and here we investigated key protocol requirements for an in-home canine food digestibility protocol. Participants were recruited via an online survey. After meeting specific inclusion criteria, 60 dogs of various breeds and ages received during 14 consecutive days, a relatively low and high digestible complete dry extruded food containing titanium (Ti) dioxide. Both foods were given for seven days in a cross-over design. Owners collected faeces daily allowing daily faecal Ti concentrations and digestibility of nitrogen (N), dry matter, crude ash, organic matter, crude fat (Cfat), starch and gross energy to be determined. Faecal Ti and digestibility values for all nutrients were not different (P>0.05) from the second day onwards after first consumption for both foods. One day of faecal collection yielded reliable digestibility values with additional collection days not reducing the confidence interval around the mean. Depending on the accepted margin of error, the food and the nutrient of interest, the minimal required sample size was between 9-43 dogs. Variation in digestibility values could in part be explained by a dog’s neuter status (N, crude ash) and age (crude ash, Cfat), but not sex and body size. Future studies should focus on further identifying and controlling sources of variation to improve the in-home digestibility protocol and reduce the number of dogs required.

Determining the protocol requirements of in-home cat food digestibility testing

“…As such, day 2.28 represented 42.7 h (2.28 × 24 h -12 h), whereas day 3.17 represented 64.1 h (3.17 × 24 h -12 h) post first food consumption. Therefore, findings indicate that fecal samples from day 3 onwards can be used for the determination of apparent fecal digestibility values, which is 1 day later than was found in our similar in-home digestibility study with 53 privately-owned dogs (8).…”

“…The differences in time to reach stable digestibility values (Figure 2; Table 2; Supplementary Figure S2) between CP, DM, Cfat and GE indicate different adaptation processes/ mechanisms. Compared to dogs (8), cats need 1 day longer to adapt, at least regarding Ti, CP, DM, Cfat and GE, which might be attributed to a less regular defecation pattern compared to dogs. The difference in ME requirements between dogs and cats (41), translates in higher amounts of food consumed by dogs compared to cats if foods with comparable ME contents are fed.…”

“…A longer adaptation period is, however, supported by differences for crude protein digestibility and wet feces output for days 8-14 compared to days 15-21 (7). The optimal period of adaptation warrants further investigation as in a recent study with dogs (n = 53) it was found that a 1-day adaptation period suffices to reach constant digestibility values (8). The digestive system adapts rapidly and digestive enzyme activity and microbiota composition changes within a few hours after changes in the amount and type of dietary protein, carbohydrate or lipid (9)(10)(11).…”

“…In the in-home study with dogs, 1 day was sufficient to reach stable fecal marker (Ti) concentrations for both a relatively high and a low digestible dog food (8). In cats, peak marker (chromium oxide) concentrations in feces have been reported at (mean ± std) 26.5 ± 5.8 h post meal consumption in 3 year-old cats (n = 6) and 35.7 ± 14.1 h in 11 year-old cats (n = 6), as determined in dedicated feline research facilities (15).…”

“…Having several fecal collection days allows to smooth out day-to-day variation in fecal composition, and the pooling of fecal samples of pigs has been shown to result in more precise digestibility estimates (12). The day-to-day variation in digestibility estimates did not show in the group of pet dogs and the inclusion of multiple days did not increase the precision of digestibility estimates (8).…”