Comparison of In Vivo and In Vitro Digestibility in Donkeys

Area of Science:

• Animal Nutrition
• Digestive Physiology
• In vitro digestibility assays

Background:

• Accurate assessment of forage digestibility is crucial for formulating donkey diets.
• In vitro methods offer a potential alternative to labor-intensive in vivo digestibility studies.
• Donkey fecal inoculum has been explored for in vitro digestibility estimations.

Purpose of the Study:

• To compare in vivo and in vitro dry matter (DM) and neutral detergent fiber (NDF) digestibility in donkeys.
• To evaluate the reliability of using donkey feces as microbial inoculum for in vitro digestibility.
• To assess the predictive capability of in vitro results for in vivo donkey nutrition.

Main Methods:

• Four donkeys were used in a 4x4 Latin square design with diets of hay with or without flaked barley.
• In vivo digestibility was determined by total fecal collection over 6 days.
• In vitro digestibility was assessed using donkey fecal inoculum in an Ankom Daisy II Incubator for 60 hours.

Main Results:

• In vivo digestibility of DM and NDF was not significantly affected by the addition of flaked barley.
• In vivo digestibility estimates for DM and NDF were consistently higher than in vitro estimates.
• Equations predicting in vivo from in vitro data showed poor reliability (R² = 0.47 for NDF, R² = 0.21 for DM).

Conclusions:

• The current in vitro method using donkey fecal inoculum is not a reliable predictor of in vivo DM and NDF digestibility in donkeys.
• The discrepancy between in vivo and in vitro results suggests limitations in the in vitro model's accuracy for this species.
• Further research is recommended to optimize in vitro digestibility assays, focusing on sample size and incubation times for donkeys.