Dosing frequency, fecal sampling, and digestibility method influence titanium dioxide-based intake estimates in dairy...

Area of Science:

• Animal Nutrition and Feed Evaluation
• Digestibility and Intake Measurement
• Marker Techniques in Animal Science

Background:

• Indigestible markers are crucial for estimating animal intake when individual feeding is impractical.
• Titanium dioxide (TiO2) is a widely used external marker for fecal output estimation.
• Accurate intake estimation requires reliable digestibility data, obtainable via feed analysis or internal markers.

Purpose of the Study:

• To evaluate the impact of diet and TiO2 dosing on intake estimates.
• To compare intake estimations using intensive versus less intensive fecal sampling.
• To assess the accuracy of TiO2 for fecal output and various digestibility methods for intake prediction.

Main Methods:

• A 2x2x2 factorial design tested two diets (grass haylage, total mixed ration), two TiO2 dosing schemes (once or twice daily), and two fecal sampling regimens (intensive vs. less intensive).
• In vitro digestibility methods included in vitro DM digestibility (IVDMD) and in vitro OM digestibility (IVOMD).
• In vivo digestibility methods included indigestible neutral detergent fiber (iNDF) and acid detergent insoluble ash (ADIA).

Main Results:

• Intake was overestimated for total mixed ration (TMR) using iNDF and underestimated for grass haylage (HLG), irrespective of TiO2 dosing or sampling.
• Neither increased TiO2 dosing nor intensive fecal collection improved intake estimation accuracy.
• Coupling TiO2 fecal estimates with in vitro digestibility methods yielded accurate intake predictions.

Conclusions:

• Accurate animal intake estimates can be achieved by combining TiO2 fecal output markers with appropriate digestibility estimation methods.
• Both iNDF and ADIA proved effective for accurate intake estimation.
• Acid detergent insoluble ash (ADIA) is a preferred method due to lower labor and no need for cannulated animals.