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

Lay Summary Accurate feed intake estimates are challenging to obtain, especially when individual animal feeding cannot be feasibly measured. Titanium dioxide is an indigestible compound, used for estimating fecal output in ruminants. Intake can then be estimated using fecal output and feed digestibility. Various methods exist for measuring feed digestibility: in vitro methods are often used for feed characterization, while in vivo methods provide digestibility on a per-animal basis. This study evaluated the accuracy of titanium dioxide to estimate intake from heifers consuming either haylage or a total mixed ration, by dosing once or twice daily with a titanium dioxide-containing bolus and comparing the intake predictions from an intensive and less intensive fecal sampling schedule. Results showed intake estimates were not improved by increasing the intensity of dosing and fecal sample collection. Once daily dosing with either an in vitro or in vivo digestibility estimate can provide accurate intake estimates. This provides researchers with alternatives for estimating feed digestibility since certain techniques rely on the use of cannulated animals or specialized laboratory equipment.