Applicability of an automated supplement feeder to dose titanium dioxide to estimate forage intake, fecal output, and diet digestibility of beef cattle

Objective

Our objective was to evaluate 2 methods of external marker dosing, at 2 levels of forage allowance, to estimate forage intake in beef cattle.

Materials and Methods

Sixteen Aberdeen Angus steers (mean age of 18 mo; 350 ± 9 kg BW), kept in in- dividual pens, were used in a quadruplicated 4 × 4 Latin square design experiment, in a 2 × 2 factorial arrange- ment. The factors were forage allowance level (4 vs. 7 kg DM/d of alfalfa plus orchard grass haylage) and supple- ment feeding method (manual vs. automatic). A supple- ment consisting of 2 kg DM of pelleted corn with 1% ti- tanium dioxide (TiO₂) per day was offered to each steer. Total DMI and diet DM digestibility were estimated using the dual-marker technique, with acid insoluble ash (AIA; 2 different methods) or ADL used as the internal marker. Fecal output was estimated by TiO₂ concentration using feces from the daily total fecal collection (TFC) samples and others from a morning subsample. The TFC was car- ried out individually and daily during the last 4 d of each 21-d period.

Results and Discussion

The overall mean recovery of TiO₂ was 104% (SD: 0.05; range: 101–107%). Fecal subsamples obtained in the morning overestimated fecal production with no difference between dosing methods. The DM digestibility was overestimated with AIA and ADL. The estimation of DM digestibility by ADL was closer than AIA to those obtained by TFC, without differ- ences between the 2 AIA techniques. The overestimation of forage intake using the dual-marker technique was more affected by the overvalued DM digestibility using the in- ternal markers than by fecal production using the external marker, without the effect of the dosing method.

Implications and Applications

It is viable and reli- able to automatically supply pelleted corn with TiO₂ for fecal production estimation. The accuracy could be im- proved by obtaining at least 2 fecal samples during the day. Under the current experimental conditions, ADL is more accurate than AIA for estimating DM digestibility when the diet offered to cattle is based on alfalfa plus or- chard grass haylage and concentrate.