03580nam a2200277 a 450000100080000000500110000800800410001902200140006002400330007410000140010724501800012126001290030150005220043052021590095265300120311165300120312365300120313565300130314765300130316065300380317370000170321170000170322870000200324570000180326570000190328310645982024-04-17       2024    bl uuuu     u00u1 u    #d  a2590-28737 a10.15232/aas.2023-024482DOI1 aRAMOS, B.  aApplicability of an automated supplement feeder to dose titanium dioxide to estimate forage intake, fecal output, and diet digestibility of beef cattle.h[electronic resource]  aApplied Animal Science. 2024, Volume 40, Issue 2, pp. 132-141. https://doi.org/10.15232/aas.2023-02448 -- OPEN ACCESS.c2023  aArticle history: Available online 27 March 2024, Version of Record 27 March 2024. -- Correspondence:  Clariget, J.; Instituto Nacional de Investigación Agropecuaria (INIA), Estación Experimental La Estanzuela, Ruta 50 km 11, Colonia, Uruguay; email:jclariget@inia.org.uy -- FUNDING: This research was supported by the Instituto Nacional de Investigación Agropecuaria (INIA), Uruguay (grant numbers N-19407, 2016). -- LICENSE: Article under a Creative Commons license (http://creativecommons.org/licenses/by/4.0/ ).  aABSTRACT.- 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 individual 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 supplement 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 carried 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 differences 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 internal markers than by fecal production using the external marker, without the effect of the dosing method. Implications and Applications: It is viable and reliable to automatically supply pelleted corn with TiO2 for fecal production estimation. The accuracy could be improved 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 orchard grass haylage and concentrate. © 2024 The Author  aGrazing  aHerbage  aMarkers  aRuminant  aSelf-fed  aSISTEMA GANADERO EXTENSIVO - INIA1 aBANCHERO, G.1 aLA MANNA, A.1 aCANOZZI, M.E.A.1 aFERNANDEZ, E.1 aCLARIGET, J.M.