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Tropentag, September 15 - 17, 2021, hybrid conference

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Predicting Voluntary Dry Matter Intake of Bos indicus Cattle: A Case for Conceptual Models

Rodrigo Beltrame1, Christian Adjogo Bateki2, Uta Dickhoefer2

1University Hohenheim, Inst. of Agricultural Engineering, Tropics and Subtropics Group, Germany
2University of Hohenheim, Animal Nutrition and Rangeland Management in the Tropics and Subtropics, Germany


Productive performance of cattle in the (Sub-)Tropics is largely determined by their voluntary dry matter intake (VDMI). Conceptual mathematical models (CMM) have been suggested as a reliable option for predicting VDMI, although they have only been evaluated using meta-data. The present study assessed the reliability of three CMM to predict VDMI of 52 stall-fed (LW = 277.2 ± 74.1 kg ) and 45 grazing cattle (LW = 237.7 ± 27.7 kg) from ICRISAT near Niamey, Niger, and the Station du Sahel in Niono, Mali, respectively. The CMM of Conrad et al. (1964) (C1), the modified Conrad et al. (1964) (C2), and modified Mertens (1987) (M4) were selected based on their reported adequacy to predict VDMI of cattle kept under tropical conditions. For C1 and C2, VDMI is estimated as 0.0107 * LW/(1-D) and as DDM/D, where 0.0107 (increased to 0.0116 for C2) is the daily fecal output (g/kg LW), LW liveweight (kg), D digestible fraction per unit of ingested dry matter, and DDM digestible DM intake (kg/d). For C1 and C2, the lower VDMI estimate of the two equations was retained as predicted VDMI, while for M4, DMI is the mean of equations, 0.0135 *LW/NDF and MEreq/MEd, where 0.0135 is the maximum intake of neutral detergent fiber (NDF) intake (g/kg LW), NDF the NDF concentration in the diet (g/kg DM), MEreq the animal’s metabolisable energy (ME) requirements (MJ/d) and MEd the dietary ME concentrations (MJ/kg DM). Daily MEreq for maintenance was estimated as 0.631 MJ ME/kg LW0.75 and for gain as 0.0243 MJ ME/g LW gain. The CMM were statistically evaluated through the mean bias (MB), root mean square error predicted (RMSEP), and relative prediction error (RPE).
The CMM predicted VDMI more accurately for grazing than stall-fed animals. For both datasets, the M4 had lower MB (-0.11 and -0.8 kg per animal and day) and RPE (18.33) than C1 and C2 (MB > 1.4 kg per animal and day and RPE > 1.48). Therefore, M4 is the most reliable CMM however, further evaluation using better data is needed under stall-fed conditions.

Keywords: Bos indicus, conceptual models, voluntary dry matter intake

Contact Address: Rodrigo Beltrame, University Hohenheim, Inst. of Agricultural Engineering, Tropics and Subtropics Group, 70593 Stuttgart, Germany, e-mail: rodrigobeltrame@yahoo.com

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