Libro de Resúmenes / Book of Abstracts (Español/English)

Resumenes 106
Pastoral agriculture occupies around 20 % of the land surface of the
globe, and is directly or indirectly responsible for meeting the economic and
material needs of a substantial proportion of its human population. This
importance is similar for Argentinean ruminant productive systems, which
are primarily under grazing conditions. In such systems, herbage intake
(originated in the plant / animal interface) is the main determinant of the
animal response. Mathematical models has shown to be and important
research tool both for understanding and prediction. Most animal grazing
models require in advance measures or estimates of animal intake and feed
quality to predict animal performance. An intake model linked to an animal
performance model are the key components for whole-farm simulation.
Model calibration and evaluation is not a straightforward issue as individual
herbage and maize grain intake are not always readily available. The
objective of this study was, as part of a combined field and modelling
experimentation project, to develop and to evaluate a beef cattle finishing
model for predicting herbage intake and animal performance under different
herbage and maize grain allowances (g feed . g live weight -1 ).
Different component from the literature were selected, adapted and
calibrated to develop a dynamic and deterministic intake model linked to an
animal performance model. Two grazing experiments were carried out (88
animals) where herbage intake, maize grain intake (n-alkane and 13C
markers) and liveweight gains were individually recorded in free grazing
beef cattle fed a combination of herbage allowances and maize grain
allowances.
From the statistical evaluation can be concluded that the model in its
present state of development can reproduce experimental information under
a wide range of grazing conditions (including maize grain supplementation)
with acceptable accuracy and without bias.