A whole-farm model applied to a dairy system
M.E. WASTNEY, C.C. PALLISER, J.A. LILE, K.A.MACDONALD, J.W.
PENNO AND K.P. BRIGHT
Dexcel Ltd, Private Bag 3221, Hamilton, New Zealand
E-Mail:
NZSAP 2002 Abstract No. 31
Proceedings of the New Zealand Society of Animal Production 62:
120-123
The complex interactions between the biological, physical and
management aspects of a farm can be represented mathematically using a
computer model. A whole-farm model has been developed that links
published sub-models for cow metabolism together with climate-driven
pasture models, in a framework that allows for different management
options. The model framework is written in VisualWorks Smalltalk, with
submodels written in several programming languages linked to the
framework using Microsoft COM protocol. Predictions of the whole-farm
model have been compared with pasture and animal production data
obtained from a dairy system trial at Dexcel in the Waikato. The system
consisted of a herd of 19 cows, at a stocking rate of 3.2 cows/ha. The
Whole Farm Model was used with Baldwin's MOLLY cow model of metabolism,
the McCall (1984) model of pasture growth, daily climate data and a
management policy whereby daily activities on the farm were enacted by
the framework. These activities included, for example, assignment of
paddock for grazing, closure and cutting of paddocks for conservation,
calving and drying off dates of each cow, and supplement feeding. At the
end of each season the whole-farm model predicted 75% of pasture growth
compared with observed values assessed by visual assessment, 98% of milk
yield and 98% of cow live weight. In addition to annual production by
the whole farmlet, the whole-farm model can simulate individual animal
and paddock production on a monthly and daily basis, so that patterns of
change can be compared over the whole season. The whole-farm model is
being used as a tool to design and analyse new dairy farm systems.
Keywords: NZSAPAB;
farm system; model; computer model; simulation
Last Updated 30/07/2002
