Preliminary study of a model describing the growth of grazing cattle
1990
Tsuiki, M. (National Grassland Research Inst., Nishinasuno, Tochigi (Japan)) | Shiyomi, M. | Koyama, N.
To estimate the various factors which affect the growth of grazing cattle, we attempted to construct a dynamic model of grazing cattle. This model simulates the input and output of energy and nitrogen which pass through grazing cattle. The model was described by the following two differential equations. DE/dt = E01 - E12 - E13 - E14, dP/dt = P01 - P12 - P13 - P14. where E and P are the amounts of energy (MJ) and crude protein (kg), t is time, E01 and P01 are the amount of energy and crude protein in grazed herbage, E12 and P12 are those in feces, E13 is the amount of energy in urine and eructation, E14 is the energy loss by respiration, P13 is the amount of crude protein in urine and P14 is that in scurf. Estimation of each parameter was based on NRC Feed Standard (Sixth Revised Edition, 1984). Data of the amount and the quality (dry matter digestibility and crude protein content) of available herbage for cattle, climatic conditions (air temperature and precipitation were necessary to calculate each parameter. As a practical example, the model was applied to data which were taken from grazing pasture at the National Grassland Research Institute, and eventually simulation experiments were carried out
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