Estimation of plant and cattle growth using the energy-flow model in grazed pasture.

对高羊茅放牧草地太阳能流动进行了系统分析。为了确定OKUBO-JACQUARD（1985）模型的初始值和参数，在放牧条件下每隔三或四周测定高羊茅的干物质生产。将植物材料分成每个植物器官，并在体外测定消化率。测定了牧草有效量、采食量、剩余有效量、可消化牧草量和体重变化（日增重），并换算成能量值。计算了能量流动各阶段的光能转化效率，分析了能量流动各阶段的光能转化效率的季节差异，结果表明，黑白花犊牛的日增重在春、秋初为1.1kg/头，夏秋末为0.0kg/头，其增重主要取决于采食量。春季和初秋，每公斤活重的日采食量约为0.03kg，夏季约为0.02kg。牧草的消化率差异不大，消化能向代谢能的转化效率有季节性变化，夏季很低。从放牧条件下产热的测量结果可以推断，小牛可能会在夏季通过减少摄入量来控制自己较低的产热。放牧犊牛的ME/DE转换率在整个季节都低于SRC（1965）的值。

A systems analytical approach was carried on the flow of solar energy in grazed pasture of Tallfescue. To determine the initial values and parameters for the OKUBO-JACQUARD model (1985), the dry matter production of Tallfescue under grazing was measured in every three or four week intervals. The plant materials were divided into each plant organ and measured in digestibility in-vitro. Herbage available, herbage intake, residual herbage available, di-gestible herbage and body weight change (daily gain) were also measured and converted into the energy values. Solar energy conversion efficiency in the each step of energy flow was calculated and it's seasonal difference was analyzed.Daily gain of Holstein-Friesian calves varied remarkably by season from 1.1 kg of live weight per head in spring and early autumn to 0.0 kg in summer and late autumn and the gain was mainly releted to their herbage intake. They grazed about 0.03 kg per kg of live weight per day in spring and early autumn but about 0.02 kg in summer. Digestibility of the grasses was not so largely different and the efficiency of energy conversion from digestible energy to metabolisable energy was varied seasonally and very low in summer. From the measurement of heat production under grazing, it was infered that the calves might control themselves in lower heat production by lower intake in summer season. Conversion ratio ME/DE was lower in our grazing calves than the values of SRC (1965) in all the season.