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Establishment of Theories for the Model to Predict Feed Intake of Cattle
本研究之目的在建立模擬牛隻生長及生產特性之模式來預測其採食量，提供作為現場飼養管理及評估之資訊與建立後續生產模式之先驅。影響採食量之因素包括動物、飼料、管理、畜舍與環境等因子，可大致分為生理、物理與心理狀態三大項，對乾物質採食量之預測非常重要。本研究使用Microsoft Excel為軟體作業平台，並應用Visual Basic Application連結模式程序，在模式發展初期將體重、種別、性別、年齡、產次、泌乳狀態、妊娠體態、飼糧成分、消化特性、飼糧物理形式、飼糧貯存與發酵品質、畜舍、光照、氣溫、風速、溼度、餵飼頻率、日糧型態、添加物等影響因子量化為輸入項變數，並以先前之模式文獻或試驗結果建構變數之關係函數。此外，飼料之基本成分資料可直接輸入系統或經由電腦飼料配方檔案轉換。本模式中，真實採食量之決定倚賴於牛隻之需要量與最大採食量比較之結果。乳牛營養需要量主要分為維持、生長及生產三大部分，其中維持之需要量在當環境溫度超出臨界點時，會依超出之溫差遞增。維持需要量由營養試驗決定，生產需要量則與生產量成線性關係。最大採食量主要受瘤胃容積與能量飽和之回饋控制所限制，其程度取決於飼糧成分之內容。瘤胃每日最大容積之取得，利用已知固定成分飼糧之營養試驗或以動態模式推算得知；所得之最大採食量則由心理因素修飾而成為實際採食量。
The main objectives of this study were to establish a model to predict feed intake of cattle by simulating its growth and production, and to provide valuable information regarding feeding, management, and evaluation, and to act as a precursor to set up the whole production model. Factors affecting feed intake included animal, feed, management, housing, and environment. These factors could be divided into three categories in terms of physiology, physics, and psychology. All were very important on predicting dry matter intake of the cattle. This model was written on the platform of Microsoft Excel in Visual Basic Application programming language. In the beginning of the development of the model, factors affecting feed intake were quantified into the variables of input item. The correlation functions of variables were established by using published papers and experimental results. Moreover, basic data of feed composition could be input into the system directly or transform files from computerized feed formulation system. In this simulation model, the decision of real intake depended on the comparison between requirement of cattle and maximum intake by cattle. The nutrient requirement of cattle was mainly attributed to maintenance, growth, and production. The requirement for maintenance increased progressively with temperature above upper critical temperature, and was decided by the experiment of nutrition. The requirement for production showed linear relationship with quantity and quality of production. The maximum intake was mainly limited by rumen volume and feedback regulation of energy fill, or could be calculated by a dynamic model. This maximum intake was then modified into the actual intake through psychological factor.
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