牛羊等草食動物的日糧需要混合乾草來調高其乾物質及可消化纖維量，以維持健康及正常的反芻生理。細莖型草種方便調製乾草，台灣位於熱帶與亞熱帶相連的多溼地區，屬於此類的草種很多，1960 年前後台灣為發展畜牧業，又從國外引進很多細莖型草種，其中如盤固草及尼羅草等已被馴化改良成栽培種，供草食動物芻料用。然而有些草種，或因產量低或品質不佳者而沒被利用，如天竺草、舖地黍及星草等，它們逐漸侵入到牧草田區，妨礙主作物生長而成為雜草。有些雜草的擴展速率大於牧草，而成為草地的優勢草種，即成為野草。牧草、雜草及野草之間的角色，會經由草種改良及栽培管理而變動，例如不當管理，包括施肥量不足、缺乏灌溉及或未適時收割等，使草質劣變，致田間雜草叢生，甚至擴展成野草。雜草木質化速度快，但若於幼嫩時，當其營養及嗜口性佳，提早收穫或放牧，亦可為動物利用，即野草牧草化。在土地資源有限下，集約式經營管理，即選用適地草種，按時栽培管理及收穫，雜草控制在5% 以下，可得良好的芻料，即產量及品質皆具經濟效益。野草亦可經由育種人員加以性狀改良及施以適當的肥培管理，使其品質適合動物利用，而成為有用之牧草草種。由此知牧草地需要適當規劃管理，讓雜草不會影響到牧草品質，畜牧業方可永續性經營。

The herbivorous animals need hay to increase dry matter intake and digestible fiberof their daily ration to maintain the ruminant work normally and healthily. The grassspecies with slender stem are easy to make hay. A lot of subtropical and tropical grassescould be found in Taiwan. Many kinds of grass species also introduced from foreigncountries in 1960. Some of the foreign grasses had been acclimatized and improved asforage crops such as pangolagrass (Digitaria decumbens) and nilegrass (Acrocerasmacrum). But, for example, guineagrass (Panicum maximum), torpedograss (Panicumrepens) and stargrass (Cynodon plectostachyum) etc., with low quality or lowproduction were not useful. After a periodic time these grasses invaded into pasture landand interfered the growth of forage crops. They became weeds. The weeds expandedfast and naturalized as wild grasses. The roles among forage crop, weed and wild grassmight be changed by breeding and management. The quality of forage crop might bedeclined owing to unsuitable management such as fertilizer application, no irrigation orcutting too late. Meanwhile, it might induce to grow weeds, and gradually become wildgrass. Usually, wild grass became aged fast. However, it could be used as fodder ofanimals while the wild grass was cut still young. The weeds could be improved bybreeding and management and produce the forage with palatability and high quality. Itwould meet the demands of economical benefits of forage yield and quality by intensivemanagement included optimal variety, suitable fertilizer, irrigation and less than 5%weed level. So, it is important to manage grassland and control weeds to promote theforage yield and quality for raising herbivores. It might be helpful to keep sustainable inanimal husbandry industry.