Concept: Animal feeds are grouped by their fibre content. High-fibre feeds are called roughages.Explanation: When a feed contains more than 18% fibre, it is considered a roughage.Roughages are bulky feeds rich in fibre but low in easily digestible nutrients.They help stimulate the digestive system and provide bulk, especially in ruminant diets.Concentrates, by contrast, are low in fibre and high in digestible energy.Answer: B. roughages