As a rough guide, a horse needs 2.5 percent of its body weight in food every day.

作为一个大致的标准，一匹马每天需要相当于它体重2.5%的食物。

《柯林斯英汉双解大词典》

However, it should be considered as a rough guide because it may not correspond to the same body fat percentage in different individuals.

但是，它应当被视为一种粗略的指导，因为在不同的个人身上，它或许不能反映为同样的身体脂肪百分比。

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They'd both looked down at the snake then, its eyes like two pebbles, its body all but indistinguishable from the length of rough wood it was stretched out on.

于是，他们俩低下头看着蛇，它的眼睛就像两粒卵石一般，躯体如粗糙的木头伸展着，几乎分辨不出它的轮廓来。

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Doctors still use a rough calculation to work out the chances of survival - if the percentage of the body burned added to the age of patient exceeds 100, then things are looking bad.

BBC: Saving your skin