When horses are fed oats, they tend to behave more energetically afterward. So if a horse is said to be "feeling his oats" it refers to energetic prancing around the field, or more assertive or excited behavior, and may be literally due to diet. When people are said to be "feeling their oats", it is because the same kind of behavior (higher energy, enthusiasm, assertiveness, or excitement) is observed, even though other causes may be assumed.
Since you're feeling your oats today, would you use some of that energy taking the dog for a walk?
by Scribhneoir January 15, 2014
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