What's the origin of "feeling your oats" or "feeling one's oats?"

When horses would eat their oats, they would be more energetic.
It also could mean "lustful" (e.g. sowing your oats), but probably not.

1. Feel frisky or animated, as in School was out, and they were feeling their oats. This usage alludes to the behavior of a horse after having been fed. [Early 1800s]
2. Display self-importance, as in He was feeling his oats, bossing everyone around. [Mid-1800s]

http://www.answers.com/topic/feel-one-s-oats

4. (Music / Instruments) Poetic a flute made from an oat straw
feel one's oats US and Canadian informal
a. to feel exuberant
b. to feel self-important

http://www.thefreedictionary.com/sow+wild+oats

oat

O.E. ate "grain of the oat plant" (pl. atan), possibly from O.N. eitill "nodule," denoting a single grain, of unknown origin. The usual Gmc. name is derived from P.Gmc. *khabran (cf. O.N. hafri, Du. haver, source of haversack). Famously defined by Johnson as, "A grain, which in England is generally given to horses, but in Scotland supports the people." Wild oats, "crop that one will regret sowing," is first attested 1564, in ref. to the folly of sowing these instead of good grain.

"That wilfull and vnruly age, which lacketh rypenes and discretion, and (as wee saye) hath not sowed all theyr wyeld Oates." [Thomas Newton, "Lemnie's Touchstone of complexions," 1576]

Hence, to feel (one's) oats "be lively," 1831, originally Amer.Eng.

http://dictionary.reference.com/browse/oat

Horses are fed a lot of different grains and grasses - oats are traditionally considered to be one of the feed components that leads to high energy (a 'hot' feed), so a horse fed oats would be expected to be more energetic than one given a 'cool' feed. Hence, they 'feel their oats' and display a high level of energy.

http://archive.today/7xnaf