For tranquilizing* a yukkuri, ramune candy is generally used. For baby yukkuris, the standard dose is usually one piece of candy. Please either grind it into powder (they are unable to chew a whole piece) or dissolve it in water. (※ If dissolved in water, it can also be applied as a spray.)
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*Tranquilize or anesthetize, I keep going back and forth on these.