Feem ntau, cov hlua khi hlua khi zoo yuav tsum kav ntev rau ntau xyoo, txawm tias tsis tuaj yeem ua lub neej ntev ntawm cov khoom siv. Hauv kev siv tsheb, cov hlua hluav taws xob tuaj yeem siv tau rau 15-20 xyoo lossis ntev dua, tsuav nws tsis raug tshav kub, noo noo, lossis kev puas tsuaj rau lub cev.
