Ntawm ntau theem ntawm kev tsim khoom, cov txheej txheem pub khoom noj yog qhov tseem ceeb, vim nws cuam tshuam ncaj qha rau kev tsim khoom thiab cov khoom zoo. Tsis siv neeg ntsia hlau feeder, ib qho khoom noj khoom haus qib siab, tab tom ua lub luag haujlwm tseem ceeb hauv qhov no.
Hauv kev xyaum, tsis siv neeg ntsia hlau feeders tau dav siv los ntawm ntau lub lag luam nrog cov txiaj ntsig zoo. Piv txwv li, ntawm cov khoom noj ua zaub mov uas phau ntawv pub mis yav dhau los tsis muaj txiaj ntsig thiab ua rau muaj kev ua yuam kev, kev teeb tsa ntawm cov ntsia hlau tsis siv neeg pub zaub mov ua rau muaj kev nce ntxiv hauv kev pub noj ceev, ntau dua cov khoom zoo sib xws, thiab kev txhim kho hauv kev tsim khoom tag nrho. Ib yam li ntawd, nyob rau hauv kev lag luam tshuaj, kev siv cov ntsia hlau tsis siv neeg feeders tau ua cov khoom siv kev nyab xeeb thiab zoo ib puag ncig, yog li txo qhov kev pheej hmoo ntawm kev nyab xeeb tshwm sim los ntawm cov khoom xau.