He knew you could never teach an animal anything if you struck it, or even shouted at it angrily.
shout
(怒鳴りつける)
[動]
speak or cry out loudly, as in calling to someone at a distance or expressing a strong emotion
彼は動物を殴ったり、怒鳴りつけたりしたら何も教えられないことを知っていた。
He must always be gentle, and quiet, and patient, even when they made mistakes.
彼は彼らが間違いを犯した時でさえ、いつも優しく、静かに、そして忍耐強くなければならなかった。
Star and Bright must like him and trust him and know he would never hurt them, for if they were once afraid of him they would never be good, willing, hard-working oxen.
trust
(信頼)
[動]
have confidence in the reliability, truth, or ability of
afraid
(恐れる)
[形]
filled with fear or apprehension
willing
(意欲的な)
[形]
ready, eager, or prepared to do something
hard-working
(勤勉な)
[形]
working with or exhibiting great effort or endurance
スターとブライトは彼を好きで、彼を信頼し、彼が決して彼らを傷つけないことを知っていなければならなかった。なぜなら、もし彼らが一度でも彼を恐れたら、彼らは決して善良で、意欲的で、勤勉な牛にはならないからだ。