Ubaydullah bin Musa (may Allah have mercy on him) narrated it with his chain, except that he said: "(He forbade) confining a living creature (to kill it); and castrating livestock is a severe confinement."
The Shaykh said: His words 'and castrating livestock is a severe confinement' are an analogy drawn from what was forbidden, namely confining a living creature, and they are the words of al-Zuhri; for others besides Ubaydullah narrated it from Ibn Abi Dhi'b as mursal and made the statement about castration the words of al-Zuhri.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب السبق والرمي / 19791