There is only very limited evidence in the form of deficiency symptoms for rubidium being possibly essential in goats; even if this is true, the trace amounts usually present in food are more than enough.
ðɛɹ ɪz ˈoʊnli vˈɛɹi lˈɪmɪɾᵻd ˈɛvɪdəns ɪnðə fˈɔːɹm ʌv dᵻfˈɪʃənsi sˈɪmptəmz fɔːɹ ɹuːbˈɪdiəm bˌiːɪŋ pˈɑːsᵻbli ᵻsˈɛnʃəl ɪn ɡˈoʊts; ˈiːvən ɪf ðɪs ɪz tɹˈuː, ðə tɹˈeɪs ɐmˈaʊnts jˈuːʒuːəli pɹˈɛzənt ɪn fˈuːd ɑːɹ mˈoːɹ ðɐn ɪnˈʌf.