This is the approved revision of this page, as well as being the most recent.
- Preferably, one should eat breakfast that contains bread (a size of a kebaytzah) and water to give one strength to serve Hashem. 
- Many say that it is sufficient to eat a filling food even if it is not bread.  Likewise, one may have mezonot in place of bread for breakfast. 
- Ideally, one should learn a little after davening before eating breakfast. However, If one regularly eats breakfast after prayers before going to the Bet Midrash, one may do so.
- One should not eat before feeding one's animals , but one may drink before watering them 
- Tur and S”A 155:2. The Kaf HaChaim 155:29 writes that the size of the bread is a kebaytzah.
- Eshel Avraham (Butchatch 155:2)
- Pri Megadim (M"Z 155:1), Sh"t Rivevot Ephraim 3:590 (21 and 35), and Rabbi Yisrael Belsky quoted in Halachically Speaking. Although the Kaf HaChaim 155:23-4 writes that one may fulfill Pat Shacharit with Pat Haba Bekisnin, he adds that a cooked mezonot food (Tavshil mezonot) does not fit the requirements of Pat Shacharit. Or Letzion 2:10(6) agrees.
- Shulchan Aruch Orach Chaim 167:6
- Mishna Brurah 167:40, in the name of Sefer Chassidim, because Rivkah says to Eliezer: "שתה וגם גמליך אשקה" (drink and I will water your camels), putting Eliezer before his camels.