A few references that talk about the differences between breastfeeding & bottle-feeding preterm babies…
Chapman DJ. Building the Evidence Base: Preterm Infants’ Energy Expenditure After Breastfeeding Versus Bottle-Feeding. J Hum Lact. 2010 Mar 19. [Epub ahead of print]
Berger I, Weintraub V, Dollberg S, Kopolovitz R, Mandel D. Energy expenditure for breastfeeding and bottle-feeding preterm infants. Pediatrics. 2009 Dec;124(6):e1149-52. Epub 2009 Nov 23.
Lubetzky R, Vaisman N, Mimouni FB, Dollberg S. Energy expenditure in human milk- versus formula-fed preterm infants. J Pediatr. 2003 Dec;143(6):750-3.
Chen CH, Wang TM, Chang HM, Chi CS. The effect of breast- and bottle-feeding on oxygen saturation and body temperature in preterm infants. J Hum Lact. 2000 Feb;16(1):21-7.
Blaymore Bier JA, Ferguson AE, Morales Y, Liebling JA, Oh W, Vohr BR. Breastfeeding infants who were extremely low birth weight. Pediatrics. 1997 Dec;100(6):E3.
If you have favorite references on this subject that aren’t mentioned above, please add them in the comments.