One hundred infants born between 28 and 30 weeks of gestational age will be enrolled in our clinical trial in two neonatal units of Marseille; they will receive small enteral feeding protocol with natural or pasteurized milk (according to the Neonatology Department). Infants monitoring will be conducted from birth until 32 weeks of gestational age through extra-uterine growth, dietary type evolution and determination of gut maturation markers levels in blood (Triglycerides and Cholesterol, PUFA, GLP-2, I and L-FABP, Gastrin, Citrullin) and faeces (Calprotectine). We will also look for new biological markers of intestinal growth, via metabolomic approach. Consumption of bioactives molecules (PUFA, sphingomyelin, sCD14, insulin, leptin, lactoferrin, sphingomyelinase acid and BSSL activity) will be quantified in milk 24h-representative samples received by each newborn. The benefits on digestive tract physiology evolution due to the molecules consumption will be observed from the 32nd week until the 36th week or the end of hospitalization.