A: Ontogeny of carboxyl ester lipase (also called bile salt dependent lipase, BSDL) in pancreas by qRT-PCR; B: CEL/BSDL ELISA; C: qRT-PCR of carboxyl ester lipase in pancreas of control and NEC mice; D–K: ‘Oil Red O’ staining (red droplets) counter stained blue nuclei with Hematoxylin stain (D–G proximal intestine and H–K distal intestine, 10 μM cryo-sections) (Ctrl, Control-Breast fed or experimental NEC treatments with hypoxia and formula feeding). PDF, pre-digested fat. **p<0.01, ***p<0.001, each dot represents data from individual mouse, scale bar =10μm.