This study will examine the safety and tolerability of supplementation with bovine lactoferrin with fructo-oligosaccharide a simple sugar in very low birth weight infants. Lactoferrin is a major whey protein in mother's milk and plays a role in promoting a mature and healthy gut. It also has antimicrobial and immunomodulation activities.

Aim 1: To evaluate the safety and tolerability of three different lactoferrin/FOS doses in preterm infants

1. Lactoferrin/FOS related adverse events and serious adverse events
2. Time reaching full feeds while receiving lactoferrin/FOS (120 ml/kg/day)
3. Episodes of not receiving enteral feedings for > 24 hours once feeding is initiated

Aim 2: To evaluate lactoferrin/FOS absorption and excretion

1. Examine lactoferrin/FOS levels in saliva, urine, plasma, and stool
2. Examine lactoferrin levels in materal and human donor milk

Aim 3: To evaluate the effect of lactoferrin/FOS on the intestinal microbiome structure

Inclusion Criteria:

• < 15 days of age and receiving enteral feedings
• < 1500 grams birth weight
• < 37 weeks gestation

Exclusion Criteria:

• Congenital bowel obstruction (esophageal, duodenal, small bowel or anal atresias, Hirschsprung disease, malrotation)
• Known necrotizing enterocolitis or bowel perforation

Specimens which have been unidentified may be shared with outside labs for analysis