A faecal sample from the recruited patients will be collected for analysis at baseline, the first stool output after initiation of EN. Once baseline sample is collected, patients will be randomly assigned to receive enteral formula with or without prebiotics. Randomisation will be generated by using the website Randomization.com (http://www.randomization.com). Patients will be monitored for at least 14 days from passage of the first faecal sample after initiation of EN.