The culprit here is likely the rice cereal and not the type of formula.
Rice cereal — a starch — is often not well digested until 4-6 months of life. When the undigested portions reach the colon, natural bacteria ferment them and release gas as a result.
While the gas will not hurt the baby, it is a sign that he is too young to properly digest rice cereal, and it should be removed from his bottle. Adding rice cereal to bottles to help sleep is a popular myth but has not been found to be true. If you are having trouble getting your newborn to sleep, your doctor can help guide your sleep training. Furthermore, the initiation of solids before 4-6 months has been associated with a host of issues including: diabetes, eczema, and obesity.
Reviewed by Dr. Sara Connolly, August 2019