Symptoms of neonatal digestive and feeding disorders can vary widely but often include excessive vomiting or spit-up, abdominal distension, poor weight gain, and irritability during or after feeding. Infants may exhibit signs of discomfort, such as arching of the back or crying, which can signal feeding intolerance. In more severe cases, signs of dehydration or lethargy may also be present, necessitating immediate medical attention.