As I suggested, the formula needs to be a higher calorie formula. He is not getting enough calories to grow. For his age he needs 1800-2000 calories a day. From your description, he is getting less than 1000 calories daily. By bolus feeding him before meals he will feel full and not want regular food. Recommend feeding at night with a tube feed pump, higher calorie tube feed (2.0 calorie), and see a Registered Dietitian (RD) to help guide you. To find an RD in your area, go to the American Dietetic Association website, www.eatright.org.
4 years ago, my son was given a feeding tube, due to failure to thrieve,(he was born prematurely his birth weight was 1 lb 13 oz). When he was dicharged from the hospital with his feeding tube, he was put on Pedisure with fiber enternal formula, 4 - 8oz cans per drip overnite. 2years later he went for another surgery to repair his hyatel hernia, they did a nissen fundalupcation. Then he had to learn to eat all over again, this has been a struggle for him. He still has the tube and we bolis feed him 8oz pediasure 1 can in the AM before school(along with some breakfast) at school he has (snacktime) then lunch at school, then another snack around 3 pm, then we bolis feed him 8oz pedisure before dinner, then dinner (not alot- feels to full), then snack before bed, then another 8oz. pedisure before bedtime. He was 24lbs before the tube at age 4 , he is 8 and only weighs 44 lbs, what else can we do?
You did not mention the type of Tube feed formula he is on. Has the Doctors tried a high calorie tube feed either 1.5 or 2.0 calorie that is more nutrient dense that may help him gain weight? If not, suggest changing Tube feed formulas to 1.5 or 2.0 calorie. Another suggestion is to do continuous feeds at night to help increase his weight and growth. During the day try to give him regular food so he develops an appetite for food (will not be full from the tube feed formula). You can try to set up feeding him 3 meals of food so he starts to become hungry between meals. Hoped this helped you