O.k.. Unless there something wrong with it physically then the problem is still most likely caused by an organism in the digestive system. And, like you already mentioned, it could be as a result of digestive development. The following mightoffer some ideas:
"Rumen development - conditions for bloat. Ruminal bloat in young calves takes place within the context of the developing rumen. The population of rumen microbes that exists at any point in time is determined by the types of feed consumed as well as other substances commonly ingested such as bedding and hair. The right set of circumstances can allow one or more of these microbes to produce excessive gas and bloat in the developing rumen. Rumen development begins in earnest when water and dry feed come together in the rumen. To assure adequate development, a dry starter feed should be made available as soon as the calf is placed on milk or milk replacer. Intake of starter will be low until the calf is a couple of weeks old, but it is still of major importance to rumen development. Butyric and propionic acids are volatile fatty acids (VFA) that are produced from grain digestion. Although butyric acid has the greatest effect, both stimulate rumen development. Feeding hay on the other hand, produces another VFA, acetic acid, which provides poor stimulation for rumen development. Since hay is not required for rumen development prior to weaning, it should be withheld from the diet until after the calf is weaned. When dry feed is consumed, it enters the rumen. For bacterial growth and feed digestion to occur, a liquid environment is needed. Since milk and milk replacer contain such a readily digestible and fermentable energy source, it is preferable that they stay out of the rumen. The esophageal groove directs milk to the abomasum preventing it from directly entering the rumen. When milk persistently flows into the rumen, calves may develop a number of symptoms including unthriftiness, growth retardation, poor appetite, abdominal distention, recurrent bloat, hard feces and a long dry hair coat. Calves that are restricted to a liquid diet, such as veal calves, are more likely to develop these symptoms. Since the esophageal groove may still be present for a while after milk feeding, water fed immediately after milk usually passes directly to the abomasum. For water to enter the rumen and facilitate feed digestion and rumen development, it must be fed separately from milk and milk replacer. A minimum of 10 minutes has been suggested as the necessary waiting period before offering water after milk feeding. Even so, water added to a bucket that still contains some milk or milk replacer may stimulate reformation of the esophageal groove. The general recommendation is to feed 4 pounds of water (2 qt) for every pound of dry feed consumed."