Bloat in calves is normally seen the first one to two weeks of life. Calves may refuse milk, have a distended abdomen (right side or both sides), grind their teeth, kick at their belly, become depressed or lethargic, have droopy ears, and may die suddenly. 
The time between the first signs of bloat and death can be as little as four hours. Any calf that dies suddenly without explanation should be necropsied (examined by a veterinarian after death) to determine the cause of death and prevent additional cases. In the case of bloat, there are several ways to adjust calf management to prevent additional cases.
When adult cattle bloat, gas becomes trapped in the rumen (the first of the four stomach compartments). Often, passing a tube through the mouth into the rumen can release the gas and provide relief. However, when calves bloat, gas is trapped in the abomasum (the last of the four stomach compartments).
This means that tubing them will not help release the gas, as a tube cannot pass from the mouth through the entire stomach and into the abomasum. It is also ill-advised to insert a needle into the calf’s side to release the gas, as this could cause stomach contents to leak into the calf’s abdomen. This can lead to infection and sepsis. Sepsis causes organ damage and inflammation throughout the body, which can kill the calf. Work with your veterinarian to create a protocol for managing bloat in calves, which may include instructions to call your veterinarian immediately if you notice a calf with signs of bloat. Bloat can kill a calf quickly if there is any delay in diagnosis or getting veterinary attention. Not all calves will respond to treatment, and catching cases before they turn deadly can be a challenge. For these reasons, preventing bloat is the best way to prevent calf loss.
While there is no consensus on exactly what causes bloat, there are several management practices that can increase or decrease the risk of calf bloat. Click here to read about preventing bloat in calves.
Source: Calf Care Corner – calfcare.ca