The stomach deflated. SC drips plus baytril antibiotics did not help. Around 2 hours later, he passed away. Toxins from Clostridial bacteria could have killed him. Gastric volvulus or distension was present. The prognosis was poor. No more hay for the other guinea pig which was still OK and eating the same hay.
Bubbles in the abdomen indicate that the intestines had lost blood supply and leak gas into the abdomen. The guinea pig died from septicaemic shock as Clostridial bacteria is highly pathogenic. No post-mortem or bacterial culture was done.