Description: This lamb is suffering from the effects of a dietary deficiency in Thiamin, also known as vitamin B1. Many of the symptoms of this deficiency are caused by an interruption of carbohydrate metabolism due to a lack of the coenzyme thiamine diphosphate, which results in failure to convert pyruvate to acetyl CoA and causes pyruvate to accumulate. This is converted to lactate to allow glycolysis to continue by removing the end product inhibition. Neural dysfunction then occurs because nerve cells can only use glucose to form ATP, so glycolysis and the TCA cycle are necessary to generate ATP for nerve conduction. This lamb is exhibiting opisthotonus or "star-gazing," where the head is drawn backward as a result of nerve degeneration. This condition can be seen in pre-ruminant calves and lambs. Opisthotonus can also occur in functional ruminants with polioencephalomalacia (PEM). In PEM, ruminal thiamin is destroyed by thiaminase. The thiaminase can arise from abnormal rumen bacteria (bacillus thiaminolyticus), or can come from plants such as bracken fern. Ruminal thiamin can also be destroyed by excessive sulfite. In Europe, this disease is called Cerebro-Cortico Necrosis (CCN).