Here are the most common reasons for regurg problems (in order most common to least common)
1. Handling too soon after a meal
2. too large a food item
3. Temperature problems (too cool or too hot)
4. feeding while in shed
5. Sudden stress causing "flight" response immediately after a meal.
6. Parasitic or bacterial infection
You need to be sure whether it was regurgitaion or vomiting before you can make an accurate diagnosis. They are different. Regurgitation occurs normally within the first 24 hours of eating. This is bringing up food from the stomach. Vomiting occurs after the first 24 hours and involves brining up partially digested food from the intestinal tract, after the stomach. The cause for vomiting are:
1. bacterial or parasitic infection
2. sudden temperature changes (this usually results in food rotting in the intestine if the temps are sudddenly lowered while there is still food in the gut)
3. Intestinal blockage, such as a looped intestine, adhered intestinal walls or impaction due to ingested foreign material.