For laparoscopic surgery long fasting periods are recommended to avoid a gas filled intestine. However, this theory is in opposite to the known fact that longer fasting periods can lead to serious disease, like typhlocolitis.
To optimize the feeding before intestinal surgery, various facts have to be taken in consideration.
The transit time through the equine gastrointestinal tract is varies for every type of feed and for every anatomic segment. The main part of the transit time is related to the hindgut. Minor differences in transit times between various concentrate feeds, but major ones exist between concentrate feed and hay. Hay causes the shortest mean retention time (26 hours), overall and feeding hay in more than two portions a day seems to decrease the mean retention time. The processing methods of feedstuffs have a minor effect on the mean retention time, but are affecting the digestibility of the feed. However, oat is the grain with the highest precaecal starch digestibility.
During the whole digestion, in addition to the fermentation of volatile fatty acids (VFA), which are irreplaceable for the energy intake of horses, large volumes of gases are released as well. Feedstuff that results in little VFA production also will produce the smallest volumes of gas. No major differences between the different typs of roughages can be found for VFA production. But when comparing roughages with concentrate feed the amount of VFAs differs significantly and is much higher in concentrate feed. This higher amount can be found in every anatomic segment of the equine gastrointestinal tract.
To reduce gas formation supplements can be considered. The addition of oil decreases the gas production with 20% (for the fermentation of cellulose). These results were obtained in ponies that had an adapting period of 53 days, and conclusion about the effect after a shorter feeding period can be drawn. Mineral oil should be used as a mild laxative.
In conclusion feeding long - stemmed hay in several small portions, supplemented with oil and mineral oil, would be the best diet before a laparoscopic surgery is done. Still a fasting period of 26 hours should be taken in account due to the mean retention time of hay is 26 hours.