Una dieta a base di fibra vs una dieta a base di amido: effetti sul tratto digestivo nel cavallo

Nutrition has a crucial role to guarantee the health and the welfare of the horse. Wrong feeding practices may lead to the occurrence of metabolic and gastrointestinal disorders and to the onset of stereotypies. Horses are grazing herbivores, monogastric and hindgut fermenters which are adapted to a diet composed mainly by fibre. Concentrates can be added to increase the energy content of the diet, but are poorly digested by the horse due to their high starch amount. The present study aimed to evaluate the effects of two diets on different intestinal compartments of the horse: small intestine, caecum, ventral diaphragmatic flexure of the colon, pelvic flexure, right dorsal colon and rectum. Nineteen horses of the Bardigiano breed (12 females and 7 males) aged 14.3 ± 0.7 months and weighted 346 ± 5.2 kg (mean ± standard deviation, SD) were involved. They were reared for meat production so were slaughtered and the chyme and faeces were collected. Analysis for faecal dry matter, organic matter, ash, particle size and volatile fatty acids were conducted. Nine horses (group fed high starch diet = HS) were fed 8 kg/animal/day of a starch-rich complementary feed (starch 49.50%, as fed). Ten horses (group fed high fibre diet = HF) were fed 3.5 kg/animal/day of a fibre‐rich complementary feed (starch 19.11%, as fed). Starch, fat, calcium and phosphorous were higher in HS. This may increase the possibility to develop osteo-articular problems in growing horses. Even digestible protein and crude protein were higher in HS, but the lysine content was lower in HS than in HF, with the following risk of a reduced average daily gain. Our results show a higher faecal dry matter in horses fed HS than HF probably due to a lower particle separation. The ash is found higher in HS than HF probably due to a reduced absorption of minerals caused by high concentrate level. The organic matter is found higher in HF than HS due to a reduced OM digestibility caused by the high fibre intake. The results for the faecal particle size show the higher digestibility of the HF diet compared to the HS. In fact, there’s a great particle retention on 8 mm in HS and a great particle retention on 2 and 4 mm in HF. The higher fraction washed through the <1 mm sieve in HS is due to the high particulate matter found in HS. Therefore, the extensive and altered fermentations to which the undigested starch is subjected are demonstrated by the higher production of butyric, iso-butyric acid, n-valeric acid and iso-valeric acid in horses fed HS compared to HF. Therefore, results highlight the low capability of the horse to digest starch due to the scarce production of amylase. The starch that escapes the digestion in the small intestine and arrive indigested in the hindgut is also confirmed by our results. For these reasons, many factors need to be taken into account when a diet for horses is formulated: the horse anatomy, physiology, feeding behaviour, age, physiological stage, BCS. Furthermore, the expert in equine nutrition becomes important in order to enforce the right feeding practices which the aim to respect and safeguard the physiological needs and accordingly welfare of the horse.