A minimum of roughage and a maximum of starch – necessary benchmarks for equine diets

Abstract

IntroductionEnergy and nutrient requirements of horses are defined by the status of the animal; maintenance, pregnancy, lactation, work or growth. The crucial role of horses in the late industrial revolution, up to the middle of the last century for farm work and for transport in the fast growing urban areas as well as in the industries like mining, initiated scientific work on their energy, protein and mineral requirements. However, knowing how to feed the horse goes beyond just consideration of energy and nutrient supply. The responses of horses to diet are a complex of gut health, endocrine interaction and behaviour.Recent studies show an impact of fibre and starch intake on this complex and thus these dietary elements need to be defined to ensure safe horse nutrition. HintergrundDepending on the season a daily workload continued for 7-10 h requiring a feed intake at about 4 % of body weight (Simms 1927 SummaryThe rations for modern leisure or performance horses are hardly influenced by the tradition of feeding horses doing farm work or serving in public infrastructure and industry as hard working animals. Typically roughage is limited and concentrates are dosed to balance the caloric needs. However, limitations in roughage are in conflict with the time budget of the horse today as it is not full time exercised. The actual roughage management often neglect the perspectives of this feed to contribute to energy and nutrient intake even in performance horses. Data on diets for 3-day eventers confirm the suitability of rations high in roughage. The huge impact of roughage on saliva production, speed of feed intake and -possibly the most important link -on behaviour requires to define this part of equine diets by the recommendation of feeding daily min 15 g roughage/ kg body weight (defined as as feed of 88 % dry matter). This amount will even at low feeding levels cover the caloric needs for maintenance. High starch intake changes the bacterial community in the entire digestion tract. This is in principle accepted as a risk factor for gut health. Consequently a limitation in starch intake is an essential factor in safe rationing. But two further factor need to be included for deriving a starch limitation. Glucose as the product of starch digestion induces an insulin response. In case of high starch intake this response is enforced and characterized by a persistency of insulin activities in blood distinctly above base levels, a situation which is in conflict to the preferential status of a horse prior exercise. Additionally epidemiological data identify high starch intake a a risk factor for the development of gastric lesions/ulcers. These facts are recognized by the recommendation to limit starch intake per meal at 1 g/kg body weight.

Factors Influencing Equine Gut Microbiota: Current Knowledge

“…When reaching the hindgut, starch is fermented and increased amounts of lactic acid are produced [28]. As a result, pH in the large intestine may drop creating undesirable conditions for beneficial acidintolerant fibrolytic bacteria to proliferate, which can represent a risk factor for digestive health [29]. However, the study of Daly, Proudman [19] had limitations, which are common to other equine gut microbiota studies.…”

Common Feeding Practices Pose A Risk to the Welfare of Horses When Kept on Non-Edible Bedding

“…This is due to the fact that for thousands of years, the vast steppes of Eurasia have offered a wide plant diversity, yet scant vegetation. Horses are adapted to a diet that is rich in structural fibres and low in energy (i.e., rapidly hydrolyzable carbohydrates) [7,8,18,26]. Due to the horses´evolutionary fitness benefit ("niche construction theory"), they have the ability to forage an unlimited amount of low energy and high fibre food (ultimate behavioural control mechanism) [27].…”

Effects of Starch Overload and Cecal Buffering on Fecal Microbiota of Horses

“…Horses exposed to corn starch overload showed reduction in the diversity and richness of the fecal microbiota, characterized by proliferation of amylolytic bacteria, to the detriment of fibrolytic bacteria. It is well known that abrupt dietary changes involving starch-based concentrates affect normal fermentation in horses’ hindgut [ 37 ], cause colic [ 3 , 38 ] and laminitis [ 1 , 39 , 40 ], and reduce the microbiota’s diversity [ 41 , 42 ], increasing proliferation of amylolytic bacteria [ 43 ]. However, there were considerable differences in microbiota changes between starch–saline (SS) and starch–buffer (SB) treatments, since the latter showed more dysbiosis, even in the presence of the cecal buffer.…”