A first group of three horses was given diet 1 (D1) allowing 1180 g per 100 kg body weight (BW) of a pelleted food rich in fibre (P1) and 556 g per 100 kg BW of straw during a 20-day period to allow for adaptation. A second group of four horses were given diet 2 (D2) allowing 1180 g per 100 kg BW of a pelleted food rich in cereals (P2) and 1000 g per 100 kg BW of meadow hay during the same period. Digesta was collected from the stomach, duodenum, jejunum, ileum, caecum, right ventral colon, left ventral colon, left dorsal colon, right dorsal colon, and small colon, and faeces were collected under general anaesthesia 2·5 h after the ingestion of the morning pelleted meal. The concentration of total anaerobic, cellulolytic and lactic acid-utilizing bacteria, lactobacilli and streptococci were determined in all these segments except for the duodenum, left ventral colon, right dorsal colon and small colon. D -/ Llactic acid, volatile fatty acids and pH were measured in all anatomic segments of the digestive tract (from stomach to small colon). The caecal concentration of total anaerobic bacteria was the lowest (7 ⋅ 9 5 10 7 colony-forming units (c. f. u. ) per ml), whereas that of the stomach was the highest (1·4 5 10 9 c. f. u. per ml) ( P < 0 ⋅ 001). Cellulolytic bacteria did not exceed 3·0 5 10 2 c. f. u. per ml in the ante-caecal segments whereas in the hindgut the average concentration was 5·3 × 10 5 c. f. u. per ml ( P < 0 ⋅ 001). Likewise, VFA concentrations were also greater in the large intestine (on average, 96·3 mmol/l v. 8·8 mmol/l in the ante-caecal segments) ( P < 0 ⋅ 001), confirming the limited extent of fibre degradation in these ante-caecal segments. Lactobacilli, streptococci and lactate-utilizing bacteria colonized all the digestive tract; the stomach and the small intestine tended to host the greatest numbers of these bacteria, which suggests a high interference of micro-organisms with the digestion of readily fermentable carbohydrates. Compared with the other ante-caecal segments, the stomach ecosystem seemed the most affected by the composition of the last pelleted meal ingested : the concentrations of lactobacilli and lactate-utilizing bacteria were higher ( P < 0 ⋅ 05) with P2. The lower concentration of D -/ L -lactate with P2 ( P < 0 ⋅ 05) was concomitant with a greater proportion of propionate ( P < 0 ⋅ 05), probably related to a greater fermentation of lactate. In the large intestine of horses given D2, cellulolytic bacteria tended to be lower, whereas VFA concentrations were higher ( P < 0 ⋅ 05). The lower [NDF/starch] ratio of D2 was probably less propitious for the proliferation of cellulolytic bacteria but was compensated by the higher cellulose intake brought by the hay.

Prebiotic compounds, such as short-chain fructooligosaccharides (scFOS), have been shown to improve health, welfare, or both, in several species, but few studies have been conducted in horses, despite the sensitivity of their hindgut microflora. We hypothesized that prebiotic oligosaccharides, known to be able to stabilize the intestinal microflora in other species, would be of importance in horses. Our study was designed to evaluate the effect of scFOS supplementation on the equine intestinal microflora and to assess its effectiveness in reducing hindgut microbial disturbances related to sudden diet changes. Four adult geldings were allotted by weight into 2 groups and assigned to diets with and without (control) scFOS supplementation for 21 d in a crossover design. Cecal and colonic contents were collected through cannulas to assess the effect of an abrupt incorporation of barley in the diet of horses on microbial populations and fermentation variables. The addition of barley to the control diet caused substantial changes in the colonic microflora, such as increases (P < 0.05) in the concentration in total anaerobes, lactobacilli, streptococci, and lactate-utilizing bacteria. The scFOS supplementation reduced the barley intake-related changes. In contrast to the control diet, Lactobacillus and Streptococcus populations did not increase. Although the colonic d-lactate concentration increased (P < 0.05) after the meal of barley in the control group, it did not accumulate with scFOS supplementation. These data indicate that a scFOS supplementation would be effective in reducing disruptions of the microbial populations in the equine hindgut under stressful situations like acute starch overloads.

The study reported in this paper was conducted to evaluate the digestibility of dietary carbohydrates (‘starch and sugars’ (S), neutral-detergent fibre (NDF), acid-detergent fibre (ADF)) and organic matter (OM) in the different parts of the equine digestive tract (stomach, jejuno-ileum, caecum, right ventral colon, left ventral colon, left dorsal colon, right dorsal colon, small colon and faeces). Three horses were given a standard diet (D1) based on fibrous pellets and straw and four were offered a high energy diet (D2) based on starch pellets and meadow hay. The digesta collection procedure, by total tract removal, permitted measurement of organ length, and dry matter and volume of digesta. Acid-detergent lignin (ADL) and acid insoluble ash (AIA) were used as natural digestibility markers. It was shown that AIA and ADL gave coherent data for ‘starch and sugars’ digestibility evaluation. ADL was a more relevant marker for parietal carbohydrates and OM digestibilities in horses given D1, whereas AIA have been preferred to evaluate these components digestibilities in horses offered D2. In horses given D1, precaecal OM digestibility coefficient varied from -0·04 to 0·20 whereas it varied from 0·46 to 0·62 in horses receiving D2. For both pellets, the results showed a considerable S digestibility occurring in the stomach (0·69 and 0·60 for D1 and D2 respectively) and this continued in the small intestine (0·88 and 0·89 for D1 and D2 respectively). With the exception of D2, structural carbohydrate fractions of the foods were poorly digested in the pre-caecal digestive parts. In the hindgut, OM digestibility coefficient varied from 0·47 to 0·60 for D1 and from 0·33 to 0·51 for D2. In horses given D1, highest digestibility was observed for each dietary carbohydrate in the left dorsal colon where it reached 0·99 for S; 0·45 for NDF and 0·40 for ADF. In horses receiving D2, the dietary components’ digestibilities increased regularly along the hindgut up to the faeces. The D2 structural fractions (NDF and ADF) digestibilities in the hindgut and faeces were lower than in horses given D1. These results not only confirmed that high energy diets like D2 can affect structural carbohydrate digestion in the horse hindgut but also indicated that a large amount of the energy part of the pelleted morning meal is broken down in the stomach.

SummaryReasons for performing study: Limited information exists about the muscle mitochondrial respiratory function changes that occur in horses during an endurance season. Objectives: To determine effects of training and racing on muscle oxidative phosphorylation (OXPHOS) and electron transport system (ETS) capacities in horses with high resolution respirometry (HRR). Methods: Mitochondrial respiration was measured in microbiopsies taken from the triceps brachii (tb) and gluteus medius (gm) muscles in 8 endurance horses (7 purebred Arabians and 1 crossbred Arabian) before training (T0), after two 10 week training periods (T1, T2) and after 2 CEI** endurance races (R1, R2

SummaryReasons for performing study: Limited information exists about the physiological training-induced changes in electrolyte balance of horses competing in long distance endurance races. Objectives: To determine the effects of endurance training and racing on hydration and electrolyte balance in horses. Methods: Blood and urine were sampled at rest in 8 endurance horses before training and after two 11 week training periods (T1 and T2). Each training was followed by a 120 km endurance ride and horses were sampled before, during and 2 h after the rides. Blood was analysed for packed cell volume (PCV), total protein (TP), urea, creatinine and electrolyte concentrations. Urine was analysed for pH, specific gravity, creatinine and electrolyte concentrations, which allowed calculation of fractional excretion of electrolytes (FE