Effect of diet composition on glandular gastric disease in horses

BACKGROUND

Nutritional factors are suggested to influence the incidence and severity of glandular gastric disease (GGD) in horses.

OBJECTIVES

To retrospectively assess whether dietary fermentable carbohydrates increase the severity of GGD and to prospectively evaluate whether the partial substitution of concentrates by dehydrated alfalfa would decrease GGD severity scores.

ANIMALS

In total, 82 trotters from 4 training centers exercised ≥5 days/week.

METHODS

Multicenter retrospective observational study, and prospective 2-arm randomized trial. Glandular mucosae were observed by gastroscopy and scored (0-4 severity scale) at day 0 (D0). Biochemical composition of the diet fed was compared between ulcerated and nonulcerated groups. After D0, horses either received the same diet (control, n = 41) or pelleted dehydrated alfalfa substituting 50% concentrates (alfalfa, n = 41). Glandular scores were recorded in both groups after 21 (D21) and 42 days (D42). The first end point was a successful outcome, defined as a horse with a glandular score of 2 to 4 on D0, decreasing to a score of 0 to 1 on days 21 or 42.

RESULTS

Horses scored 0 to 1 at D0 ingested more (P = .01) soluble sugars from concentrates than those scored 2 to 4 before D0 (77.5 g/kg BW; 95% confidence interval [CI]: 71.1-84.0, vs 59.1 g/kg BW; 95% CI: 48.0-70.3), whereas starch intake did not differ between groups (P = .24). Among horses scored 2 to 4 at D0, fewer were scored 2 to 4 in the alfalfa group (1 out of 6) compared with the control group (6 out of 6) at D42 (P = .02). Clinical success was 47.7 times more likely in horses fed alfalfa compared with horses in the control group (95% CI: 1.6-1422.8).

CONCLUSION AND CLINICAL IMPORTANCE

Relationships were found between diet composition and integrity of the glandular mucosa. Feeding pelleted dehydrated alfalfa could help to reduce the incidence and severity of GGD.

Biomarkers for monitoring the equine large intestinal inflammatory response to stress-induced dysbiosis and probiotic supplementation

Large intestine barrier disturbances can have serious consequences for the health of horses. The loss of mucosal integrity that leads to increased intestinal permeability may result from a local inflammatory immune response following alterations of the microbiota, known as dysbiosis. Therefore, our research aimed to identify noninvasive biomarkers for studying the intestinal permeability and the local inflammatory immune response in horses. Regarding the biomarkers used in other mammalian species, we measured the concentrations of lipopolysaccharides (LPS), reflected by 3-OH C14, C16, and C18 fatty acids, in blood, and fecal secretory immunoglobulin-A (SIgA). These biomarkers were evaluated in two trials including 9 and 12 healthy horses, which developed large intestinal dysbiosis experimentally induced by 5 d of antibiotic administration (trimethoprim sulfadiazine [TMS]) or 5 d of abrupt introduction of high starch levels (barley) into the diet. Horses were either control or supplemented with Lactobacillus acidophilus, Ligilactobacillus salivarius, and Bifidobacterium lactis. Correlations were performed between biomarkers and fecal bacterial diversity, composition, and function. No significant interaction between day and supplementation, or supplementation effect were observed for each biomarker. However, with the dietary stressor, a significant increase in blood concentrations of 3-OH C16 (P = 0.0125) and C14 (P = 0.0252) fatty acids was measured 2 d after the cessation of barley administration. Furthermore, with the antibiotic stressor, blood levels of 3-OH C16 progressively increased (P = 0.0114) from the first day to 2 d after the end of TMS administration. No significant day effect was observed for fecal SIgA concentrations for both stressors. These results indicate that both antibiotic- and diet-induced dysbiosis resulted in a local translocation of LPS 2 d after the cessation of the stressor treatments, suggesting an impairment of intestinal permeability, without detectable local inflammation. Blood LPS and fecal SIgA concentrations were significantly correlated with several bacterial variations in the large intestine, which are features of antibiotic- and diet-induced dysbiosis. These findings support the hypothesis that a relationship exists between dysbiosis and the loss of mucosal integrity in the large intestine of horses.

Cellulolytic bacteria in the large intestine of mammals

The utilization of dietary cellulose by resident bacteria in the large intestine of mammals, both herbivores and omnivores (including humans), has been a subject of interest since the nineteenth century. Cellulolytic bacteria are key participants in this breakdown process of cellulose, which is otherwise indigestible by the host. They critically contribute to host nutrition and health through the production of short-chain fatty acids, in addition to maintaining the balance of intestinal microbiota. Despite this key role, cellulolytic bacteria have not been well studied. In this review, we first retrace the history of the discovery of cellulolytic bacteria in the large intestine. We then focus on the current knowledge of cellulolytic bacteria isolated from the large intestine of various animal species and humans and discuss the methods used for isolating these bacteria. Moreover, we summarize the enzymes and the mechanisms involved in cellulose degradation. Finally, we present the contribution of these bacteria to the host.

Sequential Modulation of the Equine Fecal Microbiota and Fibrolytic Capacity Following Two Consecutive Abrupt Dietary Changes and Bacterial Supplementation

Simple Summary

The equine hindgut is colonized by microorganisms, some of which are involved in fiber digestion and are crucial for the horse’s nutrition and health. These key microorganisms are very sensitive to dietary changes, which have been identified as a risk factor for colics. This study assessed the stressful effect of two consecutive abrupt dietary changes on the diversity, the composition, and the activity of fecal microorganisms focusing on fibrolytic bacteria. Twelve horses were subjected to an abrupt change from forage to a concentrate-rich diet, followed by a second change from a concentrate to forage-rich diet 5 days later. Half of the horses were given a supplement of living bacteria as a probiotic. Two days after the sudden change from forage to concentrate diet, the proportions and types of microorganisms were altered drastically, as was their capacity to degrade fibers. After this dietary stress, it took 3–4 weeks of a high-fiber diet to recover the basal state. Supplementation with probiotics promoted an earlier recovery of fibrolytic bacteria after the dietary stress. Abrupt dietary changes should be limited in horse management to protect the hindgut microorganisms and their capacity to use forage fibers, and consequently to limit the development of colic.

Abstract

In horses, abrupt changes from high-fiber (HF) to high-starch (HS) diets can affect the cecal and colonic microbiota. This study investigated modifications and recovery of fecal microbiota after two consecutive abrupt dietary changes. Twelve horses fed HF for 2 weeks were changed to HS for 5 days then returned to HF for 7 weeks. Six received lactic acid bacteria supplementation. Bacterial population diversity, structure, and activity, especially fibrolysis, were assessed to obtain an overview of alteration in hindgut microbiota. Two days after the abrupt change from HF to HS, the findings in feces were consistent with those previously reported in the cecum and colon, with a decrease in fibrolytic activity and an increase in amylolytic activity. Fecal parameters stabilized at their basal level 3–4 weeks after the return to HF. A bloom of cellulolytic bacteria and lower pH were observed after 1.5 weeks, suggesting a higher level of fiber degradation. In supplemented horses the relative abundance of potentially fibrolytic genera was enhanced 2 days after HS and 2 days to 2–3 weeks after the return to HF. Fecal analysis could be a promising technique for monitoring hindgut microbial variations accompanying dietary changes.

Multidimensional Approach for Investigating the Effects of an Antibiotic-Probiotic Combination on the Equine Hindgut Ecosystem and Microbial Fibrolysis

The equine hindgut ecosystem is specialized in dietary fibers' fermentation to provide horses' energy and contribute to its health. Nevertheless, antibiotics are known to disrupt the hindgut microbiota, affecting the fibrolytic activity of bacteria and the intestinal immune balance, leading to diseases. This in vivo study used a general and comprehensive approach for characterizing the hindgut ecosystem of 9 healthy horses over 28 days in response to a 5-day challenge with oral trimethoprim-sulfadiazine (TMS), with a special emphasis on microbial fibrolytic activity and the host immune response. Horses were supplemented with two doses of Lactobacillus acidophilus, Ligilactobacillus salivarius (formerly L. salivarius), and Bifidobacterium lactis blend or a placebo in a 3 × 3 Latin square design. Changes in fecal microbiota were investigated using 16S rRNA sequencing. Clostridioides difficile was quantified in feces using quantitative polymerase chain reaction. Anaerobic microbiological culture was used to enumerate functional bacterial groups (cellulolytic, amylolytic, and lactic acid-utilizing). The environmental dimensions were assessed by measuring the concentrations of volatile fatty acids (VFAs) and lactic acid using biochemical methods, and changes in pH and dry matter weight. Systemic and local inflammation was evaluated by determination of cytokine and immunoglobulin (Ig)A concentrations in the serum and secretory IgA (SIgA) concentrations in the feces using immuno-enzymatic methods. Oral TMS treatment strongly altered the whole hindgut ecosystem by 2 days after the first administration. Bacterial diversity decreased in proportion to the relative abundance of fibrolytic genera, which coincided with the decrease in the concentration of cellulolytic bacteria. At the same time, the composition of microbiota members was reorganized in terms of relative abundances, probably to support the alteration in fibrolysis. C. difficile DNA was not found in these horses, but the relative abundances of several potential pathobiont genera increased. 2 days after the first TMS administration, fecal concentrations of VFAs and SIgA increased in parallel with fecal water content, suggesting an alteration of the integrity of the hindgut mucosa. Recovery in bacterial composition, functions, and immune biomarkers took 2-9 days after the end of TMS administration. Supplementation with this bacterial blend did not limit bacterial alteration but might have interesting mucosal immunomodulatory effects.

Dietary-induced modulation of the hindgut microbiota is related to behavioral responses during stressful events in horses

The bidirectional communication between the central and the enteric nervous system named the gut-brain axis has been widely recognized. The gut microbiota has been implicated in a variety of stress-related conditions including anxiety, depression and irritable bowel syndrome based on rodent studies or correlative analysis in human patients. The aim of the present study was to investigate to what extent changes in behavior during stressful events and in the microbial composition of the colonic ecosystem were associated in horses. The microbiota alterations were induced by a change from a high-fiber diet (100% hay, H diet) to a progressive low-fiber and high-starch diet (56% hay and 44% barley, HB diet) on six fistulated horses. Colonic total anaerobic, cellulolytic, amylolytic and lactate-utilizing bacteria were enumerated once on H diet and once on HB diet. Bacterial richness, diversity and structure at family and genus level were also determined. The behavior of horses was assessed through two standardized stressful tests: a novelty test and an umbrella test. The different alterations measured in the colonic microbiota demonstrated a lower fibrolytic capacity and a higher amylolytic capacity of the ecosystem when horses received HB compared to H diet. During the novelty test, the frequency of blowing was significantly higher in HB than in H diet and was positively correlated with the concentration of amylolytic bacteria and the Succinivibrionaceae relative abundance. During the umbrella test, behavioral variables were not significantly different between the diets but the colonic content pH was negatively correlated with the frequency of startle response. Behavioral responses of anxiety were related to hindgut microbiota indicators of a high-starch diet. Dietary-induced modulation of the gut microbiota composition may have changed the horses' behavioral reactions in stressful situations.

Technical note: Comparison of two methods to quantify exercise energy expenditure in trotters

This study aimed at quantifying energy expenditure during 4 specific training exercises, that is, promenade, jogging, parcours, and interval exercises, using field measurements of oxygen consumption and heart rate in trotters. Six animals performed 2 preliminary tests to determine their individual maximum velocity and to establish their individual oxygen consumption/heart rate relationship from an incremental test. Then, they undertook each of the 4 specific exercises separated by 1 wk to avoid fatigue. The intensity of the 4 exercises was expressed in percent of individual maximum velocity as well as duration and distance set according to current training practices of French trotter trainers. Throughout the incremental test and the 4 exercises, oxygen consumption and heart rate were continuously recorded using a portable respiratory gas analyzer. Energy expenditure of the 3 different phases (warm-up, exercise, and recovery) of the 4 exercises and the total energy expended during exercises (sum of energy expended during the 3 phases) were calculated from direct oxygen uptake measurements and from estimated oxygen uptake using heart rate and O caloric equivalent. The quantification of total energy expenditure from the 2 methods was not significantly different. However, estimated energy expenditure was significantly lower from estimated oxygen consumption than direct oxygen uptake method concerning the warm-up and exercise phase of parcours. Our results indicate that the estimated oxygen uptake from heart rate measurements could be used to evaluate total energy expenditure of exercises in trotters. Whereas this method requires previous establishment of an individual oxygen consumption/heart rate curve, it is easy to record using commercially available instruments under practical conditions and opens new perspectives to assess energy balance in trotters' nutrition.

Effects of two field continuous incremental tests on cardiorespiratory responses in Standardbred trotters

In humans, cardiorespiratory responses are widely evaluated from field incremental exercise tests. On the contrary, equine exercise physiology faces a huge lack of oxygen consumption measurements (VO2) in field conditions due to technical concerns. The aim of this study was to test the effects of two incremental continuous field tests on cardiorespiratory responses in Standardbred trotters. The two protocols were realized at trot and ended when horses galloped. The tests started at 4.2 m/s (T1) and 6.4 m/s (T2), with speed increments of 1.4 m/s every 3 min for T1 and 0.8 m/s every 2 min for T2. Velocity (v), heart rate (HR) and gas exchanges were recorded continuously, and blood lactate concentration [La(-)] was measured before and after tests. Values recorded at the end of the tests were considered as peak values. The vpeak values were 10.6 ± 0.3 and 10.7 ± 0.7 m/s for T1 and T2 respectively. Horses reached higher VO2peak (T1: 116.6 ± 11.5 ml/min/kg; T2: 88.9 ± 10.2 ml/min/kg; p < 0.05) and HRpeak (T1: 217 ± 5 bpm; T2: 209 ± 3 bpm; p < 0.05) during T1 compared with T2. T1 was significantly longer than T2 (17.5 ± 1.9 vs. 12.9 ± 1.6 min respectively, p < 0.01), and the number of steps entirely ran tended to be different (T1: 5.6 ± 0.6; T2: 6.2 ± 0.8, p = 0.07). Compared to T2, the design of T1 appeared easier to implement and allowed higher cardiorespiratory responses. The relationship between HR-VO2 obtained through T1 gave a better correlation between the two variables than T2. These findings suggest that T1 might be better than T2 for evaluating cardiorespiratory adaptations to exercise and for estimating aerobic energy expenditure in exercising trotters.

Mobile bag starch prececal disappearance and postprandial glycemic response of four forms of barley in horses

To determine prececal starch digestibili-ty and estimate glucose uptake from the digestion of 4 forms of barley in the small intestine, 4 mature cecally fistulated geldings (449 ± 41 kg BW) fed a 62:38 (wt/wt) meadow hay:concentrate diet at 1.7 kg DM/100 kg BW were included in a 4 × 4 Latin square design experiment. During each period, horses received 80% DM of their concentrate as 1 of the 4 forms of a same batch of barley, whole grain, 2.5 mm ground, steam flaked, and pelleted. Hay was offered in 2 equal meals and concentrate in 2 unequal meals. The starch supply in the morning meal amounted 2.7 g starch/kg BW. At each period, mobile bag DM and starch disappearance was determined. Except for ground barley, each form of barley was 4 mm ground before being introduced in the bag. Nylon bags containing each substrate were intubated in the horse receiving the pelleted barley. Bags were collected in the cecum for 10 h postintubation. At each period, postprandial glycemia was measured on blood samples collected on the 4 horses via an indwelling jugular catheter just before the concentrate morning meal and for 8 h. No hay in the morning meal was given the day of the measurements. Whole blood glucose was analyzed with a portable blood glucose meter. Mobile bag prececal DM disappearance and starch disappearance depended (P < 0.01) on barley form. Prececal starch disappearance of whole barley was the lowest but no difference (P > 0.05) was detected among the 3 processed grains. No significant effect of barley form was found whatever the glycemic parameters. No significant correlation was reported between glycemic parameters and the amount of prececal mobile bag disappeared starch calculated as the starch intake in the morning meal by the mobile bag starch disappearance. To conclude, the whole form of barley exhibited the lowest prececal mobile bag starch disappearance whereas, in relationship with large individual variations, no significant variation has been shown in glycemic parameters. Further investigations should be performed to improve methods for estimating prececal starch digestion of processed cereals in the different digestive segments of horses.

Training management of Standardbred trotters: a field survey in France

This study aimed to characterise the training practices of French trainers and to describe the training load undertaken by unqualified (UT) and qualified Standardbred trotters (QT). During the Paris-Vincennes 2012 meeting, 20 trainers from the Grosbois training centre were surveyed. Details of their general training practices as well as the weekly workloads for UT and QT were obtained. A nonparametric Mann-Whitney test was used to compare the UT and QT data and a principal component analysis (PCA) was carried out to examine links between trainer characteristics and particular training practices. Four main exercises used to train trotters were identified: (1) ‘promenade’ exercise: light exercise at walk and at slow trot (5.1±0.4 m/s) lasting 48±9 min; (2) ‘jogging’: moderate trot exercise (6.9±1.5 m/s) lasting 44±12 min; (3) ‘parcours’ exercise: moderate/high intensity trot session (10.3±0.9 m/s) over 2,844±1,412 meters with a final sprint; (4) ‘interval’ type exercise: fast trot sessions (10.8±0.9 m/s) over 1,010±212 meters with sprint phases. Trainers used a combination of these four exercises to train both UT and QT. Moreover, the estimated training weekly workload did not appear to differ between the two age categories, with apparently similar exercises and training loads being used to train both UT and QT. The results of the PCA suggested that as trainers become older and more successful they tend to change the composition of exercises used. They preferably used more ‘jogging’ type exercise, regardless of the horses’ age or training level. Whilst the weekly training plan varied between trainers, it seems that the individual trainer's annual programme was relatively constant, consisting of a repetition of a typical training week.

Effect of transportation on fecal bacterial communities and fermentative activities in horses: impact of Saccharomyces cerevisiae CNCM I-1077 supplementation

This study evaluated the effect of transportation on fecal bacterial communities and activities in horses with or without supplementation of live yeast and attempted to link those effects with changes in blood stress markers. Four mature horses were assigned to a crossover design and fed a basal diet (60:40 forage to concentrate; 1.45% BW on a DM basis), with or without supplementation, of 2 × 10(10) cfu/d of Saccharomyces cerevisiae CNCM I-1077. After a 14-d adaptation to dietary treatments, the 5-d experiment started 1 d before transportation (d -1). At d 0, horses were simultaneously transported in a truck for 2 h. Feces were sampled 4 h after the morning meal of concentrate at d -1, 0 (immediately after transportation), and 3 for enumeration of the main functional bacterial groups and determination of fermentative variables. Within each dietary treatment, feces were pooled before DNA extraction and molecular analysis of the bacterial communities, using temporal temperature gradient electrophoreses (TTGE). Blood samples were collected at the same time for determination of white blood cells (WBC) counts and glucose and total protein concentrations. Regardless of dietary treatment, the neutrophil to lymphocyte ratio increased during transportation (P < 0.01), indicating that horses were stressed. In both treatments, TTGE profiles were clearly different before and 3 d after transportation, and the percentage of similarity between profiles at d -1 and 3 was greater in supplemented horses compared with the controls. From d 0 to 3, the molar percentage of propionate increased and total concentration of VFA and the acetate + butyrate to propionate ratio decreased, regardless of dietary treatment (P < 0.01, P = 0.02, and P < 0.01, respectively), whereas pH decreased only in control horses (P = 0.03). Regardless of day of sampling, fecal concentrations of lactate-utilizing bacteria and cellulolytic bacteria were greater in supplemented horses than in control horses (P = 0.04 and 0.08, respectively). Our results indicate that transportation for 2 h disturbed the fecal bacterial ecosystem in horses that could increase the risk of triggering microbial dysbiosis on a longer term in the equine large intestine. Supplementing Saccharomyces cerevisiae CNCM I-1077 could help reduce the negative impact of transportation on the fecal bacterial ecosystem.

Oxygen consumption and gait variables of Arabian endurance horses measured during a field exercise test

REASONS FOR PERFORMING STUDY

Arabian horses have morphological, muscular and metabolic features designed for endurance races. Their gas exchange and gait variables were therefore measured during a field exercise test. This study presents original respiratory and locomotor data recorded in endurance horses under field conditions.

HYPOTHESIS AND OBJECTIVES

Respiratory gas exchange ratio (RER) of Arabian horses at the speed required to win endurance races (18 km/h for 120-160 km) are <1 and running economy (RE) is also low in order to maintain exercise intensity using aerobic metabolism for long intervals. The purpose of this study was to measure oxygen consumption and gait variables in Arabian endurance horses running in the field in order to estimate RER and RE.

MATERIALS AND METHODS

Five Arabian horses trained for endurance racing were test ridden at increasing speeds on the field. Their speed was recorded and controlled by the rider using a GPS logger. Each horse was equipped with a portable respiratory gas analyser, which measured breath-by-breath respiratory variables and heart rate. The gait variables were recorded using tri-axial accelerometer data loggers and software for gait analysis. Descriptive statistics and linear regressions were used to analyse the speed related changes in each variable with P < 0.05 taken as significant.

RESULTS

At a canter speed corresponding to endurance race winning speed (18 km/h), horses presented a VO(2) = 42 ± 9 ml/min/kg bwt, RER = 0.96 ± 0.10 and RE (= VO(2) /speed) = 134 ± 27 l/km/kg bwt. Linear relationships were observed between speed and VO(2,) HR and gait variables. Significant correlations were observed between VO(2) and gait variables.

CONCLUSIONS AND POTENTIAL RELEVANCE

The RER of 0.96 at winning endurance speed indicates that Arabian horses mainly use aerobic metabolism based on lipid oxidation and that RER may also be related to a good coordination between running speed, respiratory and gait parameters.

Urinary excretion of dietary contaminants in horses

REASONS FOR PERFORMING STUDY

Presence of drugs is completely prohibited in post racing urine samples by most of racing and competition authorities, even if environmental contamination might occur.

OBJECTIVES

To assess the daily dose of several contaminants absorbed through the diet that would result in detectable concentrations in urine.

METHODS

Caffeine, theobromine, theophylline, atropine, scopolamine, bufotenine, DMT or morphine were administered orally to 6 horses, in different dosages, for 3 days before their urine was sampled for regular anti-doping tests.

RESULTS

Theobromine, theophylline, bufotenine and morphine daily intake >10 mg, 2 mg, 10 mg and 200 microg, respectively, by a performance horse, were found to result in detectable urinary concentrations. At the 2 tested doses, atropine (5 and 15 mg) and dimethyltryptamine (3 and 10 mg) were not detected in urine. For caffeine and scopolamine, even the lowest dosage tested (5 mg/horse/day and 2 mg/horse/day respectively) induced detectable concentrations of the molecule in urine.

CONCLUSIONS

Horses fed dietary contaminants, even at level much below the effective dosage, may be positive to antidoping urine analysis. Further research is needed to gain more confident results on a daily safe intake for caffeine and scopolamine.

POTENTIAL RELEVANCE

Selection of feed materials appears to be of great importance to prevent non voluntary positive result to anti-doping tests.

Meal size and starch content affect gastric emptying in horses

REASONS FOR PERFORMING STUDY

Feeding practices have been associated with colic in horses. If meal size and composition have an effect on gastric emptying, this could be one of the mechanisms by which feeding practices are related to the occurrence of colic.

OBJECTIVES

To evaluate the effect of meal size and starch content on solid phase gastric emptying.

METHODS

Solid phase gastric emptying of 3 different radiolabelled meals, small low-starch (SmLS), small high-starch (SmHS) and large high-starch (LgHS) meals, was measured in 5 horses by scintigraphy using 99mTc-disofenin. Data were compared among meals using nonlinear mixed-effects models and paired t tests.

RESULTS

On a percentage basis, SmHS emptied significantly faster than LgHS and SmLS emptied significantly faster than SmHS meals. However, when meals of unequal size were compared by emptying rate in g/min and Kcal/min, LgHS emptied significantly faster than SmHS.

CONCLUSIONS

Meal size and composition affect gastric emptying.

POTENTIAL RELEVANCE

Further work needs to be performed in order to substantiate the possibility of a relationship between digestive functions and occurrence of colic and gastric ulcers.

Effects on the equine colon ecosystem of grass silage and haylage diets after an abrupt change from hay

The objective of this study was to investigate the effect of an abrupt change from grass hay (81% DM) to grass silage (36% DM) or grass haylage (55% DM), fed at similar DM intakes, and to compare the effects of silage and haylage on the composition and activities of the colon microflora. The forages were from the same swath harvested on the same day. Four adult colon-fistulated geldings were randomly assigned to diets in a crossover design. The study started with a preperiod when all 4 horses received the hay diet, followed by an abrupt feed change to the haylage diet for 2 horses and the silage diet for 2 horses. All 4 horses then had a new second preperiod of hay, followed by an abrupt feed change to the opposite haylage and silage diet. The periods were 21 d long, and the forage-only diets were supplemented with minerals and salt. The abrupt feed changes were made at 0800 h. Colon samples were taken before the abrupt feed change, 4 and 28 h after the feed change, and 8, 15, and 21 d after the feed change, all at 1200 h. Colon bacterial counts, VFA, pH, and DM concentrations were unchanged throughout the first 28 h after the abrupt feed change from hay to haylage and silage. Also, fecal pH and DM concentrations were unchanged during the first 28 h. During the weekly observations, colon lactobacilli counts increased (P = 0.023) in horses receiving the silage diet and were greater than on the haylage diet at 21 d. Streptococci counts decreased (P = 0.046) in horses receiving the haylage diet and were less than on the silage diet at 15 and 21 d. Total VFA concentrations and colon and fecal pH did not differ between diets and were unchanged throughout the weekly observations. The DM concentration of colon digesta and feces decreased (P = 0.030 and 0.049, respectively) on both diets during the weekly observations. The results suggest that in horses fed at the maintenance level of energy intake, an abrupt feed change from grass hay to grass silage or grass haylage from the same crop does not induce any major alterations in the colon ecosystem during the first 28 h. During the subsequent 3-wk period, colon and fecal DM decreased and there were alterations in the lactobacilli and streptococci bacterial counts. The changes in lactobacilli and streptococci counts need further investigation.

Effects of crude protein intake from grass silage-only diets on the equine colon ecosystem after an abrupt feed change

The objective of this study was to investigate the effect of CP intake from 2 grass silage-only diets, differing in CP concentration, fed at similar DMI on the equine colon ecosystem after an abrupt feed change between the diets. Four adult right ventral colon-fistulated geldings were fed one silage-only diet high in CP (HP, 873 g of CP/d) and one diet providing recommended intakes (RP, 615 g of CP/d). An adaptation period of 15 d on either the HP or the RP diet was followed by 2 experimental periods when the diets were fed for 22 d each in a crossover design. Colon samples were taken before and at 4, 12, and 24 h, and at 7, 14, and 22 d after the feed change. During the first 24 h after the abrupt feed change, the concentrations of total anaerobic bacteria and lactobacilli were greater on the HP than the RP diet (7.1 vs. 6.7 log(10) cfu/mL, P = 0.021, 6.0 vs. 5.5 log(10) cfu/mL, P = 0.021, respectively). During the first 24 h post feed change, VFA concentrations did not differ between the diets. From 7 to 22 d, total VFA concentrations were greater on the HP diet than on the RP diet (51.8 vs. 45.1 mmol/L, P = 0.034), and colon pH was lower on the HP diet than on the RP diet (6.9 vs. 7.2, P = 0.035). After an adaptation period of 22 d, N, ammonia, and urea concentrations and osmolality of the colon fluid did not differ between diets. Fecal pH and colon and fecal DM were unchanged throughout the experiment. The results suggest that, in horses fed at the maintenance level of energy intake, a feed change between silages with different CP content may alter the colon bacterial counts within the first 24 h. Moreover, during the subsequent 3 wk, pH decreased slightly and VFA concentrations increased, but no other major alterations occurred in the composition and activities of the colon ecosystem or fecal DM.

Effect of live yeast culture supplementation on apparent digestibility and rate of passage in horses fed a high-fiber or high-starch diet1

Eight crossbred male horses aged 12 +/- 5 yr and with BW of 305 +/- 18 kg were used in pairs in a 4 x 4 Latin square design with 4 ground and pelleted diets. Each pair included a cecum and right ventral colon-fistulated animal and a cecal-fistulated animal. The 4 horse diets were a high-fiber diet (HF+0) based on dehydrated alfalfa, a high-starch diet based on barley and wheat bran (HS+0), and the HF or HS diets supplemented with Saccharomyces cerevisiae (SC) CBS 493.94 (HF+SC and HS+SC). The probiotic preparation contained 4.5 x 10(9) cfu/g of live yeast mixed with the culture medium, and was top-dressed onto the feed pellets at a rate of 10 g/d, equally distributed between the 2 daily meals. All 4 diets were offered in the same quantities (18.0 g of pelleted feed DM + 3.5 g of long wheat straw/kg of BW per d). Each of the 4 experimental treatments was divided into a 21-d period of diet adaptation followed by a 10-d period of total fecal collection for digesta flow rate and apparent digestibility measurements. Three markers were used to measure mean retention time (MRT) of the feed particles: Yb bound to the pelleted feeds for MRT in the whole digestive tract (MRT(Yb)), Eu bound to the pelleted feeds, and Dy bound to the fecal particles for MRT in the hindgut (MRT(Eu) and MRT(Dy)). Apparent digestibilities of DM, OM, and CP were greater (P < 0.001) in the HS than HF diet, independently of SC supplementation, whereas ADF digestibility was greatest in the HF diet (P = 0.035). Cellulolytic activity estimated through the in vitro disappearance rate of the dietary ADF fraction (IVAD(ADF)) was less (P < 0.001) in the HS than the HF diet. There was no dietary effect on NDF digestibility due to the longer MRT(Eu) of small particles in the hindgut (P = 0.036), which compensated for the lower fibrolytic activity expressed per unit of time in the HS compared with the HF diet. Supplementation with SC improved ADF digestibility (P = 0.038) and stimulated DM (P = 0.030) and NDF (P = 0.038) intakes, but had no effect on the MRT of solid digesta. The absence of any significant diet x SC interaction supports the strategy of using SC to stimulate cellulose digestion and improve the nutritional status of horses under both HF and HS diets.

Postprandial kinetics of some biotic and abiotic characteristics of the gastric ecosystem of horses fed a pelleted concentrate meal

Our knowledge of the microflora of the stomach of the horse is still limited, although some data indicate its important role in nutrition. The objective of this experiment was to investigate the microbial and biochemical profiles in the stomach of the horse and to quantify the disappearance of dietary starch. Total anaerobic bacteria, lactate-utilizing bacteria, lactobacilli, and streptococci were determined, and biochemical characteristics (pH, and DM, D- and L-lactate, D-glucose, NH3, and VFA concentrations) were measured in chyme collected from 4 horses by naso-gastric intubation aided by endoscopy, at 30 min before and 60, 120, and 210 min after the meal. The total anaerobic population exhibited a linear increase (5.54 to 6.98 log10 cfu/mL; P = 0.018) within the first postprandial hour and reached 8.32 log10 cfu/mL at 210 min after the meal. The concentrations of lactobacilli, streptococci, and lactate-utilizing bacteria in the stomach contents were 5.52, 4.82, and 6.95 log10 cfu/mL, respectively. Lactate concentration increased linearly from 0.25 mmol/L before the meal to 7.98 mmol/L at the last collection point (P = 0.013). This increase was mostly due to L-lactate accumulation. The VFA concentration increased linearly (P = 0.002) during the postprandial period from 1.96 to 8.17 mmol/L. Acetate represented, on average, 78 mol/100 mol of total VFA. The average concentration of NH3 in the stomach content was 2.48 mmol/L. Dietary starch disappearance did not respond during the post-prandial period and was not consistent with previous findings. These in vivo data provide complementary information on the postprandial microbial and biochemical kinetics in the stomachs of horses and confirm its abundant microbial colonization.

Effect of diet composition and feeding pattern on the prececal digestibility of starches from diverse botanical origins measured with the mobile nylon bag technique in horses1

This trial was conducted to determine the extent of prececal starch digestibility depending on the botanical origin of starch and on diet characteristics (i.e., composition and feeding pattern). The prececal disappearance of six substrates (oats, barley, corn, horse bean, potato, and wheat) was measured in four cannulated horses fed (as-fed basis) 11.8 g/kg BW of a high-fiber (HF) or high-starch (HS) pelleted feed and 10.0 g/kg BW of meadow hay using the mobile bag technique (MBT). The daily feeding pattern was either three meals (two meals of pellets and one meal of hay) or five meals (three meals of pellets and two meals of hay). The experimental procedure was a 2 x 2 factorial arrangement tested in a Latin square design. After 2 wk of adaptation to the diet, collections were made on 5 d. Thirty nylon bags, composed of five bags of each substrate, were intubated to each horse during the ingestion of the morning meal. Bags were collected in the cecum, using a magnet, at 9 h postintubation. In spite of strong interindividual differences, approximately 80% of the intubated bags were collected. On average, the mean retention time of the bags was 6.2 h (+/-0.17). Regardless of the feeding pattern, the transit of the bags was faster when the fiber content of the diet was higher (P = 0.003). Likewise, regardless of the meal composition, transit was also faster when the ration was split into five daily meals (P = 0.001). The DM disappearance, corrected with particulate losses (DMD(c)), differed depending on the substrate tested (33.5, 57.1, 63.8, 67.7, 78.6, and 86.2% for potato, horse bean, oats, barley, corn, and wheat, respectively; P = 0.001). The DMD(c) of corn, barley, and potato was higher when HS was fed (P = 0.020); regardless of the substrate, DMD(c) was higher with five daily meals (P = 0.001). The starch disappearance (StarchD(c)) was different depending on the substrate (P = 0.001; 36.1, 71.2, 86.6, 89.2, 99.0, and 99.7% for potato, horse bean, barley, corn, wheat, and oats, respectively). Whatever the substrate, StarchD(c) was higher when HS was fed (P = 0.007), but it was not affected by the feeding pattern of the diet. Although passage rate was modified and feed intake was different, the botanical origin of starch was the main factor that affected prececal starch disappearance in horses.

Risk factors associated with colic in horses

Many factors have been identified as risk factors for colic in horses in several epidemiological studies. The aim of our paper was to review the results of 12 epidemiological studies, in order to assess the impact of each risk factor for colic. According to the literature, the factors that increase the risk of colic are feeding practices (type and quality of food, type and changes of feeding), the intrinsic factors of horses (sex, age and breed), management (type and changes of housing and activity), medical history (a previous colic, administration of a medical treatment) and parasite control (the presence of worms and type of deworming program). Several individual factors were incriminated as risk factors by all the studies. Nevertheless, the different studies did not always agree on the role of other risk factors. The conclusions were tightly related to several criteria in the selection of the study population, like the type of the epidemiological study, the number and the origin of horses included and the location of the study.