Effects of processing barley on its digestion by horses

The effects of processing barley and maize on metabolic and digestive responses in horses

The competition for customers increases the search for new grain processing methods for equine feed, but the effect on starch digestibility and metabolic responses varies. Therefore, to evaluate the effect of the processing methods, toasting and micronizing, on starch digestion and the effect on metabolic responses, the mobile bag technique (MBT) and plasma glucose and insulin concentrations in the blood were used to estimate nutrient disappearance and metabolic responses pre-cecally. Further, cecal pH, ammonium nitrogen (N), and short-chain fatty acid (SCFA) concentrations were used to estimate the metabolic response in the cecum. Four cecally cannulated horses (body weight [BW] 565 ± 35 kg) were used in a 4 × 4 Latin square design with four periods of 8 d of diet adaptation and 2 d of data collection. Diets were formulated using hay and processed grains: micronized barley (MB), toasted barley (TB), micronized maize (MM), and toasted maize (TM) and were balanced to provide 1 g starch/kg BW in the morning meal. On day 9 in each period, blood and cecal fluid samples were taken before the morning meal and hourly thereafter for 8 h. On day 10 in each period, 15 bags of either MB, TB, MM, or TM (1 × 1 × 12 cm; 15 μm pore size; 1 g feed) were placed in the stomach, respectively. The dry matter disappearance was highest for the MM at all time points compared with the other feedstuffs (P < 0.001). Maize and micronizing had the highest starch disappearance (P = 0.048) compared with barley and toasting. No treatment effect was measured for any of the glucose and insulin parameters. No feed effect was measured for the insulin parameters. Plasma glucose peaked later (P = 0.045) for maize than for barley, and TB had a larger area under the curve for glucose than MB, MM, and TM (P = 0.015). The concentration of total SCFA increased after feeding (P < 0.001), with a higher concentration for barley than for maize (P = 0.044). No treatment or feed effects were measured for ammonium N or pH, but both were affected by time (P < 0.001). In conclusion, toasting was not as efficient as micronizing to improve pre-cecal starch digestibility; therefore, the preferred processing method for both barley and maize is micronizing. Further, the amount of starch escaping enzymatical digestion in the small intestine was higher than expected.

Effects of isoenergetic quantities of a low-starch muesli feed high in fat and fibre vs. oat grains on the glycemic and insulinemic responses and feed intake patterns in sport ponies

Aim of this study was to compare glycemic and insulinemic responses and feed intake patterns in sport ponies after feeding isoenergetic quantities of low-starch muesli feed high in fat and fibre (FF) or oat grains (OG). Six sport ponies were randomly assigned to one of these two treatment groups for 2 × 3 weeks according to a crossover-design. Ponies received two equal meals/day of either semi-crushed OG (1 g starch/kg bwt*meal^-1 ) or an isoenergetic quantity of FF. Hay was also given in two equal meals/day and provided the remaining metabolisable energy up to 1.3-fold maintenance level. On day 21, blood was sampled 1 h after each pony received 0.5 kg hay (0 min). Then, the concentrate was provided and blood sampled 30, 60, 90, 120, 180, 240 and 300 min thereafter. Plasma glucose and serum insulin were analysed, and the areas under the curve (AUC) was calculated 120 and 300 min postprandial (PP). Feed intake patterns were measured in 4 ponies/group via a modified halter. OG was ingested faster than FF (feed intake time; FIT_DM in min/kg DM: 8.8 ± 1.6 vs. 15.9 ± 1.62, p < 0.05) combined with a higher chewing frequency (p < 0.05). The AUCs_{gluc120/300, ins120/300} were statistically higher with OG than FF (mmol/L*min^-1 : AUC_gluc120 : 776 ± 128 vs. 676 ± 80.4; AUC_gluc300 : 1811 ± 295.3 vs. 1569 ± 126.3; nmol/L*min^-1 : AUC_ins120 : 38 ± 18 vs. 22 ± 8.1; AUC_ins300 : 83 ± 39 vs. 35 ± 12; p < 0.05). Plasma glucose tended to decline following the intake of FF, which might be beneficial for equines with reduced glucose tolerance. This, however, requires further investigation. In this study, the ponies consumed OG unexpectedly rapidly. The rate of feed intake was similar to the results previously reported in the literature for warmblood horses.

Feeding practice and influence on selected blood parameters in show jumping horses competing in Switzerland

The aim of this study was to compare the nutritional management of show jumping horses in practice with recommendations from the literature. Additionally, the effects of these feeding practices on several blood metabolic parameters before and after exercise were studied. Blood samples were collected in the field from 27 different horses at 71 trials on the level M1 to S2 show jumping competitions in Switzerland and questionnaires on feeding practice of the studied horses were evaluated. The questionnaires revealed that during training and on tournament days horses received on average 3.1 kg of concentrate per day (min. 2.0 kg, max. 6.6 kg) divided into two to three meals. The horses were fed on average 6.9 kg of roughage per day (min. 4.0 kg, max. 13.0 kg). Additionally, it was observed that the horses received the last meal on average 6 h 10 min (min. 1 h 50 min, max. 12 h 30 min) before the start of the first show jumping turn, respectively, 7 h 30 min (min 1 h 50 min, max. 13 h 0 min) before the second turn. Seven horses (35%) had access to hay waiting in the trailer between two turns. The statistical analysis revealed no significant influence of the concentrate feeding time point on lactate, triglyceride and insulin levels, but a significant influence on free fatty acids (FFA) and blood glucose concentrations. Roughage feeding of the show jumping horses 2-4 h prior to exercise revealed the most remarkable changes in blood parameters during the show jumping course. These results received under field conditions should be approved in future under standardized conditions.

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.

Effects of feeding state on glycaemic and insulinaemic responses to a starchy meal in horses: a methodological approach

A standardised methodology is required for classification of starchy diets. One important question is what feeding status is optimal to describe glycaemic and insulinaemic responses to the respective starchy diet. Four horses were fed, in a randomised order, four different feeding protocols relative to offering hay before or after cracked corn (CC): (i) ad libitum hay for 12 h before feeding CC and ad libitum hay after CC intake for 9 h (+CC+), (ii) ad libitum hay for 12 h before feeding CC and no hay after CC intake for 9 h (+CC-), (iii) feed restriction for 12 h before feeding CC and ad libitum hay after CC intake for 9 h (-CC+) and (iv) 1.2 kg hay/100 kg body weight (BW) per day, divided into two equal portions and offered at 0900 h and 1900 h, feed restriction for 12 h before feeding CC and no hay after CC intake for 9 h (-CC-). CC intake was adjusted to a starch intake of 2 g/kg BW. The different hay offerings did not affect basal plasma glucose and insulin levels. A significant rise in plasma glucose and insulin was found after CC intake for all diets. The highest peak glucose levels were analysed for -CC+, and the lowest glucose peaks were found for +CC- (diet P < 0.05). The highest insulin peaks were monitored for -CC+ (31.27 ± 18.19 μU/ml) and lower peaks for +CC- (13.36 ± 2.93 μU/ml) (diet P < 0.05). Insulin for -CC- and +CC- returned to resting values about 300 min after CC feeding. For +CC+ and -CC+, insulin levels were still above resting levels 510 min after CC intake (diet P < 0.05). The present data suggest that feed restriction for 12 h before feeding the starchy diet and no further roughage intake during blood sampling period provide the best-defined conditions.

A survey on the feeding of eventing horses during competition

This study aims at the comparison of the actual feeding of horses with the recommendations from the literature, and it studies the effects of feeding and exercise on several blood metabolic parameters before and after exercise. Blood samples were collected from 25 horses during one-star eventing competitions and evaluated for blood glucose, insulin, lactate, free fatty acids and triglyceride levels. Questionnaires on the feeding practices of the horses were evaluated. The questionnaires revealed that during training, and on tournament days, horses received on average 4.3 kg of concentrate per day (min. 1.54 kg, max. 8 kg). The statistical analysis showed no significant effect of the amount of concentrate fed before exercise on the measured blood values. Oil was supplied as a supplementary energy source to 30% of the horses, but most of them only received very small quantities (0.02-0.4 l/day). Five horses (20%) had no access to salt supplements at all, and eleven horses (45%) had no access to salt on tournament days. Fifteen horses (60%) were supplied with mineral feed. Twenty-one horses (84%) had daily access to pasture during the training period. During competition, 55% of the horses received roughage ad libitum, compared with 37% during training. The majority of the horses received less roughage on days before the cross-country competition. It could not be ascertained whether feeding a large amounts of roughage had a beneficial effect on performance, because only a few horses in this study were fed with very restrictive roughage. Feeding of most of the horses was in agreement with the recommendations from the literature, except the need for sodium and chloride. The sodium and chloride need for sport horses may be overestimated in literature and needs to be re-evaluated.

Effect of mixing dietary fibre (purified lignocellulose or purified pectin) and a corn meal on glucose and insulin responses in healthy horses

The aim of this study was to investigate the effect of the addition of a purified soluble (pectin) and insoluble (lignocellulose) fibre to a starchy meal on post-prandial glucose and insulin responses in healthy horses. Four horses were fed in a randomized order three different diets: (i) cracked corn, (ii) cracked corn mixed with purified lignocellulose, and (iii) cracked corn mixed with purified pectin. Each diet was adjusted to a starch intake of 2 g/kg bodyweight (BW). Lignocellulose was aligned to an intake of 0.2 g/kg BW, and pectin was fed in a dosage of 0.1 g/kg BW. Each period consisted of a 10-day acclimatization to the diet (fed once per day); during this time, the horses were fed 1.2 kg hay/100 kg BW/day. Blood was collected after each acclimatization period before and after the test meal was fed, without any hay. The increase in plasma glucose and insulin, peak values, and area under the curves were similar for all diets. The present findings suggest that adding purified soluble or insoluble fibre to a corn meal does not affect post-prandial glucose and insulin responses in healthy horses. Feeding strategies for horses with a high energy requirement should include a starch reduction per meal, rather than the addition of purified fibre.