Caspar Wenk

The role of dietary fibre in the digestive physiology of the pig

Abstract Dietary fibre (DF) is usually defined as the sum of plant polysaccharides and lignin that are not hydrolysed by endogenous enzymes of the mammalian digestive system (non-starch polysaccharides and lignin). The amount and composition of DF varies over a wide range between and within feedstuffs. Furthermore, a precise distinction between dietary fibre and starch is far from easy. Therefore, the analysis as well as the physiological function of DF in the digestive tract of the pig can vary considerably. The age or body mass of the pig also interacts with the digestive processes and there is an adaptation developing in the animal over the time of exposure to fibrous diets. DF is generally considered as a fraction with a low energy content. This diluting effect of the diet is used to increase the feed intake during low performance of animals. DF influences transit time with a reduction in the upper and increase in the lower digestive tract and, therefore, decreases the digestibility of almost all nutrients and energy. On the other hand, it increases the microbial growth in the gastrointestinal tract. This can lead to an increased excretion of nutrients in faeces. Finally, DF beneficially influences well-being and health. Fibrous feedstuffs give pigs the opportunity to chew the feed over a longer time. More short chain fatty acids are produced and eventually undesired micro-organisms are excluded. A regular peristaltic action avoids the possibility of constipation.

The influence of cooking and fat trimming on the actual nutrient intake from meat.

The effects of cooking and trimming of visible fatty tissue on the content of fat, fatty acids, minerals and vitamins was studied in six meat cuts (beef rib-eye and brisket, pork neck steak and belly, veal chop and rolled breast) in order to improve the estimates of the actual nutrient intake from meat. Cooking decreased the absolute fat content by about 17.9-44.4% and therefore concomitantly influenced the content of different fatty acids. The trimming of visible fatty tissue additionally decreased the fat content by about 23.8-59.1%. Calcium, sodium, potassium, magnesium and phosphorus decreased during cooking in all cuts and cooking processes, while iron and zinc were found to increase in beef. All vitamins decreased during cooking, with thiamine showing the highest losses, from 73% up to 100%. In conclusion, the cooking and trimming of meat cuts considerably affected the nutrients in various ways and to different degrees, which should be taken into account when the nutrient intakes of meat are estimated.

Carbohydrate to protein ratio in food and cognitive performance in the morning.

The effect of different carbohydrate to protein ratios in food on cognitive functions and the relation between postprandial metabolic and cognitive changes were studied in 15 healthy male students. Subjects were tested in three sessions, separated by 1 week, for short-term changes in mood states, objective cognitive functions, blood parameters, and indirect calorimetry using a repeated-measures, counterbalanced cross-over design. Measurements were made after an overnight fast before and hourly during 3.5 h after test meal ingestion. The isoenergetic (1670 kJ) test meals consisted of three carbohydrate to protein ratios, i.e. a carbohydrate-rich (CHO[4:1]), balanced (BAL[1:1]), and protein-rich (PRO[1:4]) meal, respectively. Overall accuracy in short-term memory was best after the PRO[1:4] meal concomitant to the least variation in glucose metabolism and glucagon to insulin ratio (GIR). Related to changes in glucose metabolism and/or in the ratios of large neutral amino acids (LNAA), respectively, attention and decision times were transiently improved within the first hour after the CHO[4:1] meal, whereas after the first hour the BAL[1:1] and PRO[1:4] meal resulted in improved performance. Overall reaction times of a central task were fastest after the BAL[1:1] meal concomitant to the highest overall tyrosine (Tyr) to LNAA ratio. Our findings suggest that the carbohydrate to protein ratio in food specifically influences higher cognitive functions in the morning. Except for a transient positive effect of rising blood glucose after a carbohydrate-rich meal, a protein-rich or balanced meal seems to result in better overall cognitive performance presumably because of less variation in glucose metabolism and/or higher modulation in LNAA ratios indicated by the overall GIR.

Cognitive performance and its relationship with postprandial metabolic changes after ingestion of different macronutrients in the morning.

The effect of carbohydrate, protein and fat ingestion on simple as well as complex cognitive functions and the relationship between the respective postprandial metabolic changes and changes in cognitive performance were studied in fifteen healthy male students. Subjects were tested in three sessions, separated by 1 week, for short-term changes in blood variables, indirect calorimetry, subjective performance and different objective performance tasks using a repeated-measures counterbalanced cross-over design. Measurements were made after an overnight fast before and hourly during 3 h after test meal ingestion. Test meals consisted of either pure carbohydrates, protein or fat and were served as isoenergetic (1670 kJ) spoonable creams with similar sensory properties. Most aspects of subjective performance did not differ between test meals. For all objective tasks, however, postprandial cognitive performance was best after fat ingestion concomitant with an almost constant glucose metabolism and constant metabolic activation state measured by glucagon:insulin (G:I). In contrast, carbohydrate as well as protein ingestion resulted in lower overall cognitive performance, both together with partly marked changes in glucose metabolism and metabolic activation. They also differently affected specific cognitive functions in relation to their specific effect on metabolism. Carbohydrate ingestion resulted in relatively better short-term memory and accuracy of tasks concomitant with low metabolic activation, whereas protein ingestion resulted in better attention and efficiency of tasks concomitant with higher metabolic activation. Our findings support the concept that good and stable cognitive performance is related to a balanced glucose metabolism and metabolic activation state.

Effects of L-carnitine supplementation on physical performance and energy metabolism of endurance-trained athletes: a double-blind crossover field study.

A double-blind crossover field study was performed to investigate the effects of acute L-carnitine supplementation on metabolism and performance of endurance-trained athletes during and after a marathon run. Seven male subjects were given supplements of 2 g L-carnitine 2 h before the start of a marathon run and again after 20 km of the run. The plasma concentration of metabolites and hormones was analysed 1 h before, immediately after and 1 h after the run, as well as the next morning after the run. In addition, the respiratory exchange ratio (R) was determined before and at the end of the run, and a submaximal performance test was completed on a treadmill the morning after the run. The administration of L-carnitine was associated with a significant increase in the plasma concentration of all analysed carnitine fractions (i.e. free carnitine, short-chain acylcarnitine, long-chain acylcarnitine, total acid soluble carnitine, total carnitine) but caused no significant change in marathon running time, in R, in the plasma concentrations of carbohydrate metabolites (glucose, lactate, pyruvate), of fat metabolites (free fatty acids, glycerol, β-hydroxybutyrate), of hormones (insulin, glucagon, cortisol), and of enzyme activities (creatine kinase, lactate dehydrogenase). Moreover, there was no difference in the result of the submaximal performance test the morning after the run. In conclusion, acute administration of L-carnitine did not affect the metabolism or improve the physical performance of the endurance-trained athletes during the run and did not alter their recovery.

Hyponatremia among runners in the Zurich Marathon.

Objective:Hyperhydration and exercise-associated hyponatremia (EAH) are critical issues during endurance events. We studied a cohort of marathon runners to examine EAHs prevalence in a marathon with a short time limit and to investigate underlying mechanisms that may be responsible for its development. Design:Observational cohort study. Setting:2006 Zurich Marathon (cool and rainy weather, time limit of 5 hours). Participants:167 marathon runners were recruited the month before the race. Main Outcome Measures:Body mass, plasma sodium, and osmolality were measured just before the start and immediately after the race. Fluid intake during the race was ascertained by a recall questionnaire. Results:Five subjects (3 %) developed asymptomatic EAH, and no symptomatic EAH was found. Body mass change during the race correlated similarly with postrace sodium levels (r = −0.72, P < 0.0001) and with sodium change during the race (r = −0.66, P < 0.0001). Postrace sodium levels correlated significantly with sodium change during the race (r = 0.74, P < 0.0001). Fluid intake correlated significantly (r = −0.43, P < 0.0001) with plasma sodium change between the start and finish of the race. Postrace sodium levels and postrace osmolality were significantly correlated (r = 0.68, P < 0.0001). Conclusion:In this study we observed a relatively low incidence of EAH in subjects running the marathon in around 2.5 to 5 hours and in a cool environment. Plasma sodium change during the race and postrace sodium levels correlated with body mass change. There was also a direct correlation between fluid intake and plasma sodium change during the race.

The influence of extruded vs. untreated barley in the feed, with and without dietary enzyme supplement on broiler performance

The experiment was conducted to study the effect of extruded vs. unprocessed barley in the diet (400 g kg−1) on the response of broiler chickens to Trichoderma viride enzyme supplement (cellulase, 10 500 U g−1; endo-β-(1:3) (1:4)-glucanase; 24 000 U g−1 and xylanase, 32 000 U g−1). The four experimental diets were as follows: B, unprocessed barley; BE, unprocessed barley + enzyme (200 mg kg−1); ExB, extruded barley; ExBE, extruded barley + enzyme (200 mg kg−1). The diets were fed as pellets. Extruded compared with unextruded barley gave higher soluble fibre (28 vs. 36 g kg−1) and lower insoluble (190 vs. 163 g kg−1) and total (219 vs. 200 g kg−1) dietary fibre values. Extrusion increased extract viscosity (1.3 vs. 3.7 cP) and water binding capacity (1.6 vs. 2.2 ml g−1 dry matter) of the barley. During the first week, birds fed extruded barley in the diet increased water consumption (P ≤ 0.05). A significant depression in feed efficiency (days 7–21), feed AME, and in fat and protein utilisation was observed when extruded barley was included in the diet. Extrusion reduced the AME content of barley by 0.82 MJ kg−1 DM. Inclusion of extruded barley in the diet potentiated the weight gain (2.8 vs. 7.6%; P = 0.31) and feed efficiency (+ 0.8 vs. −6%; P = 0.07) response to dietary enzyme. Greater enzyme effects with the diet containing extruded barley were also found for feed AME (1.6 vs. 2.9%; P = 0.39), fat utilisation (0.4 vs. 5.4%; P ≤ 0.05), nitrogen utilisation (−0.5 vs. 5.6%; P = 0.12), as well as β-glucan degradability (10.4 vs. 15.6%; P = 0.41). In general, the enzyme had more impact on chick performance than barley form.

Influence of processing treatment and type of cereal on the effect of dietary enzymes in broiler diets

One thousand and six hundred 1-day-old sexed broiler chickens (Vedette; 50% male, 50% female) were randomly allocated to eight treatment groups in order to test the effect of the ROXAZYME G enzyme complex (β-glucanase, xylanase, amylase, pectinase) in pelleted and extruded high-energy diets on broiler performance. Two diets were tested. The first was a commercial diet based on wheat and corn, and in the second 20% wheat was replaced by barley. Both diets were tested in pelleted and extruded form with or without enzyme which was added before processing at the level of 0.15 g kg−1. The eight treatments tested were as follows: Treatments A and B, pelleted wheat-corn diets without and with enzyme respectively; Treatments C and D, extruded wheat-corn diets without and with enzyme; Treatments E and F, pelleted barley-wheat-corn diets without and with enzyme; Treatments G and H, extruded barley-wheat-corn diets without and with enzyme. Energy, fat, N, and fibre utilisation were determined with four diets containing barley in the 5th week of growth. The enzyme complex significantly improved feed conversion ratio (FCR) (1.81 vs. 1.77; P < 0.001) until the end of the growing period (39 days), and liveweight at Day 21 (0.66 kg vs. 0.68 kg; P < 0.001). Highly significant differences were found for liveweight and feed conversion at Day 39 between diets (20% wheat vs. 20% barley: liveweight, 1.81 kg vs. 1.75 kg; FCR, 1.76 vs. 1.81), and also between processing (pelleting vs. extruding: liveweight, 1.84 kg vs. 1.73 kg; FCR, 1.76 vs. 1.82). Birds fed on extruded feeds grew slower and utilised feed less efficiently than birds fed on pelleted feeds. The extrusion process increased the soluble fibre content in the feed, and subsequently the feed extract viscosity was also increased. The interaction between processing (pelleting vs. extrusion) and grain (wheat vs. barley) for liveweight at Days 21 and 39 was significant, indicating a greater negative impact of extrusion on broiler feed containing barley. In the metabolism studies a positive trend caused by enzyme supplementation was seen on energy metabolisability, fat, N, and fibre utilisation, but the differences were not significant.

Effects of Feeding Pigs Increasing Levels of C 18:1 Trans Fatty Acids on Fatty Acid Composition of Backfat and Intramuscular Fat as well as Backfat Firmness

Forty Large White pigs were fed from 30kg to 103kg body mass on diets supplemented with 6% of pure high-oleic sunflower oil (HO) or HO plus increasing amounts of partially hydrogenated rape seed oil (HR; 1.85%, 3.70%, 5.55%), containing high levels of j 6 to j 11 C 18:1 trans fatty acid isomers. Increasing dietary C 18: trans fatty acids resulted in a linear increase in C 18:1 trans fatty acids and conjugated linoleic acid (cis-9, trans-11 CLA) in backfat (BF) as well as in neutral lipids (NL) and phospholipids (PL) of M. long. dorsi. Thus, the rate of bioconversion of trans vaccenic acid (TVA) into CLA and incorporation of C 18:1 trans and CLA into pig adipose tissue was not limited up to 25g total C 18:1 trans fatty acids including 3.3g of TVA perkg feed. BF was higher in C 18:1 trans fatty acids and CLA than M. long. dorsi NL and PL. In BF and NL the sum of saturated fatty acids (SFA) increased with increasing dietary amounts of HR, while in PL SFA were reduced. Thus, according to their physical properties, C 18:1 trans fatty acids partly replaced SFA in PL. Firmness of backfat was also significantly increased (P<0.05) with increasing amounts of HR in feed.

Influence of different fats in pig feed on fatty acid composition of phospholipids and physical meat quality characteristics.

Two feeding experiments (i, ii) were conducted to investigate the influence of different dietary fats on the fatty acid (FA) composition of phospholipids as well as meat quality in pigs. In each experiment 12 x 4 siblings of Swiss Landrace or Large White breed were allocated to one of four feeding treatments according to sex, breed, and litter and fattened from about 25 to 105 kg liveweight. Pigs were fed a control diet (barley, wheat, soybean meal) or the control diet supplemented with 7% pork fat, 4.95% olive oil or 3.17% soybean oil (i) or 5% of olein or stearin fraction of pork fat or hydrogenated fat (ii). The dietary FA composition was reflected in the FA composition of phospholipids in M. long, dorsi and triceps brachii. However, the unsaturated to saturated ratio was not affected by the dietary intake of polyunsaturated FAs and was only slightly increased by the olive oil supplementation. Trans FAs including conjugated linoleic acid were incorporated into phospholipids only to a small extent. The dietary altered fatty acid composition of phospholipids did not cause any effect on pH, cooking loss, texture, or colour of pork, but meat quality as well as the proportion of saturated FA, arachidonic acid, and n-3 fatty acids were significantly influenced by genetic effects.