Choose an application

• Reference Manager
• EndNote
• RefWorks (Direct export to RefWorks)

Dit project werd uitgevoerd bij Kemin Europa NV in Herentals, een producent van additieven voor voeding en veevoeders. Er werd onderzoek gedaan naar de invloed van exogene voederenzymen op het fermentatieproces in de darm van eenmagige dieren. Deze fermentatie is van groot belang voor de diergezondheid en het milieu. In een eerste deel van het project werd een methode ontwikkeld om het fermentatie-proces in vitro na te bootsen. In de uiteindelijke procedure werd een mengsel van Escherichia coli, Lactobacillus salivarius, Enterococcus avium en Clostridium perfringens, geïsoleerd uit de mest van leghennen gebruikt als standaard inoculum en de fermentatie werd uitgevoerd op 37{deg}C gedurende 48 uur met 6 gram substraat. Als substraat werd in het hele experiment distillers dried grains with solubles (DDGS) gebruikt. Microbiële tellingen voor en na fermentatie toonden aan dat de stammen wel degelijk konden groeien in deze omstandigheden, metingen van vluchtige vetzuren en ammoniak toonden

Choose an application

• Reference Manager
• EndNote
• RefWorks (Direct export to RefWorks)

Wheat (Triticum aestivum L.) is one of the most widely grown cereals in the world and the most important constituent of broiler diets in Europe. In the practice of broiler production, however, there is a lot of variability in animal performance, even with the same diet composition. Today, it is still not completely known which factors of wheat are responsible for these variations. Wheat contains a very diverse concentration of non-starch polysaccharides (NSP), which have been put forward as a major factor in explaining wheat variability. The way in which the NSP exert their negative effects remains unclear. The NSP are believed to increase the viscosity of the intestinal contents, which disturbs the digestive process. In addition the NSP in the cell walls of wheat are suggested to impair nutrient availability to the animal by blocking the access to the cell contents for endogenous digestive enzymes. Because of the anti-nutritional effects associated with NSP it is standard practice to add NSP degrading enzymes to wheat-based broiler feed. Nevertheless, problems with variable animal performance occur even when feed enzymes are added to the diet. To contribute to the current knowledge about NSP and feed enzymes, the present study includes an in depth evaluation of the concentration and composition of NSP in European feed wheat, as well as in vitro and in vivo studies to investigate their functionality during broiler digestion. The first objective was to determine the ranges in variability in the chemical composition of wheat used for feed formulations in Europe. The concentration of NSP was measured in a total of 153 wheat batches destined for the feed industry. Until now, studies have mainly focused on wheat obtained from single countries, whereas in the present study, the wheat batches were obtained from commercial feed mills all over the European continent. The study demonstrated the highly variable concentration of NSP in wheat. NSP can be divided into a water-extractable (WE) and water-unextractable (WU)-fraction. The WE- and WU-fraction of the NSP ranged between 8.7 and 18.3 g kg-1 dry matter (DM) and 58.1 and 99.6 g kg-1 DM respectively. The variation was the largest in the WE-fraction of the NSP (coefficient of variation of 14.3%). It is mainly the latter fraction that is believed to be responsible for increases in intestinal viscosity in the broiler chicken and hence a disturbed digestion. The second objective was to demonstrate the importance of the NSP fraction of wheat in broiler feed. This was evaluated in a broiler digestibility trial. Because the ranges in NSP variability were defined in a first step of this research, it was possible to select wheat batches which were representative for high and low NSP wheat. Broilers were fed diets formulated with three different wheat cultivars, which mainly differed in their concentration of NSP (high vs low). The results showed that inclusion of a high NSP wheat cultivar in a broiler feed indeed caused a reduction in the digestibility of dry matter and protein and in the nutritional value (expressed as apparent metabolizable energy) of the feed, compared to two low NSP wheat cultivars. The reduced nutrient digestibility with the high NSP wheat cultivar was, in contrast to what was expected, not related to an increased intestinal viscosity. The highest intestinal viscosity (and also in vitro extract viscosity) was obtained with one of the wheat cultivars with a low concentration of NSP. The results suggest that other factors of wheat, next to its NSP concentration or composition, can cause increases in intestinal viscosity, even without further affecting nutrient digestibility. This also means that viscosity (in vitro or intestinal) alone (commonly used in the practice of broiler feed formulation) is not a good predictor for the nutritional quality (measured as apparent metabolizable energy) of wheat. The third and final objective was to gain more insight in the interaction between NSP and feed enzymes. Three factors that can explain variations in enzyme responses were explored. These were (1) the NSP concentration and composition of wheat, (2) the presence of xylanase inhibitors and grain-associated xylanases and (3) the different efficacy of commercial enzyme preparations (which contain various NSP degrading enzymes and enzymes such as α-amylase and/or peptidases). The exploration of these factors included both in vitro and in vivo studies. In vitro, it appeared that the effect of a xylanase preparation was related to the concentration of NSP initially present in wheat, but also to the arabinose to xylose ratio of arabinoxylan (the predominant NSP in wheat). Moreover, xylanase inhibitors and grain-associated xylanases affected the action of a commonly used xylanase preparation in vitro and pelleting did not eliminate their effects. To the best of our knowledge, the latter was not shown before. Also, in vitro, it was confirmed that, compared to single enzyme preparations (which originate from one single micro-organism), a complex mixture of enzyme preparations (which include enzymes from different micro-organisms) was able to degrade a larger proportion of WU-NSP.These in vitro findings were tested in vivo in broiler trials. In a first broiler digestibility trial, the effect of the NSP concentration on enzyme efficacy (the ability of the enzyme to increase the digestibility of nutrients) was evaluated. Diets contained different wheat cultivars, which differed mainly in their NSP concentration (average vs high), with and without the addition of a commercial enzyme preparation. Without the addition of the enzyme preparation, no difference was observed in nutrient digestibility (dry matter, starch, fat or protein) or nutritional value between the diets. This is in contrast to what was found in the second part of the dissertation, where the addition of a high NSP wheat did result in a depressed nutrient digestibility, compared to a low NSP wheat. This means that the relationship between the concentration of NSP and the nutritional value of wheat is inconsistent and the results suggest that the relationship might be related to the digestibility of the NSP. When the enzyme preparation was added to the diets, its effect on nutrient digestibility was improved with a high NSP wheat, compared to wheat with an average concentration of NSP. The latter confirms the in vitro results obtained earlier. In a second series of broiler trials, the efficacy of four different xylanase preparations and two enzyme mixtures was compared. As observed in the in vitro research, the addition of a mixture of enzymes resulted in an increased degradation of the WU-NSP, compared to the xylanase preparation alone. Furthermore, the two xylanase preparations which were able to degrade the largest concentration of WU-NSP, were the most effective in improving nutrient digestibility (dry matter, starch, protein and fat) and animal performance (body weight gain and feed conversion ratio).In conclusion, the present research (1) provides ranges for the NSP variability in European feed wheat, (2) demonstrates that the relationship between the concentration of NSP and the nutritional value of wheat is inconsistent and appears to be related to the digestibility of the NSP, (3) shows that it is impossible to predict the nutritional value of wheat based on the chemical and physical measurements considered in this research (4) reveals that enzyme responses are affected by the concentration and structure of the NSP fraction of wheat, by the presence of xylanase inhibitors and grain-associated xylanases and are affected by the ability of the enzyme preparations to degrade the WU-fraction of NSP. It means that in practice, it is still impossible to accurately predict animal performances based on the chemical composition of wheat, even with the inclusion of NSP characteristics in predictions. A possible improvement can be to include a measurement of the digestibility of NSP. Furthermore, for the prediction of feed enzyme responses, the concentration of NSP in wheat should be considered. In addition, feed enzyme manufacturers should focus on finding enzyme preparations which are most effective in degrading the WU-fraction of NSP.