Hadden Graham

Plant cell walls and monogastric diets

Abstract A brief summary is given of the recent and progressing research at the Swedish University of Agricultural Sciences in development of analytical methodology for plant cell wall components (dietary fiber) and mixed-linkage β-glucans. Applications of the methods for the chemical characterization of various types of human and monogastric animal foods will be presented, including heat-processed, starch-rich foods. In the latter group Maillard reaction products, “resistant starch” and chemically transformed starch increase the dietary fiber values. Nutritional studies on the role and properties of plant cell wall materials in connection with bile acid and cholesterol metabolism in hamster and with digestion of pig and poultry diets will be discussed.

The nutritive value for broiler chickens of pelleting and enzyme supplementation of a diet containing barley, wheat and rye

Abstract A diet based on barley (40%), wheat (25%), and rye (7%) was given as a mash diet or as dry or steam pelleted diets to a total of 384 broiler chickens. Diets were given with or without the addition of a fibre-degrading enzyme preparation. Pelleting increased the water solubility (at 38°C) of starch and crude protein. There were, however, no notable effects on the solubility of dietary fibre components following pelleting or enzyme supplementation. Buffer extracts from pelleted diets had a high relative viscosity, while mash diets gave the lowest relative viscosity. Enzyme supplementation diminished the high viscosity obtained for pelleted diets and reduced sticky droppings. Pelleting increased weight gain for chickens receiving the unsupplemented diets by ∼ 30% and for those fed on the enzyme-supplemented diets by ∼ 20%. This improvement, which was similar at both 14 and 20 days of age, was mainly due to a greater feed intake, particularly with the steam pelleting. Enzyme supplementation improved weight gain by 11–24%, and was more effective in the unpelleted diets and at Day 14. This improvement was due to both a higher feed intake and a better feed conversion efficiency. Pelleting tended to increase ileal digestibility of the unsupplemented diet while enzyme supplementation had a similar effect on the unpelleted diet. The latter treatment also increased whole-tract digestibility.

A comparison between degradation in vitro and in sacco of constituents of untreated and ammoniatreated barley straw

Abstract Untreated and ammonia-treated straw was incubated in vitro and in sacco for various periods. The digested residues and the ethanol insoluble fraction of the original straws were analysed for neutral sugar and uronic acid residues, permanganate lignin, NDF-crude protein, acetyl groups and bound phenolic acids. The disappearance of the degradable fraction of the straws followed first-order reaction kinetics. Although the rate and extent of digestion were higher in sacco than in vitro, the rates of degradation of hemicelluloses, cellulose, permanganate lignin and NDF-crude protein relative to dry matter disappearance were not influenced by the incubation method employed. Ammonia treatment increased the potentially degradable fraction of the straw by 23 percentage units, and also increased the rate of dry matter disappearance. The content of crude protein in the ammoniated straw was twice that of the untreated straw, most of the increase being due to the presence of soluble nitrogen-containing compounds. The differences observed in digestibility pattern due to ammonia treatment were mainly due to increased solubilisation of straw constituents. As digestion proceeded, the content of bound ferulic acid decreased, while that of p-coumaric, and to some extent acetyl groups, increased in the residues.

An in vitro method for studying digestion in the pig

1. An in vitro method, using duodenal and ileal digesta and faeces from pigs as inocula for the preparation of three incubation media for simulating the digestive processes in the pig, was proposed. The kinetics of degradation in these three media of three feed samples (pig-grower diet, sugar-beet pulp and wheat bran) with crude protein (nitrogen x 6.25) contents varying from 111 to 196 g/kg, starch contents from 10 to 446 g/kg and dietary fibre contents from 168 to 686 g/kg, were studied. 2. The method was investigated by incubating the feeds in the three media for up to 96 h, and determining the rate and extent of disappearance of feed components. 3. For each feed the 96 h dry matter disappearance was almost equal for all media, although the rate of disappearance varied considerably, with ileal digesta the most potent, particularly for the high-fibre feeds, and duodenal digesta the least. The patterns of disappearance of individual components were similar in all media, with the exception of crude protein which was apparently less degraded in ileal and especially faecal media. 4. Results suggest that a combination of a short (6-12 h) and a long (48-72 h) in vitro incubation could be employed to simulate digestion in the small and large intestine respectively of the pig.

Content and solubility of mixed-linked (1→3), (1→4)-β-d-glucan in barley and oats during kernel development and storage

The concentration of mixed-linked (1 →3), (1 →4)-β- D -glucan (mixed-linked β-glucan) increased during kernel development of two-rowed and six-rowed barley, with a levelling off or decrease at later stages of maturity. Consequently, the stage of development as well as cultivar and growing conditions influenced total mixed-linked β-glucan content. In barley and oat kernels, dry matter was largely deposited before the majority of mixed-linked β-glucan in the endosperm cells walls was synthesized. High contents of soluble mixed-linked β-glucan as well as high mixed-linked β-glucan solubilities were observed before harvest. Close to harvest and early during subsequent storage significant decreases in total and soluble mixed-linked β-glucan contents were apparent. During the remainder of the 6-month storage time studied, however, the contents of soluble and insoluble mixed-linked β-glucan remained constant, indicating no activity of endogenous mixed-linked β-glucan degrading enzymes.

Composition and digestion in the pig gastrointestinal tract of Jerusalem artichoke tubers

Abstract The digestion in the pig gastrointestinal tract of fructans from Jerusalem artichoke ( Helianthus tuberosus L.) tubers was investigated. The tuber sample, and duodenal and ileal digesta and faeces from pigs fed the tubers, were analysed for chemical composition, and the gel filtration profiles of fructans from tubers and duodenal and ileal digesta examined. The tuber sample contained, on a dry matter basis, 60 g kg −1 ash, 122 g kg −1 crude protein, 7 g kg −1 crude fat, 654 g kg −1 soluble sugars (glucose, fructose, sucrose and fructans), 6 g kg −1 starch, 6 g kg −1 permanganate lignin and 147 g kg −1 non-fructans, non-starch polysaccharides. Sucrose (319 g kg −1 ) and fructans (288 g kg −1 ) were the main components. About 50% of the fructans were degraded anterior to the duodenum, but little further degradation occurred during passage through the small intestine. The gel filtration profiles established that the molecular weight of the fructans did not significantly change between the diet and terminal ileum.

The Uppsala Method for Rapid Analysis of Total Dietary Fiber

An understanding of the nutritional effects of dietary fiber has been considerably hampered by the lack of an appropriate definition, and consequently of adequate analysis methods, for this component. Based on physiological criteria, Trowell (1972) defined dietary fiber as “the remnants of the plant cell-wall that are not hydrolysed by the alimentary enzymes of man”, and this was later simplified and expanded to include “the plant polysaccharides and lignin which are resistant to hydrolysis by the enzymes of man” (Trowell et al., 1976). In 1979 we proposed that dietary fiber could be defined as the sum of non-starchy polysaccharides and Klason lignin, and, in conjunction with this chemical definition, published the first method (the Uppsala method) for the analysis and characterization of fibers (Theander and Aman, 1979). As this analytical procedure includes ‘starch’ resistant to α-amylases and, as part of the Klason lignin complex, other indigestible components such as tannins, cutins and Maillard products, this definition conforms well with the original definitions of Trowell and co-workers.

Whole-crop peas. I. Changes in botanical and chemical composition and rumen in vitro degradability during maturation

Abstract Whole-crop peas were harvested at different stages of maturity and separated into stems, leaves, flowers + pods and peas. The yield, chemical composition and rumen in vitro degradability of the whole crop and the botanical fractions were studied. The yield of the whole crop reached around 1000 g dry matter m−2. During the rapid exponential phase of seed growth, dramatic changes occurred in botanical composition and the fully-developed peas constituted around 50% of the whole crop. During this phase, nutrients, especially carbohydrates and protein, were translocated from the stems, leaves and pods and as a consequence dramatic changes in chemical composition and solubility of nutrients occurred within the botanical fractions. However, the gross chemical composition of the whole crop remained remarkably constant, with the exception of a transfer of soluble sugars to starch and an increased content of cell-wall constituents, mainly glucose residues. The crude protein of the peas contained more total amino acids and lysine than that of the other botanical fractions. The amino acid composition of the stems, leaves and flowers + pods varied considerably with harvest date, while the contents of lysine and methionine + cysteine generally increased during maturation. The rumen in vitro degradability of dry matter, crude protein and non-starch polysaccharides in the whole crop remained fairly constant during growth and development while it decreased in the stems, leaves and flowers + pods. The peas were completely degraded. Glucose and xylose were the least degraded non-starch polysaccharide residues in the stems, leaves and flowers + pods.

Use of a nylon-bag technique for pig feed digestibility studies

1. The use of a nylon-bag technique for pig feed digestibility determination was studied. Bags, measuring 25 x 40 mm and containing feed samples, were introduced into the pig gastrointestinal tract through a duodenal cannula, and recovered in the faeces between 23 and 69 h later. The disappearance of organic matter and crude protein (nitrogen x 6.25) from the bags was compared with in vivo apparent digestibility, determined by conventional faecal-collection methods, and neutral-detergent-fibre content for eleven feeds. The residues left in the bags after passage through the intestine from whole-crop-pea (Pisum sativum) and barley-grain samples were analysed for starch, non-starch polysaccharide residues, Klason lignin, crude protein and ash. 2. Dry matter disappearance of barley or whole-crop peas was not influenced by increasing bag pore size from 10 to 36 microns or sample weight from 250 to 1000 mg. Pepsin (EC 3.4.2.1) pretreatment had no effect on the degradation in the bags of the feeds investigated. 3. Organic matter and crude protein disappearance from the bags exceeded in vivo apparent digestibility by up to 0.10 and 0.42 units respectively. In vivo apparent organic matter digestibility could be predicted (P less than 0.001) by the organic matter disappearance from the bags and the neutral-detergent-fibre content of the feed, while in vivo apparent crude protein digestibility was highly correlated (P less than 0.001) to all these indices but poorly to crude protein disappearance from the bags. 4. Klason lignin was the least degraded component measured in the whole-crop-pea and barley residues from the bags, while starch was completely digested.(ABSTRACT TRUNCATED AT 250 WORDS)

Whole-crop Peas. II. Digestion of Early- and Late- harvested Crops in the Gastrointestinal Tract of Pigs

Abstract The digestion of early- (25 July) and late- (12 August) harvested whole-crop peas ( Pisum sativum L. cv. Simo) was examined in pigs fitted with terminal ileal cannulas and fed a basal cereal-based diet alone or substituted by 33% pea crop. Diets, ileal digesta and faeces were analysed for dry matter, ash, crude protein, crude fat, soluble sugars, starch, non-starch polysaccharides and Klason lignin. Apparent digestibilities were estimated relative to Cr 2 O 3 marker. The two pea crops were similar in composition, containing about 190 g kg −1 crude protein, 180 g kg −1 starch and 340 g kg −1 non-starch polysaccharides. Cellulose and pectins were the main non-starch polysaccharides. Inclusion of whole-crop peas in the diet significantly lowered apparent digestibility of dry matter at both the ileum and faeces and of starch at the ileum. Between 15 and 28% of the non-starch polysaccharides were degraded anterior to the terminal ileum. Determination of the apparent digestibility of the pea crops by difference established that while all apparent dry matter disappearance (about 53%) from the late harvest occurred before the ileum, approximately 30% of dry matter from the early harvest disappeared in both the small and large intestine. Apparent crude protein and starch digestibilities at the ileum for the late harvest (81 and 79%, respectively) exceeded those for the early harvest (58 and 64%, respectively), but faecal digestibilities of these two components did not differ between harvests. Almost all degradation of non-starch polysac-charides from the early harvest (70%) took place distal to the terminal ileum, while in the late harvest about 40% were degraded anterior to this site. Xylose was the least degraded non-starch polysaccharide residue in both harvests, and exhibited the greatest decrease in digestibility during maturation. These results indicate that, in order to obtain optimal feeding quality of whole-crop peas for pigs, harvesting should be delayed until the seeds are near maturity.