J. B. Robertson

Digestive Efficiencies of Wild Howler Monkeys

(1) Two sets of feeding trials were carried out on temporarily caged wild howler monkeys (Alouatta palliata) to determine digestive efficiencies with respect to cell-wall constituents and protein in natural items of diet. One trial diet consisted primarily (81%) of ripe fruit; the other consisted primarily (87%) of young leaves. (2) Samples of all foods used in the trials, as well as urine and feces, were collected and preserved. These were analyzed for total cell-wall content, cell-wall components (cellulose, hemicelluloses, lignin, cutin), and crude protein. In vitro digestibility of crude protein in trial foods was examined, using pepsin in a solution of HCl. (3) Adult howler monkeys averaged a digestive efficiency of 24% with respect to total cell-wall material on the fruit diet and 42% on the leaf diet. All animals were more efficient at degrading cellulose than hemicelluloses. In both trials fecal nitrogen content was high, and apparent digestibility of protein was low. True digestibility estimates, however, indicated that an average of 77% of dietary protein was removed in transit on the fruit diet and 89% on the leaf diet. The results of the in vitro digestibility trials indicated that tannins or their precursors are present in many natural foods of howlers. (4) It is concluded that considerable fermentation of plant structural carbohydrates takes place in the digestive tract of howler monkeys. Fermentation end products may be of particular importance to howlers at times of the year when foods rich in ready energy are in short supply.

A Method for Isolating Condensed Tannins from Crude Plant Extracts with Trivalent Ytterbium

A method to precipitate condensed tannin from crude plant extracts using trivalent ytterbium has been developed. The new method requires less time and resources than the condensed isolation procedure using Sephadex LH-20 recommended by Hagerman (1991, Tannin Analysis, Miami University, Oxford, OH, USA). The absorbance of the preparations obtained by precipitation with trivalent ytterbium was similar to the preparations obtained with the original isolation procedure, when the acid butanol method (Porter et al 1986, Phytochemistry1 223–230) was used to measure condensed tannins. Condensed tannins were isolated from crude plant extracts of three plant species, Desmodium ovalifolium, Gliricidia sepium and Manihot esculenta, and the condensed tannin content of the lyophilised leaf tissue was determined. For each plant species, the amounts of the soluble, insoluble and fibre-bound condensed tannins were estimated using five different standards. These standards included two tannin preparations obtained either by (1) isolation with Sephadex LH-20, or (2) by the precipitation with trivalent ytterbium and three external standards: (3) cyanidin, (4) delphinidin and (5) purified quebracho (Schinopsis balansae). When external standards were used (cyanidin, delphinidin, purified quebracho), it was likely that the condensed tannin content of the plant tissue would be under- or overestimated. When an internal standard based on the isolated tannin from the respective plant species was used, accurate estimates were obtained.

A note on digestibility in sheep as influenced by level of intake

Digestibility of dry matter, energy and cell wall was measured in two series of digestibility trials in which sheep were fed on pelleted mixed rations containing either 32·0 or 22·6% cell wall at various levels of intake. There were significant depressions in digestibility of all nutritive components as the level of intake increased. The ration lower in cell wall showed smaller declines in dry matter and energy digestibility but a greater decline in cell wall digestibility. The results indicate that the cell wall fraction of concentrate-supplemented rations for sheep is a primary factor in the decline in digestibility observed with increase in level of intake.

Evaluation of starch analysis methods for feed samples

The objectives of this work were to evaluate the efficacies of commercial starch analyses and of starch analysis extraction and gelatinisation procedures. In Study 1, accuracy and specificity of commercially available starch analyses were evaluated with six co-operating laboratories (five commercial, one university). Results from 11 test samples showed three laboratories with recoveries of purified starch of 92 g kg−1 or less. Three and four laboratories had inflated values when samples contained glucose or sucrose, respectively. Analyses appeared to have good specificity for glucose. Incompleteness of starch detection and interference by non-starch carbohydrates can affect commercially available analyses. In Study 2, extraction with 80:20 ethanol/water (v/v; 80EtOH) or 90:10 ethanol/water (v/v; 90EtOH) to remove low-molecular-weight carbohydrates, and gelatinisation with heat, alkali (KOH), 6 M urea or 8 M urea were evaluated. Extraction with 80EtOH or 90EtOH reduced interference from non-starch carbohydrates. Gelatinisation with heat was adequate for good recoveries of starch glucose for both control (non-extracted) and 80EtOH-extracted samples; gelatinisation with alkali was required for 90EtOH-extracted samples. Recoveries of pure starch samples were greatest with no extraction and heat gelatinisation. 80EtOH extraction with heat gelatinisation appears to be an adequate preparation method when removal of low-molecular-weight carbohydrates is desired. © 2000 Society of Chemical Industry

Comparison of the Precipitation of Alfalfa Leaf Protein and Bovine Serum Albumin by Tannins in the Radial Diffusion Method

The precipitation of protein by condensed and hydrolysable tannins was evaluated with the radial diffusion method of Hagerman (1987) using bovine serum albumin (BSA) and isolated leaf protein from fresh alfalfa (Medicago sativa). Alfalfa leaf protein (AALP) was included at two concentrations, 25 and 156 mg N litre-1, at pH 6·8 and 39°C to simulate rumen conditions. The condensed tannins were purified from lyophilised samples of Arachis pintoi, Desmodium ovalifolium, Gliricidia sepium, Manihot esculenta and quebracho (Schinopsis balansae). Hydrolysable tannins from tannic acid (TA) were used as well. There was a significant interaction (P<0·001) between tannin and protein source, and protein level on protein precipitation. Most purified condensed tannins (CTs) precipitated more AALP than BSA when protein was included at the same level. Purified CT from quebracho and hydrolysable tannin from TA failed to precipitate AALP at both protein levels. In a second experiment, tannins from crude plant extracts were studied in the radial diffusion method using BSA and two levels of AALP. The crude plant extracts were obtained from lyophilised plant samples of A pintoi, Centrosema macrocarpum, Clitoria ternatea, D ovalifolium, Erythrina berteroana, E poepigiana, G sepium, M esculenta, Pueraria montana and P phaseoloides. The protein precipitated by soluble tannins in the plant samples was correlated to the total phenolic content and to the soluble CT estimated by the acid butanol assay or by the radial diffusion method. Tannins from different plant species precipitated different amounts of BSA and AALP. Therefore, the measures of the biological activity of tannins based on BSA precipitation may not reflect the ability of tannins to precipitate proteins of plant origin such as those commonly found in the diets of herbivores. The present study offers the possibility of using the radial diffusion method with plant proteins at precipitation conditions similar to those in the rumen.

The Detergent System of Fiber Analysis

Hill (31) has postulated that the microflora of the gut produce carcinogens from, most probably, bile acids, and Visek (74) has suggested that ammonia, produced from microbial degradation of dietary protein in the lower gut, is a possible carcinogen. Both hypotheses are probably secondary to what seems to be the primary cause, a deficiency of dietary fiber which has been implicated in diverticular disease of the large bowel, carcinoma of the colon, ischemic heart disease, diabetes mellitus, and gallstone formation (9, 10, 14, 16, 27, 55, 58). Although by definition fiber is indigestible by the secretions of the gastrointestinal tract, there is sufficient evidence to show that the monogastric animal, in addition to the ruminant and nonruminant herbivore, has a microbial population (23) in the tract capable of utilizing plant structural carbohydrates as a source of energy (Table 1). However, no cellulolytic organisms have yet been isolated from human feces (35), although Bryant (8) has characterized strains of Rumunococcus and Bacteroides fragilis, many of which can ferment pentoses and possibly hemicelluloses.

Use of chromium mordanted neutral detergent residue as a predictor of fecal output to estimate intake in grazing high producing Holstein cows

Abstract Two experiments were conducted to evaluate use of chromium mordanted neutral detergent residue (Cr-NDr) and cobalt EDTA (Co-EDTA) as predictors of dry matter intake (DMI) in high producing grazing dairy cows. The first experiment was conducted with 10 lactating Holstein cows individually fed a total mixed ration (TMR) in confinement, and dosed with Cr-NDr and Co-EDTA twice daily at milking times for 12-days to validate the markers used for the second experiment. The Cr-NDr accounted for 96% of the variation ( r 2 ) in DMI, while Co-EDTA underpredicted DMI by 43% ( r 2 =0.65). The second experiment was conducted on a pasture-based dairy farm, to evaluate the use of Cr-NDr to predict DMI of grazing dairy cows. 15 and 14 high producing dairy cows in trial 1 and 2, respectively, were dosed twice a day at milking times with Cr-NDr for 12-days. Mean total DMI estimated from marker recoveries were unrealistically high (5.95 and 5.52% of body weight for trials 1 and 2, respectively). It was concluded that either diurnal variation in fecal excretion of the marker or a failure in the technique of collecting pasture samples that reflected the cows’ true grazing selection in order to determine pasture composition occurred.

Dietary fiber composition of selected foods in the People's Republic of China

Abstract The content of dietary fiber and its components in food items commonly consumed in China were analyzed using more recently developed methods. These foods were collected as part of an epidemiologic study designed to investigate the relationship between diet and disease. Five hundred and twenty-seven food samples were analyzed for total dietary fiber (TDF), neutral-detergent fiber (NDF) including its constituents, hemicelluloses, cellulose, and lignin, and soluble dietary fiber. The content (% dry weight) of TDF was 1.2 to 17 for cereals, 16 to 52 for legumes, 7.7 to 37 for tubers and roots, 20 to 56 for cucurbits and fruits, and 27 to 55 for leafy vegetables. Samples of 15 of these foods were replicated in 14 or more counties permitting assessment of geographic variation for the same food. Considerable variation in fiber content was observed indicating that nutrient contents of specific foods published in composition tables are likely to be considerably more variable than generally appreciated even though replicates may be collected and analyzed at the same time of year.

Analysis of Foodstuffs for Dietary Fiber by the Urea Enzymatic Dialysis Method

Total dietary fiber (TDF) values for cereal grains, fruits, vegetables, processed foods, and purified or semi-purified dietary fiber products were determined by a new method using 8M urea and enzymes (urea enzymatic dialysis, UED, method). The results are compared with the official AOAC procedure. Soluble and insoluble dietary fiber were determined for several of these foodstuffs and compared with the NDF values. Crude protein and ash contamination was usually lower with the UED method compared with the AOAC method, particularly for samples that formed gels during ethanol precipitation. Urea and the heat stable amylase were effective in removing starch even at relatively low temperatures of the assay (50 degrees C). The new assay is relatively economical in use of equipment, enzymes, and reagents. Studies are currently in progress to minimize the assay time for the UED method while further improving its flexibility and robustness. The results of the studies will be discussed.

Dietary Fiber Intake and Colon Cancer Mortality in The People’s Republic of China

There are many unresolved questions concerning the relationship between dietary fiber and cancer of the large bowel. These include (1) inadequate knowledge of the physiological activities of the various dietary fiber constituents, (2) uncertainties about the food composition of these constituents, (3) variable constituent content for the same food grown in different geographic regions and at various stages of harvest, and (4) uncertainties about earlier intake levels of various fiber-containing foods during the time when cancers were forming. It would therefore appear to be inappropriate to put too much emphasis on the effects of individual fiber fractions not only because of these uncertainties of intake but also because the intakes of individual fiber fractions are strongly correlated with each other. Moreover, fiber intakes also correlate with many other dietary constituents that may be associated with the prevalence of large bowel cancer.