D. Ben-Ghedalia

The Effects of Starch- and Pectin-rich Diets on Quantitative Aspects of Digestion in Sheep

Abstract Rumen- and duodenal-cannulated sheep were used to study the effect of pectin-rich vs. starch-rich diets on rumen parameters, digestibility of monosaccharide residues and quantitative aspects of nitrogen (N) metabolism. The pectin-rich diet consisted of dried citrus pulp plus soya-bean meal and was coded DCP; the starch-rich diet consisted of barley plus a small proportion of citrus pulp and was coded B. The concentrate mixtures comprised 80% of the rations dry matter (DM) and were complemented with 20% lucerne hay. Both diets were equinitrogenous. Pectic uronic acid residues (PUR) and fructose comprised the bulk of rapidly fermentable carbohydrates in the DCP diet and α-glucose in the B ration. The digestibility values of PUR, fructose and glucose residues were high (91–99%), irrespective of diet; their digestion being nearly completed in the reticulo-rumen. Organic matter (OM) was equally digestible in both diets, but the cell walls (CW) in the DCP diet were 16% more digestible than in the B ration. Rumen pH was 6.42 and 6.18 in the DCP and B treatments, respectively. The acetate propionate ratio in the rumen was higher in the DCP than in the B treatment. Irrespective of diet, there was a net gain of N in the stomachs, but the flow of N to the duodenum was higher in the DCP than in the B sheep. However, the amount of total N absorbed from the intestine was somewhat higher in the DCP treatment. In conclusion, dried citrus pulp, even at a high proportion of the diet, creates favourable conditions for cellulolysis in the rumen and has a positive effect on the supply of N to the intestine.

Some aspects of cellobiose effect on bacterial cell surface structures involved in lucerne cell walls utilization by fresh isolates of rumen bacteria

Abstract The effect of the inclusion of cellobiose or lucerne cell solubles on the pattern of lucerne cell walls (CW) digestion by a mixed rumen population in vitro was followed. Inclusion of soluble sugars reduced the rate of lucerne CW degradation by a mixed rumen population without reducing the extent of overall CW digestion (59.8%). The predominant ruminal bacteria utilizing lucerne hay or lucerne CW as the sole added carbohydrate substrate were isolated, enumerated and identified. Fresh isolates of the predominant cellulolytic bacteria ( Ruminococcus flavefaciens 7a3, Ruminococcus albus 7a6 and Bacteroides succinogenes 7a8 or 7a14) were then grown on lucerne CW or cellobiose as the sole added carbohydrate substrate. The effect of substrate on bacterial cell surface topology was investigated by scanning electron microscopy (SEM) visualization using cationized ferritin pretreatment and the ability of the isolates to adhere to cellulose was determined. Lucerne CW degradability by each of these bacterial isolates was also determined. The surface topology of B. succinogenes 7a14 and 7a8, R. albus 7a6 and R. flavefaciens 7a3 cells grown on and attached to CW particles was specified by a dense layer of characteristic protuberant structures. In contrast, when grown on cellobiose the surface topology of these bacterial strains (excluding isolate 7a8 of B. succinogenes ) was smoother and contained less protuberant structures. The ability to attach to cellulose of these bacterial strains was higher when adapted to lucerne CW vs. cellobiose, indicating possible involvement of these organelles in the attachment mechanism of the bacteria. A possible explanation for the inhibitory effect of cellobiose on CW digestion in this study is discussed.

SO2 treatment for converting straw into a concentrate-like feed: A growth study with lambs☆

Abstract Thirty-nine male lambs of the Assaf dairy breed were assigned shortly after weaning, at 17.5 kg liveweight, to one of the following three nutritional treatments: I, a high energy concentrate mixture (CD); II, a diet in which 60% of the concentrate was replaced by a combination (1:1) of wheat straw+poultry litter containing 100 ppm copper (UTS) and III, as II, but the straw was treated with 3.5% sulfur dioxide at 70°C for 72h (SO 2 -TS). The diets were fed ad libitum for the entire growth experiment, which lasted 110–117 days. Daily gains were 266, 356 and 363 g for the UTS, SO 2 -TS and CD rations, respectively. The SO 2 -TS lambs were leaner than those of the CD ration and their meat was accepted well. Sulfur dioxide-treated straw and poultry litter are suggested as complementary feeds and when given in a 1:1 combination can replace 60% of the concentrate in intensive-growth lamb rations. Dietary SO 2 -treated straw exerts a protective effect against copper toxicity in high-copper lamb diets.

Subcellular distribution of glycanases and related components in Ruminococcus albus SY3 and their role in cell adhesion to cellulose

Aims: To compare the subcellular distribution of glycanase‐related components between wild‐type Ruminococcus albus SY3 and an adhesion‐defective mutant, to identify their possible contribution to the adhesion process, and to determine their association with cellulosome‐like complexes.

Effect of changing the proportion, wheat: sorghum in dairy cow rations on carbohydrate digestibility and NAN flow to the intestine

Five rumen- and abomasum-cannulated cows in mid-lactation were fed ad libitum, for two periods of 21 d each, two isonitrogenous (17% crude protein) total mixed rations (TMR) composed of 45% sorghum-wheat combination, 38% corn silage, 12% soybean meal, urea, buffers and minerals. The two TMRs differed in their sorghum (S): wheat (W) ratio, which was 7030 in S and 3070 in W treatments. Dry matter intake was 17.2 and 16.6 kg d−1 in S and W, respectively. Effect of treatments on the digestibility of carbohydrate constituents and N metabolism was examined. Neutral detergent fiber (NDF)-polysaccharides digestibility in stomachs and the entire gastrointestinal tract (GIT) was significantly higher in S than in W. The digestibility of neutral detergent soluble (NDS)-α-glucans was significantly higher in W than in S. More of NDS-α-glucans escaping ruminal fermentation was digested in the intestine of the S cows as compared with the W cows. The digestibility in entire GIT of total NDS-monosaccharide residues was 93% in W and 86% in S. Digestibility values of total carbohydrates in stomachs (49% and 52%) and entire GIT (79% and 80%) of S and W cows were similar. S and W cows were similar in rumen pH (6.15 and 6.13), rumen volatile fatty acids concentrations (133 and 136 mM) and rumen NH3 concentration (21 and 23 mg per 100 ml). Non-ammonia-N flow through the abomasum (410 and 403 g d−1) and N absorption in the intestine (67%) were also similar in S and W.

Pectin fermentation and utilization by natural microflora during ryegrass ensilage

Abstract The ability of natural silage microflora to degrade and utilize indigenous and extraneous pectic materials during the ensilage of ryegrass was assessed in 2 liter laboratory glass silos. The treatments consisted of ryegrass wilted to 24% (R) and 32% (W) dry matter (DM) and three pectic treatments applied to (R) at approximately 10% of the total DM (R + pectin, R + polygalacturonic acid and R + galacturonic acid). All silages were of a good quality, as judged from visual and analytical evaluation. Pectin, either indigenous or extraneous, was not degraded, or was hardly degraded, by the natural silage microflora. Free galacturonic acid was markedly degraded and utilized, but its fermentation did not result in a higher concentration of preserving acids.

The effect of sulphur dioxide application level or the biodegradation of wheat straw carbohydrates by rumen microorganisms and by Trichoderma viride cellulase

Abstract Wheat straw was treated with SO2 at different levels of application under mild temperature conditions, and the effect of treatment on cell wall (CW) composition and biodegradation was tested. The SO2 treatments gradually solubilized CW non-glucose polysaccharide (NGP = hemicellulose), decreasing the content of this fraction in residual CW from 31·5 g 100 g−1 CW in the untreated straw, to 17·3 g 100 g−1 CW in the 5% SO2-treated material. Lignin and cellulose were only slightly solubilized by SO2 treatments. Concomitantly, the in vitro digestibility by rumen bacteria of total straw monosaccharides increased gradually from 60·5% in the untreated straw to a plateau of 87·7% in the 4% SO2-treated straw. The digestibility of residual CW carbohydrates followed a similar pattern, increasing from 55·4% in the untreated straw to 81·1% in the 4% SO2-treated material. The 4% and 5% SO2 application levels were also the most effective as pretreatments for subsequent hydrolysis of straw by Trichoderma viride cellulases, and this was expressed by an increase in the degree of saccharification of total straw carbohydrates from 7·76% in the untreated material to 62·3% in the straw treated by the 4% SO2, plus cellulase. Data from this study support the theory that hemicellulose cellulose is the major biodegradation obstacle in the CW of wheat straw.

Characterization of some cell-wall components of untreated and SO2-treated wheat straw

Abstract Chemical and physical properties of cell walls (CW) and CW components have been studied in untreated wheat straw (WS) and SO 2 -treated wheat straw (SO 2 -WS). The concentration of water-soluble total free monomeric phenolics was 47.1 mg per 100 g and 129 mg per 100 g straw dry matter in WS and SO 2 -WS, respectively. The major solubilizing effect of the SO 2 treatment was exerted on ferulic acid, the concentration of which increased tenfold. Matrix complexes extracted by 1 N NaOH from CW of wheat straw subjected to ball-milling plus Trichoderma reesei cellulase pretreatment underwent high-per-formance size exclusion chromatography to assess the molecular weight distribution. Most (84%) of the matrix complexes extracted from WS were in the range of 1600–23000 Da, whereas those originating from SO 2 -WS showed a more dispersed pattern, with mol ecular weights of up to and beyond 125 000 Da. The weight average molecular weight (M wt ) was 10 500 Da and 35 000 Da for the matrix complexes of WS and SO 2 -WS, respectively. Total monosaccharide content of matrix complexes was 36.4 g per 100 g and 42.5 g per 100 g in WS and SO 2 -WS, respectively, with xylose as the major (70–80%) component. Solid-state cross-polarization-magic angle spinning 13 C NMR spectroscopy of neutral detergent fiber preparations of wheat straw showed a decline in the intensity of signals at 89 ppm and 65 ppm in response to SO 2 treatment and in vitro digestion, respectively. The distribution of carbons in CW chemical groups and components as determined by the NMR analysis was found to be close to values obtained by wet chemistry.

Absorption of macro- and micro-elements by sheep from barley and barley plus sulphur dioxide-treated straw rations

Abstract Sheep cannulated in the rumen, duodenum and ileum were used to study absorption of minerals from diets: I. barley only (B), and II. 70% (DM basis) barley + 30% SO2 treated wheat straw (B+S). Na and K were highly absorbed from both diets and almost completely recovered in the urine. Ca apparent absorption was low: 12.1% and 13.4% in the B and B+S treatments, respectively. The Mg net absorption in the rumen was significantly higher in diet B than in diet B+S; the difference in total tract apparent absorption of Mg was, however, much smaller and not significant: 44.5% and 38.2% for the B and B+S treatments, respectively. Animal variation in P absorption was very large, ranging from 5% to 66%. There was a trend toward net secretion of Cu, Zn and Mn in the stomachs, the trend being 2–3 times higher in the B+S than B diet. Generally, the apparent absorption of Cu, Zn and Mn was lower in the B+S than B diet; however, the most notable difference was with Cu absorption.

SO2-treated Straw as a Silage Additive: Fermentation Data on Lucerne with Particular Reference to Protein Degradation*

Abstract Untreated and sulfur dioxide-treated wheat straw (WS) were used as additives for ensiling low dry matter (DM) lucerne in laboratory silos. The negative control (L + WS) consisted of 60% lucerne + 40% untreated WS on a DM basis. SO 2 -treated WS was added to the lucerne at 2 levels: 40% (L + 40% TWS) and 50% (L + 50% TWS) of the mixture DM. Lucerne wilted to reach the DM content of the above-mentioned mixtures (30%), was ensiled and served as the positive control (WL). Silos were opened after 90 days and the silages subjected to analyses. The highest DM loss (∼ 10%) was in the negative control (L + WS), whereas in the L + TWS silages DM loss was reduced to 0.5–4%. Lactic acid production was lower in the negative control (L + WS) because of the lack of fermentable sugars and in the L + 50% TWS because of the initial low pH of the mixture at ensiling (4.3). The greatest ability to preserve forage protein was found in the L + 50% TWS, in which nearly 80% of the protein was recovered after 90 days of fermentation, as compared with 43% in the L + WS and WL silages. Threonine and the basic amino acids were extensively degraded in the L + WS silages. The recovery of those amino acids was significantly higher in the L + TWS silages. Generally, the L + 50% TWS was the most successful treatment in preserving the forage amino acids. The concentration of phenylalanine was remarkably increased in silages which underwent extensive protein breakdown (L + WS and WL). In view of its ability to preserve energy and protein, SO 2 -treated WS could be considered as a future silage additive for direct ensilage of high quality, low DM forages.