Digestion Of Polysaccharides Research Articles

Synchronising the availability of amino acids and glucose increases protein retention in pigs

Effects of synchronising the availability of amino acids and glucose within a day on protein and energy metabolism were studied in growing pigs. Ten pigs of on average 54 (s.e. 1.0) kg live weight were assigned to each of two dietary treatments (synchronous v. asynchronous nutrient supply) in a change-over design. On the synchronous treatment (SYN), pigs received two balanced meals: one at 0800 h and one at 1600 h. On the asynchronous treatment (ASYN), pigs received virtually all protein at 0800 h and all carbohydrates at 1600 h. The dietary supply of ingredients and nutrients to pigs was similar for both treatments. Pigs were housed individually in respiration chambers. Faecal apparent nutrient digestibility was determined and nitrogen and energy balances were measured. Faecal apparent digestibility of energy, organic matter and non-starch polysaccharides was higher ( P < 0.05) for SYN than for ASYN. The efficiency of utilisation of digestible protein with protein gain was higher ( P = 0.001) for SYN (56.7%) than for ASYN (47.1%). The substantial decrease ( P < 0.05) in respiratory quotient and 13C enrichment of the expired CO2 after the morning meal indicated higher amino acid oxidation for ASYN than for SYN. Heat production and energy retention as fat were not affected by nutrient synchrony. In conclusion, an asynchronous availability of glucose and amino acids within a day increases amino acid oxidation, resulting in a substantial reduction in protein utilisation but with virtually no effect on fat retention.

Gut Bug's Sensors Bag Us Carbs

Bacteria make heavy use of two-component regulatory systems to sense external signals. The membrane-localized sensor proteins have histidine kinase and phosphoacceptor domains and communicate to intracellular response regulators, which often act as transcription factors. There are also hybrid two-component systems (HTCSs), which are really "one-component," because the sensor and response regulator sequences are combined. Sonnenburg et al. analyzed the function of an HTCS in Bacteroides thetaiotaomicron , a bacterium that inhabits the human gut. Such bacteria are required for digestion of dietary polysaccharides. The human genome has a meager supply of the required hydrolases and lyases for such digestion, whereas B. thetaiotaomicron' s genome encodes more than 200 of the former and more than a dozen of the latter. The gene encoding the HTCS BT3172 was detected in a screen for genes whose expression was enhanced in bacteria residing in the gut of rats eating a diet high in polysaccharides. Loss of BT3172 caused decreased expression of α-mannosidase genes, and expression of BT3172 was enhanced by exposure of bacteria to mannosides. The predicted structure of BT3172 has three transmembrane domains and would result in sensor regions on the periplasmic and cytoplasmic sides of the bacterial inner membrane. The periplasmic sensor might sense mannosides in the environment. The authors used a yeast two-hybrid screen to detect binding partners for the cytoplasmic sensor domain of BT3172 and detected two proteins involved in glucose metabolism--glucose 6-phosphate isomerase and glucose 6-phosphate dehydrogenase. Thus, the authors speculate that BT3172 may serve to coordinate carbohydrate use and availability. They propose that more complete understanding of gut bacteria could allow "personalized nutrition where diet is matched to the nutrient processing capacity of an individual's microbiota." E. D. Sonnenburg, J. L. Sonnenburg, J. K. Manchester, E. E. Hansen, H. C. Chiang, J. I. Gordon, A hybrid two-component system protein of a prominent human gut symbiont couples glycan sensing in vivo to carbohydrate metabolism. Proc. Natl. Acad. Sci. U.S.A. 103 , 8834-8839 (2006). [Abstract] [Full Text]

The effect of level and type of cereal non-starch polysaccharides on the performance, nutrient utilization and gut environment of pigs around weaning

The influence of non-starch polysaccharides (NSP) level and solubility on performance, digestion site and gut environment was investigated in 20 Swedish Yorkshire litters between 3 and 9 weeks of age. The litters were distributed among five diets based on cereals and cereal by-products. The control diet (C) had a medium content of NSP (147 g/kg dry matter (DM)), whereas diets H and Hi had a high content of NSP (188–250 g/kg DM), and diets L and Li had a low content of NSP (95–109 g/kg DM) after dilution with starch. The proportion of insoluble (i) NSP was higher in diet Hi and Li (0.80–0.85) than in diets C, H and L (0.68–0.73). The pigs offered diet Li showed the highest (P<0.05) feed intake and grew faster (P<0.05) than pigs offered diets C, L and H. In the post-weaning period feed:gain was highest for pigs offered the C and H diets and lower for pigs offered the low NSP diets and diet Hi. During week 6, the coefficient of caecal (CCAD) and total tract (CTTAD) apparent digestibility of organic matter (OM) was lower (P<0.05) in diet Hi compared to the other diets, and the CCAD and CTTAD of crude protein (CP) was higher (P<0.05) in diet L compared to the high NSP diets. During week 7, the CCAD and CTTAD of OM was lower (P<0.05) in diet Hi compared to the low NSP diets and diet C. The CCAD of CP and starch was higher (P<0.05) in diet L compared to the control diet. Diet L showed higher (P<0.05) values of digestible energy compared to the high NSP diets, both in the 6 and 7 weeks old piglets. NSP solubility influenced (P<0.05) the caecal digestibility of arabonixylans and total NSP in the 6 and 7 weeks old piglets, as well as the caecal digestibility of total dietary fibre in the 7 weeks old piglets. The content of total organic acids (OA) was linearly related to the pH level at the ileum ( R 2 = 0.70), caecum ( R 2 = 0.57) and colon ( R 2 = 0.83). The experimental diets altered the molar proportions of lactic acid and short chain fatty acids (SCFA), of total OA, as well as the molar proportions of acetic, propionic and butyric acids, of total SCFA, in the stomach, ileum, caecum and colon of the piglets. In conclusion, NSP solubility influenced the digestibility of cell wall polysaccharides at the caecum but not at the total tract. Diet Hi promoted production of lactic acid in the stomach and small intestine and butyric acid in the large intestine.

Discovery of Pectin-degrading Enzymes and Directed Evolution of a Novel Pectate Lyase for Processing Cotton Fabric

There is a growing need in the textile industry for more economical and environmentally responsible approaches to improve the scouring process as part of the pretreatment of cotton fabric. Enzymatic methods using pectin-degrading enzymes are potentially valuable candidates in this effort because they could reduce the amount of toxic alkaline chemicals currently used. Using high throughput screening of complex environmental DNA libraries more than 40 novel microbial pectate lyases were discovered, and their enzymatic properties were characterized. Several candidate enzymes were found that possessed pH optima and specific activities on pectic material in cotton fibers compatible with their use in the scouring process. However, none exhibited the desired temperature characteristics. Therefore, a candidate enzyme was selected for evolution. Using Gene Site Saturation Mutagenesistrade mark technology, 36 single site mutants exhibiting improved thermotolerance were produced. A combinatorial library derived from the 12 best performing single site mutants was then generated by using Gene Reassemblytrade mark technology. Nineteen variants with further improved thermotolerance were produced. These variants were tested for both improved thermotolerance and performance in the bioscouring application. The best performing variant (CO14) contained eight mutations and had a melting temperature 16 degrees C higher than the wild type enzyme while retaining the same specific activity at 50 degrees C. Optimal temperature of the evolved enzyme was 70 degrees C, which is 20 degrees C higher than the wild type. Scouring results obtained with the evolved enzyme were significantly better than the results obtained with chemical scouring, making it possible to replace the conventional and environmentally harmful chemical scouring process.

Effect of extrusion, espansion and toasting on the nutritional value of peas, faba beans and lupins

An assessment was made of the effect that different treatments (toasting, expansion, extrusion) have on the nutritional value of protein plants (pea, faba bean, lupin). In a randomized block design, feeds were screened for enzymatic digestibility of starch and protein, N solubility and in vitro protein degradability. Expansion and extrusion cause increased starch enzymatic degradability while toasting produced virtually no effects. In peas this value increased from 11.80% in meal to 39.70% in the extruded product; 85.37% is the percentage for the expanded product, while 10.90% is the starch digestibility value for toasted peas. In faba beans the extrusion process increased starch digestibility from 11.39% to 85.05%, while in extruded lupins a complete starch hydrolysis was obtained, while in the meal the polysaccharide digestion was 54.48%.The expansion and extrusion processes significantly decreased rumen degradability during the first 8 hours of incubation. Toasted peas had lower degradability if compared with controls but not with the other treatments. The only potentially alternative source to soybean is the extruded faba bean. In spite of its lower protein content, this feed is characterized by a considerably lower in vitro protein degradability than soybean. This implies that the digestible food protein content is comparable (124.90 g/kg DM) to that of soybean (109.78 g/kg DM) and definitely higher than that of all other protein plants.

Large-scale carbohydrate analysis by capillary array electrophoresis: part 2. Data normalization and quantification.

Automated 96-capillary array electrophoresis (CAE) methodology described in the first part of the present work offered large-scale high-performance profiling of oligo- and monosaccharides to fulfill the needs of bioindustrial laboratories. Sensitivity at low nanomolar concentration, good resolving power and reliability achieved in the experiments is invaluable for monitoring reaction products from enzymatic polysaccharide digestion with numerous applications in agricultural, chemical and food industries. In addition to optimization of mono- and oligosaccharide separations in CAE system and necessary operational protocol modifications, capillary-to-capillary and run-to-run variation in migration time and signal intensity necessitated development of data normalization tools. Internal fluorescent standards have been incorporated into the analysis aiding migration time normalization and CAE trace alignment. Data processing, visualization, and programming tools have been developed along with quantification approaches.

Digestion of microbial biomass, structural polysaccharides, and protein by the humivorous larva of Pachnoda ephippiata (Coleoptera: Scarabaeidae)

In order to investigate whether microbial biomass and its residues are nutrient and energy sources for humivorous beetle larvae, we carried out feeding trials using soil supplemented with 14C-labeled fungal biomass ( Penicillium chrysogenum), bacterial biomass ( Bacillus megaterium), fungal or bacterial structural polysaccharide (chitin, peptidoglycan), bacterial protein, or cellulose, taking the larva of the cetoniid beetle Pachnoda ephippiata (Coleoptera: Scarabaeidae) as a model of a humus-feeding beetle larva with a highly alkaline gut. The results showed that gut passage strongly stimulated the mineralization of the structural polymers. The stimulatory effect correlated positively with the recalcitrance of the preparation in the control soil, and was accompanied by a transformation of the residual radiolabel to alkali-soluble and acid-soluble products. The solubility increase was highest in the extremely alkaline midgut. High-performance gel-permeation chromatography demonstrated that the changes in solubility were accompanied by reciprocal changes in the molecular weight of the residual material and that the residual material in the fecal pellets was more humified than in the control soil. The amount of radiolabel recovered from the body and hemolymph of the larvae indicated that microbial biomass and its structural components were assimilated more efficiently than cellulose, which supports the hypothesis that microorganisms and the nitrogenous components of humus are an important dietary resource for humivorous soil macroinvertebrates.

Dietary supplementation with multienzyme preparations improves nutrient utilization and growth performance in weaned pigs.

Two experiments with young pigs (25 d of age) were conducted to investigate the effect of multienzyme preparations on nutrient digestibility, growth performance, and P utilization and excretion. In Exp. 1, 24 pigs (six pigs per treatment) were used in a 28-d performance and digestibility trial using four diets: control (no enzyme) and control supplemented with enzyme preparation A, B, or C. The control diet was formulated to meet 95% of NRC (1998) nutrient specifications (except for available P, which was at 44% NRC) and composed of corn, wheat, wheat by-products, barley, soybean meal, canola meal, and peas. All three enzyme preparations contained xylanase, glucanase, amylase, protease, invertase, and phytase activities and differed in the type of plant cell wall-degrading activities; Enzyme A contained cellulase, galactanase, and mannanase; Enzyme B contained cellulase and pectinase; and Enzyme C contained cellulase, galactanase, mannanase, and pectinase. Pigs fed enzyme-supplemented diets had higher ADG (P = 0.02) and G:F (P = 0.01) than those fed the control diet. On average, and when compared with control diet, enzyme supplementation improved (P = 0.001 to 0.04) ileal digestibility of DM (60 vs. 66%), GE (62.8 vs. 70.4%), CP (62 vs. 72%), starch (86.7 vs. 94.2%), nonstarch polysaccharides (NSP; 10.1 vs. 17.6%), and phytate (59 vs. 70%). Compared with the control, total-tract digestibility of nutrients was increased (P = 0.001 to 0.01) owing to enzyme supplementation, with Enzyme C showing the highest improvement in DM, GE, CP, starch, NSP, phytate, and P utilization. Pigs fed enzyme-supplemented diets had decreased (P = 0.04) fecal P excretion. The benefit from improved nutrient utilization with enzyme supplementation was further substantiated in a 38-d growth performance study with 48 pigs. The control and Enzyme C-supplemented diets (same as Exp. 1) were assigned to six replicate pens (four pigs per pen). The study was conducted in three phases (Phase 1 = d 0 to 7; Phase 2 = d 7 to 21; Phase 3 = d 21 to 38). Individual BW and pen feed disappearance were monitored. Average daily gain and G:F were 231 and 257 g (P = 0.01), and 0.56 and 0.63 (P = 0.001) for the control and enzyme-supplemented diets, respectively. It is evident from this study that the use of enzyme preparations may allow for cost-effective and environmentally friendly formulation of young pig diets.

Effect of enzyme addition on the digestibilities of cell wall polysaccharides and oligosaccharides from whole, dehulled, and ethanol-extracted white lupins in chickens

Three experiments were conducted to examine the effects of a commercial enzyme preparation on chicks performance and digestibilities of nonstarch polysaccharides (NSP), raffinose (R), stachyose (S), and total oligosaccharides (O) in diets containing whole and dehulled lupin and ethanol-extracted dehulled lupin meal. Ethanol extract was also used to produce a rich oligosaccharide fraction. In the first experiment, the dehulling treatment and the addition of enzyme to the diet improved (P < 0.05) weight gain (24 and 15%), feed-to-gain ratio (13 and 9%), dry matter retention (32 and 8%), apparent protein digestibility (6 and 3%) and ileal digestibilities of raffinose (19 and 119%), stachyose (85 and 204%), and total oligosaccharides (68 and 178%), respectively. In addition, enzyme treatment improved (P < 0.05) excreta digestibility values for NSP (from -1.7 to 5.5%), R (from 64.6 to 92.6%), S (from 48.8 to 82.4%), and O (from 55.8 to 83.5%). In the second experiment, extraction of the ethanol soluble components from dehulled lupin decreased (P < 0.0001) weight gain (51%), and increased (P < 0.0001) feed consumption (34%), feed-to-gain ratio (32%), relative gizzard weight (14%), and the relative ceca length (20%). The addition of the isolated fraction of oligosacharides to the corn-extracted lupin diet (7.5 and 15%) yielded performance values similar to those obtained with the unextracted dehulled lupin. The addition of enzymes to the diets significantly improved the weight gain (11%) and feed to gain ratio (6%), and decreased relative gizzard weight (12%) and relative ceca length (7%). Ileal digestibilities of R, S, and O were considerably lower than corresponding excreta digestibilities. The excreta digestibility of NSP and excreta and ileal digestibilities of R, S, and O were lower (P < 0.05) in chicks fed the lupin diet containing the high concentration of extract compared with those fed the same diet containing the lower concentration of extract. Enzymes, when added to the diets, increased (P < 0.05) the digestibilities of R, S, and O with the relative effects being much greater for ileal than excreta samples. In the third experiment, the ethanol extract (7.5 and 15%) added to a corn-soybean diet improved weight gain, feed consumption, and feed-to-gain ratio by 19, 13, and 6%, respectively. Ileal digestibilities of R, S, and O were low (< 45%), especially in chicks fed the diets containing the high amount of added oligosaccharide fraction. There was no effect of enzyme addition on the performance parameters. However, supplemental dietary enzymes improved (P < 0.05) ileal and excreta digestibilities of oligosaccharides from 15.6 and 68.6% to 52.3 and 84.8%, respectively. In summary, dehulling greatly improved the nutritional value of lupin, while removal of the ethanol soluble materials, including raffinose and stachyose considerably decreased its value. The oligosaccharide fraction does not seem to have an antinutritive effect and the addition of enzymes increased the digestibilities of NSP, raffinose, and stachyose but did not significantly improve chick performance.

Enzymes for digestion of cellulose and other polysaccharides in the gut of longhorn beetle larvae, Rhagium inquisitor L. (Col., Cerambycidae)

The foregut, proximal and distal midgut, and hindgut of free living larvae of a bark runner, the longhorn beetle Rhagium inquisitor L., have been investigated for the presence of enzymes hydrolyzing a number of aryl-glycosides and polysaccharides representative of wood components. Speci8c activity was highest in the proximal midgut. No hydrolytic activity was found in control tissue, the extra-intestinal fat bodies. Activity was detected with CM-chitin, xylan, phosphoric-acid swollen cellulose, soluble starch, � -mannoside, :-glucoside, :-cellobioside and � -arabinoside. The highest activity was found on :-1,4-glucan and :-fucoside. No hydrolytic activity could be observed with crystalline cellulose. An identical molecular mass of 70 kDa for :-glucosidase and cellobiosidase was determined, corresponding to the major protein band. This suggests the absence of a cellobiohydrolase activity and thus a lack of 8ber degradation ability. The endo-:-glucanase had a molecular mass of 32 kDa and an extremely broad pH-activity. ? 2002 Elsevier Science Ltd. All rights reserved.

Improvement of growth and nutritive value in chicks with non-genetically modified phytase product from Aspergillus niger

1. Non-genetically modified (non-GM) phytase product derived from Aspergillus niger possesses various side active enzymes including α -amylase, protease, cellulase and hemicellulase. In contrast, the product of genetically modified (GM) phytase product has much less side active enzyme since the capacity of phytase production is reinforced by gene modification. In the present study we have tried to determine whether the difference of side enzyme activity of phytase product affects growth performances and nutritive value in chicks; in addition we tried to characterise the physiological change induced by the difference of side active enzymes. 2. Single Comb White Leghorn male chicks at 7 d of age were fed on experimental barley-based diets for 10 d. The feeding trial was of a factorial design (3 × 2 × 2), having three types of dietary phytase products (control, non-GM or GM phytase products derived from A. niger at 1000 U/kg diet), two levels of dietary available P supplement (0 or 6 g/kg diet) and two levels of dietary protein (CP 180 or 120 g/kg). 3. The non-GM phytase product caused a 6% increase in final body weight and feed efficiency com6 pared with the control and the GM phytase product without interacting with dietary protein and available P level. However, in birds given available P-free diet, both non-GM and GM phytase products induced a 20% increase in plasma P concentration, suggesting no difference in phytase activity between the non-GM and GM phytase products. 4. The balance study showed that the metabolisable energy of the non-GM phytase product (15.6 ± 0.05 kJ/g diet) was significantly higher among the treatments (control, 15.1 ± 0.05; GM phytase product 15.3 ± 0.07). The non-GM phytase product also increased the rate of food passage through the crop, and caused a drastic reduction in intestinal weight, perhaps as a consequence of digestion of non-starch polysaccharides. 5. We conclude that the side active enzymes in non-GM phytase product improve growth performance and nutritive value of the diet in chicks. However, the efficacy of phytase activity should not be different between non-GM and GM phytase products.

Ileal and total tract digestibility, and protein and fat balance in pigs fed rice with addition of potato starch, sugar beet pulp or wheat bran

A repeated 4×4 Latin square design was performed with eight ileal cannulated castrates to study the effect of source of starch and fibre on apparent ileal and faecal digestibility, and crude protein (CP) and fat balance. The experimental diets were based on cooked rice (C) and cooked rice with addition of raw potato starch (P), sugar beet pulp (S) and wheat bran (W). The inclusion of potato starch reduced ( P<0.05) the ileal digestibility of organic matter (OM) and starch, and the total tract digestibility of CP. The ileal digestibility of potato starch was calculated to be 0.75. Inclusion of fibre sources (sugar beet pulp and wheat bran) in the basal diet resulted in a reduction ( P<0.05) in the ileal and faecal digestibility of dietary components (except for starch) and energy. While there were no differences ( P>0.05) in the ileal digestibility of dietary components and energy between fibre sources, the total tract digestibility of dietary components (except for CP and starch) and energy were lower ( P<0.05) for the insoluble fibre source (wheat bran). With the exception of mannose and uronic acid the ileal digestibility of individual sugars were unaffected ( P>0.05) by diet composition. The inclusion of wheat bran negatively influenced the faecal digestibility of individual sugars (except for xylose) and non-starch polysaccharides. Nitrogen retention was unaffected ( P>0.05) by diet composition, while fat accretion tended ( P<0.10) to be lower in diet C. The latter was due to a low feed and energy intake.

Apparent Precaecal Digestibility of Nutrients and Level of Endogenous Nitrogen in Digesta of the Small Intestine of Growing Pigs as Affected by Various Digesta Viscosities

Sixteen male growing pigs of about 24kg BW were fitted with both a duodenal re-entrant and a post-valve T-shaped cannula inserted in the caecum. The animals were divided into four groups. Each group received one of the following diets: corn starch-soybean protein isolate-based diet without (diet C) and with carboxymethylcellulose (diet CMC) or a rye-wheat-based diet without (diet RW) and with xylanase addition (diet RWX). The diets provided similar levels of apparent precaecal digestible crude protein (CP), lysine, methionine+cystine, threonine and tryptophan. Additionally, [15N]-yeast was given with the diets during the first 10 days of the experiment. For estimation of digesta viscosity, N-flow of dietary and endogenous origin, apparent precaecal digestibilities of dry matter (DM), CP, amino acids and non starch polysaccharides (NSP) (only in pigs fed diets RW and RWX), ileal and duodenal digesta were quantitatively collected on day 16 and 17, respectively. The endogenous N-proportion was measured by the ratio of 15N enrichment in the digesta and urine. The duodenal and ileal digesta supernatant viscosity increased as carboxymethylcellulose was included into the diet. Xylanase addition to the rye-wheat based diet reduced the viscosity in the ileal digesta. There were no differences in precaecal digestibilities of DM, CP and amino acids between diet C and CMC. The precaecal digestibilities of DM and soluble and insoluble NSP increased from 69.5% to 73.9%, from 1.3% to 47.9% and from 17.0% to 35.4%, respectively, as xylanase was added to the rye-wheat-based diet. The apparent precaecal digestibility of most essential amino acids increased by 2 to 5 percent units. The amounts of endogenous N at the duodenal level were estimated to be 158, 233, 313 and 276mg per 12h per kg0.75 BW of pigs fed diets C, CMC, RW and RWX, respectively. The corresponding values at the ileal level were 95, 107, 164 and 150mg per 12h per kg0.75 BW. For endogenous N amounts, significant differences were observed between diets C and CMC (duodenum) and also between semi-purified and cereal-based diets (duodenum and ileum). Methodological aspects for the estimation of endogenous N using the isotope dilution technique are discussed. Obviously, the digesta viscosity per se does not affect the nutrient absorption and endogenous N flow within the small intestine of pigs. Other properties of complex dietary fibre, digesta passage rate or bacterial activity probably contribute to the observed changes.

Digestibility and energy value of non-starch polysaccharides in young chickens, ducks and geese, fed diets containing high amounts of barley

The purpose of the present investigation is to compare the ability of chickens, ducks and geese to digest and utilise a diet containing a relatively large amount of barley (40%) rich in β-glucan (18 g kg −1) and NSP (137 g kg −1) of which 35 g kg −1 were soluble non-starch polysaccharides (NSP). The diets were offered to the birds (50 chickens, 40 ducks and 30 geese) in the period from hatching to 42 days of age. The digestibility of NSP was measured during the last week of the growth period using chromic oxide as an indigestible marker. Emphasis was on total NSP, soluble and insoluble NSP and their constituent sugar residues (rhamnose, fucose, arabinose, xylose, mannose, galactose, glucose and glucuronic acid). The degradation of NSP to short chain fatty acids (SCFA) was determined in the small intestine, caeca and large intestine. Although significant differences were found between species to the extent of degradation of individual soluble, insoluble and total NSP residues in the small intestine and caeca, the overall apparent digestibility of total NSP was similar (39–42%). On the basis of the digestibility of the NSP sugar residues and the formation of SCFA in the gut, the energy value of NSP was estimated on 2.8, 3.2 and 2.7 kJ g −1 NSP ingested ( P>0.05) in chickens, ducks and geese, respectively. On average, NSP contributed approximately 3.5% of metabolisable energy (ME) in the three poultry species.

Leucaena Seeds as Protein Supplement in the Rations of Growing Sheep

The study was carried out to evaluate leucaena seeds as a protein replacement of mustard seed cake (MSC) in the concentrate mixture of growing lambs. Fifteen growing male lambs (LocalxCorridale) with an average body weight of 16.3 kg were allocated into three dietary treatments (T1, T2, and T3) with five animals in each group. Animals were offered dry mixed grass, berseem hay and concentrate mixture to meet their nutrient requirements. In concentrate mixture of T1, (Control) MSC was used as protein source, while in T2 and T3 groups, 25 and 50% of MSC was replaced by leucaena leucocephala seeds. On completion of three months (90 days) of feeding, a digestion cum-metabolism trial was conducted to determine DMI, nutrient utilization, and nitrogen balance. Changes in body weight were recorded at 15 day internals and eating patterns were recorded for 3 consecutive days at the end of the feeding trial. MSC had higher CP contents than leucaena seeds (27.0%). Mimosine contents in leucaena seeds were 1.1 compared to 0.2 and 0.4% in concentrate mixture of T2 and T3 group, respectively. Dry matter intake varied non-significantly (79.3′1.2 to 83.4′1.3 g/kg w 0 . 7 5 ) across the dietary treatments. Digestibility of DM and cell wall polysaccharides (NDF, ADF. Cellulose and hemicellulose) were comparable, however CP digestibility was relatively lower in leucaena luecocephala seeds based groups (T2 45.5′1.7 and T3 46.7′3.5) compared to MSC supplemented group (T1 47.7′0.9%). The growth rate of lambs was non-significantly higher in Tl (79.2′5.4) compared to T2 (73.8′8.8) and T3 (73.9′7.0), respectively. The animals were in positive nitrogen balance and N-balance varied from 1.8 to 2.9 g/d across treatment groups. The eating rate (% of total offered) of concentrate up-to 15 min was relatively higher in T1 (82.4) than T2 (74.2) and T3 (77.8%). However no effect of leucaena seeds was recorded on total DMI of animals. The results of the study revealed that the inclusion of up to 50% leucaena seeds, as protein source in concentrate mixture of lambs had no adverse effect on DMI, nutrient utilization, eating patterns, nitrogen balance and growth performance of lambs.

Rumen Microbes, Enzymes and Feed Digestion-A Review

Ruminant animals develop a diverse and sophisticated microbial ecosystem for digesting fibrous feedstuffs. Plant cell walls are complex and their structures are not fully understood, but it is generally believed that the chemical properties of some plant cell wall compounds and the cross-linked three-dimensional matrix of polysaccharides, lignin and phenolic compounds limit digestion of cell wall polysaccharides by ruminal microbes. Three adaptive strategies have been identified in the ruminal ecosystem for degrading plant cell walls: production of the full slate of enzymes required to cleave the numerous bonds within cell walls; attachment and colonization of feed particles; and synergetic interactions among ruminal species. Nonetheless, digestion of fibrous feeds remains incomplete, and numerous research attempts have been made to increase this extent of digestion. Exogenous fibrolytic enzymes (EFE) have been used successfully in monogastric animal production for some time. The possibility of adapting EFE as feed additives for ruminants is under intensive study. To date, animal responses to EFE supplements have varied greatly due to differences in enzyme source, application method, and types of diets and livestock. Currently available information suggests delivery of EFE by applying them to feed offers the best chance to increase ruminal digestion. The general tendency of EFE to increase rate, but not extent, of fibre digestion indicates that the products currently on the market for ruminants may not be introducing novel enzyme activities into the rumen. Recent research suggests that cleavage of esterified linkages (e.g., acetylesterase, ferulic acid esterase) within the plant cell wall matrix may be the key to increasing the extent of cell wall digestion in the rumen. Thus, a crucial ingredient in an effective enzyme additive for ruminants may be an as yet undetermined esterase that may not be included, quantified or listed in the majority of available enzyme preparations. Identifying these pivotal enzyme(s) and using biotechnology to enhance their production is necessary for long term improvements in feed digestion using EFE. Pretreating fibrous feeds with alkali in addition to EFE also shows promise for improving the efficacy of enzyme supplements. (Asian-Aust. J. Anim. Sci. 2002. Vol 15, No.11 : 1659-1676)

Chronic acarbose-feeding increases GLUT1 protein without changing intestinal glucose absorption function

As α-glucosidase inhibitor, the antidiabetic drug acarbose reduces postprandial glucose levels by retarding the intestinal digestion of polysaccharides. However, it is unknown if acarbose also affects the expression of intestinal glucose transporters, especially the Na +-glucose cotransporter (SGLT1) and the glucose transporters GLUT1 and GLUT2. To unravel this question, Wistar rats received standard powdered chow either without (control) or with acarbose (40 mg acarbose/100 g chow) for 40 days. While food intake was slightly enhanced by acarbose, the drug had no influence on weight gain or plasma glucose and insulin levels. The acarbose-treatment did not alter the SGLT1 and GLUT2 gene expression in both upper and middle small intestine, whereas GLUT1 protein was increased by 75% in middle small intestine. Despite the territorial change in GLUT1 protein, the intestinal glucose absorption in an acarbose-free perfusion study was unaltered. In conclusion, the chronic use of acarbose did not alter the acarbose-free glucose absorption profile.

Lignin and Fiber Digestion

Lignin is a polymer formed from monolignols derived from the phenylpropanoid pathway in vascular plants. It is deposited in the cell walls of plants as part of the process of cell maturation. Lignin is considered an anti-quality component in forages because of its negative impact on the nutritional availability of plant fiber. Lignin interferes with the digestion of cell-wall polysaccharides by acting as a physical barrier to microbial enzymes. Lignification therefore has a direct and often important impact on the digestible energy (DE) value of the forage. There are a number of plant-related factors that affect lignification in individual plants and plant communities. Lignification is under genetic control and there are considerable differences in lignin concentration and composition among species and even genotypes within species. Genetic differences in lignification are first expressed at the cellular level and are affected by biochemical and physiological activities of the cell. As cells differentiate, differences in lignification occur depending on the tissues and organs being developed. Lignification tends to be most intense in structural tissues such as xylem and sclerenchyma. Plant organs containing high concentrations of these tissues, such as stems, are less digestible than those containing lower concentrations. The relative proportion of lignified tissues and organs typically increases as plants mature so there is often a negative relationship between digestibility and maturity. All of these plant processes respond to environmental factors that can affect the extent and impact of lignification. Temperature, soil moisture, light, and soil fertility can have either direct or indirect effects on lignification. The most useful management practices for minimizing the negative effects of lignification are manipulation of the plant community such that it contains more desirable species and harvest management to maintain plants in a vegetative stage of development. DOI:10.2458/azu_jrm_v54i4_moore

Cloning and sequence analysis of the endopolygalacturonase gene from the pitch canker fungus, Fusarium circinatum.

The fungus Fusarium circinatum causes pitch canker disease on mature pine trees and root rot and damping-off of pine seedlings. Endopolygalacturonases (endoPGs) play a major role during penetration of plants by fungi. Digestion of the pectic polysaccharides in the plant primary cell walls is one of the earliest functions of endoPGs during infection. The research objective was to clone and characterize the gene encoding endopolygalacturonase in F. circinatum. A 970-bp DNA fragment was cloned by using degenerate PCR amplification from F. circinatum DNA. Sequence data for this fragment were used to design specific primers for use in genome walking to amplify and sequence the remaining portion of the F. circinatum endoPG gene (Fcpg). The amino acid sequence predicted from this gene showed 90% and 87% similarity to Fusarium oxysporum and Fusarium moniliforme endoPGs, respectively.

Composition and in Vitro Digestibility of Monosaccharide Constituents of Selected Byproduct Feeds

Nonforage byproduct feeds, including distillers dried grains (DDG), corn gluten feed (CGF), wheat bran (WB), beet pulp (BP), soybean hulls (SH), and dried citrus pulp (DCP), were examined for monosaccharide composition and in vitro digestibility by ruminal liquor. The dicotyledonous feeds (BP, SH, and DCP) contained more galactose, pectin, and NDF glucans and less NDF-xylan and NDF-arabinose than the monocotyledonous ones (DDG, CGF, and WB). The lowest values of lignin were found in CGF, SH, and DCP. Digestibility of total carbohydrate was around 90% in CGF, DCP, BP, and SH and around 80% in DDG and WB. Digestibility of total NDF polysaccharides was 86% in CGF and SH, 78--84% in DDG, DCP, and BP, and 56% in WB. In all byproducts, digestibility of NDF glucose and arabinose was higher than that of NDF xylose and uronic acids.