Nylon Bags In Rumen Research Articles

In Vitro Gas Production Test: towards Rapid Nutritional Evaluation of Roughages for Ruminant Feeding

The gas production in vitro method was used to evaluate the degradability and gas production of browse plants in the absence or presence of polyethylene glycol 8,000 (PEG). Substrates (leguminous and browse plants; 500mg) were incubated for 24h and the accumulated gas produced recorded. The incubation contents of the syringes were transferred into nylon bags and the undegraded residues weighed after washing and drying to constant weight (SNB method). Substrates were also incubated in the rumen in nylon bags for 24 h to determine in sacco degradability. Gas production ranged between 10.3 to 64.4ml whereas the dry matter degradability ranges between 27.3 and 70.9%. Addition of PEG, which minimised the inhibitory effects of tannin on microbial fermentation resulted in an increase in both gas production and degradability in vitro, which ranged from 25.7 to 64.2 ml and 34.2 to 75.0%, respectively. Correlation analysis of the DM degradability estimated by the SNB method and in sacco method was better in presence of PEG (y= 0.71x + 14.9; r2 = 0.92) as compared to absence of PEG (y= 0.59x + 15.0; r2 = 0.72). Partitioning factor (PF) of substrate to gas, which was expressed as mg DM degraded/ml gas, reflects the variation in microbial biomass yield. The PF figures varied from 4.94 -11.05 to PF+PEG values of 4.74-6.84 upon the addition of PEG. The present study showed that presence of tannin has a potentially beneficial effect to protein nutrition of the host animal by altering partitioning of nutrients towards more microbial yield rather than short chain fatty acids. PF values of browse plants determined both on the absence and presence of PEG may indicate the relative importance of tannins in different plant species on substrate degradability and partitioning of nutrients.

Effect of replacing barley with corn or sorghum grain on rumen fermentation characteristics and performance of Iranian Baluchi lamb fed high concentrate rations

The present study, conducted in Iran, was aimed to evaluate the effects of partial substitution of barley with corn or sorghum (slowly fermenting grains) on in situ dry matter (DM) and starch degradability and in vivo digestion characteristics and performance in finishing Iranian Baluchi lambs. In the first experiment, samples of ground barley (B), corn (C), sorghum (S) and their combinations [%: 70 barley : 30 corn (LC), 70 barley : 30 sorghum (LS), 30 barley : 70 corn (HC) and 30 barley : 70 sorghum (HS)] were incubated in nylon bags in rumen of three fistulated Holstein steers. Effective degradability (ED) for DM and starch were different (P < 0.05) among treatments. In both cases, ED was higher (P < 0.05) for B than that for C, S, HC and HS. Results of the present study confirmed previous reports that ruminal degradability of barley is higher than that of corn and sorghum, and further suggested that there may be benefits in replacing barley with ~70% of corn or sorghum. In Experiment 2, 30 Iranian Baluchi male lambs weaned at 65 days of age (BW 32 ± 2.3 kg) were divided into five equal weight groups (6 animals per group) in a complete randomised design. Lambs received a mixed diet in the form of total mixed rations (TMR), consisting of 32.5% alfalfa hay [89% DM, 43% natural detergent fibre (NDF) and 16% crude protein (CP) in diet DM basis] and 67.5% of the respective concentrates. The five iso-caloric (10.73 MJ ME/kg) and iso-nitrogenous (14% CP/kg DM) concentrates with different sources of starch used in the study were (1) barley, as the control cereal source for starch, and in the other treatments barley substituted with (2) 30% corn (LC), (3) 30% sorghum (LS), (4) 70% corn (HC) and (5) 70% sorghum (HS). Lambs in HC and HS diets recorded increases of 20 and 50 g/day in average daily gain, respectively, compared with lambs in B. Substitution of B with 70% C and S significantly (P < 0.01) improved ruminal pH and, presumably, resulted in higher starch outflow for post-ruminal digestion, as reflected by a higher blood glucose concentration, particularly for lambs in the HS diet. Results of the present study reaffirmed the advantages of feeding a mixture of grains with differing fermentation rates and, as previously reported, also suggested that the inclusion rate of slowly degradable grains should be ~70% so as to enhance animal performance.

Profile of digested feed amino acids from untreated and expander treated feeds estimated using in situ methods in dairy cows

Guar meal, sunflower meal, rapeseed cake, peas, maize, rye, wheat and barley were subjected to expander treatment at different temperatures (95–150 °C), and effect on amino acid availability was assessed using rumen nylon bag and mobile bag in situ methods. Expander treatment of rapeseed cake at 142 °C decreased feed lysine content, probably due to formation of complex compounds. Effective rumen degradability and total tract digestibility of protein, total amino acids, lysine, methionine, threonine, isoleucine, leucine, valine, and phenylalanine were compared to values for the untreated feeds. Effective rumen degradability seemed to decrease due to expander treatment for all cereals, except maize. Effective rumen degradability for sunflower meal and rapeseed cake was unaffected by expander treatment at 115 °C, whereas expander treatment at 142 °C appeared to decreased effective rumen degradability for rapeseed meal. Total amino acid digestibility was not decreased by expander treatment. Both for untreated and heat treated feeds rumen degradability and total tract digestibility of individual amino acids were generally in agreement with results for crude protein. Observed amino acid profiles supplied by digestible rumen undegraded feed amino acids were compared to a theoretical optimal profile obtained from the literature using a χ 2-index. A low index is equivalent to a high biological value. Smallest and largest index for the difference between the observed and theoretical optimal amino acid profile were obtained for peas and maize, respectively. Lysine was the first limiting amino acid for cereals, sunflower meal, expander treated (142 °C) rapeseed cake and untreated guar meal, leucine for untreated and expander treated (115 °C) rapeseed cake, and methionine for peas and expander treated guar meal. It was concluded that based on the assumed ideal amino acid profile, expander treatment only changed the first limiting amino acid for rapeseed cake and guar meal, and that although expander treatment decreased the index, and thereby improved the biological value of the intestinally digested feed amino acids, the ranking of feeds based on the index was unaffected by expander treatment.

Ruminal Degradability and Intestinal Digestibility of Protein and Amino Acids in Treated Soybean Meal Products

Four lactating dairy cows equipped with ruminal and duodenal cannulas were used to determine the impact of different methods of treating soybean meal (SBM) on the ruminal degradability and intestinal digestibility of crude protein and AA. Solvent-extracted SBM (SE), expeller SBM (EP), lignosulfonate SBM (LS), and heat and soyhulls SBM (HS) were incubated in the rumen in nylon bags for 48, 24, 16, 8, 4, 2, and 0h according to National Research Council (2001) guidelines. Additional samples of each SBM product were also incubated for 16h in the rumen; the residues from these bags were transferred to mobile bags, soaked in pepsin HCl, and then used for determination of intestinal digestibility in situ or in vitro. Treatment of SBM (EP, LS, HS) protected the crude protein and AA from ruminal degradation, increasing rumen undegradable protein from 42% in SE to 68% in EP. Kinetic analysis of crude protein and AA degradation in the rumen revealed that, compared with LS and HS, EP exhibited slower rates of degradation but a shorter lag phase and a higher proportion of soluble protein. For all SBM products, the pattern of ruminal degradation, at 16h of incubation, was characterized by extensive degradation of Lys and His, whereas Met and the branched-chain AA were degraded to the least extent. Estimates of intestinal digestibility of AA and crude protein were lower when measured in vitro than in situ; the magnitude of the difference between the 2 methods was greater (25%) with treated SBM products than with SE (10%). The availability of essential and nonessential AA was consistently greater (30%) with treated SBM than with SE. Among the treated SBM products, 4 essential AA (Ile, Leu, Phe, and Val) showed differences in availability, with values consistently lower for HS than for LS. This study showed that, based on in situ measures, heat and chemical treatment of SBM enhanced AA availability, and that compared with HS, EP and LS had a higher potential to enhance the AA supply to the small intestine of high-producing dairy cows.

Partitioning of energy and degradability of browse plants in vitro and the implications of blocking the effects of tannin by the addition of polyethylene glycol

The gas production in vitro method was used to evaluate the degradability and gas production of browse plants in the absence or presence of polyethylene glycol 8000 (PEG). Substrates (leguminous and browse plants; 500 mg) were incubated for 24 h and the accumulated gas produced recorded. The incubation contents of the syringes were transferred into nylon bags and the undegraded residues weighed after washing and drying to constant weight (syringe-nylon bag (SNB) method). Substrates were also incubated in the rumen in nylon bags for 24 h to determine in sacco degradability. Gas production ranged between 10.3 and 64.4 ml whereas dry matter degradation ranges between 27.3 and 70.9%. Addition of PEG, which minimised the inhibitory effects of tannin on microbial fermentation resulted in an increase in both gas production and degradability in vitro, which ranged from 25.7 to 64.2 ml and 34.2 to 75.0%, respectively. Correlation analysis of the DM degradability estimated by the SNB method and in sacco method was greater in the presence of PEG ( y=0.71 x+14.9; r 2=0.92) compared with absence of PEG ( y=0.59 x+15.0; r 2=0.72). Partitioning factor (PF) of substrate to gas, which was expressed as mg DM degraded/ml gas, reflects the variation in microbial biomass yield. The PF figures, which varied from 4.94–11.05 to PF +PEG values of 4.74–6.84 upon the addition of PEG, indicate the inhibitory effects of tannins on gas production. This suggests the presence of tannin has a potentially beneficial effect to protein nutrition of the host animal by altering partitioning of nutrients towards higher microbial yield rather than short chain fatty acids. PF values of browse plants determined both in the absence and presence of PEG may indicate the relative importance of tannins in different plant species on substrate degradability and partitioning of nutrients.

Immunogold labelling of feruloyl-arabinose of maize stem after rumen microbial degradation

Immunogold labelling of feruloyl-arabinose was performed on the base and the top of the apical internode of the stem of Co125 and W401 maize, harvested at anthesis +5 days, after incubation in the rumen in nylon bags for 4, 8 and 24 h. The description of labelling evolution during rumen degradation was permitted by the quantification of the intensity of labelling in four tissues: sclerenchyma, fibres, xylem and parenchyma. The results are discussed in relation to maize digestibility. © 1999 Society of Chemical Industry

Immunogold labelling of feruloyl‐arabinose of maize stem after rumen microbial degradation

Immunogold labelling of feruloyl-arabinose was performed on the base and the top of the apical internode of the stem of Co125 and W401 maize, harvested at anthesis +5 days, after incubation in the rumen in nylon bags for 4, 8 and 24 h. The description of labelling evolution during rumen degradation was permitted by the quantification of the intensity of labelling in four tissues: sclerenchyma, fibres, xylem and parenchyma. The results are discussed in relation to maize digestibility. © 1999 Society of Chemical Industry

Immunocytochemical localisation ofpara-coumaric acid in the cell walls of maize stem after rumen microbial degradation

Immunogold labelling of para-coumaric acid was performed on the base and the top of the apical internode of the stem of Co125 and W401 maize, harvested at anthesis + 5 days, after incubation in the rumen in nylon bags for 4, 8 and 24 h. The description of labelling evolution during rumen degradation was permitted by the quantification of the intensity of labelling in four tissues: sclerenchyma, fibres (surrounding vascular bundles), xylem and parenchyma. The results are discussed in relation to maize digestibility.

Immunocytochemical localisation of para‐coumaric acid in the cell walls of maize stem after rumen microbial degradation

Immunogold labelling of para-coumaric acid was performed on the base and the top of the apical internode of the stem of Co125 and W401 maize, harvested at anthesis +5 days, after incubation in the rumen in nylon bags for 4, 8 and 24 h. The description of labelling evolution during rumen degradation was permitted by the quantification of the intensity of labelling in four tissues: sclerenchyma, fibres (surrounding vascular bundles), xylem and parenchyma. The results are discussed in relation to maize digestibility. © 1998 Society of Chemical Industry.

Nutrient metabolism and rumen micro-organisms in sheep fed a poor-quality tropical grass hay supplemented with sulphate

SUMMARYA feeding trial was performed during 1986, in Townsville, Australia, to describe alterations in nutrient metabolism, and the coincident gross changes in rumen microbiology, when a sulphurdeficient diet was supplemented with inorganic sulphur. Eight Merino sheep were fedad libituma spear grass (Heteropogon contortus) hay of low sulphur content (0·4 g/kg DM), supplemented with all other essential minerals. Upon supplementation, daily sulphur intake was increased toc.0·75 g and four animals continued to be fedad libitum(group A) whilst the remaining animals were restricted in feed intake (group B). Sulphur supplementation caused a twofold increase in the feed intake of group A (P< 0·05). In both groups of animals, sulphur supplementation increased the fermentation of cotton thread cellulose (P< 0·05), as well as of ground plant dry matter (P< 0·05), suspended in the rumen in nylon bags for 24 and 48 h. The apparent digestibility of organic matter (AOMD) was also increased by sulphur supplementation; from 30·6 to 39·3% in group A (P< 0·05) and from 35·1 to 41·5% in group B (P> 0·05). The difference in AOMD between groups with sulphur supplementation was not significant, despite group B maintaining a longer retention of fluid digesta in the rumen (20·7 v. 25·3 h) with a significantly lowered rumen volume (4·68 v 3·67 litres,P< 0·05) and outflow of fluid digesta from this site (5·31 v 3·58 litres/day,P< 0·05). Sulphur supplementation increased the molar proportion of acetic acid in rumen fluid (P< 0·05) but lowered propionic and butyric acids in group A (P< 0·05). Only the molar proportion of propionic acid in rumen fluid was significantly lowered in group B (P< 0·05). In both groups of animals, counts of fluid-borne rumen bacteria, protozoa and sporangia of rumen anaerobic fungi (RAF) all increased significantly with sulphur supplementation (P< 0·05 in all instances), but no significant differences were observed between groups in microbial counts, despite the different feeding regimes. The increase in sporangial forms of RAF was most marked; no sporangial forms were detectable until the diet was supplemented with sulphate and measurable concentrations of rumen sulphide were observed. This is the first account of nondetectable concentrations of RAF brought about by the nutritional status of the diet.

The Influence of the Position in the Rumen on Dry Matter Disappearance from Nylon Bags

Abstract The dry matter disappearance was measured from either barley straw or rye grass hay incubated in the rumen in nylon bags attached to cords, with a distance of 25,40, 75 or 105 cm from the rumen cannulae. The experiment was performed using two different feeding conditions, and on one of these the concentrations of ATP were measured both inside the bags and in the rumen content close to the bags. The results showed that an increasing cord length increased the dry matter disappearance from the bags as well as the microbial activities in the nylon bags, the latter expressed by the ATP concentration. The dry matter disappearance depends on the microbial activities, but is apparently also influenced by the extended mobilities of the bags obtained using increased cord lengths. The effect of the cord lengths should be taken into account when experiments involving feed evaluations with nylon bags are planned.

Rumen anaerobic fungi and plant substrate colonization as affected by diet composition

The influence of diet composition on rumen fungal population was studied by offering successively to a rumen fistulated cow 11 different diets rich in fibre, starch or soluble carbohydrates. At the same time, the colonization of four different plant substrates introduced into the rumen in nylon bags (soya bean teguments, lucerne stems, maize stalks and beet pulps) was investigated. The population of rumen anaerobic fungi, particularly abundant with lignocellulose-rich diets, decreased with starch or soluble-carbohydrate-rich diets; the fungi selectively colonized the plant tissues with thick or lignified cell walls of soya bean tegument, lucerne or maize stalks, but seldom the beet pulp. The development of rumen fungi depended both on the substrate on which they became attached and on the ruminal medium. The fungi, which were normally present in the duodenum, caecum and faeces, were eliminated by the unfavourable diet but rapidly proliferated once the feed ingredients became more favourable.

Rumen degradation of straw 2. Botanical fractions of straw from two barley cultivars

ABSTRACTTwo varieties of barley straw, Corgi and Gerbel, which varied in degradability when incubated in the rumen in nylon bags, were chosen for further examination of botanical fractions and to see how each fraction responded to treatment with ammonia. The straws were separated into leaves, internodes, nodes and chaff. The average proportions of these fractions were respectively 0·499, 0·380, 0·055 and 0·065 in Corgi straw and 0·404, 0·512, 0·059 and 0·025 in Gerbel straw. For both varieties the degradability of the botanical fractions were leaves > chaff > nodes > internodes.Despite a similar chemical composition, the dry-matter loss (DML) values of leaves, internodes and nodes of Corgi were higher than those of Gerbel straw.The differences between varieties were larger for internodes and nodes than for leaves. The difference in DML of the two varieties at 48-h incubation was 132 g/kg DM. Of this difference, 25 g were due to differences in distribution of the botanical fractions and 107 g to differences in DML of the fractions.Ammonia treatment significantly increased the DML of all fractions except the nodes. The overall improvement due to ammonia treatment of the different fraction was internode > chaff > leaves > nodes.

Microbially corrected amino acid composition of rumen-undegraded feed protein and amino acid degradability in the rumen of feeds enclosed in nylon bags.

1. In the previous work (Varvikko & Lindberg, 1985), 15N-labelled rapeseed (Brassica napus), barley, ryegrass (Lolium perenne) and barley straw were incubated in the rumen in nylon bags for 5, 12 and 24 h and microbial nitrogen in the residues was quantified using the feed 15N-dilution method. In the present study, residual amino acids (AA) of these feeds were analysed, and microbially corrected AA of feed origin (feed AA) were estimated as the difference between total residual AA and respective microbial AA, assuming a constant AA composition for the microbial protein. 2. In barley and barley-straw residues, and also in ryegrass incubated in the rumen for 24 h, very large enrichment by microbial N and AA-N was found. The microbial enrichment was rather small in rapeseed residues and ryegrass incubated for 5 or 12 h. During the rumen incubation, feed N and AA-N (g/kg feed dry matter (DM] decreased very clearly in all the feeds, and feed and incubation time effects were always statistically significant (P less than 0.001). 3. The slow degradation of essential (E) feed AA compared with the respective non-essential (NE) AA degradation increased the proportion of feed EAA (g/kg determined feed AA) in barley and barley-straw residues. In rapeseed and ryegrass, residual feed EAA:NEAA remained very similar to the original. Branched-chain (Br) AA tended to increase proportionally in all the feed residues, suggesting these AA to be, on average, more resistant against microbial degradation in the rumen than other AA. Similarly, lysine was clearly increased in barley residues. A rumen degradation faster than the average rate caused decreased residual feed glutamic acid in rapeseed; methionine, alanine and glycine in barley; arginine and alanine in ryegrass; and methionine, asparagine and tyrosine in barley straw. Feed and incubation time effects were significant (P less than 0.05-0.001) for feed AA (g/kg determined feed AA) grouped as EAA, BrAA or NEAA, and for most individual AA, as well as for feed AA disappearance (%) and relative amounts (%) of feed AA in the respective residual AA. 4. According to present findings, AA composition of the rumen-degraded vegetable feed residues may markedly differ, either quantitatively or qualitatively (or both), from their original AA composition. When determining the feed AA composition of nylon-bag residues, the microbial error may be very large with starchy or fibrous feeds of low protein content. The microbial AA do not, however, considerably confuse the AA determination of protein-rich feeds.

Effects of Particle Size and Forage Composition on Functional Specific Gravity

Functional specific gravity of forage particles influences the rate at which they pass from the rumen. Effects of forage constituents (neutral detergent fiber, acid detergent fiber, lignin, protein, fat, and ash) and particle size on change of functional specific gravity in vitro were investigated. Rate of change of functional specific gravity was higher in legumes than in grasses.Hay samples were ground through 1-, 2-, 4-, and 6-mm screens in a Wiley mill and immersed in water. Specific gravity measurements were at 1, 2, 4, 6, 8, 10, 12, 24, and 48h. Specific gravities of samples with small particles were higher at all times than those of samples with large particles. Particle size influenced rate of change of specific gravity.Specific gravities of four hays that had been placed in the rumen in nylon bags for 1, 2, and 4h were measured by flotation technique. Prior to incubation in the rumen, approximately 80% of the particles were lighter than .9 specific gravity in three of the forages. After 1h in the rumen, no more than 28% of any of the samples floated in the .9 specific gravity solution. Specific gravity of ground forage samples changed rapidly in vivo.

The effect of formaldehyde treatment of soya-bean meal and rapeseed meal on the amino acid profiles and acid-pepsin solubility of rumen undegraded protein

SUMMARYSoya-bean meal and rapeseed meal treated with 0, 0·4 or 0·8 g formaldehyde/100 g crude protein (N × 6·25) was incubated in the rumen in nylon bags with 10 and 40 μm aperture.Disappearance of dry matter and nitrogenous compounds was reduced with increasing formaldehyde treatment.The proportion of acid-pepsin soluble nitrogen in the undegraded residues of untreated and treated soya-bean meal was similar to the original samples. For rapeseed meal the proportion of acid-pepsin soluble nitrogen in the undegraded residues decreased with increasing rumen incubation time. This reduction decreased with increasing formaldehyde treatment.Concentration of amino acids in the undegraded residues did not generally deviate from those in the original samples. However, a distinguishable decrease in the methionine concentration was observed in all the rapeseed meal samples and in glutamic acid concentration in rapeseed meal treated with 0 and 0·4 g formaldehyde/100g- crude protein.Most of the changes due to rumen incubation were smaller using the 10 μm bags than using the 40 μm bags. However, the bag pore size did not play a decisive role in the conclusions of the results given.

Intake and digestion of formaldehyde-treated red clover silages offered to calves either alone or with a urea supplement

SUMMARYIn a 3 × 3 latin-square design experiment, 12 British Friesian steer calves with rumen cannulae were offered three red clover silages to appetite, either alone or with a urea supplement of 18.9 g/kg total dietary dry matter (D.M.). The silages were prepared from a second cut of red clover using additives of 2·11 formic acid/t fresh crop together with formaldehyde at 0, 31 or 123 g/kg crude protein (CP) in the crop.The control silage was well preserved, as indicated by a low content of volatile fatty acids and ammonia N. Formaldehyde treatment generally restricted silage fermentation, although there was an increase in the content of butyric acid at the intermediate level of application, and an increase in 2, 3-butanediol content at the high level of application. A decline in ammonia-N content and an increase in insoluble-N content, with increasing level of formaldehyde application, indicated that formaldehyde had been effective in reducing protein degradation in the silages.Formaldehyde treatment depressed intake, the apparent digestibility of D.M., organic matter (OM), N, cellulose and energy, and N retention, the effect being particularly evident at the high level of application. Behavioural observations showed an increase in eating time on the formaldehyde-treated silages. Urea supplementation increased intake of the formaldehyde-treated silages, but did not influence intake of the control silage, and increased N retention on all silage diets. Apart from an improvement in apparent N digestibility, urea supplementation did not influence the digestibility of other dietary components.Within the rumen, formaldehyde treatment reduced ammonia-N concentration and the molar proportions of propionate and butyrate, and increased the molar proportion of acetate. The rate of D.M. and cellulose disappearance from treatment silages suspended in the rumen in nylon bags was reduced by formaldehyde treatment, the effect being most evident at the high level of formaldehyde application. A similar effect on rate of D.M. disappearance was observed when the control silage was placed in nylon bags, indicating that the adverse effect of formaldehyde was probably due to an effect on the rumen environment. Urea supplementation increased rumen ammonia-N concentrations, although this effect was not as great on the high formaldehyde silage, and increased the rate of D.M. and cellulose disappearance from silage in nylon bags.It appears that the lower intake and the poorer utilization of dietary N on the high formaldehyde silage may have been due to a reduction in the rate of digestion within the rumen. While there was some response to urea supplementation, it could not restore the apparent rate of digestion in the rumen to levels observed on the control diet. Hence, factors other than the supply of rumen-degradable N in the diet must have been responsible for the depression of digestion within the rumen.

The Rumen Ciliate Epidinium in Primary Degradation of Plant Tissues

Pieces of lucerne stem suspended in a sheep rumen in nylon bags were removed after different time intervals and examined by scanning electron microscopy. By 15 min large numbers of the ciliate protozoan Epidinium Crawley were attached to damaged areas of the stem, although a complex protozoal fauna was present in the rumen contents. Highest concentrations were on cortex and phloem tissues, with densely packed protozoa forming a complete ring around the transversely cut end of the stem between the epidermis and the vascular cylinder. Within 2 h there was extensive degradation of thin-walled tissues, as indicated by the amount of exposed vascular cylinder. Epidermis was not degraded but slid down the side of the stem as the underlying tissues were removed. This rapid degradation of plant tissue is explained by direct ingestion of tissues by the protozoa on the plant fragments. Many of the epidinia attached to the stem pieces were ingesting phloem elements and chlorophyllous tissue. The rumen protozoa have not previously been shown to participate on this scale in the physical degradation of plant material.

Polysaccharides and associated components of mesophyll cell-walls prepared from grasses

Mesophyll cells have been prepared from rye-grass leaves by a procedure similar to that used by Edwards and Black 1 for crab-grass. Successive filtrations through nylon cloth of 300-, 80-, 45-, and 15-μm mesh yielded suspension consisting chiefly of single cells, some broken. Passage through a French pressure cell brought the total breakage to near 100%. Microscopic examination of the walls showed that very little of the cell contents remained. The walls were thin (0.1–0.2 μm) and had numerous pit fields; torn surfaces revealed a randomly oriented, fibrillar structure. Determinations of the polysaccharide content, protein, phenolic esters, lignin, and ash accounted for ∼85% of the dry matter. The proportion of glucose in the polysaccharides of these walls was similar to that in the leaf cell-wall fraction as a whole, but the proportions of arabinose, galactose, and uronic acid were higher, and that of xylose lower. The acetyl content was 1.0–1.2%. The walls were readily digested by fungal culture filtrates, by snail digestive juice, and by immersion in the sheep rumen in nylon bags. These findings are discussed in relation to the digestion of forage cell-walls in ruminants.

Chemical and in vivo evaluation of a brown midrib mutant of Zea mays. I. Fibre, lignin and amino acid composition and digestibility for sheep.

AbstractTwo types of corn (maize) were used which were genetically identical except for a mutant gene (bm1) in one which reduced the type and amount of lignin produced compared with the normal plant (Tr). The Tr plant appeared to have only slightly lower digestibilities of dry matter and fibre for sheep even though the protein contents of the cornstalks, normally less in the Tr, were equalised by supplementation with soya bean protein. Comparing the acid‐detergent method of fibre and lignin determination with an acid‐pepsin method revealed that the former method gave values considerably lower than the latter. The alkali—lignin contents of the bm1 were higher than the acid—detergent lignins which must under‐estimate the true lignin content. The acid—pepsin method gave fibre and lignin concentrations which were more closely correlated with rumen digestion of the diets as shown by dry matter loss of the diets suspended into the rumen in nylon bags. This technique also revealed there was a significant increase in the rate of rumen digestion after 69 to 74 h of incubation. Digestion of lignin on the Tr diet could be explained by loss of ferulic and p‐coumaric acids. The reduced lignin and p‐coumaric acid content of the bm corn was associated in young plants with a low phenylalanine content but normal tyrosine content suggesting that the genetic block in lignin synthesis in this plant may occur between prephenic acid and phenylalanine.