Spear Grass Research Articles

Lignin in the ‘cell contents’ fraction of tropical forages

AbstractIn several tropical forage species the neutral detergent extraction used to determine cell wall and cell contents fractions solubilised a substantial UV‐absorbing polymeric fraction which appeared to be a soluble lignin–carbohydrate complex. A crude product was isolated from spear grass (Heteropogon contortus) with a yield of 30 g kg−1. In other forages an acetyl bromide method was used to estimate lignin extractable by neutral detergent. For eight species of tropical grasses this gave the following values: Aristida calcyna, 38; Mitchell grass (Astrebla squarrosa), 37; Chloris gayana, 31; Eragrostis sp, 37; spear grass, 49; Iseilema membranaceum, 35; Panicum maximum, 36; Sorghum sp, 42; Themeda triandra, 79 g kg−1. The levels in two legumes were: Alysicarpus bupleurifolius, 29; Macroptilium atropurpureum, 27 g kg−1 dry matter. Sequential extractions on spear grass and Mitchell grass showed that most of the 50% dioxan‐soluble fraction was also soluble in neutral detergent, raising the possibility that ‘dioxan lignin’, on which studies of forage lignin structure in other species have been conducted, would be found in the cell contents fraction rather than in the fibre fractions on which lignin analyses have been performed. Addition of dioxan extractives reduced the in vitro neutral detergent fibre (NDF) digestibility of spear grass and Mitchell grass.© 2002 Society of Chemical Industry

Phosphate rather than surfactant accounts for the main contribution to enhanced fibre digestibility resulting from treatment with boiling neutral detergent

It is known that extraction of some grasses with neutral detergent (ND) increases the in vitro digestibility [Kennedy, P.M., Lowry, J.B., Conlan, L.L., 1999. J. Sci. Food Agric. 79, 544]. Here, we report experiments which defined the contribution of ND components to digestibility increases. Substrates were prepared from spear grass ( Heteropogon contortus) by boiling at neutral pH in solutions of 0.05 M disodium EDTA, 0.018 M sodium borate, and 0.03 M sodium phosphate, and a mixture of the three solutions. Phosphate was the most effective single component in increasing ND fibre (NDF) digestibility in vitro, after 120 h of fermentation, from 472 to 522 g/kg NDF, equivalent to 68% of the increase found with boiling ND. NDF digestibility of bagasse at 120 h increased from 162 to 186, 230 and 277 g/kg NDF after boiling for 1 h in water, neutral phosphate and ND, respectively. Phosphate treatment of bagasse produced a 44% increase in NDF digestibility, compared to increases of 5, 8, 14, and 16 % for rhodes grass ( Chloris gayana), spear grass, angleton grass ( Dicanthium aristatum) and carpet grass ( Axonopus affinis), respectively. Increases of cumulative gas production against incubation time indicated that most of the increased fermentation had occurred by 24 h of fermentation for the grasses, whereas 72 h was needed for bagasse. There were also improvements in NDF digestion with neutral phosphate treatment of spear grass at temperatures of 75, 85 or 95°C, with prolonged treatment times required at lower temperatures. These treatments reduced the content of acid insoluble ash in NDF and increased the rate of production of gas during fermentation. Removal of minerals from the cell wall matrix appeared to be responsible for the increase in NDF digestibility caused by phosphate treatment. The possible commercial use of phosphate on-farm to upgrade nutritional quality of straws is discussed.

An acetylxylan esterase and a xylanase expressed from genes cloned from the ruminal fungus Neocallimastix patriciarum act synergistically to degrade acetylated xylans.

A Neocallimastit patriciarum acetylxylan esterase (BnaA) was expressed from the cloned gene in Escherichia coli. Purified recombinant BnaA efficiently released acetate from soluble acetylated birchwood xylan (ABX), with a specific activity of 76 U mg-1. In contrast, release of acetate was very inefficient from the insoluble substrates, spear grass and delignified spear grass. Addition of a recombinant xylanase, XynA, also expressed from a cloned N. patriciarum gene, had no effect on the release of acetate from ABX. However, the combination of recombinant BnaA and XynA released more acetate from spear grass and delignified spear grass than did BnaA alone. Significantly more reducing sugar was also released from all three substrates by the combination of recombinant XynA and BnaA than by XynA alone. Thus the extent of digestion of acetylated xylans by XynA appears to be limited by the acetylation. In this system BnaA does not appear to increase the rate of cleavage of insoluble substrates by XynA, but probably allows the release of shorter xylose oligomers from already solubilised acetylated xylan polymers.

Isolation of grass cell walls as neutral detergent fibre increases their fermentability for rumen micro-organisms

Cell wall isolated from grasses as neutral detergent fibre (NDF) is fermented more readily than cell wall in the unfractionated forage by rumen organisms in vitro. In several experiments with Heteropogon contortus and Astrebla squarrosa the NDF digestibility at 48 h for the isolated cell wall was 8–18 units higher than for the unfractionated forage, with most of the difference appearing in the first 24 h of fermentation. Similar in vitro increases were obtained for Sorghum sp, wheat hay, bagasse and Lolium perenne and less so for Panicum maximum. The difference was not significant for Chloris gayana, nor for the tropical legumes Stylosanthes hamata, Clitoria ternatea and Lablab purpureus. For those grasses in which the above effect was statistically significant there was a significant relationship between NDF content of the unfractionated grass (x) and the ratio of NDF digestibility of isolated NDF to that of the unfractionated grass, as described by y=0.018x (P<0.01). For H contortus, kinetic analysis of gas produced from 0 to 48 h of in vitro incubation with rumen microbes showed an increased (from 0.016 to 0.020 h −1, P<0.001) rate of production from the slowly-digested pool. Spear grass NDF incubated in the rumen in polyester bags had a higher NDF loss than unfractionated forage between 9 and 24 h and the difference was maintained after 24 h. Treatments in which amorphous silica was precipitated within NDF or leached from a grass substrate indicated that the enhanced rate in grasses was not due to removal of biogenic silica by the neutral detergent treatment. © 1999 Society of Chemical Industry

Diversity of Ruminococcus strains: a survey of genetic polymorphisms and plant digestibility

Twenty‐three strains of Ruminococcus isolated from ruminants were assessed for digestive ability on different plants and purified cellulose. Genetic diversity was assessed by ERIC, REP and 16–23S rDNA spacer polymorphisms. All ruminococci could be typed by ERIC, REP or 16–23S rDNA spacer, but all three typing methods had to be used in concert to differentiate closely related strains. Digestibility of lucerne (Medicago sativa), rhodes grass (Chloris gayana) and spear grass (Heteropogon contortus) were assessed. Dry matter (DM) digestibility was highly correlated (> 0·93) with neutral detergent fibre (NDF) digestibility, but cellulose disc digestibility was a poor indicator of DM and NDF digestibility. Studies demonstrate the wide variation in ability of ruminococci to digest forages, and some recently isolated strains (Y1, LP‐9155, AR67, AR71 and AR72) were superior to reference strains (FD‐1 and Ra8). Multivariate analysis showed that groupings derived from genotyping data closely resembled those determined by digestibility data. This study indicated that ruminococci are diverse in digestive ability and genotype, and this diversity suggests that there may be highly fibrolytic strains in nature that could be utilized for animal production.

Adoption of improved fallows in West Africa: lessons from mucuna and stylo case studies

Traditional shifting cultivation systems can no longer be sustained in West Africa because of rapid increases in human and livestock populations. Short-duration, improved fallows are among the alternative land-management strategies that have evolved. This paper reviews how velvetbean or mucuna (Mucuna pruriens) and stylo (Stylosanthes hamata and Stylosanthes guianensis) management systems were developed and disseminated in West Africa. Mucuna was first adopted by farmers in southwestern Benin between 1988 and 1992, and the number of testers of the innovation rose to 10,000 farmers throughout Benin by 1996. Suppression of spear grass (Imperata cylindrica) was perceived as the main benefit of mucuna fallows. The stylo technology was introduced in the late 1970s, and it was primarily targeted to livestock production in the subhumid monomodal rainfall zone. The uptake of stylo has been relatively slow and modest in West Africa in contrast to the faster rate of adoption of mucuna in southwestern Benin. Some of the contributory factors to the slower adoption of stylo than mucuna include rainfall regime, lack of motivation of livestock keepers, insecure land tenure, limited capability and facilities of extension staff, poor communication among scientists, and unsatisfactory establishment of the crop. Recommendations to increase the adoption of improved fallows include the use of a participatory approach in problem identification, expansion of the genetic base of cover crops for use in fallows, optimization of the multiple benefits of cover crops, management of the improved system, promotional strategies, and appropriate policies.

Butyrivibriospp. and Other Xylanolytic Microorganisms From the Rumen have Cinnamoyl Esterase Activity

High concentrations of hydroxycinnamic acids in the hemicellulosic fraction of dry season tropical grasses may influence the rate of microbial degradation of arabinoxylans by ruminant animals. The ability of 22 strains ofButyrivibrio fibrisolvens, other ruminal bacteria (Ruminococcus albusSY3,Ruminococcus flavefaciensRF1,Prevotella ruminicolaAR20) and the ruminal phycomyceteNeocallimastix patriciarumCX to digest the tropical grassHeteropogon contortus(spear grass) and hydrolyse esterified ferulic and p-coumaric acid was examined. Significant digestion (8–36%) of spear grass occurred with theB. fibrisolvensstrains H17c, A38, LP92-1-1, 49,R. albusSY3 andN. patriciarum. Hydrolysis of ester-linked ferulic and p-coumaric acid occurred with all organisms exceptB. fibrisolvensstrains GS113, OB156 and LP1028 andP. ruminicolaAR20. The ratio of ferulic to p-coumaric acid hydrolysed by different strains ofButyrivibriospp. varied markedly from 0.96 for AR 51 to 0.16 for A38. Butyrivibrios which were fibrolytic (H17c and A38) had higher extracellular cinnamoyl esterase activity than bacteria that did not digest spear grass fibre (LP 91-4-1 and AR 20) which had low activities or only produced cell associated enzyme. Cell associated and extracellular esterase activity were induced whenButyrivibriospp. strains H17c, A38 and E14 and theRuminococcusspp. were grown on birchwood xylan but induction did not occur to the same extent withN. patriciarum. This is the first reported observation of cinnamoyl esterase activity in the genusRuminococcus. The fungusN. patriciarumhad significantly higher digestibility of spear grass and solubilisation of phenolic acids than the bacteria. The study shows that high levels of extracellular cinnamoyl esterases are characteristic of a selection of fibre-degrading ruminal bacteria and fungi which probably indicates that these enzymes are common amongst xylanolytic ruminal microorganisms.

Rumen bacterial and protozoal populations in cattle being relocated in tropical Queensland

Rumen microbial populations were measured in Brahman-cross steers that were relocated from spear grass (Heteropogon contortus) dominant pastures in northern Queensland to buffel grass (Cenchrus ciliasis) dominant pastures in central Queensland, to assess whether aspects of rumen function may contribute to the sometimes reported depressed growth rates following relocation. Nine genera of ciliate protozoa (Isotricha, Dasytricha, Entodinia, Epidinium, Diplodinium, Ostracodinium, Metadinium, Elytroplastron, and Eudiplodinium) were recorded in the rumen fluid of the steers. In most steers all genera were present at any time and the generic mix persisted throughout the 10 months over which the study was conducted. Protozoal population composition fluctuated only slightly over the sampling period. Entodinia were predominant, occupying 50-70% of the population. Population density varied according to season, with the highest density (4-8×105 /mL rumen fluid) occurring in the wet season. Bacterial and protozoal populations were remarkably stable and little affected by relocation. Again, the major impact on population density was the season, with all carbohydrate (soluble sugar, starch, xylan, and cellulose) utilising bacterial subpopulations reaching the greatest density with the onset of the wet season.

Use of a multi-exponential model to assess the effect of fermentation in the reticulorumen on particle fragmentability as simulated from artificially macerating leaf and stem fractions of two tropical grasses

This study reports the use of a mechanical macerating device to characterise the patterns of, and resistance to, fragmentation of leaf and stem fractions of spear grass ( Heteropogon contortus) and sabi grass ( Urochloa mosambicensis). The four substrates, cut to a length of 1.5–2 cm, were exposed to microbial fermentation in the rumen of cattle for periods of between 0 and 96 h. A novel macerating device was used to grind substrates in a water medium for a series of predetermined number of rotor revolutions of the macerator. The extent of fragmentation was then measured by wet sieving. Statistical modelling, using phase-type distributions, was used to describe the numbers of revolutions required to fragment the substrates into three compartments defined by particles retained on screens of 1180, 600, and 50 μm pore size. The study identified multi-exponential patterns of fragmentation of tropical grass fractions. Resistance to fragmentation of large particles, estimated by the number of rotor revolutions required for 0.75 of particles to be removed from that pool, was high for both stem fractions, and was not markedly affected by time of microbial fermentation. Spear grass leaf had high resistance to fragmentation until exposed to microbial fermentation for 24 h, after which it attained the low resistance to fragmentation typical of sabi grass leaf at all microbial fermentation times. Fragmentability of large particles, defined as the proportion of small particles originating from the large particle pool which did not pass through the medium particle pool, was always high for leaf (> 0.66), but for stem fractions it was quite variable. Sabi grass stem achieved maximum fragmentability values typical of leaf (0.70), but for spear grass stem fragmentability was lower at 0.52. The potential digestibility of particle fractions following various degrees of maceration, was assessed after in vitro fermentation for 120 h. Extensive maceration of samples not exposed to rumen fermentation increased sample digestibility of the leaf fractions by 3 to 7%, and of stem of spear grass and sabi grass by 380 and 120% respectively. For sabi grass stem, the relative increase in potential digestibility after maceration progressively declined in samples after rumen fermentation; no such decline was seen for spear grass stem. The implications of the results to nutritive value for the ruminant eating forage diets are discussed. It is suggested that the phase-type statistical modelling techniques used are of value in the study of particle movements and fragmentation in the reticulorumen.

Defending Wordsworth, Defending Poetry

Defending Wordsworth, Defending Poetry Mark Edmundson Near the close of Wordsworth’s first great poem, The Ruined Cottage, there arrives an extraordinary moment. Armytage has been telling the story of his friend Margaret’s decline and death to the young narrator of the poem, who is in some sense Wordsworth’s stand-in. Part of the poem’s achievement, Coleridge thought, was the way that Wordsworth conferred a tragic dignity on the sufferings of a common person. Margaret loses her husband, who enlists to fight in America so that he can leave his family his enlistment bonus, saving them from terrible want, perhaps starvation. Margaret never ceases to hope that her husband will return. Whenever a stranger passes by her gate, she stops him and asks for news about Robert. Years go by, Robert does not return home, and Margaret pines gradually away. Each time the wandering Armytage comes back to her door, Margaret is more gaunt and distracted. She neglects her children: one goes off to a meager apprenticeship; the other, the younger boy, dies. Armytage is a stoical character, though not a frigid one. He has withdrawn his energies from the world of human things, and dispersed them throughout nature where they cannot, presumably, be betrayed. Nature will always regenerate itself; the world grows older, but returns each spring to its youth. Nature offers a sort of perfection that’s far removed from the human course of birth, decay, and death. Armytage tells the young narrator Margaret’s story for many reasons, but one, I think, is to instruct him in the management of grief. The wanderer unfolds the tale with such patient eloquence, poise, and restraint that the young man ends up overwhelmed by feelings for Margaret that are, we can assume, much like the ones that Armytage has locked up in himself, has subdued with his reasoning powers. When [End Page 207] the tale is over, Armytage, compassionately if a touch formulaically, tries to salve the young man’s grief: “Enough to sorrow have you given,” he says, “the purposes of Wisdom ask no more.” But if Armytage teaches the young man a measure of stoicism, the narrator’s strongly felt response also succeeds, however transiently, in restoring to the old man his life of feeling. For the lines that follow from Armytage—and that comprise the moment I want to call attention to—convey both force of feeling and supple but sure intellectual power. This synthesis is the culmination of the poem: it dramatizes the rich interpenetration of mind and emotion that The Ruined Cottage has been working toward: “She sleeps in the calm earth, and peace is here. I well remember that those very plumes, Those weeds, and the high spear grass on that wall, By mist and silent raindrops silvered o’er, As once I passed, did to my mind convey So still an image of tranquility, So calm and still, and looked so beautiful Amid the uneasy thoughts which filled my mind, That what we feel of sorrow and despair From ruin and from change, and all the grief The passing shows of being leave behind, Appeared an idle dream that could not live Where meditation was. I turned away, And walked along my road in happiness.” We praise poets, and rightly, when they make fine metaphors, finding the likeness in apparently unlike things. So Robert Frost asked his critics to be more responsive to his figurative breakthroughs: he talked about how we should note what an achievement it was to “turn that that way, and what a feat it was to remember that, to be reminded of that by this.” Yet it can also be a feat to resist the act of metaphor making. And this I think is what Wordsworth is doing in the culminating passage. What calms Armytage is the remembered image of the weeds and the high spear grass silvered by mist and silent rain drops. The fact that this is weeds and grass, that the vegetation is dispersed and multiple, matters a great deal. What we are not getting here is a natural image for Margaret. Such an image—one lovely blowing wand of spear grass, say...

Energy and protein evaluation of tropical feedstuffs for whole tract and ruminal digestion by chemical analyses and rumen inoculum studies in vitro

A range of tropical feedstuffs used in feeding ruminants were analysed for metabolisable energy ( ME) and nitrogen fractions. The ME content was predicted from the extent of fermentation in in-vitro incubation with rumen inoculum and N was evaluated based on solubility in borate-phosphate buffer, protease enzyme and acid detergent solution. The range in predicted ME content and the rate of organic matter fermentation for grains, byproduct feeds, cultivated fodders and nonlegume straw were respectively, 11.8–13.9 and 0.05–0.11; 6.0–13.7 and 0.05–0.15; 7.1–9.4 and 0.05–0.13; 5.7–7.7 and 0.02–0.04. Potentially digestible N was more than 90% for most feedstuffs with the exception of finger millet grains (73.9%), rice bran (88.0%), napier grass (79.3%), spear grass (82.6%) and nonlegume straw (66.0–88.6%). N insolubility in protease enzyme (PIN) was maximum in rice bran, solvent extracted (s.e.) (56.6%) and minimum in sesame meal (3.3%), with cottonseed meal and rapeseed meal > sunflower meal, coconut meal, groundnut meal, s.e. > groundnut meal, expeller (exp). However, the buffer insoluble N soluble in protease enzyme (considered as slowly degraded N) was found to be maximum in sesame meal (90.6%), followed by coconut meal (60.2%), cottonseed meal (50.6, 61.6%), sunflower meal (45.7%), groundnut meal, s.e (45.1%) and groundnut cake, exp. (22.7%). In situ N undegradability reported in the literature for similar feedstuffs indicated too wide a range making it difficult to take these values as standards for comparison with any of the N fractions obtained from the laboratory analysis.

Solubilization of lignin by the ruminal anaerobic fungus Neocallimastix patriciarum.

The ability of the ruminal anaerobic phycomycete Neocallimastix patriciarum to digest model lignin compounds and lignified structures in plant material was studied in batch culture. The fungus did not degrade or transform model lignin compounds that were representative of the predominant intermonomer linkages in lignin, nor did it solubilize acid detergent lignin that had been isolated from spear grass. In a stem fraction of sorghum, 33.6% of lignin was apparently solubilized by the fungus. Solubilization of ester- and either-linked phenolics accounted for 9.2% of the lignin released. The amounts of free phenolic acids detected in culture fluid were equivalent to the apparent loss of ester-linked phenolics from the sorghum substrate. However, the fungus was unable to cleave the ether bond in hydroxycinnamic acid bridges that cross-link lignin and polysaccharide. It is suggested that the majority of the solubilized lignin fraction was a lignin carbohydrate complex containing ether-linked hydroxycinnamic acids. The lignin carbohydrate complex was probably solubilized through dissolution of xylan in the lignin-xylan matrix rather than by lignin depolymerization.

Alteration of supplement nitrogen:Sulphur ratio by increasing sulphate supplementation affects the rate rather than the extent of fibre degradation in cattle fed a matured tropical grass hay

AbstractThere is a need to understand how supplement N: S ratios can affect ruminal fermentation and ultimately, nutrient supply, in grazing animals. The following experiment was undertaken to describe the effect(s) of supplement N : S ratios upon the rate and extent of ruminal degradation of poor quality native pasture hay. Four rumen fistulated Brahman × Shorthorn (Drought master) steers, fed chopped Black Spear Grass hay, received either no intraruminal supplement, or urea plus sodium sulphate to give supplement N: S ratios of 23:1, 16:1, 11.5:1, 10:1 and 4:1. The level of urea supplementation was kept constant and maintained rumen ammonia concentrations in excess of 100 mg litre−1. No differences were observed in voluntary feed intake in response to different supplement N: S ratios. The extent of rumen fermentation as measured by the nylon bag technique and apparent organic matter digestibility in vivo were similar for supplement N : S ratios of 16:1 and lower, and total intake of digestible organic matter was maximal with a supplement N : S ratio of 10: I. Increasing levels of S supplementation were found to increase the rate of rumen fermentation.

Intake and digestion in swamp buffaloes and cattle. 2. The comparative response to urea supplements in animals fed tropical grasses

SUMMARYSwamp buffaloes (Bubalus bubalis) and crossbred cattle (B. indicusxB. taurus) were offered two forages in two experiments. In Expt 1, four animals of each species were offered mature Rhodes grass hay (Chloris gayana) with a mineral supplement or with a supplement of minerals and urea (17·6 gN/d). In Expt 2, another group of four buffaloes and four cattle were offered mature spear grass hay(Heteropogon contortus) with mineral supplementation at intervals of 3 h. Four levels of urea (0, 5, 21 and 97 g/day) and35S-sulphate were continuously infused in four periods.Rhodes grass was consumed in greater amounts by cattle, whereas buffaloes ate more spear grass. Urea supplements increased intake of Rhodes grass by 12% in buffaloes and 22% in cattle, and of spear grass by 34% in buffaloes and 41 % in cattle. Digestibility of cell wall constituents and acid-detergent fibre of spear grass was lower (P&lt; 0·05) in buffaloes than in cattle (417v. 499; 471v. 560 g/kg respectively). In Expt 2, dry matter digestibility progressively increased (P&lt; 0·05) from 364 to 408 g/kg with increased urea infusion. Rumen dry matter pool increased by 11–21 % on infusion of 97 g urea/day, compared with no urea. Digestion of ground forages incubatedin situin the rumen was depressed below rumen ammonia levels of 30–60 mg N/l, while digestion of cotton thread was depressed below 60–80 mg N/l (Expt 1) or 150–200 mg N/l (Expt 2).Patterns of N content in cotton thread suggested that more microbes attached in buffaloes and there was subsequently faster detachment than in cattle, particularly with increased urea infusion.

Effect of superphosphate application on macro-nutrient and micro-nutrient concentrations in grazed stylo-native grass pasture in tropical Australia

Soils of northern Australia are generally old, strongly weathered, and of low fertility status. Some knowledge of the status of nitrogen, phosphorus and sulfur and its effects on pasture productivity is available from small plot trials, but few detailed studies of macro-nutrient and micro-nutrient levels in grazed pastures have been reported. Such a study from a site near Mareeba in north Queensland has recently been completed. The major components of the pasture were kangaroo grass ( Themeda triandra), giant speargrass (Heteropogon triticeus) and the legumes, Stylosanthes scabra cv. Seca and S. hamata cv. Verano, which were oversown into the native grass pasture 6 years previously. Generally, the effects of superphosphate on nutrient concentration were minor compared with the effects of season, plant part and species. Superphosphate application increased concentrations of P and S, but decreased concentrations of Zn and Mo and the N/S ratio in both sets of legume and grass. There was no effect on the concentrations of N, K, Na, Ca, Cu and Co. Fertilizer effects did not often interact significantly (P &lt; 0.05) with season, species and plant part (green leaf and stem). Seasonal changes in nutrient concentration were not consistent for all nutrients. As the growing season progressed from December to June, concentrations of the mobile nutrients, N, P, K, Na, Cl, S, Se and I decreased, the immobile nutrients Ca and Mo increased, but Mg, Cu and Co and the N/S ratio remained relatively constant. Both Zn and Mn concentrations remained constant with season in the legumes, but increased in the grasses. Season * species interactions were often significant for the grasses possibly due to the differing maturity patterns of kangaroo grass and giant spear grass. Cattle grazing the native pasture during the wet season are likely to be deficient in N, P, Na, S and Cu based on the nutrient concentrations in plucked pasture samples and published dietary requirements. However, cattle grazing productive stylo - native grass pasture which has received adequate single superphosphate are likely to suffer only from Na deficiency. At suboptimal levels of superphosphate, a deficiency of P in the diet is also indicated.

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&lt; 0·05). In both groups of animals, sulphur supplementation increased the fermentation of cotton thread cellulose (P&lt; 0·05), as well as of ground plant dry matter (P&lt; 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&lt; 0·05) and from 35·1 to 41·5% in group B (P&gt; 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&lt; 0·05) and outflow of fluid digesta from this site (5·31 v 3·58 litres/day,P&lt; 0·05). Sulphur supplementation increased the molar proportion of acetic acid in rumen fluid (P&lt; 0·05) but lowered propionic and butyric acids in group A (P&lt; 0·05). Only the molar proportion of propionic acid in rumen fluid was significantly lowered in group B (P&lt; 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&lt; 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.

Cyclodimers of p‐coumaric and ferulic acids in the cell walls of tropical grasses

AbstractCell walls from leaves and stems of three tropical grasses (Setaria anceps cv Nandi (Schumach) Moss), pangola grass Digitara decumbens Stent and spear grass Heteropogon contortus (L) Beauv ex Roemer &amp; Schultes were extracted with alkali, and ether‐soluble fractions were prepared from the acidified solutions. Cyclobutane dimers derived from p‐coumaric acid (CA: 3‐(4‐hydroxypheny) propenoic acid) and ferulic acid (FA: 3‐(4‐hydroxy‐3‐methoxyphenyl) propenoic acid) were found in all plant residues. Structural information on the dimers was obtained by gas chromatography‐mass spectrometry. Stem cell walls differed from those of leaf in having major dimer components which contained residues tentatively identified as coniferyl alcohol (3‐(4‐hydroxy‐3‐methoxyphenyl)‐2‐propen‐l‐ol). Species differences in leaf cell wall cyclodimers were evident. Pangola and setaria grasses had dimers mainly derived from FA, whereas spear grass had over 70% of dimers derived from CA. Di‐esterification of some dimers in the cell walls was confirmed by the release of dimers containing the reduced forms of CA and FA (coumaryl and coniferyl alcohols respectively) when leaf cell walls were extracted with borohydride. Head to tail dimerisation giving derivatives of truxillic acid (t‐2, c‐4‐diphenyl‐r‐l, t‐3‐cyclobutanedicarboxylic acid) predominated, although evidence was obtained for the presence of head‐to‐head coumaric acid dimers (derivatives of truxinic acid, t‐3, t‐4‐diphenyl‐rl, c‐2‐cyclobutanedicarboxylic acid) in setaria stem and spear grass leaf. The results suggested that cyclodimers in grass cell walls occurred in cross‐linking structures of varying complexity between macromolecules, where they would possibly contribute to fibre strength and thus have an adverse efect on the nutritional value of forage.

Focal ulceration of the mouth in ruminants fed spear grass.

Focal ulceration of the mouth in ruminants fed spear grass.

The effect of supplements of rumen-degradable protein and formaldehyde-treated casein on the intake of low-nitrogen roughages by Bos taurus and Bos indicus steers at different stages of maturity

The response in voluntary feed intake, firstly to supplements of rumen-degradable protein and then to additional supplements of formaldehyde-treated casein (FTC) was studied in Aberdeen Angus (Bos taurus) and Brahman (Bos indicus) steers fed long-chopped spear grass (Heteropogon contortus) and pangola grass (Digitaria decumbens). The intake responses were measured at four stages of maturity of the steers ranging from soon after weaning to near maturity. On diets deficient in nitrogen the magnitude of the intake response to rumen-degradable protein was greater in Angus than in Brahmans. With the exception of the Angus steers fed spear grass soon after weaning, there was no significant response to FTC with either diet beyond that achieved with rumen-degradable protein. From published values of the digestible protein supplied by the diets and the protein requirements of cattle for maintenance, it was calculated that pangola grass, prior to supplementation with FTC, supplied sufficient digestible protein for maintenance. On the other hand, that supplied by spear grass, prior to supplementation with FTC, was substantially below that required for maintenance. These experimental and calculated data are discussed in terms of factors limiting feed intake, and conclusions drawn about protein requirements for the expression of maximum feed intake of roughage diets.

Dry Season Decomposition of Leaf Litter from Five Common Plant Species of West Africa

ABSTRACT The rates of decomposition of litter from five plant species common to West Africa namely: Chromolaena odorata (Siam weed), Anacardium occidentale (cashew), Acioa batteri, Imperata cylindrica (spear grass) and Pentaclethra macrophylla (oil bean) were investigated in the laboratory and the field during the dry season using respiration and litter bag techniques. There were significant differences (P Chromolaena > Anacardium > Pentaclethra > Acioa. Unexpectedly, the particle size of litter (ground versus unground) did not affect the rates of respiratory activity in any regular pattern although the unground samples were in nylon mesh bags. Possibly, fungi were the main agents of decomposition since by their mycelial habit, they ramify into a substrate. Under adequate moisture conditions, the highest amount of litter decomposed—58.3%, 52.3% and 34.3% were obtained with Chromolaena, ...