R.E. Estell

Estimating digestibility and faecal output in lambs using internal and external markers

Twenty fine-wool, ruminally cannulated lambs (average weight 45–9 kg) were used in a completely random design to evaluate the ability of three internal markers to predict dry matter digestibility and two external markers to estimate faecal output. Lambs were allotted randomly to one of four diets: 100% prairie hay (PH), 100% lucerne hay (LH), 50% prairie hay:50% sorghum grain (PS) and 50% lucerne hay: 50% sorghum grain (LS). The trial consisted of a 14-day adaptation period followed by a 7-day total faecal collection period. Feed and faecal samples were subjected to 96 h ruminal fluid and 48 h acid-pepsin digestions, followed by extraction with acid detergent (IVADF) or neutral detergent (IVNDF) solution. Dry matter digestibility (DMD) calculated from feed:faeces ratios of IVADF, IVNDF and acid detergent lignin (ADL) was compared with in vivo apparent digestibility. Ytterbium-labelled forage (YLF) and dysprosium-labelled faeces (DLF) were pulse-dosed via ruminal cannulae, and faecal Yb and Dy excretion curves were fitted to a one-compartment, agedependent model for estimation of faecal output, paniculate passage rate (PPR) and mean gastrointestinal retention time. In vivo DMD in lambs fed PH was greater (P 005) than DMD calculated from IVNDF, IVADF and ADL. In lambs fed LH and LS, in vivo DMD did not differ (P > 005) from marker estimates. In vivo DMD for lambs fed PS did not differ from IVNDF or IVADF estimates but was greater than (P 005) the ADL estimate. No differences ( P > 005) were observed in recovery among the three internal markers for any of the diets. Faecal output for lambs fed PH did not differ {P > 005) from marker estimates but was overestimated by 15 to 20% by YLF and DLF. Faecal output for lambs fed LH was similar to the estimate from YLF, but less than (P 0–05) the estimate with DLF. For lambs fed PS, faecal output did not differ from marker estimates, but YLF and DLF values were 16% lower and 17% higher, respectively. No significant differences were observed in actual and estimated faecal output for lambs fed the LS diet. Estimates of PPR with DLF were numerically greater than YLF estimates for all diets except LS. Correspondingly, mean gastrointestinal retention time was less (P 005) for DLF compared with YLF for all diets except LS.

Distribution and concentration of total phenolics, condensed tannins, and nordihydroguaiaretic acid (NDGA) in creosotebush (Larrea tridentata)

This paper focuses on the presence and distribution of secondary phenolic compounds found within creosotebush [Larrea tridentata (Sess. & Moc. ex DC.) Cov.]. Total phenolics, condensed tannins and nordihydroguaiaretic acid (NDGA) were measured in nine categories of tissue within creosotebush. Total phenolic and condensed tannin concentrations were determined using colorimetric methods while NDGA content was determined with high performance liquid chromatography (HPLC). Phenolics were present throughout the plant with the highest concentrations in leaves (36.2 mg/g), green stems (40.8 mg/g) and roots (mean for all root categories=28.6 mg/g). Condensed tannins were found in all tissues with highest concentrations in flowers (1.7 mg/g), seeds (1.1 mg/g), and roots less than 5 mm in diameter (1.1 mg/g). Flowers, leaves, green stems and small woody stems (<5 mm in diameter) all contained NDGA with highest concentrations in leaves (38.3 mg/g) and green stems (32.5 mg/g).This is the first report we are aware of giving secondary chemical characteristics of creosotebush roots. Data reported here will be used to support further research into the dynamics of shrub replacement and dominance of arid grasslands.

Extracts of Flourensia cernua (L): volatile constituents and antifungal, antialgal, and antitermite bioactivities.

The chemical components of tarbush (Flourensia cernua) leaves were fractionated by extracting successively with hexanes, diethyl ether, and ethanol. Volatile profiles of each fraction were identified by using GC-MS. The hexanes fraction contained mostly monoterpenoids, while the ethanol fraction volatiles were primarily sesquiterpenoids. Crude fractions were tested for activity against fungi, algae, and termites. Application of as little as 1 μg of the essential oil from the hexanes fraction was sufficient to provide visible antifungal activity in bioautography assays. The diethyl ether fraction showed selective activity against the cyanobacterium responsible for the 2-methylisoborneol-induced off-flavor sometimes associated with catfish farming operations. All three fractions exhibited a high degree of antitermite activity.

Relationship of Tarbush Leaf Surface Terpene Profile with Livestock Herbivory

Tarbush (Flourensia cernua DC.) is a Chihuahuan Desert shrub with a resinous leaf surface containing terpenes that may affect livestock herbivory. Cattle, sheep, and goats were densely stocked in paddocks containing tarbush in two consecutive years for six to nine days and defoliation of 160 plants was recorded daily. Plants were categorized as exhibiting high or low defoliation. Leaves were collected from these plants the third year for chemical analysis. A selection procedure was used to generate two variable sets closely related to defoliation category. One set contained 14 variables (dry matter, ash, α-pinene, sabinene, 3-carene, p-cymene, limonene, camphor, borneol, cis-jasmone, β-caryophyllene, α-humulene, ledene, and flourensadiol) and the other set contained 14 unidentified compounds. When subjected to multivariate analysis, each group distinguished between the two defoliation categories (P < 0.001 and P < 0.0019 for known and unknown variable sets, respectively). These data support the hypothesis that leaf surface chemistry of individual tarbush plants is related to extent of defoliation by livestock.

Increasing Shrub Use by Livestock in a World with Less Grass

Abstract Much of the worlds rangeland is dominated by woody species. Competing land uses and continued encroachment of woody species into non–woody-dominated rangelands have reduced grasslands in many parts of the world. Land use conversions to fuel and feed global populations, especially the increasing number of middle class people seeking broader, meat-based diets, will certainly continue. Halting and/or reversing further encroachment of woody species into grasslands is slow, expensive, and in some cases not possible. Yet, global livestock numbers continue to increase to meet the growing demand for red meat and other livestock products. How do we reconcile a world with less grass and the concurrent increased demand for forages to feed livestock? Strategies and mechanisms are needed to safely enhance shrub use by ruminants in order to capitalize on a presently underutilized forage resource. A number of approaches are presently available (e.g., choosing appropriate species and breeds, providing dietary supplements and additives, behavior modification, genetic selection) to increase shrub consumption, and new technologies such as biochemical markers of shrub intake need to continue to be identified and developed. Such strategies could provide important means for rural communities to adapt to changing land cover and climate. Resumen La mayor parte de los pastizales del mundo están dominados por especies leñosas. El cambio de uso de suelo y la continua expansión de especies leñosas dentro de pastizales dominados por no-leñosas ha reducido los pastizales en muchas partes del mundo. La conversión de tierras para abastecer y alimentar la población global, especialmente con el aumento en el número de personas de clase media que buscan dietas basadas en carne ciertamente continuara. El vacilante y/o posible re vertimiento de la invasión de especies leñosas en los pastizales es lento, caro y en algunos casos imposible. De hecho, el número global de ganado continuara creciendo para cubrir la demanda de carne roja y otros productos derivados del ganado. ¿Cómo podemos conciliar a un mundo con menos pasto y la creciente demanda de forrajes para alimentar el ganado? Se necesitan estrategias y mecanismos que de manera segura promuevan el uso de arbustos por los rumiantes con el fin de capitalizar los recursos forrajeros subutilizados actualmente. Hay disponibilidad de puntos de vista (ejm. Seleccionar razas y especies apropiadas, proveer suplementos dietéticos y aditivos, modificar el comportamiento, selección genética) para aumentar el consumo de arbustos y nuevas tecnológicas tales como los marcadores bioquímicos en consumo de arbustos que se necesita continuar en la identificación y desarrollo de estos. Estas estratégicas pueden ofrecer importantes medios en las comunidades rurales para adaptar en la cambiante cobertura del suelo y el clima.

A Retention Index Calculator Simplifies Identification of Plant Volatile Organic Compounds

INTRODUCTION Plant volatiles (PVOCs) are important targets for studies in natural products, chemotaxonomy and biochemical ecology. The complexity of PVOC profiles often limits research to studies targeting only easily identified compounds. With the availability of mass spectral libraries and recent growth of retention index (RI) libraries, PVOC identification can be achieved using only gas chromatography coupled to mass spectrometry (GCMS). However, RI library searching is not typically automated, and until recently, RI libraries were both limited in scope and costly to obtain. OBJECTIVE To automate RI calculation and lookup functions commonly utilised in PVOC analysis. METHODOLOGY Formulae required for calculating retention indices from retention time data were placed in a spreadsheet along with lookup functions and a retention index library. Retention times obtained from GCMS analysis of alkane standards and Koeberlinia spinosa essential oil were entered into the spreadsheet to determine retention indices. Indices were used in combination with mass spectral analysis to identify compounds contained in Koeberlinia spinosa essential oil. RESULTS Eighteen compounds were positively identified. Total oil yield was low, with only 5 ppm in purple berries. The most abundant compounds were octen-3-ol and methyl salicylate. The spreadsheet accurately calculated RIs of the detected compounds. CONCLUSION The downloadable spreadsheet tool developed for this study provides a calculator and RI library that works in conjuction with GCMS or other analytical techniques to identify PVOCs in plant extracts.

Relationship of tarbush leaf surface secondary chemistry to livestock herbivory.

Tarbush (Flourensia cernua DC.) is an abundant but generally unpalatable shrub native to the Chihuahuan Desert. The objective of this study was to examine the leaf surface chemistry of tarbush in relation to degree of use by ruminants. Mature tarbush leaves were collected on 2 sites during 2 periods approximately 2 weeks apart from plants exhibiting either high (> 45%) or low (< 10%) use when browsed by cattle, sheep, and goats confined to a small area (5 plants per use category for each site/period combination). A greater (P < 0.05) concentration of epicuticular wax was detected on the leaf surface of plants that were used to a lower degree (82 and 10.3% of the leaf dry matter for high- and low-use plants, respectively). Several leaf surface compounds were related to period, while site and degree of use were seldom related to individual mono- and sesquiterpenes measured in this study. Camphene and 10 unidentified compounds differed between periods (P < 0.10). Two unidentified compounds were related to site (P < 0.10) and 2 others were related to use (P < 0.10). In summary, individual leaf surface compounds on tarbush do not appear to greatly affect degree of use of tarbush by livestock, but collectively (based on epicuticular wax data), these compounds may influence the diet selected by browsing ruminants.

Essential Oil of Flourensia cernua DC.

Abstract The leaf oil of Flourensia cernua DC. collected from the Jomada Experimental Range in southcentral New Mexico was analyzed. GC/MS and retention indices were used to identify 89 components. β-Eudesmol (24.5%), α-eudesmol (6.9%), limonene (6.6%), γ-eudesmol (4.6%), myrcene (3.8%), borneol (3.3%), and δ-3-carene (3.0%) were the major components of the steam distilled oil. In an ethanol extract of intact leaves, flourensadiol (44.6%), artemisia alcohol (5.5%), viridiflorol (2.7%), and borneol (2.0%) were the main components.

Effects of ruminant digestion on germination of Lehmann love-grass seed

Lehmann lovegrass (Eragrostis lehmanniana Nees) seed (germination 96%, dormant 0%) was used in 4 experiments to study the potential of sheep as a dispersal agent. Five, 4-year-old, ruminally cannulated wethers were used to examine effects of ruminant digestion on seed recovery and germination. All wethers were ruminally evacuated, and rumens were cleansed and reinoculated with strained ruminal fluid. After a 21-day adaptation to pelleted alfalfa, 4 experiments were conducted. Experiment 1 was designed to test viability of Lehmann lovegrass seeds exposed to ruminal and postruminal digestion. Lehmann lovegrass seed (10 g) was dosed intra-ruminally via ruminal fistula, and total fecal collections made. Of the viable seed ruminally dosed, 37% germinated within 21 days after recovery. Also, 98 to 100% of the seed that germinated was recovered within 72 hours of dosing. Experiment 2 was designed to test the influence of ruminal microbial digestion on seed degradation and viability, using in sacco nylon bag techniques. In sacco dry matter disappearance increased linearly from 5.5% at 3 hours of incubation to 16% at 120 hours. Germination of seed was not greatly affected until after 72 hours of ruminal incubation. Experiment 3 was designed to examine the effect of mastication on viability of Lehmann lovegrass seeds. Seeds were mixed with seed-free Lehmann lovegrass straw in a proportion of 1 to 10 (seed to straw) and 10 g fed to each wether. Boli were recovered manually via ruminal fistula. Thirty five percent of the seed fed entered the rumen without damage due to mastication. Experiment 4 compared in vitro techniques and in sacco techniques used to estimate the effect of digestion on seed viability. In vitro incubation techniques yielded similar results as in sacco techniques. We conclude that ruminants are potential disseminating agents of Lehmann lovegrass seed.

Secondary chemistry of the leaf surface of Flourensia cernua

Abstract Epicuticular wax accounted for 9.2% of the dry wt. of whole Flourensia cernua (tarbush) leaves. Leaf surface extracts of tarbush were analyzed for mono- and sesquiterpenoids with gas chromatography-mass spectrometry. Camphene, β-myrcene, 3-carene, limonene, 1,8-cineole, borneol, cis -jasmone, β-caryophyllene, caryophyllene oxide and globulol were consistently present on the leaf surface of tarbush. Concentrations of several unidentified compounds were estimated. A great deal of plant-to-plant variability was detected in leaf surface mono- and sesquiterpenoidi concentration. Information obtained on surface chemistry might be exploited to enhance the use of tarbush as a forage for domestic herbivores.