Carbon partitioning in forage crops

The paper describes the conceptual models used to understand the processes determining plant growth rates in response to environmental changes. A series of experiments and growth models were used at three organizational levels: the specific plant organs, the whole plant and the plant canopy. The energy conversion efficiency and the total plant carbon balance were first examined. The carbon partitioning amongst the plant parts was then studied. The energy conversion efficiency is generally understood. In modelling carbon partitioning it was first necessary to establish the carbon demand for each plant organ. The carbon partitioned amongst plant organs was then calculated in two ways. The first one based on empirical data consisted in defining which organ received the carbon prior to other organs. The second one was based on the relationship between the carbon mass of specific organs and their trophic activity. This hypothesis allowed the optimization of the carbon partitioning in order to maximize the whole plant growth rate. The opportunities to use these theoretical approaches in plant growth modelling are discussed.     

Assessment of forage availability in ecological studies

In this study we describe and calibrate a quantitative index method to estimate leaf biomass and forage availability for browsers at different feeding heights. The method is based on an index relating leaf biomass to a number of leaf contacts with a vertical, three-dimensional (25×25×165 cm) metallic quadrat with a central rod and takes into account the characteristics of leaves (shape, size, and thickness) to define plant categories and then produce general allometric equations per category. We then discuss the use of this biomass index to evaluate the quality of habitats for browsers in terms of food resources.     

Seasonal range selection in bighorn sheep: conflicts between forage quality,forage quantity,and predator avoidance

Summary The migratory and foraging behavior of individually marked bighorn ewes (Ovis canadensis) was studied to test the hypothesis that forage quality determined seasonal range selection. Forage quality was monitored through analysis of fecal crude protein. Ewes in the study population utilized two distinct ranges differing in elevation and possibly predation risk. Pregnant ewes migrated in May from the low-elevation winter range to lambing areas at higher elevation, before plant growth had started there. In so doing, they moved from a range of high-quality forage to one of low-quality forage, apparently to avoid predation on newborn lambs. Non-pregnant adult ewes migrated later. Most yearling ewes (which are not pregnant) migrated with the adult ewes to the lambing areas, but returned to the winter range within a few days, then migrated again to high-elevation areas in June. Forage quality was higher at high elevation from mid-June at least through July, but forage availability appeared to be lower than in the winter range. Seasonal range selection is likely determined by a combination of nutritional and antipredator constraints. The antipredator strategy of bighorn ewes does not always allow them to utilize the range with the best forage.     

Introduction to automatic forage stations and measurement of forage intake rate in an active open barn for horses

Interest in the use of open barns on Swedish horse farms is increasing as an alternative to keeping horses in box stalls and as a 2007 law requires phasing out of tie stalls. To provide adequate forage to satisfy welfare requirements for nutrition, gut health and behavioural needs, the use of automated feeding is also increasing. Studies on forage intake rate report wide variation but provide little information on how to introduce horses to an automatic forage station and on how forage intake rate varies in individual horses fed using an automatic forage station. This study documented the process of training 22 horses to use a transponder-controlled automatic forage feeding station and measured forage intake rates. Observations on the learning period of horses for transponder-controlled automatic forage stations showed that after 4 days, 48% of the horses had reached the goal of 90% intake. After 8 days, learning was completed in 71% of horses and at 16 days in 95% of horses. Measurements of forage intake rate revealed significant differences between individual horses. Overall mean intake rate ± SD, based on 314 observations, was 22.4 ± 6.7 min/kg forage DM. Evaluation of the number of intake measurements required to set a representative average ration in the automatic station for an individual horse showed that the variation levelled off at four samples. In conclusion, horses quickly learned how to use an automatic forage station, with two-thirds of horses achieving this within 7 days. To ensure the correct ration in a timed transponder-controlled automatic forage station, each horse’s forage intake rate must be measured at least four times to obtain a representative average.     

Seed and forage yield,and forage quality determinants of nine legume shrubs in a non-tropical dryland environment

The objective was to identify legume shrub species for development of agroforestry technologies based on seed and forage (leaves and twigs < 10 mm diameter) yield, and determinants of forage quality. Ten individual plants of Bituminaria bituminosa ‘Ecotypes 1’, B. bituminosa ‘Ecotypes 2’, Medicago citrina, and M. arborea from Spain; Colutea istria and Onobrychis aurantiaca from Syria; C. istria from Jordan; Chamaecytisus mollis from Morocco; and Coronilla glauca from France were randomly selected from plots established in a non-tropical dryland environment in northwest Syria in 2000. Five individual plants of each species were cut back to 0.5 m above ground in March 2004. Coppice regrowths were pruned in December 2004 and April 2005 to determine forage yield and proportion of forage in the total above ground biomass (PEFB). Forage samples were analyzed for concentrations of crude protein (CP), lignin(sa), acid detergent fibre (ADFom), neutral detergent fibre (aNDFom), in vitro organic matter (OM) digestibility (IVOMD), and in vitro 24 h gas production (IVGP24h). Matured seeds were hand harvested from the remaining five plants of each species to estimate seed yield. Forage (21–250 kg DM/ha) and seed (0–200 kg DM/ha) yields; PEFB (0.22–0.96); and concentrations of CP (85–115 g/kg DM), lignin(sa) (14–42 g/kg DM), ADFom (94–170 g/kg DM), aNDFom (122–217 g/kg DM), IVOMD (456–617 g/kg OM), and IVGP24h (27–42 ml 200 mg/DM) varied (P<0.05) among shrub species. The IVOMD and IVGP24h were positively correlated (r = 0.75, P<0.032), whereas IVOMD and IVGP24h were negatively correlated with ADFom, lignin(sa) and aNDFom. In terms of forage and seed yields and determinants of forage quality, C. istria from Jordan, M. arborea, B. bituminosa ‘Ecotype-2’, C. istria and O. aurantiaca have higher potential than C. mollis, C. glauca and B. Bituminosa ‘Ecotype-1’ for the development of agroforestry technologies in non-tropical dry areas.     

Modeling forage mediated aggregation in a gregarious ruminant

Two explanations exist for the evolutionary origin of grouping in primary consumers: reduction of individual predation risk and resource‐mediated aggregation. While several studies have assessed relationships between aggregation and predation risk, few studies have examined the circumstances under which resource‐mediated aggregation can lead to stable group formation. Using a model, we examined if forage preference alone can generate stable aggregation, and what were the circumstances of its emergence and stability. The model was a spatially explicit grazing model using empirically derived parameters to simulate large ruminant foraging in a meadow. Simulation results indicated that aggregation can spontaneously arise if grazers exhibit preference for forage of higher nutritional quality, usually associated with intermediate stages of forage growth. In this case, foragers could establish and maintain ‘islands’ of high quality forage as a result of revisiting continuous paths of previously grazed patches. However, aggregation was an intermittent phenomenon and occurred only within a narrow range of parameters. If grazer density was low compared to the amount of forage, the grazers’ foraging paths intersected too rarely to form contiguous islands of high forage quality; if their density was too high, the entire available area was uniformly utilized and foraging movements resembled unbounded random walks. We conclude that it is difficult to conceive of the evolution of grouping without the involvement of predators, since the relationship between grazer and forage abundance is ultimately co‐regulated by predator abundance, and because in modern grazers, predator avoidance and foraging behavior seem to be functionally inseparable. Future research should consider the reinforcing effects of predator avoidance as well as foraging behavior on consumer aggregation.     

Sheep prefer clean forage over forage contaminated with military explosives TNT, RDX and HMX

The common military explosives 2-methyl-1,3,5-trinitrobenzene (TNT), 1,3,5-trinitroperhydro-1,3,5-triazine (RDX) and 1,3,5,7-tetranitro-1,3,5,7-tetrazocane (HMX) are distributed in many military training areas, and are thus encountered by grazing animals. The aim of this study was to examine small ruminant's intake of forage contaminated with explosives. An indoor, experimental setup was used to determine if contamination of forage by these compounds affected intake by sheep. The results clearly demonstrate that contamination by any of the three explosives reduced forage intake in sheep; in order of increasing avoidance: RDX < TNT < HMX. The results are discussed in a risk assessment context.     

Nitrogen fixation in perennial forage legumes in the field

Nitrogen acquisition is one of the most important factors for plant production, and N contribution from biological N₂ fixation can reduce the need for industrial N fertilizers. Perennial forages are widespread in temperate and boreal areas, where much of the agriculture is based on livestock production. Due to the symbiosis with N₂-fixing rhizobia, perennial forage legumes have great potential to increase sustainability in such grassland farming systems. The present work is a summary of a large number of studies investigating N₂ fixation in three perennial forage legumes primarily relating to ungrazed northern temperate/boreal areas. Reported rates of N₂ fixation in above-ground plant tissues were in the range of up to 373 kg N ha^–1 year^–1 in red clover (Trifolium pratense L.), 545 kg N ha^–1 year^–1 in white clover (T. repens L.) and 350 kg N ha^–1 year^–1 in alfalfa (Medicago sativa L.). When grown in mixtures with grasses, these species took a large fraction of their nitrogen from N₂ fixation (average around 80%), regardless of management, dry matter yield and location. There was a large variation in N₂ fixation data and part of this variation was ascribed to differences in plant production between years. Studies with experiments at more than one site showed that also geographic location was an important source of variation. On the other hand, when all data were plotted against latitude, there was no simple correlation. Climatic conditions seem therefore to give as high N₂ fixation per ha and year in northern areas (around 60°N) as in areas with a milder climate (around 40°N). Analyzing whole plants or just above-ground plant parts influenced the estimate of N₂ fixation, and most reported values were underestimated since roots were not included. Despite large differences in environmental conditions, such as N fertilization and geographic location, N₂ fixation (Nfix; kg N per ha and year) was significantly (P<0.001) correlated to legume dry matter yield (DM; kg per ha and year). Very rough, but nevertheless valuable estimations of Nfix in legume/grass mixtures (roots not considered) are given by Nfix = 0.026DM + 7 for T. pratense, Nfix = 0.031DM + 24 for T. repens, and Nfix = 0.021DM + 17 for M. sativa.     

The role of Lactobacillus buchneri in forage preservation

In 1996 Wienberg and Muck proposed to implement Lactobacillus buchneri in silage starters. The main reason for the use of heterofermentative lactic acid bacteria is the increased stability of silages against deterioration by yeasts and moulds when exposed to air. In the following years, the unique activity of L. buchneri in silages was evaluated. It was proven that acetic acid formed from lactic acid by L. buchneri is solely responsible for the increased stability of silages. Recently, a novel metabolic pathway from lactic acid to acetic acid and 1,2-propanediol was proposed.     

Studies in the nutrition of the forage legumes

Summary The effect has been studied of varying levels of copper supply on the copper, iron and manganese contents of plants ofT. subterraneum in which the growth rate had been altered by variation in nitrate supply and light intensity.It has been found that the copper content of the plants is related logarithmically to the level of copper in the nutrient and is not affected by nitrate supply or intensity of illumination. Within the limits set, there is no change in the copper content of the tops with time, but the concentration in the roots shows a progressive increase, particularly at the higher levels of copper supply. Between one-fifth and one-quarter of the copper present in the roots is in the free space.The concentration of both iron and manganese decline with increase in copper supply. Although this is largely an indirect result arising from increased growth at the higher copper supply, a considerable distortion of the Fe/Mn ratio can occur. In the roots, however, there appears to be a direct restrictive effect of the higher copper supply on manganese concentration, over and above the indirect effect of growth dilution.The data on which this paper is based are mainly from the these submitted by M. G. Yates, P. E. Cansfield and J. T. Saul for the degree of Ph.D. of the University of Nottingham.     

Common and newly-recorded forage crop diseases in Ireland

Surveys of forage crop diseases in the Republic of Ireland have been conducted annually since 1965. Over fifty fungal diseases have been noted, about half of which are of likely economic importance. Disease control investigations were carried out on the more prevalent diseases, such as crown rust and Ophiobolus patch of ryegrass, leaf fleck of cocksfoot and powdery mildew of tall fescue. Some pathogens previously unrecorded in the British Isles were found. These included Spermospora lolii and Lolium mottle virus on ryegrass, and Mastigosporium kitzebergense on timothy.     

Diallel tests of competition in establishing forage stands

Summary In a diallel layout of eight forage plant varieties in pure stand and all possible mixtures of alternate rows in the field, the first year's growth was studied and an interpretation of competitive relations was attempted by a number of recent statistical techniques. The diallel test proved valuable for pin pointing superior combinations. Although the first year's results cannot be regarded as typical for mature forages, many results were comparable with an earlier long-term study ofCaputa (1948). Significant correlations were found between productivity and light interception estimates in these plant communities.Contribution No. 252 from the Ottawa Research Station, Canada Agriculture, Ottawa. Dedicated to the 85th birthday of Dr.J. Braun-Blanquet.     

Distribution of deoxynivalenol inFusarium-infected forage maize

A time course study was carried out to assess the appearance and distribution of DON in different organs of forage maize cultivated in the field. DON was produced after the flowering period and increased until harvest to high amounts in the rudimentary ears and leaf sheaths/leaf blades deriving from nodes located below the ear node, whereas nodes and internodes were either not or only slightly contaminated with DON. Genrally, DON was not detected in the ears, including husks, during the whole cultivation time.Fusarium biomass determined in the infected organs confirmed these findings. It seems that the contribution of DON containing rudimentary ears, leaf sheaths and leaf blades to the total DON contamination of forage maize is so far widely underestimated. Therefore advanced evaluation procedures are recommended to get a better understanding of the infection and contamination process and to prove genotypic differences in the resistance of forage maize genotypes againstFusarium infection.     

Responses to drought and flooding in tropical forage grasses

Seasonal drought and flooding severely limit pasture growth in tropical savannas. The objective of this study is to analyze and compare yield, biomass allocation, leaf growth rate and nutrient concentration of four important perennial C₄ forage grasses to short term flooding and moderate drought under controlled conditions. The grasses studied were the tufted Andropogon gayanus (CIAT 621) and Hyparrhenia rufa and the stoloniferous Echinochloa polystachya and Brachiaria mutica. All grasses were able to adjust their growth and development in response to flooding and drought: leaf growth and total biomass decreased under both treatments but the specific responses to these treatments differed markedly. Considering only total yield and leaf area, A. gayanus and H. rufa were relatively more tolerant to and less affected by drought whereas B. mutica and E. polystachya were more flood tolerant. In A. gayanus and H. rufa, both treatments reduced the proportion of assimilates devoted to roots and culms while increasing that of leaves decreasing the root/shoot ratio. In contrast, in B. mutica and E. polystachya only the proportion devoted to culms or stolons increased under flooding but the root/shoot ratio remained relatively stable under both treatments. All grasses produced adventitious rootlets except A. gayanus which was the most affected by flooding. Waterlogging decreased leaf nutrient concentration in all grasses which contributed to growth reduction. All species were relatively tolerant to both stresses. The results confirm the empirical observation that stoloniferous species B. mutica and E. polystachya are more tolerant to flooding thanks to adaptations typical of wetland plants such as hollow stolons which enhance oxygen diffusion to the roots and the development of adventitious rootlets that promotes water and nutrient absorption.     

Toxic constituents of legume forage plants

In this review, the toxic and antinutrient compounds biosynthesized by legumes used as forage crops in the United States are described under the categories alkaloids, amino acids, cyanogens, isoflavone and coumestan estrogenic principles, nitro compounds, protease inhibitors, phytohemagglutinins, saponins, selenium compounds and tannins. The legume-related livestock conditions, bloat, locoweed poisoning and photodermatitis are also discussed. Relevant veterinary, phytochemical and toxicological literature citations are presented.