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PubMed2004

Genetic and molecular basis of grass cell-wall biosynthesis and degradability. III. Towards a forage grass ideotype.

Lignification of cell walls is the major factor controlling the digestibility of forage grasses. Thus far, from QTL analysis, about 15 locations involved in cell-wall lignification or digestibility have been identified in the maize genome, many of which colocalise with QTLs involved in corn borer susceptibility. Genetic diversity for enhancing cell-wall digestibility in maize must be identified in novel germplasm, but genetic engineering is also a relevant way both to design specific cell-wall characteristics for improved digestibility and to identify genes involved in these traits for further discovery of alleles of interest in grass germplasm.

Animal Feed↗
PubMed2006

Management of forages for stocker cattle.

Successful grazing management of stockers requires knowledge of plant growth characteristics. Maintaining abundant leaf area is critical to support photosynthesis and plant growth as well as to provide nutritious grazing for the animals. Controlling stocking rate, stock density, and lengths of grazing and recovery periods can optimize individual animal rates of gain and gain per acre while maintaining pasture productivity. Various plant resources, perennial and annual, can be used strategically to provide the quantity and quality of forage needed by stockers throughout the year.

Animal Feed↗
PubMed2005

Foraging behaviour of the slender loris (Loris lydekkerianus lydekkerianus): implications for theories of primate origins.

Members of the Order Primates are characterised by a wide overlap of visual fields or optic convergence. It has been proposed that exploitation of either insects or angiosperm products in the terminal branches of trees, and the corresponding complex, three-dimensional environment associated with these foraging strategies, account for visual convergence. Although slender lorises (Loris sp.) are the most visually convergent of all the primates, very little is known about their feeding ecology. This study, carried out over 10 (1/2) months in South India, examines the feeding behaviour of L. lydekkerianus lydekkerianus in relation to hypotheses regarding visual predation of insects. Of 1238 feeding observations, 96% were of animal prey. Lorises showed an equal and overwhelming preference for terminal and middle branch feeding, using the undergrowth and trunk rarely. The type of prey caught on terminal branches (Lepidoptera, Odonata, Homoptera) differed significantly from those caught on middle branches (Hymenoptera, Coleoptera). A two-handed catch accompanied by bipedal postures was used almost exclusively on terminal branches where mobile prey was caught, whereas the more common capture technique of one-handed grab was used more often on sturdy middle branches to obtain slow moving prey. Although prey was detected with senses other than vision, vision was the key sense used upon the final strike. This study strongly supports the notion that hunting for animal prey was a key ecological determinant in selecting for visual convergence early on in primate evolution. The extreme specialisations of slender lorises, however, suggest that early primates were not dedicated faunivores and lend further support to the emerging view that both insects and fruits were probably important components of the diet of basal primates, and that exploitation of fruits may account for other key primate traits.

Animals↗
PubMed2005

Pandora neoaphidis transmission and aphid foraging behaviour.

Pandora neoaphidis is an aphid-specific entomopathogen that produces infective conidia. As aphid movement increases, so does the likelihood of contact with conidia. Volatile distress signals released in response to aphid infestation as an indirect defence against herbivory may affect aphid foraging and, therefore, the fungus-aphid interaction. In this study, two different methods were used to investigate the effect of plant volatiles and P. neoaphidis-sporulating cadavers on (1) the colonisation of Vicia faba plants by Acyrthosiphon pisum and (2) P. neoaphidis transmission. This study indicates that A. pisum does not avoid bean plants containing P. neoaphidis and that transmission of conidia occurs during plant colonisation and, to a lesser extent, during in situ feeding. Although significantly more aphids were recovered from damaged plants compared to undamaged plants, the likelihood of infection was not affected by previous infestation by aphids.

Animals↗
PubMed2005

Understanding foraging behaviour in spatially heterogeneous environments.

The role of stochasticity and spatial heterogeneity in foraging systems is investigated. We formulate a spatially explicit model which describes the behaviour of grazing animals in response to local information using simple stochastic rules. In particular the model reflects the biology in that decisions to move to a new location are based on visual assessment of the sward height in a surrounding neighbourhood, whilst the decision to graze the current location is based on the residual sward height and olfactory assessment of local faecal contamination. It is assumed that animals do not interact directly, but do so through modification of, and response to a common environment. Spatial heterogeneity is shown to have significant effects including reducing the equilibrium intake rate and increasing the optimal stocking density, and must therefore be taken into account by resource managers. We demonstrate the relationship between the stochastic spatial model and its non-spatial deterministic counterpart, and in the process derive a moment-closure approximation to the full process, which can be regarded as an intermediate, or pseudo-spatial model. The role of spatial heterogeneity is emphasized, and better understood by comparing the results obtained from each approach. The relative efficiency of random and directed searching behaviour in spatially heterogeneous environments is explored for both clean and contaminated pastures, and the impact of faecal avoidance behaviour assessed.

Animals↗
PubMed2005

Path efficiency of ant foraging trails in an artificial network.

In this paper we present an individual-based model describing the foraging behavior of ants moving in an artificial network of tunnels in which several interconnected paths can be used to reach a single food source. Ants lay a trail pheromone while moving in the network and this pheromone acts as a system of mass recruitment that attracts other ants in the network. The rules implemented in the model are based on measures of the decisions taken by ants at tunnel bifurcations during real experiments. The collective choice of the ants is estimated by measuring their probability to take a given path in the network. Overall, we found a good agreement between the results of the simulations and those of the experiments, showing that simple behavioral rules can lead ants to find the shortest paths in the network. The match between the experiments and the model, however, was better for nestbound than for outbound ants. A sensitivity study of the model suggests that the bias observed in the choice of the ants at asymmetrical bifurcations is a key behavior to reproduce the collective choice observed in the experiments.

Animal Communication↗
PubMed2006

Use of chemical tracers in assessing the diet and foraging regions of eastern North Pacific killer whales.

Top predators in the marine environment integrate chemical signals acquired from their prey that reflect both the species consumed and the regions from which the prey were taken. These chemical tracers-stable isotope ratios of carbon and nitrogen; persistent organic pollutant (POP) concentrations, patterns and ratios; and fatty acid profiles-were measured in blubber biopsy samples from North Pacific killer whales (Orcinus orca) (n=84) and were used to provide further insight into their diet, particularly for the offshore group, about which little dietary information is available. The offshore killer whales were shown to consume prey species that were distinctly different from those of sympatric resident and transient killer whales. In addition, it was confirmed that the offshores forage as far south as California. Thus, these results provide evidence that the offshores belong to a third killer whale ecotype. Resident killer whale populations showed a gradient in stable isotope profiles from west (central Aleutians) to east (Gulf of Alaska) that, in part, can be attributed to a shift from off-shelf to continental shelf-based prey. Finally, stable isotope ratio results, supported by field observations, showed that the diet in spring and summer of eastern Aleutian Island transient killer whales is apparently not composed exclusively of Steller sea lions.

Adipose Tissue↗
PubMed2006

Queuing theory under competitive social foraging may explain a mathematical equivalence of delay and probability in impulsive decision-making.

Intertemporal and probabilistic decision-making has been studied in psychiatry, ecology, and neuroeconomics. Because drug addicts and psycopaths often make risky decisions (e.g., drug misuse and aggression), investigation into types of impulsivity in intertemporal and probabilistic choices (delay and probability discounting) are important for psychiatric treatments. Studies in behavioral ecology proposed that delay and probability discounting are mediated by the same psychological process, because a decrease in probability of winning corresponds to an increase in delay until winning. According to this view, odds-against winning (=1/p-1) in probabilistic choice corresponds to delay in intertemporal choice. This hypothesis predicts that preference of gambling (low degree of probability discounting) may be associated with patience, rather than impulsivity or impatience, in intertemporal choice (low degree of delay discounting). However, recent empirical evidence in psychiatric research employing pathological gamblers indicates that pathological gamblers are impulsive in intertemporal choice (high degrees of delay discounting). However, a hyperbolic discounting function (usually adopted to explain intertemporal choice) with odds-against (instead of delay) explain experimental data in probabilistic choice dramatically well. Therefore, an alternative explanation is required for the hypothetical equivalence of odds-against to delay. We propose that queuing theory (often adopted for analyzing computer network traffic) under a competitive social foraging condition may explain the equivalence. Our hypothesis may help understand impulsivity of psychiatrics in social behavior (e.g., aggression and antisocial behavior) in addition to non-social impulsivity in reward-seeking (e.g., substance misuse).

Behavior, Addictive↗
PubMed2005

The sectored foraging field: a novel design to quantify spatial strategies, learning, memory, and emotion.

Although Norway rats are naturally gregarious, males typically live alone at some point during adulthood. Different social ecologies often require different learning strategies and also modulate response to stressors and gonadal development. To measure effects of the social environment on the interaction between cognition and emotion during aging, we focused on a natural learning context and devised the sectored foraging field, a progressively difficult spatial navigation task. Here, we describe how this apparatus and protocol permits multiple learning strategies in a minimally stressful environment, enabling finely graded analyses of cognition and emotionality. Male Sprague-Dawley rats living alone throughout adulthood adopted a sex-typic discernible spatial strategy. In contrast, males housed in group contexts utilized an algorithmic kinesthetic strategy, repeating the same motor action until they found food. Removal of food and distal, but not local cues, elicited anxious alertness, particularly in group-housed males. Cognitive performance of group-housed rats subsequent to food and cue removal was significantly impaired, yet enhanced in isolates.

Animals↗
PubMed2005

Antimicrobial and insecticidal protein isolated from seeds of Clitoria ternatea, a tropical forage legume.

The tropical forage legume Clitoria ternatea (L.) has important agronomic traits such as adaptation to a wide range of soil conditions and resistance to drought. It is resistant to a number of pathogens and pests. These important traits gave us reasons to look more closely at the plant. A highly basic small protein was purified from seeds of C. ternatea to homogeneity by using ultrafiltration with Centricon-3 membrane tubes and preparative granulated-bed isoelectric focusing (IEF). A single protein band was obtained on both sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and IEF gels. The protein, designated 'finotin', has broad and potent inhibitory effect on the growth of various important fungal pathogens of plants, namely Rhizoctonia solani, Fusarium solani, Colletotrichum lindemuthianum, Lasiodiplodia theobromae, Pyricularia grisea, Bipolaris oryzae and Colletotrichum gloeosporioides. It also inhibits the common bean bacterial blight pathogen Xanthomonas axonopodis pv. phaseoli. Moreover, finotin has powerful inhibitory properties against the bean bruchids Zabrotes subfasciatus and Acanthoscelides obtectus.

Animals↗
PubMed2005

Heavy metals effects on forage crops yields and estimation of elements accumulation in plants as affected by soil.

Heavy metals (Cu, Cd, Pb, Zn) effect on the productivity of forage crops (clover and perennial cereal grasses) and their accumulation in plants, depending on the concentration of these elements in a soil, has been studied in micro-field experiments on three types of soil. The principle objective was to determine regularities of heavy metals migration in a soil-plant system aiming the estimation of permissible levels of heavy metals content in soils with the following elaboration of methods, which regulate the toxicants transfer to plants. Methods of field experiments, agrochemical and atomic absorption analysis were used. Results were statistically treated by Statistica 6.0, S-Plus 6. Experimental results have shown that the intensity of heavy metals accumulation in plants depends on the type of the soil, the species of plants, the physicochemical properties of heavy metals and their content in the soil. Logarithmic interdependency of heavy metals concentration in soils and their accumulation in plants is suggested. However, the strong correlation between the different heavy metals concentrations in the various soils and the yield of crops was not observed. Toxicants accumulation in crops decreased in time.

Crops, Agricultural↗
PubMed2005

Inhibition of return is not a foraging facilitator in saccadic search and free viewing.

The ability to search and scan the environment effectively is a prerequisite for spatial behavior. A longstanding theory proposes that inhibition of previously attended loci (Inhibition of return; IOR) serves to facilitate exploration by increasing the likelihood to inspect new areas instead of returning to locations that have been inspected before. In this eye movement study we tested whether we could find evidence in favor of this hypothesis. Here we report that IOR does occur during search and free viewing, because we found increased fixation times preceding return saccades (eye movements that return to previously fixated locations). Meanwhile we observed no influence of IOR on the search strategy. Rather than the predicted low number we found many return saccades. Therefore, IOR does not serve as a foraging facilitator in saccadic search and free viewing. We hypothesize that IOR is an intrinsic aspect of shifting attention and gaze direction and furthermore that it is not always advantageous to prevent return saccades.

Attention↗
PubMed2003

Effect of tidal cycle and food intake on the baseline plasma corticosterone rhythm in intertidally foraging marine iguanas.

In most species, plasma levels of baseline glucocorticoids such as corticosterone (B) have a circadian rhythm. This rhythm can be entrained by both photoperiod and food intake and is related to aspects of energy intake and metabolism. Marine iguanas (Amblyrhynchus cristatus) offer a unique opportunity to better understand the relative importance of the light:dark cycle versus food intake in influencing the rhythm in baseline B in a natural system. Compared to other species, food intake is not as strictly determined by the phase of the light:dark cycle. Animals feed in the intertidal zone so feeding activity is heavily influenced by the tidal cycle. We measured baseline plasma B levels in free-living iguanas over several 24-h periods that varied in the timing of low tide/foraging activity. We found that baseline B levels were higher during the day relative to night. However, when low tide occurred during the day, baseline B levels dropped coincident with the timing of low tide. Whether the baseline B rhythm (including the drop during foraging) is an endogenous rhythm with a circatidal component, or is simply a result of feeding and associated physiological changes needs to be tested. Together, these data suggest that the baseline B rhythm in marine iguanas is influenced by the tidal cycle/food intake as well as the light:dark cycle.

Animals↗
PubMed2000

Lipid content and energy density of forage fishes from the northern Gulf of Alaska.

Piscivorous predators can experience multi-fold differences in energy intake rates based solely on the types of fishes consumed. We estimated energy density of 1151 fish from 39 species by proximate analysis of lipid, water, ash-free lean dry matter, and ash contents and evaluated factors contributing to variation in composition. Lipid content was the primary determinant of energy density, ranging from 2 to 61% dry mass and resulting in a five-fold difference in energy density of individuals (2.0-10.8 kJg(-1) wet mass). Energy density varied widely within and between species. Schooling pelagic fishes had relatively high or low values, whereas nearshore demersal fishes were intermediate. Pelagic species maturing at a smaller size had higher and more variable energy density than pelagic or nearshore species maturing larger. High-lipid fishes had less water and more protein than low-lipid fishes. In some forage fishes, size, month, reproductive status, or location contributed significantly to intraspecific variation in energy density. Differences in quality are sufficient to potentially affect diet selection of breeding seabirds, especially when transporting food for their young to the nest site.

Journal Article↗
PubMed2003

Larval juvenile hormone treatment affects pre-adult development, but not adult age at onset of foraging in worker honey bees (Apis mellifera).

Previous research has shown that juvenile hormone (JH) titers increase as adult worker honey bees age and treatments with JH, JH analogs and JH mimics induce precocious foraging. Larvae from genotypes exhibiting faster adult behavioral development had significantly higher levels of juvenile hormone during the 2nd and 3rd larval instar. It is known that highly increased JH during this period causes the totipotent female larvae to differentiate into a queen. We treated third instar larvae with JH to test the hypothesis that this time period may be a developmental critical period for organizational effects of JH on brain and behavior also in the worker caste, such that JH treatment at a lower level than required to produce queens will speed adult behavioral development in workers. Larval JH treatment did not influence adult worker behavioral development. However, it made pre-adult development more queen-like in two ways: treated larvae were capped sooner by adult bees, and emerged from pupation earlier. These results suggest that some aspects of honey bee behavioral development may be relatively insensitive to pre-adult perturbation. These results also suggest JH titer may be connected to cues perceived by the adult bees indicating larval readiness for pupation resulting in adult bee cell capping behavior.

Aging↗
PubMed2001

Feed and forage toxicants affecting embryo survival and fetal development.

Early embryonic and fetal development in mammals is sensitive to deficiencies and excesses of specific nutrients and toxicants. Operating directly and/or indirectly, these deficiencies and excesses can result in embryonic death or, in less severe circumstances, disruption of normal embryo and fetal growth. This paper explores the threats posed by feed and forage toxicants to the developing embryo and their impact on early programming of fetal development. Using significant examples, we consider the relevance of temporal sensitivities during early development in utero, and their implications for the morphology and functional competence of specific organs and tissues.

Animal Feed↗
PubMed1999

Homing with locale, taxon, and dead reckoning strategies by foraging rats: sensory hierarchy in spatial navigation.

Studies on foraging rats suggest that they can use visual, olfactory, and self-movement cues for spatial guidance, but their relative reliance on these different cues is not well understood. In the present study, rats left a hidden refuge to search for a large food pellet located somewhere on a circular table, and the accuracy with which they returned to the refuge with the food pellet was measured. Cue use was manipulated by administering probe trials from novel locations, blindfolding, moving the home cage relative to the table, rotating the table and using combinations of these manipulations. When visual cues were available and a consistent starting location used, a visual strategy dominated performance. When blindfolded, the rats used olfactory cues from the surface of the table and from the starting hole. When olfactory stimuli were made uninformative, by changing the starting hole and rotating the table, the rats still homed accurately, suggesting they used self-movement cues. In a number of cue combinations, in which cues gave conflicting information, performance degraded. The results suggest that rats display a hierarchical preference in using visual, olfactory and self-movement cues while at the same time being able to reaffirm or switch between various cue combinations. The results are discussed in relation to ideas concerning the neural basis of spatial navigation.

Animals↗
PubMed2001

Fluoride accumulation in pasture forages and soils following long-term applications of phosphorus fertilisers.

Ingestion of soils with high fluoride (F) concentration may cause chronic fluorosis in grazing animals. Analysis of New Zealand pasture soils with long-term phosphorus (P) fertilisation histories showed that total surface soil (0-75 mm depth) F concentration increased up to 217-454 mg kg-1 with P fertiliser application. One-third to two-thirds of F applied in fertilisers resides in the top 75 mm soil depth. Pasture forage accumulation of F was low, and therefore, F intake by grazing animals through pasture consumption is expected to be much lower than F intake by soil ingestion. Ten annual applications of single superphosphate (30 and 60 kg P ha-1 year-1) to a Pallic Soil (Aeric Fragiaqualf) significantly increased total F and labile F (0.01 M CaCl2 extract) concentrations to 200 and 120 mm depths, respectively, of the 300 mm depth investigated. The mobility of F in the soil profile was similar to two other elements, P and cadmium derived from the fertiliser.

Agriculture↗