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At least 1,315 records · Page 73Linked to original sources
PubMed1995

Engineering gut flora of ruminant livestock to reduce forage toxicity: progress and problems.

The rumen bacterium Butyrivibrio fibrosolvens has been genetically modified to detoxify fluoroacetate (a poisonous component of trees and shrubs in Australia, Africa and Central America) and has been shown to persist when it is returned to the rumen. Such bacteria may save animals from poisoning and, therefore, reduce economic losses for livestock industries in those countries. The ability to make genetic changes to rumen bacteria raises important questions about their practicality, and about the environmental factors that must be considered before releasing modified strains. The fluoroacetate-detoxifying bacterium provides an important model by which these issues can be examined.

Animals↗
PubMed2003

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.

Animals↗
PubMedDate not supplied

Computational models of collective foraging.

In this paper the behaviour of a bee colony is modelled as society of communicating agents acting in parallel and synchronising their behaviour. Two computational approaches for defining the agents behaviour are introduced and compared. Their common features as well as the complementary aspects making them suitable for merging together into a more complex model.

Animals↗
PubMed2003

Developmental control of foraging and social behavior by the Drosophila neuropeptide Y-like system.

Animals display stereotyped behavioral modifications during development, but little is known about how genes and neural circuits are regulated to turn on/off behaviors. Here we report that Drosophila neuropeptide F (dNPF), a human NPY homolog, coordinates larval behavioral changes during development. The brain expression of npf is high in larvae attracted to food, whereas its downregulation coincides with the onset of behaviors of older larvae, including food aversion, hypermobility, and cooperative burrowing. Loss of dNPF signaling in young transgenic larvae led to the premature display of behavioral phenotypes associated with older larvae. Conversely, dNPF overexpression in older larvae prolonged feeding, and suppressed hypermobility and cooperative burrowing behaviors. The dNPF system provides a new paradigm for studying the central control of cooperative behavior.

Age Factors↗
PubMed2003

Effect of forage type on claw horn lesion development in dairy heifers.

In a continuous design study the claw health of 54 Holstein-Friesian heifer calves was recorded from three months of age until six months after first calving (30 months of age). Pre-calving heifers were either fed a wet, fermented grass silage-based diet (WF) or a dry, unfermented straw and concentrate based diet (DU), apart from grazing during their first summer. Approximately one month before calving both groups were fed a silage-based diet and afterwards all received a silage and concentrate lactation ration. Claws were examined four times during rearing, once pre-calving, and four times during lactation. Both white line and sole lesions were significantly worse for WF than DU both during rearing and throughout first lactation although the effect was not as consistent over time for white line lesions. It is concluded that for optimal claw health youngstock diets should not be heavily based on wet grass silage (less than 25% DM).

Animal Feed↗
PubMed2000

The flow of forage particles and solutes through segments of the digestive tracts of cattle.

An experiment was conducted to investigate the compartmental mean residence time, (CMRT) of feed residues in segments of gastrointestinal digesta of mature Holstein steers. The objective was to evaluate assumptions that feed residues flow through ruminal digesta as sequential mixing pools having age-dependent (GN) and age-independent (G1) distributed residence times respectively (GN-->G1 flow). The basal diet was a semi-tropical hay containing 98 g crude protein and 503 g apparently digestible DM per kg DM. The hay was consumed and feed residues of different size and/or previous digestion from the hay were inserted into the reticulo-rumen (rumen) and abomasum. Marker profiles appearing at the duodenum and faeces were fitted to various compartment models to estimate CMRT. Post-abomasal CMRT did not differ among solutes or feed residues of different size and previous digestion and constituted only 5.8% of the CMRT for the entire gastrointestinal tract. Markers initially applied to orally or ruminally dosed feed residues exhibited profiles in duodenal digesta and faeces conforming to GN-->G1 flow. Previously undigested, masticated feed residues inserted into the dorsal rumen digesta had longer ruminal CMRT in the GN pool but not the G1 pool than did similarly inserted faecal small particles or normally ingested hay. These results support model assumptions of GN-->G1 flow within rumen digesta. The results support mechanisms proposed for the GN pool as the 'lag-rumination pool' and the G1 pool as the 'mass action turnover pool'. If further validated, rumen CMRT in cattle could be estimated from marker profiles in more easily obtained faeces to estimate ruminal CMRT required for feed evaluation systems.

Abomasum↗
PubMed2000

Epidemiology and optimal foraging: modelling the ideal free distribution of insect vectors.

Existing models of the basic case reproduction number (R0) for vector-borne diseases assume (i) that the distribution of vectors over the susceptible host species is homogeneous and (ii) that the biting preference for the susceptible host species rather than other potential hosts is a constant. Empirical evidence contradicts both assumptions, with important consequences for disease transmission. In this paper we develop an Ideal Free Distribution (IFD) model of host choice by blood-sucking insects, predicated on the argument that vectors must have evolved to choose the least defensive hosts in order to maximize their feeding success. From a re-analysis of existing data, we demonstrate that the interference constant, m, of the IFD can vary between host species. As a result, the predicted distribution of insects over hosts has 2 desirable and intuitively plausible behaviours: that it is heterogeneous both within and between host species; and that the intensity of heterogeneity varies with host and vector density. When the IFD model is incorporated into R0, the relationship with the vector:host ratio becomes non-linear. If correct, the IFD could add considerable realism to models which seek to predict the effect of these ecological parameters on disease transmission as they vary naturally (e.g. through seasonality in vector density or host population movement) or as a consequence of artificial manipulation (e.g. zooprophylaxis, vector control). It raises the possibility of targeting transmission hot spots with greater accuracy and concomitant reduction in control effort. The robustness of the model to simplifying assumptions is discussed.

Animals↗
PubMed2000

Effects of supplementing a basal diet of Chloris gayana hay with one of three protein-rich legume hays of Cassia rotundifolia, Lablab purpureus and Macroptilium atropurpureum forage on some nutritional parameters in goats.

Growth and digestibility experiments were conducted on growing East African type goats offered Chloris gayana hay supplemented with one of three high-protein (119-128 g CP/kg DM) legume hays, Cassia rotundifolia (cassia), Lablab purpureus (lablab) or Macroptilium atropurpureum (siratro), and crushed maize to investigate the feed intake, digestibility, growth and urinary excretion of purine derivatives. Goats in the supplemented groups had higher total dry matter and nitrogen intakes and higher N retention and body mass gains than unsupplemented counterparts. The digestibility of dry matter, organic matter and neutral detergent fibre were increased by protein supplementation. Animals on supplemented diets had higher fractional outflow rates of particulate matter from the rumen. The production of protein by ruminal microbes and the efficiency of microbial N production were increased by supplementation. It was concluded that a mixture of low-quality grass hay (61.9 CP/kg DM) and either cassia, lablab or siratro hay, and maize grain can provide a productive balanced diet for growing goats.

Animal Feed↗
PubMed1999

Protein extraction from Atriplex lampa leaves: potential use as forage for animals used for human diets.

The purpose of this study was to evaluate the effect of pH on the extraction of protein nitrogen from Atriplex lampa leaves (Moquin) Dietrich. The chemical characterization of the dry matter indicated the following (g/100 g): protein, 26.93; ash, 21.80; ether extract, 4.65; dry matter, 37.30; sodium, 6.05; and calcium, 0.41. Non-critical values were obtained for saponins and nitrates. The high concentration of oxalic acid (8.52 g/100 g), together with elevated salt content account for the low palatability of the studied species. In order to determine the parameters needed to improve the extraction in protein nitrogen from leaves, fresh material was macerated with 2% sodium metasulfite, followed by pulping with a hand-driven grinder. Extractions were performed at different pH values (2-12) adjusting the value with 5N HCL or NaOH, with agitation followed by centrifugation and pressing. Supernatants were collected and kept. The last extraction was performed with Tween 20 in order to obtain maximum nitrogen recovery from the residue cake. Highest extraction (41.23%) was obtained at pH 10 with a 1:5 ratio (leaf: deionized water, w/v). It is proposed that this regional natural resource may be used to elaborate a protein concentrate, which can be made more palatable by decreasing potassium and sodium salt content with the use of membrane technology.

Animal Feed↗
PubMed2003

Effects of molasses grass, Melinis minutiflora volatiles on the foraging behavior of the cereal stemborer parasitoid, Cotesia sesamiae.

Olfactory responses of the cereal stemborer parasitoid Cotesia sesamiae to volatiles emitted by gramineous host and nonhost plants of the stemborers were studied in a Y-tube olfactometer. The host plants were maize (Zea mays) and sorghum (Sorghum bicolor), while the nonhost plant was molasses grass (Melinis minutiflora). In single-choice tests, females of C. sesamiae chose volatiles from infested and uninfested host plants and molasses grass over volatiles from the control (soil). In dual-choice tests, the wasp preferred volatiles from infested host plants to those from uninfested host plants. There was no discrimination between molasses grass volatiles and those of uninfested maize, uninfested sorghum, or infested maize. The wasp preferred sorghum volatiles over maize. Combining uninfested maize or sorghum with molasses grass did not make volatiles from the combination more attractive as compared to only uninfested host plants. Infested maize alone was as attractive as when combined with molasses grass. Infested sorghum was preferred over its combination with molasses grass. Local growth conditions of the molasses grasses influenced attractiveness to the parasitoids. Volatiles from Thika molasses grass were attractive, while those from Mbita molasses grass were not. Growing the Thika molasses grass in Mbita rendered it unattractive and vice versa with the Mbita molasses grass. This is a case of the same genotype expressing different phenotypes due to environmental factors.

Animals↗
PubMed2003

Role of trail pheromone in foraging and processionary behavior of pine processionary caterpillars Thaumetopoea pityocampa.

Although caterpillars of Thaumetopoea pityocamnpa may mark their pathways with silk, this study shows that the material is essential to neither the elicitation nor maintenance of trail-following or processionary behavior. Trail following is dependent upon a pheromone the caterpillars deposit by brushing the ventral surfaces of the tips of their abdomens against the substate. Earlier instars are strongly bound to their trail system; in the laboratory, caterpillars followed circular trails continuously for as long as 12 hr before breaking away from them. The trail pheromone is long-lived and soluble in nonpolar solvents, but its volatilization or degradation allows the caterpillars to distinguish new from aged trails. In contrast to trail following, processionary behavior, the head-to-tail, single-file movement of the caterpillars is dependent on neither silk nor the trail pheromone. Stimuli associated with setae found on the tip of the abdomen of the precedent caterpillar serve to hold processions together, and such stimuli take priority over those associated with either the trail pheromone or silk. Although the caterpillars discern trail strength and choose stronger over weaker trails, the trail marking system of the processionary caterpillar appears less sophisticated than those of other, previously studied species of social caterpillars, and colonies are relatively inefficient in abandoning exhausted feeding sites in favor of new food finds. In laboratory studies, females were more likely to lead processions than males, and leaders, regardless of gender, expended more energy in locomotion than followers.

Animal Communication↗
PubMed2004

Growth performance and nutrient utilization in male and female Mithun calves on green forage-based diet.

A comparative study of growth rate and feed intake and its utilization in male and female Mithun calves was carried out in hilly tracts of Nagaland. The animals of both sexes were fed fresh jungle grasses ad libitum and 2.0 kg of rice bran fortified with 1% mineral mixture and 1% salt daily. Growth rates of 369.50 and 305.67 g/day were observed in male and female calves, respectively. Sex-related differences in feed and nutrient intakes were statistically significant, whereas no significant difference was found in digestibility coefficients of nutrients between the groups as well as among the animals. Dry matter, digestible crude protein and total digestible nutrient intakes were recorded to be 107.81, 8.08 and 74.73 g/kgW0.75 per day, respectively, irrespective of sex. Feed conversion efficiency (FCE) and nutritive value of the ration were similar in both male and female calves. Results obtained from the study indicate that the growth rate and nutrient intakes were higher in male than female calves but the sex of the animal did not have any significant effect on nutrient utilization.

Animal Feed↗