Impact of barley form on equine total tract fibre digestibility and colonic microbiota

This study aimed at assessing the impact of four barley forms on total tract apparent digestibility of dietary fibre in horses fed a large amount of starch in the morning meal (0.27% BW). Processed barley forms had a greater pre-caecal starch digestibility than the whole form. Based on this result, we hypothesised that using barley-processing methods would limit the potential dumping of undegraded starch in the hindgut of horses and, consequently, the potential negative effect on fibre degradation in the hindgut. In a 4×4 latin square design, four mature geldings fitted with a right ventral colon-fistula were fed a meadow hay : concentrate (62 : 38; dry matter (DM) basis) diet at 1.7% BW. The concentrate was made of 80% barley distributed either as whole grain or as processed forms: 2.5 mm ground, pelleted or steam-flaked. For each period, total tract apparent digestibilities of DM, NDF and ADF were determined over 3 consecutive days by total faecal collection, whereas pH, volatile fatty acids (VFA) concentrations and cultural functional bacteria counts (total anaerobic, cellulolytic bacteria, lactic acid producers, amylolytic bacteria and lactic acid utilisers) in colonic content were evaluated on 1 day 4 h after the morning meal. Total tract apparent digestibility of DM and dietary fibre was influenced (P<0.05) by barley form. Diets including thermo-mechanically treated barley forms led to a higher (P<0.05) total tract apparent digestibility of NDF than those constituted of ground barley and also led to a greater (P<0.05) total tract apparent digestibility of ADF than those made of whole or ground barley forms. However, no significant difference was observed in colonic pH, VFA concentrations and cultural bacteria concentrations. Owing to a high starch supply in the morning meal, the concentration of the functional bacteria in the colonic content averaged 7.8 log CFU/ml, 5.9 NPM/ml, 6.9 and 7.3 CFU/ml for total anaerobic, cellulolytic, amylolytic and lactic acid-utilising bacteria, respectively. Consequently, providing horses with pelleted or steam-flaked instead of ground barley forms may limit the negative impact of starch on fibre digestibility in horses fed a high level of starch in the morning meal (0.27% BW). Moreover, the fibre-to-starch ratio fed in this experiment did not cause any digestive upset.     

Physiological factors affecting the rapid decrease in protein assimilation efficiency by a caterpillar on newly‐mature tree leaves

Lymantria dispar L. caterpillars have a decreased ability to assimilate protein from mature leaves of red oak (Quercus rubra) compared with young, expanding leaves. The present study determines whether the drop in protein assimilation efficiency (PAE) occurs during the rapid phase of leaf maturation. Several mechanisms that might account for decreased PAE are also examined: mature leaf tissues could resist being chewed efficiently, protein in mature leaf tissues could become difficult to extract, and other nutrients in mature leaves might become growth limiting. The entire seasonal decrease in PAE occurs rapidly (in less than 2 weeks), when the leaves finished expanding. The maturation process is characterized by increased levels of fibre and decreased levels of water but no significant changes in the levels of protein or carbohydrates. Despite increased fibre in mature leaves, they are not chewed into larger food particles than are immature leaves. Carbohydrate assimilation efficiencies remain high on mature leaves, and signs of limiting water levels in larvae of L. dispar on mature leaves are not observed. The most important finding in the present study is the decreased extractability of protein in food particles from mature leaves, which plays a major role in explaining the rapid decrease in PAE. It is hypothesized that structural changes in cell walls during the rapid process of leaf maturation decrease protein extractability, which, in turn, greatly decreases the nutritional quality of mature oak leaves for caterpillars. The results of the present study therefore suggest a general mechanism to help explain the widely documented decrease in the nutritional quality of the mature leaves of many tree species for herbivorous insects.     

The parasitoid of a fruit moth caterpillar utilizes fruit components as nutrient source to increase its longevity and fertility

Longevity and fecundity of female wasps are two decisive factors for the effectiveness of parasitoid species as biological control agents. Accessibility and suitability of nutrient sources determine parasitoid survival and reproduction. Host, nectar and honeydew feeding are frequent adult parasitoid behaviors to cover nutritional needs. Here we postulate that especially parasitoid species of endophytic herbivores might use plant tissue as a nutrient source that becomes accessible upon herbivory. We investigated the influence of plant consumption and host feeding on longevity and fecundity of Hyssopus pallidus, a gregarious ecto-parasitoid of caterpillars of the codling moth that feed inside apple fruits. Longevity of unmated and mated ovipositing female parasitoids was highest in treatments with fruit pulp. While longevity in this treatment was not significantly different from that with honey, it was significantly higher than in treatments without food, with water or with a host alone.Reproduction was significantly increased by these sugar-rich nutrient sources compared to the control with a host alone. In contrast, host feeding did not yield any significant contribution to longevity and fecundity in a series of bioassays with different host–parasitoid ratios and with differently aged and sized hosts, compared to controls without food.We conclude that in this synovigenic species host feeding does not contribute to longevity and fecundity, but females can increase survival and reproduction in the field relying solely on the plant tissue damaged by their host caterpillar.     

Relative susceptibility to predation of two species of caterpillar on plantain

Summary The relative susceptibility to predators of a cryptic generalist caterpillar (Spilosoma congrua: Arctiidae) and a non-cryptic specialist (Junonia coenia: Nymphalidae) using the same hostplant species (Plantago lanceolata) was examined. In a laboratory experiment using predatory stinkbugs (Podisus maculiventris), more Junonia caterpillars than Spilosoma caterpillars were killed (70% vs. 16%). This result was a consequence of the Spilosoma spending some time under cover, moving frequently, feeding on leaves while under or adjacent to them, and spending little time on the leaves. In a field experiment using predatory wasps (Polistes fuscatus), the wasps found 7 times as many of the Junonia as the Spilosoma, and overall 6 times as many Junonia were killed as Spilosoma. Initially, 71% of the Junonia caterpillars encountered by wasps were killed, but by the fourth day of the test, only 22% of the Junonia encountered by wasps were killed. Over three full days of observations, a constant 50% of the Spilosoma caterpillars encountered by the wasps per day were killed. For the Junonia, evasion of predators rested on passive chemical defense. For the Spilosoma, evasion depended on being unapparent, speedy movement between feeding and resting sites and, if found, on fleeing immediately and quickly. These results indicate that Spilosoma caterpillars, by way of cryptic and escape behaviors, can be less susceptible to insect predators than Junonia caterpillars.     

Relative nutritional quality of C3 and C4 grasses for a graminivorous lepidopteran,Paratrytone melane (Hesperiidae)

Summary We tested the hypothesis that C₄ grasses are inferior to C₃ grasses as host plants for herbivorous insects by measuring the relative performance of larvae of a graminivorous lepidopteran, Paratrytone melane (Hesperiidae), fed C₃ and C₄ grasses. Relative growth rates and final weights were higher in larvae fed a C₃ grass in Experiment I. However, in two additional experiments, relative growth rates and final weights were not significantly different in larvae fed C₃ and C₄ grasses. We examined two factors which are believed to cause C₄ grasses to be of lower nutritional value than C₃ grasses: foliar nutrient levels and nutrient digestibility. In general, foliar nutrient levels were higher in C₃ grasses. In Experiment I, protein and soluble carbohydrates were digested from a C₃ and a C₄ grass with equivalent efficiencies. Therefore, differences in larval performance are best explained by higher nutrient levels in the C₃ grass in this experiment. In Experiment II, soluble carbohydrates were digested with similar efficiencies from C₃ and C₄ grasses but protein was digested with greater efficiency from the C₃ grasses. We conclude (1) that the bundle sheath anatomy of C₄ grasses is not a barrier to soluble carbohydrate digestion and does not have a nutritionally significant effect on protein digestion and (2) that P. melane may consume C₄ grasses at compensatory rates.     

Nutritional performance of first and penultimate-final Instar bagworm larvae on two unrelated hosts as influenced by host of origin

Nutritional performance of early and late instar bagworm (Thyridopteryx ephemeraeformis Haworth) larvae was investigated as a function of host of origin and host type, using two taxonomically distant wild hosts, Salix nigra (Marshall) and Juniperus virginiana (L.). First instar growth and survival were higher on S. nigra; overall performance was similar on the two hosts in penultimate-final instars. There was no evidence for host associated differentiation with respect to nutritional performance. There were, however, significant genotype x environment interactions for several characters studied, suggesting that the potential for host associated differentiation exists.     

A study of polynucleotide phosphorylase production by <Emphasis Type="Italic">Escherichia coli</Emphasis> in a hollow fibre reactor

A 30-l hollow fibre reactor with continuous fermentation for cell recycling of Escherichia coli AS 1.183 was used to remove the inhibitory effects on cell growth and extend the fast growth phase to increase the yield of polynucleotide phosphorylase (PNPase) in E. coli cells. When the dilution rate was 1.5 h⁻¹, the cell concentration of E. coli reached 235 g/l (wet wt, 70% moisture content), with PNPase activity above 90 u/g (wet wt). With the dilution rate is 1.0 h⁻¹, the fermentor volumetric productivity of PNPase in a hollow fiber reactor can reach 974 (u/h * l) compared to 20 (u/h * l) in a conventional batch culture.     

Changes in the composition of cotton fibre cell walls during development

Purified cell walls, prepared from cotton fibres (Gossypium arboreum L.) at different growth stages, were subjected to successive extractions to give pectic, hemicellulosic, and -cellulosic fractions. The protein content and sugars obtained after hydrolysis of the total cell walls and of the various fractions were quantitatively estimated. The amount of protein in the fibre cell walls from one ovule reached a maximum value at the end of the elongation growth, decreased, and then reached a second maximum at the end of the secondary wall deposition. The absolute amounts of fucose, galactose, mannose, rhamnose, arabinose, uronic acid, and non-cellulosic glucose residues all reached a maximum at the end of the primary wall formation or at the beginning of the secondary wall formation. Only the absolute amounts of xylose and of the cellulosic glucose residues increased until the end of the fibre development. Most conspicuous was the decrease in the absolute amounts of non-cellulosic glucose and of arabinose residues during the secondary wall formation, possibly indicating a turnover of at least some of the hemicellulosic wall material.Abbreviations DPA days post anthesis - TLC thin layer chromatography - SDS sodium dodecyl sulphate     

Functional and safety aspects of Enterococci isolated from different Spanish foods

The incidence and diversity of enterococci in retail food samples of meat, dairy and vegetable origin was investigated. Enterococci were present, at concentrations of 10(1) to 10(4) CFU/g. Fifty selected isolates from food samples grouped in two separate clusters by RAPD analysis. Cluster G1 (72% of the isolates) contained the E. faecium CECT 410T type strain, and also showed a high degree of genetic diversity. Cluster G2 (28% of the isolates) contained the E. faecalis CECT 481T type strain and was genetically more homogeneous. Virulence traits (haemolysin, gelatinase or DNAse activities, or the presence of structural genes cylL, ace, asal and esp) were not detected. All isolates were sensitive to the antibiotics ampicillin, penicillin, gentamicin, streptomycin and chloramphenicol. A high pecentage of isolates were resistant to erythromycin and rifampicin. Many isolates showed intermediate sensitivity to several antibiotics (tetracycline, ciprofloxacin, levofloxacin, or quinupristin/dalfopristin). Vancomycin and teicoplanin resistance was detected in one strain, but vanA, vanB, vanC1, vanC2 or vanC3 genes were not detected. Many of the isolates showed functional properties of food or health relevance. Production of antimicrobial substances was detected in 17 of the isolates, and 14 of them carried structural genes for enterocins A, B and/or P.     

Simultaneous effects of potassium, rutin and temperature on performance ofManduca sexta caterpillars

the simultaneous effects on an insect herbivore (third instar tobacco hornwormManduca sexta (L.): Sphingidae) of temperature (daytime temperatures of 20 °C, 25 °C and 30 °C), a mineral that may play a role in plant defense (potassium) and a common allelochemical (rutin) were examined in a factorial experiment. To manipulate potassium levels, a modified diet with limited plant material was used as the base and KCl and rutin added. Temperature affected efficiency of conversion of ingested food (ECI), efficiency of conversion of digested food (ECD), time to head-capsule slippage, stadium duration, relative consumption rate (RCR) and relative growth rate (RGR) but not food consumed, biomass gained and approximate digestibility (AD). Potassium concentration influenced all of the variables except AD, time to head-capsule slippage (HCS), duration of the stadium and percent of stadium time to HCS. Rutin impacted negatively on all of the variables except food consumed. Compared to larvae on the non-rutin diets, fewer larvae fed rutin survived through molt initiation to ecdysis and fewer successfully completed ecdysis. Temperature and rutin had interactive effects for AD, ECD, RCR, RGR, time to HCS, and percent of stadium required to reach HCS. Rutin and potassium had interactive effects for biomass gained, RCR, ECI, time to HCS, duration of stadium, and percent of stadium required to reach HCS. Comparison of larval responses on an average potassium concentration (3.1%) versus high concentration (6.1%) showed that at the low daytime temperature increasing potassium concentration depressed biomass gained, but at the warmer temperatures potassium concentration had little effect unless rutin was present. In addition, potassium concentration had little impact on ECI unless rutin was present. These results indicate that significant interactive effects occur among temperature, potassium and rutin, and thus suggest that such interactive effects on larval performance may be common under field conditions, which are characterized by varying temperature and different concentrations of minerals and allelochemicals in hostplants.     

High altitude tissue adaptation in Andean coots: capillarity,fibre area,fibre type and enzymatic activities of skeletal muscle

Capillarity, fibre types, fibre area and enzyme activities of different skeletal muscles (pectoralis, extensor digitorum longus), tibialis anterior, plantaris and the myocardium were compared in Andean coot (Fulica americana peruviana) native to high altitude (Junín, Perú, 4200 m) and the same species nesting at sea level. Numbers of capillaries per square millimeter were higher in all high-altitude muscles when compared with sea-level muscles (P<0.0001). Moreover, values for capillaries per fibre and capillaries in contact with each fibre were higher in digitorum and tibialis high-altitude muscles. Muscle fibres were classified as Type I, Type IIA or Type IIB on the basis of their myofibrillar ATPase pH lability. Pectoralis muscle of high-altitude and sea-level coots presented only fibres of Type IIA. In contrast, all the leg muscles studied showed a mosaic pattern of the three fibre types. Fibre areas were determined using a Leitz Texture Analysis System. Significant differences in fibre area were observed (P<0.01) between high-altitude and sea-level muscles. Mean muscle fibre diameters were also lower in the high-altitude group than in the sea-level group. The enzyme activities studied were hexokinase, lactate dehydrogenase, citrate synthase and 3-hydroxyacyl-CoA-dehydrogenase. The oxidative capacity, as reflected by citrate synthetase and hydroxyacyl-CoA-dehydrogenase activities, was greater for myocardial and pectoralis than for leg muscles. However, analysis of maximal enzyme activities showed that there were no significant differences between the glycolytic and oxidative enzyme activities of high-altitude and sea-level coots. These results suggest that in Andean coots genetically adapted to high altitude, changes in muscle capillarity and fibre size, in addition to high haemoglobin O₂ affinity and low haemoglobin concentration, are sufficient to allow adequate energy production without increases in enzymatic activities.Abbreviations BSA bovine serum albumin - C:F ratio Capillaries per fibre - CAF Capillaries in contact with each fibre - CD capillary density (mm^-2) - CS citrate synthetase - EDL muscularis digitorum longus - fra fraction reduction area - HA high altitude - HAD hydroxyacyl-CoA-dehydrogenase - HK hexokinase - LDH lactate dehydrogenase - P ₅₀ PO₂ at which hemoglobin is half saturated with O₂ - P _aO₂ arterial partial pressure of oxygen - PAS periodic acid-schiff - PEC muscularis pectoralis - PLA muscularis planaris - P _tO₂ mean tissue oxygen pressure - P _vO₂ mixed venous partial pressure of oxygen - SD standard deviation - SL sea level - TA muscularis tibialis anterior - TAS texture analysis system     

Natural diets and self-selection: Heliothis zea larvae and maize

Although the first two instars tend to eat the silks, last instar larvae of the corn earworm, Heliothis zea (Boddie) (Lepidoptera: Noctuidae), prefer to feed on the kernels rather than on the other components of the maize ear. They feed preferentially on the germ of the kernel, but when offered whole kernels also eat some of the endosperm. Larvae that eat cut portions of the kernels that include all of the germ and some endosperm utilize their food for growth more efficiently than do larvae that eat portions of the kernel that include only endosperm. Adults that ate germ portions or endosperm portions of the kernel as larvae do not differ significantly in longevity, number of days on which they oviposit, number of eggs laid per day or the percentage of the eggs that hatched. We suggest that the larvae use self-selection to increase their intake of germ, thus increasing utilization efficiency and decreasing the amount of food that they must eat. When they feed on plants (other than maize) with small fruits, this probably increases their ability to compete for food when it is scarce and minimizes exposure to predation by decreasing the number of foraging trips and the distance that they must travel in search of food.

---

Résumé Bien que les deux premiers stades larvaires d'H. zea (Lepid.: Noctuidae) tendent à consommer les soies, les trois derniers stades préfèrent les grains aux autres parties de l'épi de maïs. La chenille du dernier stade consomme de préférence le germe du grain, mais quand on lui offre l'ensemble du grain, elle consomme aussi une partie de l'albumen. Les chenilles qui coupent des morceaux du grain comprenant la totalité du germe et une fraction d'albumen ont une alimentation permettant une croissance plus efficace que les chenilles qui consomment des portions de grain ne contenant que de l'albumen. Ainsi, les chenilles qui mangent des fractions de germe ont besoin de consommer moins, pour atteindre le même poids que les chenilles qui consomment des morceaux d'albumen. Les longévités, les nombres de jours de ponte, les fécondités quotidiennes et les fertilités des oeufs sont les mêmes pour les papillons provenant des chenilles ayant consomme des morceaux de germe ou des morceaux d'albumien. L'albumen seul est un aliment suboptimal, et H. zea pourrait théoriquement améliorer ultérieurement son régime en mangeant plus de germes. Nous estimons que ceci ne serait pas rentable puisque la durée des stades devrait être prolongée et que la manutention et les rejets d'albumen devraient être accrus. H. zea se serait adapté à une solution de compromis pour l'optimalisation du régime alimentaire. Il réduit le temps de récolte et perd en efficacité en consommant de l'albumin suboptimal; mais il regagne autant que possible en efficacité en mangenat le germe de pratiquement tous les grains attaqués. Cette augmentation de l'efficacité diminue la quantité d'aliments qui doit être ingéré, et fournit un potentiel adaptatif quand les chenilles consomment des plantes (autres que le maïs) avec des petits fruits. L'exposition à la prédation est réduite, puisque la distance parcourue pour la recherche des fruits est diminuée.

     

The effect of carbon supply on allocation to allelochemicals and caterpillar consumption of peppermint

Summary The carbon supply of peppermint plants was manipulated by growing clonal propagules under three carbon dioxide regimes (350, 500 and 650 l l^-1). Feeding by fourth instar caterpillars of Spodoptera eridania increased with elevated CO₂ hostplant regime, as well as with low leaf nitrogen content and by a high proportion of leaf volatile terpenoids. Leaf weight increased significantly with the increased carbon supply, but the amount of nitrogen per leaf did not change. The amount of volatile leaf mono-and sesquiterpenes increased proportionately with total leaf dry weight and hence was not influenced by CO₂ supply. These results are consistent with ecological hypotheses which assume that allocation to defense is closely regulated and not sensitive to carbon supply per se.     

Protein limitation of a tree leaf feeding Lepidopteran

The hypothesis that arbivorous insects are protein limited was tested by feeding larvae of Datana ministra mature leaves of Tilia americana that were coated with a mixture of protein. Larvae fed the protein supplement had a lower ingestion rate and net growth efficienty but higher apparent digestion efficiency and apparent assimilation rate than control larvae. Protein supplement had no effect on the rate of growth of 5th instar larvae although larvae fed added protein pupated at a lower weight than control larvae. The added protein placed a metabolic load on the larvae, perhaps by excessive nitrogen excretion demands and osmotic imbalance. The results do not support the hypothesis that arbivorous insects are protein limited.

---

Résumé L'hypothèse suivant laquelle la croissance des larves d'insectes est limitée par l'insuffisance des protéines disponibles dans les feuilles d'arbres a été examinée par l'alimentation des chenilles de Datana ministra Drury sur feuilles développées de Tilia americana L. enduites d'une mixture de protéines d'oeuf et de lait. Des chenilles de second stade, prélevées dans des colonies naturelles, ont été séparées en un lot témoin élevé en masse sur feuilles coupées et un lot expérimental élevé sur feuiles coupées mais enduites de protéines. Le bilan en matière sèche, le taux de croissance, la relation entre ce taux de croissance et la quantité de matière ingérée, le poids des prénymphes ont été déterminés sur 10 chenilles de dernier stade dans chaque lot. Les chenilles ayant consommé un supplément de protéine ont présenté un plus faible taux d'ingestion et un plus faible rendement de croissance, mais une meilleure efficacité apparente d'ingestion et un meilleur taux apparent d'assimilation que les témoins.Le complément protéique n'a pas eu d'effet sur le taux de croissance des chenilles de 5ème stade bien que l'alimentation avec addition de protéines ait provoqué la nymphose à un poids larvaire plus faible. L'addition de protéines avait provoqué une chargé métabolique pour les chenilles, peut-être en provoquant une demande d'excrétion d'azote excessive ou en créant un déséquilibre osmotique, ce qui aurait provoqué une réduction du taux de croissance et du poids des chenilles malgré un taux d'assimilation supérieur. Ces résultats ne confirment pas l'hypothèse que les insectes des arbres sont carencés en protéines.

     

Ontogeny of flight initiation in the fly <Emphasis Type="Italic">Drosophila melanogaster</Emphasis>: implications for the giant fibre system

There are two modes of flight initiation in Drosophila melanogaster—escape and voluntary. Although the circuitry underlying escape is accounted for by the Giant fibre (GF) system, the system underlying voluntary flight initiation is unknown. The GF system is functionally complete before the adult fly ecloses, but immature adults initially fail to react to a stimulus known to reliably evoke escape in mature adults. This suggests that escape in early adulthood, ∼2-h post-eclosion, is not automatically triggered by the hard-wired GF system. Indeed, we reveal that escape behaviour displays a staged emergence during the first hour post-eclosion, suggesting that the GF system is subject to declining levels of suppression. Voluntary flight initiations are not observed at all during the period when the GF system is released from its suppression, nor indeed for some time after. We addressed the question whether voluntary flight initiation requires the GF system by observing take-off in Shak-B ² mutant flies, in which the GF system is defunct. While the escape response is severely impaired in these mutants, they displayed normal voluntary flight initiation. Thus, the escape mechanism is subject to developmental modulation following eclosion and the GF system does not underlie voluntary flight. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Cytochemical localization and function of the 3-linked glucan callose in the developing cotton fibre cell wall

Summary Several recent biochemical studies concerning the hemicellulosic content of the developing cotton fibre wall have pointed to an important increase of 1,3-linked glucans at the onset of the secondary wall formation and their slow decrease until the end of fibre development (Meinert andDelmer 1977,Huwyler et al. 1978, 1979,Maltby et al. 1979). These almost insoluble glucans are extra-cellular and possibly associated with the S₁ or winding layer, but no other data on their exact localization were given.By means of a specific fluorescence method, using a 0.05% decolourized aniline blue solution, we show that one of these 3-linked glucans,callose, is always localized, independently of the fibre age, in the innermost wall layer bordering the cell lumen, from the onset of the secondary thickening up to the end of fibre development. Some possible roles assumed by these callose deposits are suggested and discussed. They may be involved in the normal mechanism of cellulose biosynthesis, as being effectively consumed by turnover or, more probably, as forming a permanently restored interface or matrix where cellulose microfibrils undergo a sort of maturation and are oriented before their definitive incorporation in the organized cell wall. They are not to be confused with the wound callose deposits which characterize damaged or immature fibres.     

Response of last instar Heliothis zea larvae to carbohydrates: stimulation of biting, nutritional value

Several carbohydrates were tested for their ability to stimulate last instar Heliothis zea larvae to bite and, as a measure of nutritional value, for their ability to prolong the lives of H. zea larvae in the absence of a protein. Sucrose, fructose and glucose strongly stimulated biting. Maltose and sorbose were weakly stimulating, and mannitol, rhamnose, galactose, and lactose did not stimulate biting at the concentrations tested. Sucrose, fructose, mannitol, maltose, glucose, galactose, corn starch, and lactose all prolonged life, but larval longevity varied among these carbohydrates. Rhamnose did not prolong life, nor did sorbose, which was slightly toxic. When fructose, glucose, or mannitol replaced sucrose in a nutritionally complete defined diet containing protein, utilization efficiencies were minimally affected. When sorbose was substituted for sucrose, it did not cause mortality, but it did depress the efficiency of utilization significantly below that of a control diet that lacked any carbohydrate except cellulose powder.

---

Résumé L'étude a porté sur l'apitude de plusieurs carbohydrates à stimuler les morsures des chenilles du dernier stade de H. zea et à prolonger leur vie, (mesure de la valeur nutritive), en absence de protéines. Sucrose, fructose et glucose stimulent fortement les morsures. Maltose et sorbose ont été faiblement stimulants, et rhamnose, galactose, lactose et mannitol n'ont pas stimulé aux concentrations examinées. Sucrose, fructose, mannitol, maltose, glucose, galactose, amidon de maïs et lactose ont tous prolongé la vie, mais d'une façon différente suivant les carbohydrates.La rhamnose n'a pas prolongé la vie, tout comme le sorbose, qui s'est révélé légèrement toxique. Quand le fructose, le glucose ou le mannitol ont remplacé le sucrose dans un régime complètement défini contenant des protéines, la perturbation de l'efficacité d'utilisation a été minimale, mais la substitution du sorbose par le sucrose, bien qu'elle n'ait pas provoqué de mortalité, a donné une efficacité d'utilisation significativement plus faible qu'un témoin négatif ayant perdu tous les carbohydrates, à l'exception de poudre de cellulose.