Variation In Nutritional Quality Research Articles

Seasonal Variation in Nutritional Quality of Pittosporum floribundum in Mid Hills of Himachal Pradesh

The present study was carried out to analyse nutrient and anti-nutritional principles in Pittosporum floribundum on seasonal basis to determine its best cultivation time and to assess its value as potential fodder species in the mid Himalayan zone, H.P. The highest CP (14.58%), DM (58.86%), OM (90.97%), P (0.24%), K (2.55%), Mn (47 ppm) contents were higher during spring season while CF (16.63%), ADF (23.30%) and NDF (34.92%) levels were the maximum during summer season. Winter season exhibited the highest NFE (62.06%), total carbohydrates (74.58%), Ca (4.38%), Cu (21.80 ppm), Fe (696.20 ppm) and Zn (54.40 ppm) contents. Anti-nutritional principles viz., phenol (1.32%) and tannins (0.22%) were the lowest during summer season and the highest during autumn season. Nitrate content was the highest (4.99 ppm) in spring season while saponins levels were the maximum (32.40%) during winter season. All anti-nutrients except saponins were observed to be below the toxic level for animal consumption in P. floribundum. Hence, P. floribundum has a high potential as feed for livestock.

Seasonal Variation in Nutritional Quality of Catfish (Clarias gariepinus) from Upper Jebba Basin, Nigeria

Fish protein is regarded as quality protein being rich in essential amino acids with a high digestibility value. The biochemical composition of the fish differs with the change in habitat as well as season. Samples of freshwater catfish (Clarias gariepinus) from Upper Jebba Basin, Nigeria were analyzed during the dry and wet seasons to study the variation in proximate composition of nutrients and mineral content using standard procedures in dry weight basis. The results revealed the presence of the moisture content with an average mean of 4.26 ± 1.04% in dry season while wet season recorded 5.63 ± 1.27%. The ash content in dry and wet season is 6.10 ± 0.85% and 4.66 ± 0.46% respectively while the crude fibre were generally low with significantly variation (P<0.05) between 0.84 ± 0.12% in dry months and 0.57 ± 0.25% in wet months. The average mean values of crude protein were slightly higher at 64.47 ± 0.58% in wet months than 63.10 ± 2.10% in dry months. Variation in crude fat content for both season were within a narrow range with an average mean of 4.03 ± 0.16% and 4.09 ± 0.03% for dry and wet season respectively. Average Nitrogen Free Extract (Carbohydrate) of 20.76 ± 1.43% in dry season was comparatively higher than 19.86 ± 1.55% in wet months. The mineral composition of the fish in both seasons varied significantly (P<0.05) in Ca, K, Cu and Zn% mean concentration.

Species interactions in a grassland mixture under low nitrogen fertilization and two cutting frequencies. II. Nutritional quality

AbstractMixtures and pure stands of perennial ryegrass, tall fescue, white clover and red clover were grown in a three‐cut and a five‐cut system in southern Norway, at a low fertilization rate (100 kg N ha−1 year−1). The nutritional quality (annual weighted averages) of the dried forage from the two‐first harvesting years was analysed. There was no significant effect of species diversity on crude protein (CP) concentration. In the three‐cut system, we found a significant species diversity effect leading to 10% higher concentrations of acid detergent fibre (ADF), 20–22% lower concentrations of water‐soluble carbohydrate (WSC) and 4% lower net energy for lactation (NEL) concentrations in mixtures compared with pure stands (averaged across the two‐first years). In the five‐cut system, similar effects were seen in the first year only. This diversity effect was associated with a reduction in WSC and NEL concentrations and an increase in ADF, NDF and CP concentrations in the grass species, and not in red clover, when grown in mixtures. This is thought to be a combined result of better N availability and more shading in the mixtures. Species diversity reduced the intra‐annual variability in nutritional quality in both cutting systems.

Foliar Nutritional Quality Explains Patchy Browsing Damage Caused by an Invasive Mammal.

Introduced herbivores frequently inflict significant, yet patchy damage on native ecosystems through selective browsing. However, there are few instances where the underlying cause of this patchy damage has been revealed. We aimed to determine if the nutritional quality of foliage could predict the browsing preferences of an invasive mammalian herbivore, the common brushtail possum (Trichosurus vulpecula), in a temperate forest in New Zealand. We quantified the spatial and temporal variation in four key aspects of the foliar chemistry (total nitrogen, available nitrogen, in vitro dry matter digestibility and tannin effect) of 275 trees representing five native tree species. Simultaneously, we assessed the severity of browsing damage caused by possums on those trees in order to relate selective browsing to foliar nutritional quality. We found significant spatial and temporal variation in nutritional quality among individuals of each tree species examined, as well as among tree species. There was a positive relationship between the available nitrogen concentration of foliage (a measure of in vitro digestible protein) and the severity of damage caused by browsing by possums. This study highlights the importance of nutritional quality, specifically, the foliar available nitrogen concentration of individual trees, in predicting the impact of an invasive mammal. Revealing the underlying cause of patchy browsing by an invasive mammal provides new insights for conservation of native forests and targeted control of invasive herbivores in forest ecosystems.

Validation of the FSA nutrient profiling system dietary index in French adults-findings from SUVIMAX study.

Population-wide nutritional recommendations give guidance on food groups' consumption, though a wide variability in nutritional quality within groups may subsist. Nutrient profiling systems may help capturing such variability. We aimed to apply and validate a dietary index based on the British Food Standards Agency nutrient profiling system (FSA-NPS DI) in French middle-aged adults. Dietary data were collected through repeated 24-h dietary records in participants of the Supplémentation en Vitamines et Minéraux Antioxydants study (N=5882). An aggregated dietary index at the individual level was computed using the FSA-NPS for each food consumed as well as compliance to the French nutritional guidelines using the Programme National Nutrition Santé-Guideline Score (PNNS-GS). Cross-sectional associations between FSA-NPS DI and nutrient intake, PNNS-GS, socio-demographic factors, lifestyle and nutritional biomarkers were computed using ANOVAs. The FSA-NPS DI was able to characterize the quality of the diets at the individual level in terms of nutrient intake and of adherence to nutritional recommendations: +37.6% in beta-carotene intakes between subjects with a healthier diet versus subjects with a poorer diet, +42.8% in vitamin C intakes; +17% in PNNS-GS, all P<0.001. FSA-NPS-DI was also associated with nutritional status at the biological level: +21.4% in beta-carotene levels between subjects with a healthier diet versus subjects with a poorer diet, +12.8% in vitamin C levels, all P<0.001. The FSA-NPS DI is a useful and validated tool to discriminate individuals according to the quality of the diet, accounting for nutritional quality within food groups. Taking into account nutritional quality of individual foods allows monitoring change in dietary patterns beyond food groups.

Performance of a five category front-of-pack labelling system - the 5-colour nutrition label - to differentiate nutritional quality of breakfast cereals in France.

BackgroundBreakfast cereals exhibit a wide variability in nutritional quality, and differences are not easily grasped by consumers. A simplified nutritional information system might contribute to help consumers make healthier food choices. A five-category colour label based on the Food Standards Agency Nutrient profiling system (FSA score) has been proposed in France to be implemented on the front-of-pack of foods (the five-colour nutrition label - 5-CNL). Objectives were to evaluate the ability of the 5-CNL to discriminate nutritional quality between types of breakfast cereals, within a category and in equivalent products, as well as its ability to change through product reformulation.MethodsNutritional information was collected through an Internet and supermarket research for N = 433 breakfast cereals (N = 380 complete data included in the analyses). Breakfast cereals were categorized according to common attributes in terms of processing and/or ingredients used. The FSA score and 5-CNL category allocation were computed for each cereal. Nutrient content and FSA score were compared across types of cereals. Distribution within the 5-CNL categories was assessed across types of cereals and for equivalent products. Impact of reformulation (reduction of 5 and 10% in simple sugar, saturated fat and sodium) on the 5-CNL category allocation was compared to original allocation with Bapkhar’s tests of homogeneity of marginal distribution.ResultsVariability in nutritional quality of breakfast cereals was high, as reflected by the FSA score (range −7- 22 for a theoretical range of −15-40) and the 5-CNL (all five categories represented). The 5-CNL allowed for discrimination across types of cereals, within categories of breakfast cereals and for equivalent products (at least 3 categories of the 5-CNL represented). Reformulation scenarios allowed for significant change in 5-CNL allocation: 5% reduction in sugar lead to a modification of the label for 4.21% of products while a reduction of 10% of sugar, saturated fat and sodium lead to a modification of the label for 19.2% of products.ConclusionThe 5-CNL adequately discriminates between breakfast cereals. It would therefore be an adequate tool for consumer information on nutritional quality of foods in the French context.Electronic supplementary materialThe online version of this article (doi:10.1186/s12889-015-1522-y) contains supplementary material, which is available to authorized users.

Variation in nutritional quality and chemical composition of fresh strawberry fruit: combined effect of cultivar and storage.

Bioclimatic air ionisation system (BI) works by neutralising air pollutants and microorganisms by means of oxidation with "activated oxygen". We investigated the effects of storage on changes in weight loss, chemical and sensory fruit properties in eight cultivars of strawberries (Fragaria x ananassa Duch.). All cultivars were evaluated for their standard parameters of quality (soluble solids content, total acidity, vitamin C content, total antioxidant activity - TAC, total phenolic and anthocyanins content) at different store conditions: fresh fruits-control, cold stored (at 4 °C) fruits without controlled atmospheres and cold stored (at 4 °C) fruits in BI. The present study outlines that anthocyanins of the strawberries stored in BI were subjected to significant degradation. These strawberries have prolonged shelf-life accompanied by weight loss reduction, TAC increment, and sensory properties improvement in tested cultivars, retaining other nutritional fruit qualities.

Parasitization preference of Diaeretiella rapae (Hymenoptera: Braconidae) among different aphids in vegetable ecosystem

Solitary, polyphagous, endoparasitoid Diaeretiella rapae (Mc’Intosh) is considered as one of the prominent parasitoid of aphids on several host plants under natural field conditions. However, knowledge about its affinity and host preference towards different prey aphids is very scanty. So the present study on host preference of D. rapae revealed differential response for its parasitization to different aphid species infesting vegetable crops. It preferred maximum to cruciferous aphids, viz. Myzus persicae (59%) followed by Brevicoryne brassicae (51%) and Lipaphis erysimi (46%) than the other vegetable aphids like Aphis craccivora (23.67%) and Aphis spiraecola (19.67%). Seasonal incidence of D. rapae also indicated that its first occurrence was observed on M. persicae (13.67%) and L. erysimi (5.67%) during second fortnight of January, 2013 whereas spiraecola feeding on brinjal parasitized last indicating the preference of cruciferous aphids over other vegetable aphids. However, among the cruciferous aphids, highest parasitoid emergence was observed from L. erysimi (88%) followed by B. brassicae (81%) and M. persicae (80%). Comparatively higher body size (2.81 ± 0.23 mm) and tibial length (0.51 ± 0.05 mm) of M. persicae by the parasitoid for its parasitization and variation in nutritional quality in L. erysimi as food substrate towards D. rapae for its higher emergence might be responsible for their preference over the other host aphids.

Nutritional composition of the preferred prey of insectivorous birds: popularity reflects quality

Food availability is emerging as a key determinant of avian occurrence and habitat use in a variety of systems, but insectivores have received less attention than other groups and the potential influence of nutritional quality has rarely been considered. Rather than a uniform food source, arthropods vary greatly in terms of nutritional composition, but does this variation translate into differential consumption? Building on previous work that demonstrated clear preference for some arthropod groups by 13 species of ground‐foraging insectivores, we compare the nutritional composition of these arthropod groups with other groups commonly encountered but seldom consumed in the same habitat types. Using samples of arthropods collected from a eucalypt woodland in southern Australia, we found the high frequency prey groups (Coleoptera, Lepidoptera, Orthoptera and Araneae) consistently contained higher fractions of crude protein and total fat than the low frequency groups (Diptera, Hymenoptera and Odonata). Even more clear‐cut differences were noted in terms of micronutrients; high frequency prey containing significantly greater concentrations of seven elements than low frequency prey and significantly greater amounts per individual arthropod for all eleven elements measured. These results indicate that the nutritional quality plays an important role in prey selection in insectivores and suggests that micronutrients may be more important determinants of prey choice than previously recognized. Integrating these findings with previous work suggesting food limitation may constrain distribution patterns of birds in fragmented landscapes, we contend that variation in nutritional quality helps explain observed patterns in insectivore diets and occurrence. In addition to explaining why smaller and more disturbed habitats are unable to support resident insectivore populations, this bottom‐up mechanism may underlie the disproportionate sensitivity of insectivores to land‐use intensification.

Edaphic, Nutritive, and Species Assemblage Differences between Hotspots and Matrix Vegetation: Two African Case Studies

AbstractAreas of locally intense and frequent grazing, or ‘hotspots’, are pervasive features in tropical grasslands and savannas. In some ecosystems, hotspot presence is clearly associated with edaphic factors (e.g., high clay content and elevated soil fertility), such as those that develop in abandoned cattle bomas. Studies in a range of other savanna ecosystems, however, have failed to find intrinsic soil differences between hotspots and the surrounding matrix. Also, it remains unclear to what extent hotspots are associated with specific assemblages of nutrient‐rich plant species, as opposed to being a manifestation of intraspecific variation in nutritive quality. We conducted simultaneous studies in Kruger (South Africa) and Serengeti (Tanzania) National Parks to re‐evaluate the role of edaphic correlates of hotspot occurrence and to test whether intraspecific variation in plant quality occurs across hotspot‐matrix boundaries. We sampled soils and plants in paired hotspot and matrix plots at multiple sites within each ecosystem to test our a priori hypothesis that hotspots would be associated with distinct species assemblages and differences in soil fertility. We found clear hotspot‐matrix differences in foliar N, particularly within species, despite finding no differences in any soil or plant–soil variables, including N mineralization potential and mycorrhizal inoculation levels. We found only weak differences in community composition across the boundary, suggesting that intraspecific variation in foliar N rather than species turnover is mainly responsible for the enhanced nutritive value of hotspot vegetation. We propose that grazer–plant interactions may be stronger drivers of hotspot maintenance in these systems than plant–soil interactions.

Shoot Feeding as a Nutrient Acquisition Strategy in Free-Living Psylloids

Shoot feeding by sucking insects is accepted as an adaptation to feeding where plant nutrients are most concentrated and/or of higher quality. Psylloids are an important hemipteran taxon, most of which are free-living and comprise many shoot feeding species, whose nutritional ecology has been largely ignored. I conducted a longitudinal study of Ctenarytaina eucalypti (Maskell) and C. bipartita Burckhardt et al. (Aphalaridae) feeding on eucalypts to document how within-plant (ontogenic) variation in nutritional quality, in particular of free amino acids, determines host suitability and hence the distribution and abundance of nymphs. Nymphs were most abundant within developing apical buds but were not more abundant on branchlets of greater vigour (indicated by rate of extension). Nymphs could be found up to two (C. bipartita) to three (C. eucalypti) alternate leaf pairs distant from apical buds but infrequently and in low numbers; they were never found on older, fully expanded leaves. The position of a leaf on a branchlet (indicative of age) determined its nutritional quality. Younger leaves had higher water contents, lower chlorophyll contents and differed in amino acid (essential and non-essential) composition compared to older leaves. The abundance of C. eucalypti nymphs on expanding leaves and in buds was positively correlated with the concentrations of methionine, valine and threonine in E. globulus leaves at the same or comparable position on a branchlet. The abundance of C. bipartita nymphs was positively correlated with foliar leucine concentrations. Shoot feeding by these two psyllids facilitates access to more concentrated, better quality plant nutrients but may not entirely explain the adaptive significance of their behaviour. The humid microclimate created by the architecture of the hosts’ apical buds protects eggs and nymphs from desiccation and is suggested to have had a significant influence on the evolution of host utilisation strategies of psyllids within this genus.

Variation in nutritive quality and mineral content of grazed and clipped forage from native range in southwest Idaho

Changes in nutrient content of grazed and clipped forages during the growing season were evaluated over a 2-yr period via samples from native range in southwestern Idaho. Mature, ruminally fistulated beef cows were used from April to September (yr 1; n = 4) and May to October (yr 2, n = 3) to collect masticated diet samples every 2 to 4 wk. Clipped samples were also collected concurrent with grazed samples. Attempts were made to clip forage similar to what the cows had been observed to be consuming; however, cattle selected (P < 0.05) a diet higher in nutritive quality than what was clipped for some nutrients. In yr 1, forage CP was greater (P = 0.05) in grazed than clipped samples in July, whereas in yr 2 grazed CP tended (P = 0.06) to be greater in August and was greater (P < 0.05) in September than clipped samples. Nutrient content of samples was adequate to meet lactating beef cow needs (NRC requirements) for CP and TDN until mid to late summer and adequate for K but deficient for P, Na, Ca, Mg, and S throughout the grazing season. Micronutrients Fe, Mn, and Mo were adequate during the grazing season, whereas Cu and Zn were deficient. Based on the variation in nutrient content by month, we report that forage quality is highly variable throughout the grazing season. Furthermore, clipped sample nutrient content is generally similar to grazed sample content and provides an adequate prediction of consumed forage quality.

Intra-plant differences in seaweed nutritional quality and chemical defenses: Importance for the feeding behavior of the intertidal amphipod Orchestoidea tuberculata

As a result of their morphological complexity, large macroalgae show intra-thallus variations in their nutritional composition and secondary metabolite content, which influences the trophic ecology of herbivorous invertebrates, and ultimately their fitness. In this study, we evaluated for the first time the variability in nutritional quality (protein content, carbohydrates, lipids, and total organic matter), secondary metabolites (phlorotannins), and structure (shape and toughness) between blades and stipes of the macroalgae Durvillaea Antarctica. Specifically, we looked at their effect on feeding preference, rate of consumption, absorption efficiency, and growth rate of the amphipod Orchestoidea tuberculata, one of the most abundant organisms on Chilean sandy beaches. Proteins, carbohydrates, total organic matter and phlorotannin contents were significantly higher in blades than in stipes. Preference experiments revealed that the amphipods preferred blades when fresh pieces of blades and stipes were offered at the same time. Similar results were found when artificial food (in which structures of both parts of the alga were standardized) was offered, suggesting that shape and toughness of the two different parts of the alga did not influence preference patterns of O. tuberculata. Absorption efficiency of O. tuberculata was higher on blades compared to stipes. When the amphipods were kept with each of the algal parts separately (i.e. no choice), they consumed a significantly higher amount of stipe, which suggests that O. tuberculata used food quantity to compensate for the lower nutritional quality of stipes. The higher nutritional values of blades compared to stipes appears to explain observed preference patterns by O. tuberculata. Phlorotannin content did not appear to inhibit blade consumption, suggesting that the nutritional quality of the food could be more important than chemical defense in determining food choice in O. tuberculata. Growth did not differ between the amphipods maintained with either blades or stipes (i.e. no choice), which is consistent with the hypothesis of compensatory feeding. To conclude, O. tuberculata can actively select specific parts of an alga and this selection appears to be based on nutritional quality. The capacity for using different feeding strategies allow O. tuberculata, in some cases, to successfully exploit food types with different nutritional qualities.

Consequences of constitutive and induced variation in plant nutritional quality for immune defence of a herbivore against parasitism

The mechanisms through which trophic interactions between species are indirectly mediated by distant members in a food web have received increasing attention in the field of ecology of multitrophic interactions. Scarcely studied aspects include the effects of varying plant chemistry on herbivore immune defences against parasitoids. We investigated the effects of constitutive and herbivore-induced variation in the nutritional quality of wild and cultivated populations of cabbage (Brassica oleracea) on the ability of small cabbage white Pieris rapae (Lepidoptera, Pieridae) larvae to encapsulate eggs of the parasitoid Cotesia glomerata (Hymenoptera, Braconidae). Average encapsulation rates in caterpillars parasitised as first instars were low and did not differ among plant populations, with caterpillar weight positively correlating with the rates of encapsulation. When caterpillars were parasitised as second instar larvae, encapsulation of eggs increased. Caterpillars were larger on the cultivated Brussels sprouts plants and exhibited higher levels of encapsulation compared with caterpillars on plants of either of the wild cabbage populations. Observed differences in encapsulation rates between plant populations could not be explained exclusively by differences in host growth on the different Brassica populations. Previous herbivore damage resulted in a reduction in the larval weight of subsequent herbivores with a concomitant reduction in encapsulation responses on both Brussels sprouts and wild cabbage plants. To our knowledge this is the first study demonstrating that constitutive and herbivore-induced changes in plant chemistry act in concert, affecting the immune response of herbivores to parasitism. We argue that plant-mediated immune responses of herbivores may be important in the evaluation of fitness costs and benefits of herbivore diet on the third trophic level.

Seasonal variation in plant nutritive quality for Greater Snow Goose goslings in mesic tundra

Variation in nutritive quality over time and among forage plants is important for herbivores such as geese. We examined the seasonal variation of some nutritive attributes (nitrogen, neutral detergent fibre, and phenolic compounds) of five plant species consumed by Greater Snow Geese ( Chen caerulescens atlantica ) L. in mesic tundra, a habitat where goose feeding ecology has been little studied compared with wetlands. We sampled ungrazed, aboveground plant tissues five times at 10–14 d intervals between 1 July and 15 August 2003 on Bylot Island, Nunavut. The species were Arctagrostis latifolia (R. Br.) Griseb. (Gramineae), Luzula nivalis (Laest.) Beurl. (Juncaceae), Oxytropis maydelliana Trautv. (Leguminosae), Oxyria digyna (L.) Hill, and Polygonum viviparum L. (both Polygonaceae). All species showed a seasonal decline in nitrogen content in both leaves and flowering heads (includes flowers and fruits) but the amplitude was variable among species (from 10% to 62% decline depending on the species). Neutral detergent fibre concentration in leaves remained stable or increased slightly over time in contrast to flowering heads where it increased in all species (from 7% to 94%). Fibre content was higher in flowering heads than in leaves. The total content of phenolic compounds varied throughout the summer. In some cases, the content of phenolic compounds remained stable but in others it initially increased and then decreased later on, or it increased throughout the summer. Seasonal variations in plant nutritive quality were smaller than interspecific differences. The nitrogen content of forbs (especially Oxytropis ) was high and their fibre content low compared with the grass and rush species (Luzula), particularly during the early summer.

Seasonal variations in nutritional components of green asparagus using the mother fern cultivation

Abstract Harvesting season for green asparagus can be extended by the use of the mother fern method and greenhouse cultivation . To evaluate seasonal variations in nutritional quality of green asparagus, the compositional profiles of fresh spears ( Asparagus officialis L. cv. UC157 F1) harvested each month from March to October were compared in two locations of China using mother fern method. During the harvest season, dry matter content, soluble sugar, crude fiber, rutin and total soluble phenol in spears exhibited marked variation. Although there was no significant difference in total amino acid contents among most of months throughout the season, but quantitative changes in some specific amino acids occurred. Fresh spears harvested in warm season (from June to July) contained lower level of soluble sugars, dry matter, ascorbic acid and higher nitrate, crude fiber, total phenolics and rutin contents compared with those in cooler months. Asparagus harvested in spring accumulated relatively higher level of soluble sugar, carotenoid and chlorophyll contents than those in autumn, but total phenol and rutin contents were higher in autumn than in spring. The relationships between weather data and nutritional quality parameters of asparagus spear during harvest season were also discussed.

Russian wildrye nutritive quality as affected by accession and environment

High-quality forage for spring and fall grazing is an important need of ranchers in the Northern Great Plains and Intermountain-West regions of the United States of America and in the prairie provinces of Canada. Russian wildrye [Psathyrostachys juncea (Fischer) Nevski] has been used to meet this grazing need, especially in Canada. However, its use has probably been limited by its reputation for seedling establishment difficulties and scattered reports of grass tetany. The purpose of this research was to characterize the variation in nutritive quality of Russian wildrye accessions used in a multi-location grass tetany project, to access the effect of environment on quality components, and to determine the relationship between forage nutritive quality components and entities associated with grass tetany. Sixty-seven Russian wildrye accessions from the US National Plant Germplasm System were established in spaced-plant nurseries at Logan, UT, Mandan, ND, and Swift Current, SK, Canada. Plants were sampled at two stages of development over 2 yr. Location, year, and stage of development effects were significant (P &lt; 0.01) for in vitro true dry matter digestibility (IVDMD), crude protein (CP), and neutral detergent fiber (NDF). At the early stages of development used in this study the range in nutritive quality traits among entries was rather narrow. Relatively high positive correlation coefficients between K and IVDMD, and K and CP suggest that breeding for higher nutritive quality may also produce a more tetany-prone forage, because high K concentration is usually associated with grass tetany. On the other hand, Mg concentrations were also highly correlated with IVDMD and CP, and higher Mg concentrations would be beneficial in preventing grass tetany. The K/(Mg + Ca) ratio, which has been suggested as an indicator of grass tetany, was only moderately related to IVDMD, CP, and NDF. Key words: Digestibility, crude protein, neutral detergent fiber, stage of plant development

Life history and phenology of the eucalyptus psyllid, Ctenarytaina eucalypti in Ireland

SummaryDuring the early 1990s, the eucalyptus psyllid, Ctenarytaina eucalypti Maskell, was accidentally introduced into Ireland and began to threaten economically a newly developing ornamental foliage production industry based in the south west. The life cycle of the psyllid was studied at three field sites in Co. Kerry. The psyllid exhibited a complex seasonal population dynamic suggesting that two, largely overlapping population cohorts over‐winter as eggs and nymphs, respectively, in a state of reduced development or temporary dormancy. The duration of this dormancy is short. Evidence of a resumption of activity was monitored at all sites in early February with increasing adult numbers and renewed egg laying being seen before any significant rise in temperatures. This strongly suggests that retarded development, and resumption of psyllid activity in early spring, are at least partially consequences of the changing nutritional quality of the food plant, probably mediated by changing day length. As a consequence of seasonally inhibited development, individual egg and nymphal over‐wintering cohorts probably alternate in the completion of two or three generations per growing season. Analysis of psyllid numbers on shoot samples showed that greater population densities were found on shoots at the top of the food plant compared with lower‐placed shoots. Evidence was also found that the distribution of nymphal instars changed seasonally, probably in response to population density and increased competition for preferred feeding sites. Overall psyllid abundance, and the finer details of seasonal population dynamics, varied between plantations. In the absence of effective predation or parasitism by indigenous natural enemies, these differences were also likely to be due to variation in nutritional quality of the host plant and may be influenced by crop husbandry factors such as the timing and severity of crop pruning.

Variations in Nutritional Quality and Biomass Production of Semiarid Grasslands

The effect of the growing season and topographic zone on biomass production, protein content, cell content (CC), lignin, cellulose, hemicellulose, digestibility (DMD), and mineral element concentrations (P, K, Ca, Mg, Na, Mn, Fe, Cu, Zn) were studied in herbage samples collected from semiarid grasslands in Central Western Spain. Protein and mineral contents decreased as the growing season progressed whereas fibre properties tended to increase. Topographic gradient significantly affected peak biomass production, fibre properties, protein and mineral contents. Stepwise multiple regression showed that the prediction of biomass production on these areas was related to cellulose, Na, Fe, and Mg contents in the grassland community whereas fibre properties were mainly predicted by Ca, Na, and Cu. Principal component analysis indicated that the temporal evolution (component II) of the organic variables determined pasture quality whereas most of the variation in mineral content was related to the topographical gradient (component I). Some organic and inorganic parameters may cause deficiencies in cattle grazing en the upper and middle zones, mostly at the end of the growing season. The data suggest that information about the temporal and spatial variations of the production and nutritional quality of semiarid grassland is necessary for making correct management.

Variation in phenology and nutritional quality between host plants and its effect on larval performance in a specialist butterfly, Zerynthia rumina

AbstractThe main host plants of the butterfly Zerynthia rumina L. (Lepidoptera: Papilionidae) in southern Spain occur in different habitats and in general do not grow sympatrically. Therefore, each single local butterfly population uses the particular host available within its range. Aristolochia longa L. is a tuberous perennial herb available only in the spring, while A. baetica L. is an evergreen perennial vine with indeterminate growth. However, because of the toughness of older leaves, newly hatched larvae feed only on new leaves of A. baetica, and most of these leaves are produced well before the larvae hatch. In laboratory experiments, caterpillars feeding on either new or mature A. longa leaves grew faster and converted food into biomass more efficiently than those feeding on new A. baetica leaves. These differences are related to variation in nutritional quality among the host plants. Estimates of butterfly abundance were lower in sites where Z. rumina uses A. baetica, compared with those where the host is A. longa. The potential differential effect of these two food plants on the densities of local butterfly populations relying on them is discussed here.