Foraging Choices Research Articles

Post-ingestive effect of plant phenolics on the feeding behaviour of the honeybee Apis cerana

As the staple food of honey bees, honey is rich in plant phenolics derived from pollen, nectar and resin. Most studies concentrate on the temporary response of bees' peripheral chemoreceptors to these chemicals, and the post-ingestive effects of plant phenolics are largely ignored. In the present study, a series of feeding experiments are conducted to test whether plant phenolics modulate the response thresholds and rhythmic behaviour of the honeybee Apis cerana (Ruttner). The results of the study demonstrate that bees fed with syrup containing high concentrations of phenlics reduce their response thresholds greatly, and shift their feeding rhythms significantly. Because the forager response thresholds determine their foraging choice, and their rhythmic behaviour is required for timing visits to flowers, enhanced plant phenolics as a result of global environment change may change the bees' pollination service in our changing world.

Differences in yield among annual forages used by the dairy industry under optimal and deficit irrigation

While perennial forages dominate the feed base on Australian dairy farms, poor persistence of perennial ryegrass (Lolium perenne L.) and relatively poor forage nutritive value of kikuyu (Pennisetum clandestinum Hochst. ex. Chiov.) and paspalum (Paspalum dilatatum Poir.) has led to an increasing interest in growing annual forages. Thus, this study was conducted to identify annual forage species that are more productive than the commonly used perennial pasture species. Seventeen annual forages were investigated under ‘optimal’ irrigation and two deficit irrigation treatments (nominally 66 and 33% of irrigation water applied of the optimal level) over 3 years at Camden, New South Wales, on a brown dermosol in a warm temperate climate. The forages evaluated were: Italian ryegrass (Lolium multiflorum Lam.), oats (Avena sativa L.), triticale (Triticosecale rimpaui Wittm), wheat (Triticum aestivum L.), balansa clover (Trifolium michelianum Savi), berseem clover (Trifolium alexandrinum L.), maple pea (Pisum sativum L.), Persian clover (Trifolium resupinatum L. var. majus Boiss.), subterranean clover (Trifolium subterraneum L.), forage rape (Brassica napus L.), forage radish (Raphanus sativus L.), maize (Zea mays L.), Japanese millet [Echinochloa esculenta (A. Braun) H. Scholz], pearl millet [Cenchrus americanus (L.) Morrone], sorghum [Sorghum bicolor (L.) Moench], cow pea [Vigna unguiculata (L.) Walp.] and lablab [Lablab purpureus (L.) Sweet]. There was more than a 4-fold range in annual yield between forages, but the length of the growing season and season of growth made direct comparisons difficult. Under optimal irrigation, maize produced the highest mean yield of 29.0 t DM/ha in only 125 days, which was over three times greater than cow pea (9.2 t DM/ha) grown in the same season yet requiring 190 days. Of the cool season annuals, wheat had the highest mean yield of up to 20.6 t DM/ha in 230 days, which was more than three times the yield of the lowest yielding forage, subterranean clover, at only 6.5 t DM/ha in 215 days. The forages which require harvesting generally had higher yields within a growing period of similar length than those that were defoliated to reflect being ‘grazed’. Combining annual forages in an annual cycle (e.g. maize and wheat) had the potential to produce up to 47 t DM/ha. Deficit irrigation reduced annual yield of all warm season-grown forages ranging from 8% for sorghum up to 48% for maize. In contrast, annual yield reductions were generally smaller for cool season forages, there being no reduction for forage rape, subterranean clover or oats, but up to 35% for Persian clover. However, while yield is an important criterion for choosing dairy forages, it is only one factor in a complex system, and choice of forages must be considered on a whole-farm basis and include water use efficiency, nutritive value, cost of production and risk.

Safflower seeds in corn silage and alfalfa hay based early lactation diets: A practice within an optimum forage choice

Safflower seed (SS), Carthamus tinctorius L., has the highest concentration of linoleic acid among 80 oilseeds. It was hypothesized that an Iranian variety of SS can be effectively fed with cottonseeds (CS) to maintain feed intake, energy metabolism and productivity of early lactation cows under negative energy balance. Our objective was to determine effects of feeding diets containing 100 g whole CS with (1) no SS (SS0), (2) 75 g CS + 25 g SS (SS25), or (3) 50 g CS + 50 g SS (SS50), per kg of dietary DM, on feed intake, rumen fermentation, blood metabolites and milk production of early lactation cows fed diets based on a uniform mixtures of alfalfa hay and corn silage. Nine multiparous early lactation Holstein cows (46 ± 7 d in milk) were used in a replicated 3 × 3 Latin square design study with three 21-d periods. Each period had 14 d of adaptation and 7 d of data collection. Dietary inclusion of SS did not affect ( P>0.10) DM intake, rumen pH and concentrations of ammonia and VFA, blood concentrations of insulin, non-esterified fatty acids, urea and triglycerides, and milk production. Adding SS linearly reduced blood glucose ( P=0.05) and beta-hydroxybutyric acid ( P<0.05), and increased blood total cholesterol ( P<0.01) and low-density lipoproteins ( P<0.05) concentrations. Results demonstrated that SS as an economical and rich source of essential fatty acids can be included up to 50 g/kg of dietary DM alongside CS for early lactation cows without affecting feed intake while maintaining rumen fermentation, peripheral energy supply and milk production.

Difference in yield and persistence among perennial forages used by the dairy industry under optimum and deficit irrigation

Perennial ryegrass (Lolium perenne L.) is the dominant forage grazed by dairy cows in Australia; however, poor persistence has led to an increasing interest in alternative forages. This study was conducted to identify more productive and/or persistent perennial forage species than perennial ryegrass. We evaluated 15 perennial forages under optimum irrigation (I1) and 2 nominated deficit irrigation (I2, 66% of irrigation water applied to I1; I3, 33% of irrigation water applied to I1) regimes, over 3 years at Camden, NSW (34°3′S, 150°39′E), on a brown Dermosol in a warm temperate climate. The forages were: perennial ryegrass, cocksfoot (Dactylis glomerata L.), phalaris (Phalaris aquatica L.), prairie grass (Bromus catharticus M. Vahl), tall fescue (Schedonorus phoenix (Scop.) Holub), kikuyu (Pennisetum clandestinum Hochst. ex. chiov.), paspalum (Paspalum dilatatum Poir.), birdsfoot trefoil (Lotus corniculatus L.), lucerne (Medicago sativa L.), red clover (Trifolium pratense L.), strawberry clover (Trifolium fragiferum L.), sulla (Hedysarum coronarium L.), white clover (Trifolium repens L.), chicory (Cichorium intybus L.), and plantain (Plantago lanceolata L.). Under non-limiting conditions of water and fertility, tall fescue, kikuyu, and prairie grass had the highest mean annual yield over the 3 years of this experiment (24.8–25.5 t dry matter (DM)/ha), which was significantly greater (P &lt; 0.05) than perennial ryegrass (21.1 t DM/ha). Kikuyu was significantly higher than all forages under the extreme I3 deficit irrigation treatment, with mean annual yields of 17.0 t DM/ha. In contrast, the mean yield of white clover was significantly lower (P &lt; 0.05) than of any other forage at only 5.0 t DM/ha, a 70% decline in yield compared with I1. Lucerne was the most tolerant species to deficit irrigation, with a mean annual yield decline (P &lt; 0.05) between the I1 and I3 treatment of only 22%. This study has shown that there are large differences in the relative yield potential of forages and, importantly, indicates the possibility of increasing yield of perennial forages by at least 2-fold on commercial farms, by improving water, and fertiliser management. However, while yield is an important criterion for choosing dairy forages, it is only one factor in a complex system, and choice of forages must be considered on a whole-farm basis and include water-use efficiency, nutritive value, costs of production, and risk.

Grazing preferences by dairy cows for 14 forage species

The objective of this study was to quantify the grazing preference of dairy cows for eight grass, four legume and two herb species in eight seasons over 2 years. All species were grown at the same site, under the same climatic conditions, and with soil moisture and nutrient availability being non-limiting to plant growth. The forage species evaluated were cocksfoot (Dactylis glomerata cv. Kara H0265), perennial ryegrass (Lolium perenne cv. Bronsyn), short rotation ryegrass (Lolium multiflorum cv. Concord), fescue (Festuca arundinacea cv. Advance Maxp.), phalaris (Phalaris tuberose cv. Holdfast), paspalum (Paspalum dilatatum cv. Poir. Common), kikuyu (Pennisetum clandestinum cv. Whittet), prairie grass (Bromus willdenowii cv. Matua), lucerne (Medicago sativa cv. Sceptre), persian clover (Trifolium resupinatum cv. Maral), red clover (Trifolium pretense cv. Astred), white clover (Trifolium repens cv. Kopu II), chicory (Cichorium intybus cv. Grouse) and plantain (Plantago lanceolata cv. Tonic). The 14 forage species treatment plots were laid out in a completely randomised block design with three replicate blocks. The treatment plots were around the circumference of a circle so that the three cows used in each test had unbiased access to all forage species within the blocks. The tests comprised observing the forage being grazed at 10-s intervals for 1 h. The cow preference was recorded as time (min) spent grazing on each forage species. Three Holstein Friesian dairy cows of similar dominance were selected and had grazed all 14 forage species before tests. Cows were fed to requirements before each test so that they would be selective in choice of forages. The most preferred species over the whole year was prairie grass followed by kikuyu and then white clover, despite the fact that kikuyu was not available in winter. Fescue was the least preferred grass species. The mean grazing times for prairie grass and kikuyu during the 1-h test periods of grazing was 11.6 and 10.5 min, respectively. White clover and lucerne were the most preferred legumes (9.6 and 9.0 min, respectively), whereas chicory and plantain were little consumed (3.5 and 3.2 min, respectively). A prediction equation comprising water soluble carbohydrates (WSC%) and nitrate-nitrogen [NO3-N (g/kg DM)] over all seasons and forage species accounted for more variation in cow preference than any other single or combination of variables measured: cow preference [time (min) on plots] = 1.86 + 0.67 WSC% – 1.9 NO3-N (g/kg DM) (r2 = 0.76; s.e. = 2.22; n = 109). The results indicate that the relative palatability of forages can be reasonably well predicted from WSC% and NO3-N concentration, having a positive and negative effect on cow preference, respectively. The prediction equation was improved for groups of species if neutral detergent fibre (NDF%) was included: grasses, cow preference [time (min) on plots] = 24.5 + 0.42 WSC% – 1.31 NO3-N (g/kg DM) – 0.39 NDF% (r2 = 0.87; s.e. = 1.62; n = 57); legumes, cow preference [time (min) on plots] = 3.02 + 0.98 WSC% – 2.15 NO3-N (g/kg DM) – 0.08 NDF% (r2 = 0.92; s.e. = 1.38; n = 36); and herbs, cow preference [time (min) on plots] = 19.41 + 0.22 WSC% – 1.74 NO3-N (g/kg DM) – 0.69 NDF% (r2 = 0.53; s.e. = 1.81; n = 19).

Persuasive companions can be wrong: the use of misleading social information in nutmeg mannikins

Animals sample their surrounding environment to collect information, which can be obtained personally or by tracking the behavior of others (i.e., social information). Although social information appears to be generally advantageous, it can also be detrimental and may even conflict with personal information. We tested the effect that the strength of social information, and ultimately its persuasiveness, can have on an animal’s decision to use it or not by conducting an experiment using single nutmeg mannikins (Lonchura punctulata), which were offered a foraging choice after observation of videos of feeding or nonfeeding conspecifics. The persuasiveness of social information was amplified by increasing the number and changing the behavior of conspecifics that had previously been seen feeding at 1 of 2 feeders. In addition, we modulated the certainty of an individual’s personal information. Some birds had prior experience of a marked feeder always containing easily accessible food, whereas other birds experienced that this was only the case in half of the trials. Our results show that animals provided with sufficiently persuasive social information will tend to reduce the weight of even highly reliable personal information. This provides the first experimental evidence consistent with the propagation of informational cascades in nonhuman animals, which have been invoked to explain market crashes in economics or panic rushes in human crowds.

In situ degradability of corn stover and elephant-grass harvested at four stages of maturity

Among tropical forages, corn silage is largely used by farmers trying to explore the maximum genetic potential from the animals. However, other tropical forages, such as elephant-grass (Pennisetum purpureum), are more productive and therefore cheaper to use than corn silage. Our objective was to compare the in situ degradability of elephant-grass with that from corn hybrids, all harvested at four stages of maturity. The experimental design followed a randomized block design with nested subplots. Two corn hybrids: AG5011, ZN8392 were harvested with 25, 30, 35, and 40% dry matter (DM) in the whole plant, and separated in stem + leaf sheath + leaf blade (stover), and cobs. Elephant-grass was harvested with 30, 40, 50 and 60 days after a leveling cut. Dried and ground samples were incubated in nylon bags inside the rumen for 0, 6, 12, 24, 48 and 72 h to estimate the kinetics of ruminal DM and neutral detergent fiber (NDF) degradation. The advance of maturity increased the NDF and acid detergent fiber (ADF) content in elephant-grass, and reduced its DM degradability. However, maturity had little or no effect on fiber content and DM degradability of corn stover. Elephant-grass had a higher NDF degradability than corn stover, and there was no effect of maturity on NDF degradability of either elephant-grass or corn stover. Fiber degradability of elephant-grass was not worse than that of corn stover, and therefore the choice of forage should be made on economical analysis rather than assuming an intrinsic low production potential for elephant-grass based diets.

The effects of high ungulate densities on foraging choices by beaver (Castor canadensis) in the mixed-wood boreal forest

In some areas of North America previous management policies have created competition between beaver ( Castor canadensis Kuhl, 1820) and ungulates, resulting in dramatic declines in beaver populations. Some authors attribute this decline to competitive exclusion. Generally, the less niche overlap between competitors, the lower potential competition between them. Differences between foraging behaviour of beaver and ungulates suggest that they could not compete to the point of either competitive exploitation or complete exclusion except in restricted habitats. We tested this assumption under two levels of foraging intensity by ungulates by examining the effects of resource competition on beaver forage choices in the context of central place foraging theory. Ungulate densities and foraging intensity within Elk Island National Park (EINP) in Alberta, Canada, were significantly higher than those immediately adjacent to the park, where foraging pressure was lower. Within EINP, forage availability (e.g., stem densities and stem diameters) of many woody plants preferred by beaver, such as Populus L. and Salix L., were depressed by intense foraging by ungulates. Beaver adapted to the effects of high ungulate densities on forage resources by adapting their foraging behaviour. This finding suggested that competitive exploitation, rather than exclusion, exists in EINP. EINP is a productive system that offers an array of forage species, which potentially buffers the effects of competition between ungulates and beaver.

Optimal Choice of Dairy Forages in Eastern Australia

Although several forage species such as perennial ryegrass are predominant, there is a wide range of forage species that could be grown in subtropical and temperate regions in Australia as dairy pastures. These species have differing seasonal patterns of growth, nutrient quality, and water-use efficiency, as demonstrated in a large experiment evaluating over 30 species at the University of Sydney (Camden, New South Wales, Australia). Some species can be grazed, whereas others require mechanical harvesting, which incurs a further cost. Previous comparisons of species that relied on yield of dry matter per unit of some input (typically land or water) did not simultaneously take into account the season in which forage is produced, or other factors related to the costs of production and delivery to the cows. To effectively compare the profitability of individual species, or combinations of species, requires the use of a whole-farm, multiperiod model. Linear programming was used to find the most profitable mix of forage species for an irrigated dairy farm in a warm temperate irrigation region of New South Wales, Australia. It was concluded that for a typical farmer facing the prevailing milk and purchased feed prices with average milk production per cow, the most profitable mix of species would include a large proportion of perennial ryegrass (Lolium perenne) and prairie grass (Bromus willdenowii). The result was robust to changes in seasonal milk pricing and a move from year-round to a more seasonal calving pattern.

Nectar availability and flower choice by eastern spinebills foraging on mountain correa

Nectarivorous birds are known to make choices at the landscape, plant species and individual plant levels when selecting foraging sites. However, little attention has been given to the fine-scale foraging choices that nectarivorous honeyeaters (Meliphagidae) make, such as those between individual flowers. We examined the variability in nectar availability between individual flowers of mountain correa, Correa lawrenciana, and used this information to predict the foraging behaviour of the eastern spinebill, Acanthorhynchus tenuirostris, a small (10–15 g) member of the Meliphagidae. Eastern spinebills preferentially foraged upon mountain correa flowers that were at the developmental stage offering the greatest volume of nectar. They did not discriminate between the flowers on the basis of corolla length (size), but this was not unexpected as nectar production was not correlated with flower size. Eastern spinebills were significantly less likely to forage at flowers with visual evidence of having been robbed of nectar by vertebrate and invertebrate competitors. They did not discriminate against flowers containing the flower mite, Hattena floricola, even though the flowers produced significantly less nectar when mites were present. This is the first study to show that a member of the Meliphagidae is capable of discriminating between individual flowers, favouring those most likely to contain most nectar.

Influence of age, kinship, and large-scale habitat quality on local foraging choices of Siberian jays

The dynamics of natural populations may be influenced by a variety of factors, ranging from feeding interference and territoriality to the risk of predation and climatic effects. The relative influence of these factors may be contingent upon the quality of the habitat in which individuals reside. A factor that can largely affect population dynamics and that often covaries with habitat structure is predation risk. However, the combined effect of habitat and predation risk can vary according to the social context and intrinsic characteristics that affect individual behavioural responses. This thesis investigates the effects of habitat quality at the level of the population and the individual, and examines how it relates to the above factors in Siberian jays (Perisoreus infaustus), a territorial, group-living species in which the main cause of mortality is predation. The results demonstrate a strong effect of habitat on survival, reproduction and behaviour. Mortality was generally higher in open areas and managed forests and reproductive success decreased after forest management. Breeding females were more sensitive to environmental factors than males, possibly because of higher reproductive costs. Estimates of spatial demography suggested that there were more sinks than sources, and that they were located in open, managed forests. Behavioural decisions confirmed that open forests were associated with higher predation risks. However, decisions depended on social context; immigrants took highest risks and were the recipients of most aggression, largely an effect of social subordination. Also, parents provide their offspring with benefits that are withheld from immigrants. As a result, first-year survival was higher in retained offspring. Investigating the effects of multi-scale habitat quality on individual behaviour and population dynamics has generated an increased understanding of the effects of forest management on the dynamics of this population. This approach should facilitate development of an effective conservation management policy for this species.

Importance of nutritional and anti‐parasite strategies in the foraging decisions of horses: an experimental test

The primary goal of foraging herbivores is to maximise the net rate of intake of digestible energy (or of a limiting nutrient). However, foraging strategies of herbivores are also sensitive to other selective forces (e.g. predation, parasites), which may modify their choice of feeding patches. Horses feed in spatially complex swards, and allocate their time among patches which vary both in terms of their nutritional benefits, and the risk of parasitism. It has long been suggested that horses allocate time among patches principally in relation to the risk of parasitism, though the nutritional costs and benefits of different foraging choices must play some role too. In this study, we investigated the roles of nutritional and anti‐parasite factors in foraging decisions by horses. Six naturally parasitized and six unparasitized two‐year‐old geldings were allowed to graze from pairs of trays (112×72 cm) with swards at two heights (tall: 52 cm, medium: 15 cm) and two levels of contamination (280 g m−2 of faeces, no faeces) in a latin square, pair‐wise design with six different choices. In nutritional terms the differences between the swards were slight: the tall sward provided larger bite sizes and higher intake rates (+36%). Feeding motivation was not high, and the faecal stimulus was strong. The horses selected uncontaminated swards when the nutritional benefits were identical, and tall swards in virtually all circumstances. Contamination of the preferred tall sward (i.e. a test of the tradeoff between anti‐parasite and nutritional strategies) had little effect on its selection by the horses. Their parasite status also had little effect: both groups selected the tall sward in the tradeoff (though this was only a trend for the non‐parasitised group in one analysis). We conclude that patch selection by horses in these particular conditions was driven principally by their nutritional strategy.

An extensive study of the foraging ecology of beavers (Castor canadensis) in relation to habitat quality

The objective of this study was to examine the foraging behaviour of the beaver (Castor canadensis Kuhl, 1820) and to explain its selection of terrestrial woody plant species according to central place foraging theory. Limitations in variety of food items in most studies with regard to size and (or) distance from the central place and information on availability of forage choices give a partial view of the subject. In this study, the theory is tested in a natural environment with high variability in food items with regard to these factors. Foraging choices by beavers were inspected by measuring variables on cut and uncut trees of every species encountered within 1 m of trail systems made by 25 beaver colonies in Kouchibouguac National Park in New Brunswick, Canada, thereby quantifying the availability of the different food items. The effect of habitat quality (food availability) on the foraging behaviour of beavers was also tested. The results of this study suggest that with increasing distance from the pond, beavers in high-quality habitats selected fewer, but larger, trees and are more species selective. This selectivity was diminished in habitats of lower quality. The results of this study are consistent with the predictions of the central foraging theory.

Recent Advances in Gut Microbiology and Their Possible Contribution to Animal Health and Production - A Review -

Although gut microbial functions have been analyzed through cultivation of isolated microbes, molecular analysis without cultivation is becoming a popular approach in recent years. Gene cloning studies have partially revealed the mechanisms involved in fiber digestion of individual microbe. The molecular approach finally made it possible to analyze full genomes of the representative rumen cellulolytic bacteria Fibrobacter and Ruminococcus. The coming database may contain useful information such as regulation of gene expression relating to fiber digestion. Meanwhile, unculturable bacteria are still poorly characterized, even though they are main constituents of gut microbial ecosystem. The molecular analysis is essential to initiating the studies on these unculturable bacteria. The studies dealing with rumen and large intestine are revealing considerable complexity of the microbial ecosystems with many undescribed bacteria. These bacteria are being highlighted as possibly functional members contributing to feed digestion. Manipulation of gut bacteria and gut ecology for improving animal production is still at challenging stage. Bacteria newly introduced in the rumen, whether they are genetically modified or not, suffer from poor survival. In one of these attempts, Butyrivibrio fibrisolvens expressing a foreign dehalogenase was successfully established in sheep rumen to prevent fluoroacetate poisoning. This expands choice of forages in tropics, since many tropic plants are known to contain the toxic fluoroacetate. This example may promise the possible application of molecular breeding of gut bacteria to the host animals with significance in their health and nutrition. When inoculation strategies for such foreign bacteria are considered, it is obvious that we should have more detailed information of the gut microbial ecology. (Asian-Aust. J. Anim. Sci. 2004. Vol 17, No. 6 : 877-884)

The communal crop: modulation of sucrose response thresholds of pre-foraging honey bees with incoming nectar quality

We examined whether the quality (concentration) of incoming sucrose solutions returned by foraging honey bees affected the response thresholds of pre-foraging members of the colony. Six pairs of colonies were given ad libitum access to sucrose solution feeders. A colony from each pair was switched from 20–50% sugar concentration feeders while the other continued to have access to 20% sucrose feeders. Proboscis extension response (PER) scores to an increasing series of sucrose concentrations were significantly higher in pre-foragers of colonies foraging on 20% sucrose throughout compared to pre-foragers in colonies where foraging was switched to 50% sucrose. Although all colonies had honey stores, the concentration of sugar solution in non-foraging bees’ crops were significantly lower in bees from colonies foraging on 20% sucrose compared to those from colonies foraging on 50% sucrose. Because response thresholds to sugar of young bees were modulated by the concentration of sucrose solution returned to colonies, we repeated the 2000 study of Pankiw and Page that potentially confounded baseline response thresholds with modulated scores due to experience in the colony. Here, we examined PER scores to sucrose in bees within 6 h of emergence, prior to feeding experience, and their forage choice 2 to 3 weeks later. Pollen foragers had higher PER scores as newly emerged bees compared to bees that eventually became nectar foragers. These results confirm those of the 2000 study by Pankiw and Page. Combined, these experiments demonstrate that variation in pre-forager sucrose response thresholds are established prior to emerging as adults but may be modulated by incoming resources later on. Whether this modulation has long-term effects on foraging behavior is unknown but modulation has short-term effects and the potential to act as a means of communication among all bees in the colony.

Harvesting Winter Forages to Extract Manure Soil Nutrients

Harvested hay captures soil manure nutrients, which, if not utilized, could cause pollution of surface water or aquifer. This study determined yields of hay and N, P, K, Mg, Mn, Ca, Fe, Zn, and Cu of three winter forages for five harvest systems. Dormant bermudagrass [Cynodon dactylon (L.) Pers.] sod fertilized with swine (Sus scrofa domesticus) effluent was fall seeded with ‘Kenland’ red clover (Trifolium pratense L.), ‘Bigbee’ berseem clover (T. alexandrinum L.), or ‘Marshall’ annual ryegrass (Lolium multiflorum Lam.). Forage was removed for three springs with single 1 June harvest or with one of four two‐harvest‐day systems: 1 April and 1 June, 15 April and 1 June, 1 May and 1 June, and 15 May and 1 June. Mean herbage yields were similar for the forages, but nutrient yields and best harvest date varied. Ryegrass yields across harvests were similar except for a reduced 1 May and 1 June harvest. 1 April and 1 June was usually the best harvest for the clovers while the single 1 June was the poorest. The use of two spring harvests for the legumes increased yields up to 130% of the single harvest. The legumes yielded up to 64% more N, 24% more P, and 40 and 72% more of the metals Zn and Cu than the ryegrass. The 1 April harvest of berseem clover removed &gt;30 kg ha−1 yr−1 of soil P. Management of soil nutrients is critically affected by choice of winter forage and harvest system.

Effect of pheromones, hormones, and handling on sucrose response thresholds of honey bees (Apis mellifera L.).

The responsiveness of bees to sucrose is an important indicator of honey bee foraging decisions. Correlated with sucrose responsiveness is forage choice behavior, age of first foraging, and conditioned learning response. Pheromones and hormones are significant components in social insect systems associated with the regulation of colony-level and individual foraging behavior. Bees were treated to different exposure regimes of queen and brood pheromones and their sucrose responsiveness measured. Bees reared with queen or brood pheromone were less responsive than controls. Our results suggest responsiveness to sucrose is a physiologically, neuronally mediated response. Orally administered octopamine significantly reduced sucrose response thresholds. Change in response to octopamine was on a time scale of minutes. The greatest separation between octopamine treated and control bees occurred 30 min after feeding. There was no significant sucrose response difference to doses ranging from 0.2 mug to 20 mug of octopamine. Topically applied methoprene significantly increased sucrose responsiveness. Handling method significantly affected sucrose responsiveness. Bees that were anesthetized by chilling or CO(2) treatment were significantly more responsive than control bees 30 min after handling. Sixty minutes after handling there were no significant treatment differences. We concluded that putative stress effects of handling were blocked by anesthetic.

Larval feeding experience influences adult predator acceptance of chemically defended prey

AbstractGeneralist predatory paper wasps, Polistes dominulus, experience plant secondary defensive compounds as developing larvae through their herbivorous lepidopteran caterpillar prey and as adults through attacking caterpillars while foraging. We evaluated the role that larval and early adult experience with unpalatable prey plays in subsequent foraging choices by adult wasps. For periods of two or four weeks, caged wasps were raised exclusively on caterpillars of either unpalatable Buckeye, Junonia coenia, that sequester substantial levels of iridoid glycosides (IG) or on Painted Lady, Vanessa cardui, that contain very low levels of IG. Wasps were then allowed to forage on both caterpillar species simultaneously. Patterns of prey capture differed significantly based on previous prey experience. Regardless of previous feeding experience, adult wasps overwhelmingly preferred to take Vanessa. Yet Junonia‐experienced wasps continued to attack and take back to the nest over 50% more Junonia than did Vanessa‐experienced wasps. The longer the wasps' larval experience with Junonia, the more likely they were to capture Junonia caterpillars. However, the life stage at which the wasps experienced Junonia was also influential as young adult experience with the unpalatable prey was more of a deterrent than was experience strictly as larvae for Junonia‐experienced wasps. The results demonstrate that, in these predators, previous experience with deterrent chemicals during their larval development alters patterns of prey acceptability to the adult insects.

Genotype and colony environment affect honeybee ( Apis mellifera L.) development and foraging behavior

We examined the interaction of genotype and environment on foraging-behavior development and forage choice in honeybees. High- and low-pollen-hoarding strains and unselected wild-type bees were co-fostered in pairs of colonies manipulated to differentially stimulate high and low pollen foraging. The high-pollen-foraging stimulus consisted of high amounts of larvae, a known stimulus for pollen foraging, plus low amounts of pollen, known to induce pollen foraging. The low-pollen-foraging stimulus consisted of low amounts of larvae plus high amounts of pollen. We estimated the median age at which bees initiated foraging, determined forage choice, and the quality and quantity of resources collected. High-strain bees consistently foraged at younger ages than workers from the other sources. High-strain bees appeared to be more sensitive to the pollen-foraging-stimulus treatments, showing greater differences in foraging age and behavior. Three-way interactions of genotype, pollen foraging stimulus, and colony pair (replicate) were statistically significant for most foraging variables measured suggesting that additional, unknown environmental factors also affect foraging behavior. Our results suggest there is a functional relationship between age of first foraging and forage choice with a strong genetic component that is modulated by colony environment.

Coping with chemical complexity in mammal-plant interactions: near-infrared spectroscopy as a predictor of Eucalyptus foliar nutrients and of the feeding rates of folivorous marsupials.

We investigated the utility of near-infrared reflectance spectroscopy (NIRS) as a means of rapidly assaying chemical constituents of Eucalyptus leaves and of directly predicting the intake of foliage from individual trees by greater gliders (Petauroides volans) and common ringtail possums (Pseudocheirus peregrinus). The concentrations of total nitrogen, neutral detergent fiber, condensed tannins and total phenolics could be predicted accurately by partial least squares regression models relating the near-infrared reflectance spectra of foliage samples to analyses performed using standard laboratory procedures. Coefficients of determination (r 2) for all four constituents ranged between 0.88 and 0.98, and standard errors of prediction between 0.80mgg-1drymatter (DM) for total nitrogen and 5.14quebrachoequivalentsg-1DM for condensed tannins. Near-infrared spectral-based models of food intake had r 2 values of 0.90 and 0.95 with a standard error of prediction of 3.4 and 8.3g DMkg-0.75day-1 for greater gliders and common ringtail possums respectively. We used the predictive model of food intake for greater gliders to examine the relationship between leaf palatability and documented food preferences of animals in the wild. Ranked differences in leaf palatability across four Eucalyptus species were consistent with documented food preferences of greater gliders in the wild. We conclude that NIRS provides a powerful tool to predict foraging behaviour of herbivores where forage choices are determined by compositional attributes of food.