Acorn Species Research Articles

Influence of feed substitution with acorns on fattening performance, carcass characteristics, and meat composition of Prestice Black-Pied pigs finished in a conventional indoor system

With their considerable nutritive value, acorns have long been a natural feed source for pigs and, in recent years, fattening pigs with acorns has become very popular even in countries where it has not traditionally been customary. The meat of pigs finished with acorns has a unique flavour and fat profile as reflected by fatty acids content. We decided to determine the nutritional value of the most common species of acorns in Central Europe (Quercus robur) and examine the effects of this feed upon fattening performance, carcass value, and the composition of meat and fat produced by indoor finishing of pigs, as forest grazing is prohibited here. We conclude that the Prestice Black-Pied breed can be fattened utilizing a mixed feed containing acorns at the level of 10% under intensive conditions without significantly changing the performance parameters (average daily gain was 750 g versus 761 g in the control group). We found improvements in fatty acid profiles of intramuscular fat away from saturated toward monounsaturated. The improvements in the fatty acid profiles, similar to those seen in pigs raised in sylvan settings, create pork that may benefit human health. Acorns can constitute an alternative feedstuff even for pigs finished indoors and bring new benefits to agriculture in modern times.

Unraveling the Effect of Dehulling Methods on the Nutritional Composition of Acorn Quercus spp.

The nutritional composition of different acorn species (Q. pyrenaica, Q. robur, and Q. ilex) harvested in Peneda-Gerês Park, Braga (north of Portugal) was determined after being dehulled by different methods (manually, thermally by scalding with boiling water, and drying at 30 °C). Ash and protein contents remained unaltered, but the fat and carbohydrate contents increased and/or decreased depending on the dehulling method and Quercus spp. The thermal dehulling and dehulling by drying significantly increased the total fiber contents between 37-87% and 31-50%, whereas the energy values decreased between 3-10% and 3-7%, respectively. Resistant starch content decreased between 42-76% and 26-35% after thermal dehulling and dehulling by drying, respectively. The lipidic and amino acid profiles also remained unaltered after both dehulling methods, but elements and soluble sugars contents increased and/or decreased depending on the dehulling method and Quercus spp. The harvested dried acorns had significantly lower energy, fat, and fatty acid contents, but a higher carbohydrate content (more total fiber and resistant starch, and fewer sugars) when compared to commercial acorns (Q. suber and Q. ilex blend) from Alentejo (south of Portugal). Protein, amino acid, and ash contents were similar, but the harvested acorns had more potassium than the commercial ones.

Morphology and structure of acorn starches isolated by enzymatic and alkaline methods

Abstract Morphology and structure of starch from fruits of two acorns species, Quercus rotundifolia Lam. (QR) and Quercus suber Lam. (QS), isolated by enzymatic (ENZ) and alkaline (A3S) methods were studied. Acorn starches granules presented a round and oval shape, consisting of medium/small granules, with a mean granule size ranging between 9 and 13 µm. Isolated acorn starches appear as light grayish-brown in naked eye, with high values of L* for starches isolated by the ENZ method, and QR starches were duller than QS. No differences were observed for all the samples in FTIR spectra results. Acorn starches showed a C-type pattern, with a relative crystallinity between 43.1 and 46.6%. The 13C CP/MAS NMR spectra are different for the used isolation methods but are similar for both acorn species. However, acorn-isolated starches presented a predominant A-type allomorph packing type, and the A3S starches showed a higher degree of crystalline material. Those differences in the structure of acorn starches would be helpful to better understand the relationships among structure and functional properties for a possible potential industrial application of chestnut starches.

Body Size Plasticity of Weevil Larvae (Curculio davidi) (Coleoptera: Curculionidae) and Its Stoichiometric Relationship With Different Hosts.

Parasites obtain energy and nutrients from the host, and their body size is also usually limited by host size. However, the regulatory mechanisms that control the plasticity of parasite body sizes and the stoichiometric relationships with their hosts remain unclear. Here we investigated the concentrations of 14 elements (C, H, O, N, P, S, K, Na, Ca, Mg, Al, Fe, Mn, and Zn) in the acorns of three oak species (Quercus spp.), in their endoparasitic weevil (Curculio davidi Fairmaire) (Coleoptera: Curculionidae) larvae and in the larval feces, and the weight of weevil larvae within different hosts in a warm-temperate zone of China. Our results showed that the three acorn species exhibited significant differences in C, H, O, P, K, Mg, and Mn concentrations. However, in the weevil larvae, only P, Mn, and C:P ratio revealed significant differences. Weevil larvae preferentially absorbed and retained N, Zn, Na, and P, whereas Mn, K, Ca, and O were passively absorbed and transported. The weevil larvae weight was associated with acorn stoichiometry, and positively correlated with acorn size. Weevil larvae P decreased, but Mn and C:P increased with their weight, implying highly variable in somatic stoichiometry are coupled with the plasticity of body size. Interestingly, weevil larvae weight was negatively correlated with acorn infection rate, indicating small-size parasitic insects might have higher fitness level in parasite–host systems than larger-size ones. Our results suggest that variation in P, Mn, and C:P in parasites may play critical roles in shaping their body size and in improving their fitness.

Tick control bait box use by Peromyscus spp. influenced by habitat placement but raises questions on disease ecology

AbstractWhite‐footed mice, Peromyscus leucopus (Rafinesque), and deer mice, Peromyscus maniculatus Gloger, are considered important reservoir hosts for Borrelia burgdorferi sensu stricto, the causative agent of Lyme disease. Host‐targeted and nonlethal Select TCS bait boxes have been shown to be effective at killing ticks by delivering small doses of fipronil to wild Peromyscus spp., attracted to the provided bait. This results in reductions in the tick Ixodes scapularis, the vector of Borrelia burgdorferi, in the environment. However, habitat influences on bait box use, interactions with bait boxes, and overall use of bait by small mammals have not been evaluated. These factors may influence the use of this tick control measure. In the current study, bait box use by small mammals was evaluated at five field sites in Maryland, USA, during a two‐year study period. Bait consumption in relation to specific described habitats evaluated at each site was recorded, and bait nutrition was compared to nutrition from common northeastern acorn species. Rodent behavior around bait boxes was analyzed using camera traps as well. Bait boxes were used more frequently in herbaceous and shrub habitats than those placed in areas with bare ground or canopy cover alone. Significant amounts of bait were consumed throughout the study, but in some habitat types bait boxes were not used. The bait was found to be similar to native acorns in energy content, suggesting that it may serve as a supplement for natural foods which may have population dynamic implications. Behavioral analysis suggested that Peromyscus spp. foraged around bait boxes regardless of bait presence, but they did not forage in unbaited boxes as frequently. This may suggest the use of odors alone could be enough for attracting rodents to bait boxes potentially reducing the negative effects of baiting while maintaining protective tick control measures.

Elemental stoichiometry and compositions of weevil larvae and two acorn hosts under natural phosphorus variation

To understand how different trophic organisms in a parasite food chain adapt to the differences in soil nutrient conditions, we investigated stoichiometric variation and homeostasis of multiple elements in two acorn trees, Quercus variabilis and Quercus acutissima, and their parasite weevil larvae (Curculio davidi Fairmaire) at phosphorus (P)-deficient and P-rich sites in subtropical China where P-rich ores are scattered among dominant P-deficient soils. Results showed that elemental stoichiometry and compositions of both acorns and weevil larvae differed significantly between P-deficient and P-rich sites (p < 0.05), with the largest contribution of acorn and weevil larva P in distinguishing the stoichiometric compositions between the two site types. The two acorn species were statistically separated by their acorn elemental stoichiometry and compositions (p < 0.05), but no difference was observed on weevil larvae between the two acorn species. P was one of the few elements that were non strict homeostasis in both acorns and weevil larvae. These findings highlight the importance of both environmental influence in elemental stoichiometry and composition and physiological regulations of nutritional needs in organisms and provide possible stoichiometric responses of both plants and animals to P loading, a worldwide issue from excess release of P into the environment.

Acorn – weevil interactions in a mixed-oak forest: Outcomes for larval growth and plant recruitment

Weevils are the most important pre-dispersal acorn predators in the Mediterranean region, where oaks often form mixed forests and different weevil species can coexist. The performance of weevil larvae depends in great extent on their feeding activities inside the infested acorns that, in turn, are known to reduce the viability of acorns. In this paper, we have analysed the interactions among the weevil community and four oak species (Quercus pyrenaica, Quercus suber, Quercus faginea and Quercus ilex) coexisting in a Mediterranean mixed-oak forest. DNA sequencing of weevil larvae revealed four different weevil species (Curculio elephas, Curculio glandium, Curculio pellitus and Curculio venosus) infesting the acorns of the four oak species. Oak species differed in acorn size, and weevil species also differed in body size. Weevil species showed some degree of specificity among the four oak species, but specificity was not related to variations in acorn size. By contrast, larval development and seedling recruitment were mostly driven by inter-specific differences in larval and acorn size. Larger seeded species suffered less seed damages by weevils (i.e. embryo predation and cotyledon consumption), thus reducing the impacts of acorn infestation in seedling emergence and seedling size. Larval development for the largest weevil species C. elephas was constrained by cotyledon depletion in all acorn species. Yet, this pattern was not observed for other weevil species. Larval size of the same weevil species also varied among different oak species after controlling for the amount of cotyledon eaten by larvae, thus, variation of other acorn traits among acorn species (e.g. chemical composition) may also have consequences for the performance of weevil larvae. It is likely that other variables operating at population level, such as temporal and spatial changes in acorn production or phenological variations of weevils and oaks, are also implicated in the complex functioning of these outstanding mixed-oak forests where natural regeneration seems to be threatened.

The effect of starch isolation method on physical and functional properties of Portuguese nut starches. II. Q. rotundifolia Lam. and Q. suber Lam. acorns starches

A new starch was isolated from fruits of two acorn species, Quercus rotundifolia and Quercus suber by alkaline (A3S) and enzymatic (ENZ) methods and physical and functional properties were studied. The isolation method induced changes in most of those properties in the isolated starches, mainly in resistant starch content, syneresis, pasting, thermal and rheological properties. Isolated acorn starches presented high amylose content (53–59%) and resistant starch content (30.8–41.4%). Acorn starches showed limited and similar solubility values and swelling power values, showing a gradual increase from 60 °C to 90 °C. The pasting temperatures ranged from 67.5 to 72.0 °C and pastes did not present breakdown, which is suggestive of a high paste stability of acorn starches during heating. At ambient temperature the turbidity and syneresis values were low, but when held at freezing temperatures the syneresis significantly increased. Thermal analysis revealed that the acorn starches easily undergo transition phenomena as shown by the low To and enthalpy values (4.1–4.3 J/g), these effects were more evident in starches isolated by ENZ method. Pastes are more elastic than viscous and form strong gels after cooling. Q. suber starch was shown to be more sensitive to the effect of isolation method. Generally, starch isolated by enzymatic method presented less interesting functional properties, since this isolation procedure greater affected the raw structure of starches.

Does multiple seed loading in Blue Jays result in selective dispersal of smaller acorns?

Studies from both tropical and temperate systems show that scatter-hoarding rodents selectively disperse larger seeds farther from their source than smaller seeds, potentially increasing seedling establishment in larger-seeded plants. Size-biased dispersal is evident in many oaks (Quercus) and is true both across and within species. Here, we predict that intraspecifc variation in seed size also influences acorn dispersal by the Blue Jay (Cyanocitta cristata Linnaeus), but in an opposite manner. Blue Jays are gape-limited and selectively disperse smaller acorn species (e.g. pin oaks [Quercus palustris Münchh]), but often carry several acorns in their crop during a single dispersal event. We predict that jays foraging on smaller acorns will load more seeds per trip and disperse seeds to greater distances than when single acorns are carried in the bill. To test this, we presented free-ranging Blue Jays with pin oak acorns of different sizes over a 2-year period. In each of 16 experimental trials, we monitored the birds at a feeding station with remote cameras and determined the number of acorns removed and the distance acorns were dispersed when cached. Jays were significantly more likely to engage in multiple seed loading with smaller seeds in both years of the study. During the second year, these smaller acorns were dispersed farther than larger acorns, and during the first year, larger acorns were dispersed farther, revealing an inconsistent response to seed size during our study. We suggest that in some circumstances, multiple seed loading by Blue Jays may favor dispersal in some plant species.

Acorn dispersal estimated by radio-tracking

Bird-dispersed seeds are difficult to track, especially in the case of long-distance dispersal events. To estimate the oak dispersal distance and the seed shadow generated by the European jay (Garrulus glandarius), we inserted radio-transmitters in 239 acorns, placed them in bird-feeders and then located them by radio-tracking. Using this methodology we located the exact caching site of 94 Quercus ilex and 54 Q. suber acorns and determined the caching habitat characteristics (vegetation type, distance, spatial distribution). The results show that: (1) there is no differences in the dispersal distance distribution between the different acorn species or sizes, (2) dispersal distances range from approximately 3 m up to approximately 550 m (mean = 68.6 m; median = 49.2 m), (3) recently abandoned fields and forest tracks were the sites preferred by jays to cache acorns, whereas fields and shrublands were avoided and (4) seed shadows showed acorn aggregation zones (i.e. clusters of caches) close to the feeder as well as isolated caches at longer distances. The results also suggest that radio-transmitters are a cheap and reliable way to determine seed shadows and quantify both seed dispersal and post-dispersal seed predation for medium to large seeds.

Not only size matters: Acorn selection by the European jay (Garrulus glandarius)

Abstract A strong selection for acorn characteristics is expected to have evolved in the mutualistic relationship between the European jay (Garrulus glandarius) and the oak (Quercus spp.). Bossema's pioneer work suggested that jays do not select acorns randomly, but rather they preferentially select some size and species. Preference for some seeds over others may have implications on plant community dynamics by conferring advantages (or disadvantages) on the selected (avoided) seed characteristics. In this paper we test to what extent jays select acorns by species and/or by size and the relation between these two traits in Mediterranean oak species. The experiments consist of a set of field tests in which acorns from four different coexisting Mediterranean oak species (Quercus ilex, Quercus faginea, Quercus suber, and Quercus coccifera) were placed in artificial feeders accessible to wild jays. The acorns were previously measured to control individual acorn characteristics. Using video-recording techniques, we followed jay activity and the fate of each acorn (sequence of acorn selection and method of transport). Q. ilex acorns were preferred over other acorns, and Q. coccifera acorns were avoided when other acorns were available. Preference for Q. faginea and Q. suber acorns was intermediate, that is, they were preferred over Q. coccifera acorns but not over Q. ilex acorns. Large acorns were also preferred although acorn species selection was stronger than size selection. Jays selected species and size both by visual means and by using acorn area as an indicator of size. Acorns wider than 17–19 mm were carried in the bill because of throat limitation. Our results confirm Bossema's study on temperate oaks and extend it to Mediterranean oak species, revealing implications on mixed oak forest dynamics.

Rodent acorn selection in a Mediterranean oak landscape

AbstractQuercus suber, Quercus ilex and Quercus coccifera (Cork, Holm and Kermes oaks, respectively) are common evergreen oak species that coexist in the landscapes of the western part of the Mediterranean basin. Rodents are the main acorn predators and thus one of the main factors for understanding recruitment patterns in oaks. In this paper we analyse to what extent mice prefer acorns from one oak species over another in three oak species studied using acorn removal experiments and video tape recordings. Twenty labelled acorns from each of the three Quercus species (60 acorns) were placed in 40 cm×40 cm quadrats on each plot. Because selection might vary as a result of the vegetation context, we performed the trials in the five main vegetation types within the study area (four replicates in each vegetation type) in order to control for habitat influences on rodent acorn preferences (a total of 20 plots). The removal of 1,200 acorns occurred within 68 days. Mice removed 98.7% of the acorns. Q. ilex acorns were preferred over Q. suber and Q. coccifera in all vegetation types except in pine forest, where no acorn preferences were detected. Acorn removal rates differed with vegetation type, correlating positively with shrub cover. The distance at which acorns were displaced by rodents (mean =4.6 m±5.1 SD) did not differ between acorn species, but varied among vegetation types. Bigger acorns of Q. coccifera were selected only after Q. ilex and Q. suber acorns were depleted, while no size selection was detected for the latter two species. Thus, we conclude that rodents show preference for some oak acorns and that landscape context contributes significantly to rodent activities and decisions.

True Metabolizable Energy for Wood Ducks from Acorns Compared to Other Waterfowl Foods

Acorns of bottomland red oaks (Quercus spp.) are an important food of North American wood ducks (Aix sponsa). Barras et al. (1996) demonstrated that female wood ducks selected willow oak (Q. phellos) acorns over other species. We measured true metabolizable energy (TME) derived by captive, wild-strain, adult female wood ducks from acorns of willow oak, water oak (Q. nigra), cherrybark oak (Q. pagoda), and pin oak (Q. palustris) to determine whether female wood ducks' preference for willow oak acorns was related to TME. Estimates of TME within acorn species were relatively precise, yet we did not detect variation in TME among acorn species (P = 0.31); hence, we estimated TME across species (2.76 ± 0.033 [SE] kcal/g dry moss; n = 34). We concluded that TME apparently did not explain female wood ducks' preference for willow oak acorns and hypothesized that morphological characteristics of willow oak acorns may be proximate cues related to selection by wood ducks. We also summarized known TME estimates for acorns fed to wood ducks and mallards (Anas platyrhynchos), and natural and agricultural foods fed to mallards, northern pintails (A. acuta), blue-winged teal (A. discors), and Canada geese (Branta canadensis). We found that acorns and moist-soil plant seeds and tubers provided, on average, about 76% of the TME in agricultural seeds. Thus, bottomland-hardwood and moist-soil habitats have potential to provide significant amounts of dietary energy, as well as greater diversity of foods and nutrients than croplands. Researchers should continue to determine TME of common foods (plant and animal) of waterfowl, and use TME in estimating waterfowl habitat carrying capacity (e.g., Reinecke et al. 1989). Additionally, large-scale, reliable estimates of plant and animal food availability in bottomland-hardwood and moist-soil habitats are needed to evaluate carrying capacity of landscapes important to waterfowl, such as the Mississippi Alluvial Valley (MAV).

Hoarding behaviors of two wood mouse species: Different preference for acorns of two Fagaceae species

Two species of wood mouse, Apodemus argenteus and A. speciosus, were observed consuming and hoarding acorns of Quercus serrata and Castanopsis cuspidata. When each species of acorn was supplied individually, both species of mice used each species of acorn for eating and hoarding. When both species of acorn were supplied, A. argenteus consumed or hoarded only C. cuspidata, whereas A. speciosus tended to eat C. cuspidata acorns at the feeding site, and disperse or hoard Q. serrata acorns. Apodemus speciosus is unlikely to disperse C. cuspidata acorns (their utilization was biased towards consumption) when Q. serrata acorns are also available. Apodemus argenteus will make almost no contribution to the dispersal of Q. serrata when the two acorn species coexist.

Mycotoxin Occurrence in Oak Acorn Species Native to Tennessee

Agricultural plants and domestic animals are subject to mycotoxin contamination or infection, respectively, during unusually wet or dry growing seasons. This study was designed to assay mycotoxin levels in a major wildlife food source. Acorn and corn samples were collected at the Ames Plantation in Grand Junction, Tennessee, from both bottomland and upland regions. Samples were gathered during Fall 1998 after adroughty summer. Forty-eight acorn samples were tested, using thin-layer chromatography, for six different toxins at the Animal Disease Diagnostic Laboratory at Purdue University. This determined the concentrations and types of mycotoxins present in each sample. Two of the six toxins showed up regularly and at fairly high concentrations throughout the samples. Acorn samples closer to cornfields yielded higher frequencies of one of the toxins. Wildlife that eat these acorns are receiving levels of mycotoxins at least twice that of the recommended levels for any domestic animal. Further research needs to be conducted during a year when there is little or no environmental stress to see if the 1998 acorn samples showed unusually high levels of toxins. These toxins can pose a threat to wildlife, and more research should be carried out to test the extent to which wildlife are exposed to and damaged by these toxins.

Tannins and Partial Consumption of Acorns: Implications for Dispersal of Oaks by Seed Predators

-A common assumption in studies of seed predation is that seeds survive attack and are dispersed only 'when animals fail to find seeds, drop undamaged seeds or fail to recover seeds after they are cached. This study, however, suggests that many acorn consumers consistently eat only a portion of the cotyledon of several species of acorns and thereby permit embryo survival. Several vertebrates [gray squirrels (Sciurus carolinensis), common grackles (Quiscalus quiscula) and blue jays (Cyanocita cristata)] were observed to consume only 30-60% of the cotyledon from the basal portion (cap end) of willow oak (Quercus phellos) acorns. Gray squirrels exhibited a similar preference for the basal end of acorns of several other species of red oaks (Q. rubra, Q. laevis, Q. nigra, Q. palustris and Q. coccinea) from a wide geographic region. In addition, acorn weevil larvae (Curculio sp.) were observed significantly (>35%) more often in the basal portion than in the apical end of Q. alba acorns. Chemical analyses of acorns from two tree species revealed that the concentration of protein-precipitable phenolics (primarily tannins) was 12.5% (Q. phellos) and 84.2% (Q. laevis) higher in the apical portion of the seeds where the embryo is located. Moreover, germination experiments revealed equal or greater germination frequencies for partially consumed acorns than for intact acorns. We suggest that the higher tannin levels may render the apical portion less palatable, and thereby increase the probability of embryo survival after attack by seed consumers.

Selection of Nuts by Gray Squirrels and Optimal Foraging Theory

The choice of food by free-living gray squirrels (Sciurus carolinensis Gmelin) was determined by recording the selection of nuts from the natural nutfall of four species of nut-bearing trees, where abundance of nuts of each species was determined by sampling. The rate of energy intake the squirrels achieved while consuming nuts of the four species was measured separately. The ranking of the three species of acorns by use-availability ratios was the same as the ranking of the acorns by the rate of energy intake. However, hickory nuts were consumed disproportionately even though they gave a low rate of energy intake. Foraging models based on maximizing the rate of energy intake do not predict the preference for hickory nuts. The incorporation of nutrient constraints or risk minimization may be necessary to accommodate the models to observation when the foods available to the consumer differ in composition.

Patch by Gray Squirrels and Optimal Foraging

The use of a naturally patchy distribution of tree seeds by gray squirrels was investigated. In most patches the acorn species allowing the highest rate of energy intake was consumed disproportionately in relation to its low abundance. Foraging was particularly intense in patches where an acorn species offering a lower rate of energy intake was abundant. Calculations made with a model of optimal foraging show that these heavily used patches were those yielding high patch—specific rates of energy intake. The squirrels selected patches yielding high rates of energy intake even though these patches were not sites of concentration of the preferred food.

Acorn Consumption by Chipmunks and White-Footed Mice

During the course of an investigation of factors affecting oak mast production, considerable attention was directed toward determining the biotic agencies responsible for the utilization of the fall acorn crop. Particular emphasis was focused on the possible influence of certain small mammals in competing with game animals for this food. In order to adequately interpret the extent of acorn competition, a controlled feeding study was initiated in mid-October, 1952, and continued to mid-November. Five wild eastern chipmunks (Tamias striatus rufescens) and four white-footed mice (Peromyscus leucopus noveboracensis) were live-trapped in the vicinity of East Lansing, Michigan, for use as test animals and confined in cages. Four species of acorns, previously collected and examined for soundness, were the only food available during the tests, and these were fed periodically depending upon the quantity of uneaten food remaining. During the aggregate 98 chipmunk-days of feeding, the average consumption was 6.1 acorns per animal per day, based on a total of 600 acorns eaten (Table 1). Only slight variations from this mean were noted; a high daily average of 6.8 acorns for one animal was probably the result of greater energy expenditure, since this animal had use of a rotary exerciser cage. The lowest individual consumption, averaging 5.3 acorns per day, appeared to result from a distaste for red oak (Quercus rubra) acorns rather than a lower food requirement.