Variation In Diet Composition Research Articles

The distinct mechanism regulating taurine homeostasis in mice: Nutrient availability affects taurine levels in the liver and energy restriction influences it in the intestine

AimsOur previous findings indicate that caloric restriction (CR) stimulates the production and secretion of taurine-conjugated bile acids in mice. Subsequent processing by gut microbiota leads to increased levels of deconjugated bile acids, taurine, and various taurine conjugates in the intestine. Furthermore, we demonstrated that carbohydrate restriction and protein restriction, to a smaller extent, mirror the impact of CR in terms of hepatic production of bile acids but not their secretion. We hypothesized that modulating dietary macronutrient levels would influence taurine homeostasis in the liver and intestine of ad libitum-fed and CR animals. Materials and methodsAd libitum-fed male mice were allocated to receive either a control, low-protein (LP), low-fat (LF), or low-carbohydrate (LC) diet. Meanwhile, CR groups were given 80 % of their regular voluntary food intake as a control, high-protein (HP), high-fat (HF), or high-carbohydrate (HC) diet. Key findingsWhile CR did not affect the taurine levels and its conjugates in the liver, alteration in carbohydrates and protein intake impacted it. Conversely, in the intestine, CR increased the amount of free and conjugated taurine, whereas the various diets did not affect it or disrupt the CR-specific phenotype. Notably, variations in diet composition impacted the expression of the taurine transporter (Slc6a6) and glutathione-S transferases (GST) in the intestine as well as cysteine dioxygenase (Cdo) in the liver. SignificanceThe liver and the intestine show distinct responses to dietary interventions, with hepatic taurine being affected by the diet composition, while intestinal taurine is governed by energy availability.

Prey diversity in the deep ocean: metabarcoding feeding ecology of the commercially important queen snapper in the US Caribbean

The queen snapper, Etelis oculatus, is experiencing a growing fishery presence across the wider Caribbean, yet our understanding of its distribution, biology, and ecology remains limited. To address this gap, we investigated the feeding ecology of this demersal deep-water snapper using two molecular approaches: single-species barcoding and multispecies metabarcoding. Between November 2019 and July 2020, we collected 157 queen snapper from seven locations along the west coast of Puerto Rico. Our analysis identified a diverse array of prey items in the stomachs, comprising 61 species from 31 families, 18 orders, and 38 genera. Our findings suggest that E. oculatus is a large carnivore, primarily preying on squids, shrimps, and deep-water fishes. Notably, common fish prey included Diaphus brachycephalus, D. dumerilii, Dasyscopelus selenops, Coccorella atlantica, Sigmops elongatus, and Zaphotias pedaliotus. In contrast, prevalent invertebrate prey consisted of Abralia veranyi, Doryteuthis pealeii, Abralia redfieldi, Oplophorus gracilirostris, and Systellaspis debilis. Although our data suggest potential variation in diet composition across locations, definitive conclusions remain elusive. However, we observed heightened prey richness at seamount Pichincho, possibly attributable to the high structural complexity of the karst terrain on the seafloor. Additionally, we noted variation in prey species composition across size classes, with certain species more prevalent in larger or smaller queen snapper. Given the challenge of examining the prey of deep-water fish species, our study showcases the utility of both single-species barcoding and multispecies metabarcoding methodologies in characterizing the dietary range of queen snapper and similar demersal deep-water carnivorous fishes. The multispecies metabarcoding approach, in particular, offers a rapid, comprehensive, and effective means of identifying prey species. As the commercial value of the queen snapper continues to rise, our investigation into its feeding behavior provides critical baseline information for future species management efforts. By enhancing our understanding of its ecological dynamics, we aim to contribute to informed conservation and sustainable fisheries practices in the region.

Seasonal variation in the food composition of the Bolkar Mountain Viper, Montivipera bulgardaghica (Nilson & Andren, 1985), in the Central Taurus Mountains, Anatolia

The Bolkar Mountain Viper, Montivipera bulgardaghica (Nilson & Andren, 1985), is a mountain viper found in the eastern Mediterranean region. In this study, we present data on the seasonal variation in diet composition across two different habitats in the Central Taurus Mountains of Anatolia, Türkiye. The Karboğazı population inhabits a subalpine shrubland, while the Göller Yaylası population resides in forested land. The vipers primarily consumed Lacertidae (47%), followed by Orthoptera (27%), Chilopoda (18%), and Scincidae (8%) in number. In spring, the diet of the Karboğazı population was mainly composed of Lacertidae but shifts toward Orthoptera during summer and autumn. In contrast, the Göller Yaylası population fed on Lacertidae throughout the entire active season. Overall, the Karboğazı population primarily consumed invertebrates, whereas the Göller Yaylası population predominantly fed on lizards. Both populations exhibited partial niche overlap. There was no significant difference in diet composition between sexes, but prey type and quantity varied with the season. Prey diversity increased in summer and decreased in autumn and spring, corresponding with the prey availability in the environment.

Variation of parental and chick diet in opportunistic insectivorous European Bee-eaters

Insectivorous Palaearctic bird species associated with open habitats rely on high prey abundances, which are currently declining due to habitat loss and intensive agricultural practices. The European Bee-eater (Merops apiaster) is an opportunistic insectivore of open habitats, preying mainly on medium to large-sized flying insects. Its diet composition received some attention in the past, but the current variation in diet composition of birds breeding across different habitats, and between adults and chicks remains poorly known. In this study, we determine variation in bee-eaters’ diet in colonies located in five common habitats at the Iberian Peninsula. We also assess differences in the diet composition of chicks and adults and investigate seasonal diet selectivity of adults. Finally, we explore the variability in the size of prey provided to chicks throughout their growth period. Hymenoptera and Coleoptera were the most important groups for bee-eaters, with adults and chicks consuming 58.8% and 64.1% of hymenopterans and 37.6% and 28.6% of coleopterans, respectively. The proportion of Hymenoptera (42.3–55.7%) and Coleoptera (43.3–53.5%) in the diet was similar in colonies in pasture and oak habitats. But Hymenoptera dominated (83.8% and 95.7%) in meadow and mixed forest colonies. Despite being a generally opportunistic predator, adult bee-eaters provide their progeny with an increasing proportion of larger insects through chick development. Moreover, they equally take Hymenoptera and Coleoptera for themselves and their chicks, even when the abundance of these insects decreases seasonally. Overall, these results suggest that local prey availability associated with specific habitats influences diet composition and that regional declines in certain groups may, therefore, affect insectivore species differently according to their dietary and habitat preferences.

Long-term anthropogenic drivers of diet composition and niche breadth in an endangered avian scavenger: The scant role of sanitary regulations

The widespread and accelerated transformation experienced by our planet results in populations of endangered species having to survive in highly-altered environments and increasingly relying on resources provided by human subsidies. Presently, vultures rank among the most imperiled functional groups of large vertebrates globally, a situation that is largely attributed to the rapid intensification of agriculture and the subsequent transformation of farming practices and agro-grazing landscapes. Hence, documenting the long-term fluctuations in the vultures’ dietary patterns in response to environmental changes, particularly in livestock management, is of utmost significance. Here, by means of bulk stable isotope analysis (δ13C and δ15N), we examined long-term variations in diet composition and niche breadth in a population of the endangered Egyptian vulture (Neophron percnopterus) in the north of the Iberian Peninsula. We specifically focused on the effect of European sanitary regulations enacted in 2014, which allow sheep farmers to abandon livestock remains for consumption by scavenging birds, except for pig carcasses. We found that the implementation of these new regulations did not cause a change in the diet of vultures. Changes were only detected in scrubland areas and were driven by an increase in the consumption of wild rabbit which, in turn, lead to expansion of the trophic niche. These results indicate that these endangered vultures are heavily dependent on food sources derived from intensive farming, mostly of pigs illegally disposed in the wild, and moreover, highlight the importance of carcasses of small vertebrates, often disregarded in conservation programs in favor of the contribution of livestock remains. Our research provides valuable insights into the spatiotemporal dynamics of trophic strategies among avian scavengers, specifically in the context of changes resulting from intensified human-pressures on agro-grazing Mediterranean landscapes.

Dietary habits of fishing cats in a human-dominated wetland in Coastal Thailand

Abstract. Wongson T, Khaewphakdee S, Mongkonsin W, Serieys LEK, Wong W-M, Yindee M, Pattanarangsan R, Suksavate W, Promkuntod P, Klakhaeng C, Sukmasuang R. 2024. Dietary habits of fishing cats in a human-dominated wetland in Coastal Thailand. Biodiversitas 25: 2788-2797. Fishing cats, intimately connected to wetland habitats, face an escalating threat from human activities and environmental change. With its significant findings, this study offers a comprehensive insight into the dietary habits of fishing cats in a human-dominated wetland in coastal Thailand. By examining the scats of 192 fishing cats (Prionailurus viverrinus Bennett 1833) and the remains of 328 prey items, we detailed the fishing cat's diet and assessed its seasonality. Consequently, we identified 16 prey species consumed by fishing cats during the study period. The primary prey was fish, followed by rodents, birds, Indo-Chinese rat snakes (Ptyas korros (Hermann Schlegel 1837)), insects, crabs, and snails. The most crucial prey was the climbing perch (Anabas testudineus Bloch 1792) (n=69), followed by bandicoot rats (Bandicota indica Bechstein, 1800) (n=54), domestic chicken (Gallus gallus Linnaeus 1758) (n=48), and snakehead murrel (Channa striata Bloch 1793) (n=38). The niche breadth index indicated the highest specialization during the summer, while the dietary diversity index was 0.44, 0.52, and 0.38 during the summer, rainy, and winter seasons, respectively. Seasonal variations in dietary composition were not statistically significant. The niche overlap index was 0.95 between the summer and the rainy season, 0.91 between the rainy season and winter, and 0.87 between the summer and winter. These findings, with their direct implications for the conservation of fishing cats, highlight the urgent need for effective land-use management in species preservation.

Properties of vertebrate predator-prey networks in the high Arctic.

Predation is an important ecological process that can significantly impact the maintenance of ecosystem services. In arctic environments, the relative ecological importance of predation is thought to be increasing due to climate change, partly because of increased productivity with rising temperatures. Therefore, understanding predator-prey interactions in arctic ecosystems is vital for the sustainable management of these northern regions. Network theory provides a framework for quantifying the structures of ecological interactions. In this study, we use dietary observations on mammalian and avian predators in a high arctic region, including isolated peninsulas on Ellesmere Island and north Greenland, to construct bipartite trophic networks. We quantify the complexity, specialization, and nested as well as modular structures of these networks and also determine if these properties varied among the peninsulas. Mammal prey remains were the dominant diet item for all predators, but there was spatial variation in diet composition among peninsulas. The predator-prey networks were less complex, had more specialized interactions, and were more nested and more modular than random expectations. However, the networks displayed only moderate levels of modularity. Predator species had less specialized interactions with prey than prey had with predators. All network properties differed among the peninsulas, which highlights that ecosystems often show complex responses to environmental characteristics. We suggest that gaining knowledge about spatial variation in the characteristics of predator-prey interactions can enhance our ability to manage ecosystems exposed to environmental perturbations, particularly in high arctic environments subject to rapid environmental change.

Variation in dietary composition of the Banna fanged frog (Limnonectes bannaensis Ye, Fei, Xie & Jiang, 2007) from Vietnam

Abstract The Banna fanged frog (Limnonectes bannaensis) is known from China, Laos, and Vietnam; however knowledge about the natural history and dietary requirements of this species is virtually lacking. In this study, we provide data on the variation in dietary composition of L. bannaensis based on stomach-flushing of 117 individuals (41 males and 76 females) captured and subsequently released during our recent field work in Son La Province, northwestern Vietnam. A total of 19 prey categories with 513 items, comprising 502 items of invertebrates, seven items of vertebrates, and four unidentified items were found in the stomachs of L. bannaensis. The most important groups among the prey of L. bannaensis were Coleoptera (38.04%), followed by Hymenoptera (9.31%), Araneae (7.93%), Polydesmida (7.07%), Orthoptera (6.37%), Hemiptera (5.23%), and Lepidoptera (5.01%). Adult males (16 prey categories) consumed preys with slightly lower diversity than adult females (17 prey categories). There was 88.25% overlap in the diet between males and females and in both sexes the trophic spectrum was similar, predominantly consisting of Coleoptera, Polydesmida, Araneae, Hymenoptera, Orthoptera, Lepidoptera, and Hemiptera.

Diet of the Invasive Atlantic Blue Crab Callinectes sapidus Rathbun, 1896 (Decapoda, Portunidae) in the Guadalquivir Estuary (Spain)

The Atlantic blue crab Callinectes sapidus (Decapoda, Portunidae) Rathbun, 1896 is native to the east coasts of North and South America and has recently expanded its distribution in the non-native range into the Gulf of Cadiz (SW Iberian Peninsula, Europe). Considering the impacts caused by this invasive species in numerous estuarine ecosystems and its generalist feeding behavior, this study aims to provide the first account of the Atlantic blue crab diet on the East Atlantic coast. We studied the species’ feeding habits using stomach content analyses to predict food web interactions and putative impacts. Samples were obtained in the Guadalquivir estuary (SW Spain, Europe), which was colonized in 2017. The main food items identified on their stomach were, fish (49.9%), mollusks (44.4%) and crabs (32.3%). They also consumed plant material (27.2%), and the sediment (32.3%) in their digestive tract was likely the result of secondary ingestion. The Atlantic blue crab exhibited the same omnivorous behavior as in the native area. There was no sexual variation in diet composition or feeding activity in general, but there was a seasonal variation in the diet composition of females. The decrease of the caramote prawn Penaeus kerathurus (Forskål 1775) observed in the Guadalquivir estuary since 2021 is likely not due to the Atlantic blue crab because they seldomly eat this prey. Overall, our study provides clear baseline information to expand the knowledge about the ecological roles of the Atlantic blue crab in non-native ecosystems.

Variation of the Montezuma Quail's Diet in Arizona, New Mexico, and Texas

The Montezuma quail (Cyrtonyx montezumae) is a game bird that inhabits oak-juniper-pine savannas of Arizona, New Mexico, and Texas, extending its range south into montane grasslands of Mexico. The species occurs within a complex matrix of public and private rangeland in which land management regimes and habitat quality are disparate. Given that food limitation can be a driver of wildlife populations, studies of the Montezuma quail diet can inform the management of its habitat. Our objective was to determine the composition and variation of the Montezuma quail's diet in Arizona, New Mexico, and Texas by macrohistological analysis of crops (n = 175) collected in 2016−2020 during winter in all three states and during spring in Texas. We used Dirichlet regression to determine the effects of ecological factors on diet composition. Winter diet in Arizona was mainly represented by woodsorrel bulbs (Oxalis spp.; 35.22% of dry weight), sedge rhizomes and bulbs (Cyperus spp.; 30.92%), and acorns (Quercus spp.; 7.17%). Winter diet in New Mexico consisted mainly of sedge bulbs (64.13%), bushbean seeds (Macroptilium sp.; 15.82%), and Hall's panicum seeds (Panicum hallii; 10.11%). Winter diet in Texas was composed of sedge rhizomes and bulbs (28.17%), Texas snoutbeans (Rhynchosia senna; 22.49), Hall's panicum seeds (19.54%), and wild onions (Allium spp.; 8.58%). Spring diet in Texas included sedge rhizomes and bulbs (67.90%), woodsorrel bulbs (19.49%), and Texas snoutbeans (5.55%). Geographic variation in diet composition was related to climatic, ecological, and intrinsic factors. For instance, in addition to being consumed by males at a higher rate, woodsorrel bulbs were also consumed at a greater rate in hotter and wetter locations. Along with novel information about the Montezuma quail diet in Texas, our investigation will stimulate questions relevant to rangeland and wildlife management, including determinants of habitat quality and the effects of climate change on wildlife populations.

Long-term effects of 3-nitrooxypropanol on methane emission and milk production characteristics in Holstein-Friesian dairy cows

The objective was to determine the long-term effect of 3-nitrooxypropanol (3-NOP) on CH4 emission and milk production characteristics from dairy cows receiving 3-NOP in their diet for a full year, covering all lactation stages of the dairy cows. Sixty-four late-lactation Holstein-Friesian cows (34% primiparous) were blocked in pairs, based on expected calving date, parity, and daily milk yield. The experiment started with an adaptation period of 1 wk followed by a covariate period of 3 wk in which all cows received the same basal diet and baseline measurements were performed. Directly after, cows within a block were randomly allocated to 1 of 2 dietary treatments: a diet containing on average 69.8 mg 3-NOP/kg DM (total ration level, corrected for intake of nonsupplemented GreenFeed bait) and a diet containing a placebo. Forage composition as well as forage-to-concentrate ratio altered with lactation stage (i.e., dry period and early, mid, and late lactation). Diets were provided as a total mixed ration, and additional bait was fed in GreenFeed units (C-Lock Inc.), which were used for emission measurements. Supplementation of 3-NOP did not affect total DMI, BW, or BCS, but resulted in a 6.5% increase in the yields of energy-corrected milk and fat- and protein-corrected milk (FPCM). Furthermore, milk fat and protein as well as feed efficiency were increased upon 3-NOP supplementation. Overall, a reduction of 21%, 20%, and 27% was achieved for CH4 production (g/d), yield (g/kg DMI), and intensity (g/kg FPCM), respectively, upon 3-NOP supplementation. The CH4 mitigation potential of 3-NOP was affected by the lactation stage dependent diet to which 3-NOP was supplemented. On average, a 16%, 20%, 16%, and 26% reduction in CH4 yield (g/kg DMI) was achieved upon 3-NOP supplementation for the dry period, and early, mid, and late-lactation diets, respectively. The CH4 mitigation potential of 3-NOP was affected by the length of 3-NOP supplementation within a lactation stage dependent diet and by variation in diet composition within a lactation stage dependent diet as a result of changes in grass and corn silage silos. In conclusion, 3-NOP reduced CH4 emission from cows receiving 3-NOP for a year, with a positive effect on production characteristics. The CH4 mitigation potential of 3-NOP was influenced by diet type, diet composition, and nutrition value, and the efficacy of 3-NOP appeared to decline over time but not continuously. Associated with changes in diet composition, increased efficacy of 3-NOP was observed at the start of the trial, at the start of a new lactation, and, importantly, at the end of the trial. These results suggest that diet composition has a large effect on the efficacy of 3-NOP, perhaps even larger than the week of supplementation after first introduction of 3-NOP. More studies are needed to clarify the long-term effects of 3-NOP on CH4 emission and to further investigate what influence variation in diet composition may have on the mitigation potential of 3-NOP.

Biology of Length-weight and Feeding in Juveniles and Adults of Air-breathing Perch <i>Anabas testudineus</i> (BLOCH)

The biology of feeding and growth pertaining to seasonal variations in diet composition, length-weight relationship and condition factor of Anabas testudineus was studied for a period of one year in two size group fishes (Group I: juveniles of <100 mm and Group II: adults of >100 mm). The length-weight relationship of the fish for Group I was W=0.00849 L3.2168 and for Group II was W=0.00877 L3.1502. The relative condition factor fluctuated from 1.032 to 1.372 indicating a significant variation (p < 0.05) in two size groups. The feeding intensity was maximum during October to December. Diet composition indicated the highest occurrence of insects followed by crustaceans and decayed organic matter. It also showed variations in different size group of fishes.

Spatiotemporal variability in diet composition of Greenland halibut (Reinhardtius hippoglossoides) from the eastern Canadian Arctic.

Greenland halibut (Reinhardtius hippoglossoides) sustain one of the most lucrative fisheries in the eastern Canadian Arctic and Labrador Sea. This species also plays an important role in food web connectivity and benthic-pelagic coupling. Despite the relatively rich knowledge of this species, R. hippoglossoides ecology in these specific areas remains poorly understood. The main aim of this study was to characterize the diet of this deepwater fish in the Labrador Sea and Davis and Hudson Straits and characterize the predator-prey relationship with northern shrimp (Pandalus borealis), another commercially important species in the region. Stomach contents analyses were conducted on 1199 fish captured from 2018 to 2020. Small specimens (<20 cm) fed on invertebrates, whereas larger individuals (>60 cm) fed primarily on fish, indicative of size-related changes in diet composition. The relative abundance of Pandalus shrimp species in the environment was reflected in the diet. Location appeared to be the most influential variable on feeding patterns. Distinct oceanographic conditions among areas, resulting in differences in prey availability, could explain these results. Arctic cod (Boreogadus saida) and redfish (Sebastes sp.) were selected in locations where fish prey were the most abundant. These results shed light on the opportunistic nature of R. hippoglossoides and its preference for fish at large size. With the rapidly changing oceanographic conditions of Arctic waters, a distributional change in the biomass of shrimp is expected. Results suggest that an increase in abundance of predatory groundfish species in the system (e.g., Sebastes sp.) could lead to acute predation on shrimp and competition with R. hippoglossoides. By revealing key trophic links within the demersal ecosystem, this work provides valuable information on the development of ecosystem approaches to fisheries management for the region.

DNA metabarcoding reveals seasonal changes in diet composition across four arthropod-eating lizard species (Phrynosomatidae: Sceloporus).

Diet composition and its ecological drivers are rarely investigated in coexisting closely related species. We used a molecular approach to characterize the seasonal variation in diet composition in four spiny lizard species inhabiting a mountainous ecosystem. DNA metabarcoding revealed that the lizards Sceloporus aeneus, S. bicanthalis, S. grammicus, and S. spinosus mostly consumed arthropods of the orders Hemiptera, Araneae, Hymenoptera, and Coleoptera. The terrestrial lizards S. aeneus and S. bicanthalis mostly predated ants and spiders, whereas the arboreal-saxicolous S. grammicus and saxicolous S. spinosus largely consumed grasshoppers and leafhoppers. The taxonomic and phylogenetic diversity of the prey was higher during the dry season than the rainy season, likely because reduced prey availability in the dry season forced lizards to diversify their diets to meet their nutritional demands. Dietary and phylogenetic composition varied seasonally depending on the species, but only dietary composition varied with altitude. Seasonal dietary turnover was greater in S. spinosus than in S. bicanthalis, suggesting site-specific seasonal variability in prey availability; no other differences among species were observed. S. bicanthalis, which lives at the highest altitude in our study site, displayed interseasonal variation in diet breadth. Dietary differences were correlated with the species' feeding strategies and elevational distribution, which likely contributed to the coexistence of these lizard species in the studied geographic area and beyond.

Seasonal and spatial variations in the diet of the Egyptian mongoose in its north-eastern Iberian range edge

The Egyptian mongoose (Herpestes ichneumon) is considered a generalist and opportunistic predator whose European distribution is restricted to Iberia. However, all the previous studies on the Egyptian mongoose’s diet in the Iberian Peninsula have been performed in Portugal and Doñana National Park (southwestern Spain), covering a small region of the species’ current distribution. To improve the knowledge on the trophic ecology of the species, we estimated the feeding habits of the Egyptian mongoose in central Spain, its north-eastern range edge. Our study was based on the analysis of (1) scats (n = 251) and (2) stomach contents (n = 32); samples were collected between 2018 and 2022. We calculated the relative frequency of occurrence (%RFO) and the percentage consumed biomass (%CB) for 12 food groups across central Spain and we assessed site-seasonal variations in diet composition in three study areas. We also estimated rabbit densities in the three study areas to assess the effect of rabbit abundance on mongoose diets. Overall, our results showed that European rabbits were the group with highest %CB (30.7%) in the diet of the Egyptian mongoose, followed by reptiles (19.9%) and small mammals (19.9%). In the intensively studied areas, the %CB of rabbits was the highest in the area with the highest abundance of this prey, whereas reptiles had the highest %CB in the area with the lowest availability of rabbits. Diet diversity (Shannon index) varied between 1.73 and 2.47 in those areas and was inversely related to the availability of rabbits. Our results confirm the dietary flexibility of this predator that adapts its diet to the relative availability of different prey species in different habitats.

Length–weight relationship and seasonal variations in diet composition of whiting (Merlangius merlangus) in the South-eastern Black Sea

ABSTRACT The sex ratio, length–weight relationship (LWR) and diets based on stomach contents of whiting (Merlangius merlangus) were investigated in the south-eastern Black Sea, Turkey. A total of 3507 females (7.5–24.0 cm), 1602 males (9.4–20.0 cm), and 78 unidentified sex (5.5–16.5 cm) whiting were caught during monthly sampling from February to December 2017. The sex ratio was dominated by females, and their ratio (♀:♂, 1:0.46) significantly deviated from 1:1. The LWR indicated a negative allometric growth for males, while females had a positive allometric growth pattern. The stomach content analysis based on the relative importance index (IRI%) indicated exclusively piscivorous diets dominant by Sprattus sprattus and Engraulis encrasicolus made up more than 91 IRI% of the total diets of M. merlangus. The modified Costello-Amundsen’s graphical analyses evinced the specialized feeding strategy of M. merlangus throughout this study. The contribution of these two preys to the diets of M. merlangus showed considerable seasonal variations that were totally dependent on their abundance. Sprattus sprattus contributed to more than 98% of the total diets during June, July and August, while in the following months, E. encrasicolus appeared to take its position. Based on fish size, a general trend of a rise in prey diversity was found with increasing fish size. Also, the contribution of S. sprattus tended to decrease with increasing predator size, which is replaced by a rise in E. encrasicolus contribution. Hence, larger M. merlangus predominantly fed on E. encrasicolus while smaller size predators preferred to feed on S. sprattus.

Does variation in plant diversity and abundance influence browsing intensity in black rhinos?

AbstractVariations in forage availability, selection and preferences can lead to intense foraging competition and depletion of food consequently lowering diet quality and population performance of black rhino species. This study investigated seasonal variations in rhino diet, foraging, preference and browsing intensity and how this is influenced by plant diversity and availability in Mkomazi National Park (MKONAPA). Fifty‐eight square grids were randomly selected in each season, and plots were laid for vegetation assessment during wet and dry seasons in the sanctuary. Browsed species by rhinos were compared with rhino feeding data from fourteen rhino range areas within Africa. More than 85% of species edible in MKONAPA were similar to those in rhino range areas. Acalypha ornata, Grewia similis and Commiphora africana were highly utilised specie in both seasons. Diversity and abundance of consumed browses decreased towards the dry season while browsing intensity increased with forage preference in both seasons and was prominent when browse availability was low in dry seasons. Our study established seasonal variation in dietary composition, browsing intensity and preferences for black rhinos. We suggest establishing nutritional composition of preferred forages, assessing density of competitor browsers, translocating excess rhinos or expanding the sanctuary to meet the recommended ecological carrying capacity.

Intraguild predation is increased in areas of low prey diversity in a generalist predator community.

Niche differentiation and intraguild predation (IGP) can allow ecologically similar species to coexist, although it is unclear which coexistence mechanism predominates in consumer communities. Until now, a limited ability to quantify diets from metabarcoding data has precluded the use of sequencing data to determine the relative importance of these mechanisms. Here, we pair a recent metabarcoding quantification approach with stable isotope analysis to examine diet composition in a wolf spider community. We compare the prevalence of resource partitioning and IGP in these spiders and test whether factors that influence foraging performance, including individual identity, morphology, prey community and environmental conditions, can explain variation in diet composition and IGP. Extensive IGP is likely the primary coexistence mechanism in this community, and other factors to which foraging variation is often attributed do not explain diet composition and IGP here. Rather, IGP increases as prey diversity decreases. Foragers are driven to IGP where resource niches are limited. We highlight the need to examine how drivers of predator-prey interaction strengths translate into foraging in natural systems.

Relationships among total mixed ration nutritional components and reproductive performance in high-producing dairy herds

The main objective of the present study was to determine whether composition of total mixed ration influences reproductive performance in high-producing commercial dairy farms. Dairy producers and nutritional consultants from 48 dairy farms located in Wisconsin agreed to provide reproductive data and dietary information on high milk production pens during the main breeding period for the previous 12 mo. Dietary components (percentage of dry matter) were crude protein (CP), rumen degradable (RDP) and undegradable (RUP) protein, neutral detergent fiber (NDF), nonfiber carbohydrates (NFC), starch, and fat. Reproductive data were service rate (SR), overall pregnancy per artificial insemination (P/AI) and P/AI at the first service, 21-d pregnancy rate (PR), days open, and percentage of cows pregnant by 150 d in milk (PREG150). Participating herds had lactating Holstein cows (range = 143 to 2,717) housed in freestall facilities. Statistical analyses were performed with CORR and GLIMMIX of SAS (SAS Institute Inc.). Daily average milk production of herds was 38.9 ± 0.60 kg/d (30.0 to 50.4 kg/d). Overall SR was 58.5% (39–73) and P/AI was 36.1% (22–49). Overall 21-d PR was 20.3% (10–42%). Correlation between SR and PR was 0.59, whereas correlation of overall P/AI and P/AI at first service with PR were both 0.72. Similarly, for PREG150, correlation with overall P/AI (0.63) and P/AI at first service (0.66) were greater than with SR (0.48). There was large variation in diet composition, with CP varying from 16.0 to 18.7%, NDF from 24.9 to 35.1%, NFC from 31.7 to 46.6%, starch from 20.1 to 30.8%, and fat from 3.1 to 6.7%. Overall, there were no detectable associations of CP, RDP, and RUP with reproductive measures. The strongest relationship was a decrease in reproductive performance with increasing dietary NFC including overall P/AI (−0.48), P/AI at first service (−0.51), and PREG150 (−0.33). Starch also had a negative relationship with P/AI at first service (−0.35). Conversely, greater NDF was positively associated with P/AI at first service (0.34). Fat content was also positively associated with P/AI at first service (0.34). When NFC was divided in tertiles (<40, 40 to 42.2, and >42.2% NFC), the highest tertile had lower overall P/AI (39 vs. 36 vs. 31%), P/AI at first service (43 vs. 40 vs. 33%), and PREG150 (54 vs. 53 vs. 47%). In conclusion, farms with greater dietary NFC may have compromised reproductive performance. Correspondingly, herds with greater NDF content may achieve high milk production with potentially positive associations with reproduction. Other relationships of dietary components on reproduction were not as obvious in this herd-level analysis.

Immune Responses of the Black Soldier Fly Hermetia illucens (L.) (Diptera: Stratiomyidae) Reared on Catering Waste.

The black soldier fly (BSF), Hermetia illucens L. (Diptera: Stratiomyidae), has a great bioconversion potential and ability to develop on diverse substrates. Although the use of catering waste and food by-products containing meat and fish would reduce the footprint of the insect sector, to date, in Europe, their use is still facing legal obstacles for insects as food and feed. Since a major request from the EU insect sector is to diversify the spectrum of allowed substrates, and considering that variations in diet composition could influence insect immune responses, we evaluated the impact of different catering wastes on BSF prepupae immunity. Insects were reared on five diets: one based on feed for laying hens and four based on catering waste containing (i) fruits and vegetables; (ii) fruits, vegetables and bread; (iii) fruit, vegetables, bread and dairy products; (iv) fruits, vegetables, bread, meat and fish. The gene expression of two antimicrobial peptides (AMPs), one defensin and one cecropin, was assessed. Moreover, the hemolymph inhibitory activity against Escherichia coli DH5α and Micrococcus yunnanensis HI55 was evaluated using diffusion assays in solid media. The up-regulation of both AMPs' encoding genes was observed in insects fed a bread-added and dairy product-added diet. All hemolymph samples showed inhibitory activity against both bacteria, affecting the colony size and number. The obtained results show how catering waste positively influences the H. illucens immune system. The possibility of modulating AMP expression levels through the diet opens up new perspectives in the management of insect health in mass rearings.