Diet Composition Research Articles

Seasonal changes in invertebrate diet of breeding black-necked cranes (Grus nigricollis).

Invertebrates greatly support the growth, development, and reproduction of insectivorous birds. However, the influence of human activity (e.g., pesticide use, deforestation, and urbanization) inevitably leads to a decrease in global arthropods. The diversity and variation in invertebrate diet influence the food composition of birds, especially species living in rapidly changing environments, such as the Tibetan Plateau. However, little is known of the seasonal variation in invertebrate diet in response to environmental changes. Here, we characterized the invertebrate diet composition in pre- and post-breeding black-necked crane (Grus nigricollis) using fecal metabarcoding. We identified 38 invertebrate genera; the top three were Tipula (82.1% of relative abundance), Ceramica (3.0%), and unclassified_Hymenoptera (2.5%), with Tipula predominated the diet in both seasons. We also observed 20 and 16 unique genera in the pre- and post-breeding periods, and the genera composition was distinct between seasons (R = .036, p = .024). In pre-breeding, black-necked cranes tended to consume more diverse foods, and individual cranes exhibited greater heterogeneity at the genus level. At the genera and species level, pre-breeding black-necked cranes showed a wider dietary niche than post-breeding cranes. We observed season-specific features, with Tipula (common crane fly) and Stethophyma (grasshoppers) being enriched in the post-breeding period and Ceramica (moth) being more abundant in the pre-breeding period. Three Tipula species had the greatest importance in discriminating between seasonal diets. This study demonstrated a seasonal pattern of invertebrate diet in the black-necked crane, suggesting diet composition in response to resource and species availability. These results elaborate on the foraging ecology of highland birds and can inform the management of black-necked crane conservation.

Effect of breed and dietary composition on the miRNA profile of beef steers divergent for feed efficiency

Identifying and breeding cattle that are more feed efficient is of great benefit to beef production. Additionally, it is crucial that genes contributing to feed efficiency are robust across varying management settings including dietary source as well as being relevant across contrasting breeds of cattle. The aim of this study was to determine miRNAs that are contributing to the expression of residual feed intake (RFI) across two breeds and dietary sources. miRNA profiling was undertaken in Longissimus dorsi tissue of Charolais and Holstein–Friesian steers divergent for RFI phenotype following two contrasting consecutive diets (high-forage and high-concentrate). Ten miRNA were identified as differentially expressed (adj. P < 0.1) across the breed and diet contrasts examined. Of particular interest was the differential expression of miR-2419-5p and miR-2415-3p, both of which were up-regulated in the Low-RFI Charolais steers across each dietary phase. Pathway analysis of target mRNA genes of differentially expressed miRNA revealed enrichment (P < 0.05) for pathways including metabolic related pathways, insulin receptor signalling, adipogenesis as well as pathways related to skeletal muscle growth. These results provide insight into the skeletal muscle miRNAome of beef cattle and their potential molecular regulatory mechanisms relating to feed efficiency in beef cattle.

Foraging Habitat Availability and the Non-Fish Diet Composition of the Grey Heron (Ardea cinerea) at Two Spatial Scales.

Habitat structure on foraging ground is one of the crucial factors determining diet diversity in colonially breeding avian predators. Quantifying the habitat and diet composition at different spatial scales (regional and local inter-colonial) can help provide understanding of the drivers of diet composition. In this study, we examined the composition of the non-fish diet of an opportunistic predator, the Grey Heron (Ardea cinerea), based on pellets. We compared pellets from 21 colonies in two different regions of Poland that differing in composition of foraging habitats. Multivariate statistical techniques were used to analyze the relationship between diet and habitat compositions in a 20 km radius around these colonies. Significant inter-regional and inter-colony differences in Grey Heron diet and habitat composition were detected in foraging areas. However, some prey were present in the diet only from one of the regions. Around the heronries with a predominance of farmland habitats, the European water vole (Arvicola amphibius) and terrestrial invertebrates were present in relatively low frequencies, and the striped field mouse (Apodemus agrarius) was present in high frequencies. Voles (Microtus sp.) were more frequent in colonies with prevalence of non-irrigated arable land around the colony, in contrast to the bank vole (Myodes glareolus), which was less common in heronries with a higher contribution of this habitat type. Remains of aquatic invertebrates were less abundant in colonies surrounded by extensive forests. The results of our research indicate the opportunistic character of the non-fish part of the diet of the Grey Heron adapted to the local foraging habitat and prey availability.

Cutthroat trout responses to increased light via conventional and alternative riparian buffers

Forested headwaters, particularly in the Pacific Northwest, USA, are typically heavily shaded by dense stands of riparian vegetation. Reduced riparian cover can occur from natural or anthropogenic events, resulting in increased light which can increase fish biomass by promoting in-stream food resources. We conducted a 5 y before-after-control-impact (BACI) study on 10 small streams in the Oregon Coast Range, USA, and investigated how changes to the magnitude of stream light, mediated by conventional and alternative riparian buffer configurations adjacent to upland timber harvest, changed Coastal Cutthroat Trout (Oncorhynchus clarkii clarkii) abundance, biomass, bioenergetics, diet composition, and the availability of aquatic food resources. Riparian buffer treatments reduced canopy cover as much as 34 % cover (98–99 % pre; 64–98 % post-treatment) and enhanced total available sunlight reaching the stream surface by 8–31 % relative to unharvested references that only changed by 3–4 %. In the first year following the treatments, young-of-year trout (YOY, age 0) densities changed by between +0.1 and +0.78 #/m2 in treatment streams while densities changed by –0.001 and +0.02 #/m2 at reference streams. Although change in YOY densities was positively correlated with change in stream light (rs=0.81, p=0.02), changes in basal resources (periphyton and macroinvertebrates) were both positive and negative and did not increase with change in stream light. Adult (age 1+) trout responses were mixed in the first year post-treatment, but changed by –0.14 to +0.24 #/m2 at treatment sites (–0.02 to –0.05 at reference sites) in the second year post-treatment, likely due to increased recruitment from the strong cohort of YOY in the first year. Bioenergetics analysis in one post-treatment year showed that adult trout did not experience greater summer growth (–0.003 to +0.0005 g g−1 d−1) or proportions of maximum consumption (0.18–0.25) in streams with more light than at reference streams (–0.001 and +0.001 g g−1 d−1, 0.19 and 0.23). Overall, while standing stock assessments suggest that fish showed some increases after experimental treatments that increased light, our data did not provide the clear mechanistic evidence for bottom-up drivers that was expected. The relationship between canopy removal and fish production is not always predictable in small headwater streams, and even though fish populations were generally resilient to riparian manipulation, evaluations of terrestrial food resources, the dynamic between canopy cover and light reaching the stream, and changes to temperature may lend valuable insight on the impacts to fish populations.

Feeding gut microbes to nourish the brain: unravelling the diet-microbiota-gut-brain axis.

The prevalence of brain disorders, including stress-related neuropsychiatric disorders and conditions with cognitive dysfunction, is rising. Poor dietary habits contribute substantially to this accelerating trend. Conversely, healthy dietary intake supports mood and cognitive performance. Recently, the communication between the microorganisms within the gastrointestinal tract and the brain along the gut-brain axis has gained prominence as a potential tractable target to modulate brain health. The composition and function of the gut microbiota is robustly influenced by dietary factors to alter gut-brain signalling. To reflect this interconnection between diet, gut microbiota and brain functioning, we propose that a diet-microbiota-gut-brain axis exists that underpins health and well-being. In this Review, we provide a comprehensive overview of the interplay between diet and gut microbiota composition and function and the implications for cognition and emotional functioning. Important diet-induced effects on the gut microbiota for the development, prevention and maintenance of neuropsychiatric disorders are described. The diet-microbiota-gut-brain axis represents an uncharted frontier for brain health diagnostics and therapeutics across the lifespan.

Feeding habits and diet composition of Schizothorax plagiostomus in Panjkora River, Malakand region, Pakistan

Snow trout (Schizothorax plagiostomus) is a member of the Cyprinidae familyand commonly found in cold waters. We collected fish samples using cast nets and studied seasonal variations in the food consumption of this species. We analysed the gut content of 160 S. plagiostomus. Gut content revealed that S. plagiostomus feeds mainly on plant parts (45.14 %), followed by stones and muds (30.01 %), and insect parts (13.97 %), while unidentified detritus matter (5.42 %) and algae (5.33 %) are in small volume regarding the average percentage on a monthly basis. Maximum food consumption occurred in the summer and minimal food consumption occurred in winter. Seasonal variation in consumption of foods items showed that in summer it feeds mainly on plant parts (0.54 ± 0.86), followed by animal parts (0.19 ± 0.41), and algae (0.06 ± 0.25). In winter it feeds at a relatively minimal level (0.28 ± 0.56), (0.05 ± 0.22), (0.02 ± 0.16), respectively. Detritus (unidentified) was also observed as part of its diet, with a maximum in summer (0.06 ± 0.24), and less in autumn (0.03 ± 0.18). Lastly, materials uch as stones and mud were observed at a maximum level in winter (0.58 ± 0.76) and a minimum level in summer (0.12 ± 0.34). In conclusion, we found that the diet composition of S. plagiostomus changes with season, revealing a diverse diet that includes plants and animal fragments (caddis flies), algae, detritus, stones, and mud.

Ecological Niche Characteristics of the Diets of Three Sympatric Rodents in the Meili Snow Mountain, Yunnan.

Understanding the dietary preferences and ecological niche characteristics of mammals not only reveals their adaptive strategies under environmental changes but also reveals the interspecific relationships and coexistence mechanisms among sympatric species. Nevertheless, such data are scarce for rodents inhabiting areas spanning a wide altitude range. This study employed DNA metabarcoding technology to analyze the stomach contents of Apodemus ilex, Apodemus chevrieri, and Niviventer confucianus, aiming to investigate their dietary compositions and diversity in the Meili Snow Mountain in Yunnan Province, China. Levins's and Pianka's indices were used to compare the interspecific niche breadth and niche overlaps. The results revealed the following: (1) Insecta (relative abundance: 59.4-78.4%) and Clitellata (relative abundance: 5.2-25.5%) were the primary animal food sources for the three species, while Magnoliopsida (relative abundance: 90.3-99.9%) constitutes their main plant food source. Considerable interspecific differences were detected in the relative abundance of primary animal and plant foods among the three species; (2) There was partial overlap in the genus-level animal food between A. ilex and N. confucianus (Ojk = 0.4648), and partial overlap in plant food between A. ilex and A. chevrieri (Ojk = 0.3418). However, no overlap exists between A. chevrieri and N. confucianus, either in animal or plant food; (3) There were no significant interspecific differences in the α-diversity of animal and plant foods among the three species. The feeding strategies and ecological niche variations of these rodents support the niche differentiation hypothesis, indicating that they have diversified in their primary food sources. This diversification may be a strategy to reduce competition and achieve long-term coexistence by adjusting the types and proportions of primary foods consumed.

Impact of Seasonal Variation in Pasture on Rumen Microbial Community and Volatile Fatty Acids in Grazing Yaks: Insights from High-Altitude Environments.

The environment is one of the most important factors influencing the variation and diversity of the host gut microbiome in plateau areas. It is well-established that dietary variations substantially alter the rumen microbiota. However, there is limited research on the response of the rumen microbiota of grazing yaks to changes in seasonal diet composition under high-altitude environments. This study investigates the seasonal variations in rumen fermentation parameters, bacterial, and fungal communities in yaks, with a focus on the cold and warm seasons. Quantitative data revealed that in the cold season, yaks had an increased acetic acid proportion (p < 0.05) and acetic acid/propionic acid ratio (p < 0.05) compared to the warm season. The relative abundance of Bacteroidetes and Firmicutes were 64.67% and 25.82% in the cold season, respectively, and 66.77% and 26.87% in the warm season. The fungal community showed a higher abundance of Ascomycetes (58.72% to 76.91%) and Neocallimastigomycota in the cold season. These findings highlight the adaptation mechanisms of yaks to seasonal dietary changes and their implications for optimizing yak husbandry practices.

Foraging ecology of southern sea otters at the northern range extent informs regional population dynamics

Sea otters Enhydra lutris are vital keystone predators throughout the North Pacific that were nearly extirpated during the maritime fur trade. Recovery of southern sea otters E. l. nereis has proceeded slowly, with much of their historical range remaining unoccupied, resulting in reduced ecosystem functioning. Numerous studies have used foraging metrics to assess the population status of southern sea otters throughout their current range, but little is known about the northern range extent, where a stall in expansion has limited recovery. Thus, we collected census and foraging data of sea otters at Año Nuevo State Park, California, from 2019 to 2021 to determine sea otter abundance, diet composition, diet diversity, and average energy intake rate at the northern range edge. We then assessed regional population status by comparing values from Año Nuevo with previously collected data from other locations in California, including high-density, range center sites and low-density, range periphery sites. We found that sea otter density at Año Nuevo was greater than surrounding areas at the northern range periphery, and the average (±95% CI) energy intake (9.51 ± 0.91 kcal min-1) more closely resembled values observed at high-density sites. Further, dietary diversity (using the Shannon-Wiener index, H) was intermediate between previously studied high- and low-density populations (H = 1.81), with crabs making up the largest proportion of the diet (~56%). Overall, this study highlights possible effects of occupation time and range stagnation, identifies unique aspects of the prey resource base at Año Nuevo, and provides insight into the ongoing lack of northern range expansion.

Microbiota but not immune modulation by a pro- and postbiotic was associated with the diet-additive interaction in broilers

This study investigated the diet-additive interactions of a Lactobacilli-based probiotic (Pro) and postbiotic (Post) on immune parameters and cecal microbiota composition, with subsequent effects on the metabolome in broilers. A completely randomized block design was employed with 2 diets [standard (SD), and challenge (CD)] and 3 additive conditions (Control, Pro, Post) involving 1,368 one-day-old male Ross 308 broilers equally distributed among 36 pens in a 42 d study. Diets were formulated to contain identical nutrient levels, with CD higher than SD in non-starch polysaccharide content by including rye and barley. Total non-specific serum Ig A, M and G concentrations were determined weekly from d14 to 35. Following vaccination, titres of specific antibodies binding Newcastle disease virus (NDV) and infectious bursal disease virus (IBDV) were measured. Microbiota composition was analyzed by 16S rRNA gene sequencing at d14 and 35, and α- and β-diversity indexes (Observed, Chao1, Bray, Jaccard) were calculated. Cecal short-chain fatty acids and the semi-polar metabolome were determined in the Control SD and all CD groups at d35. At d35, a diet-additive interaction was observed on cecal microbiota composition. Within SD, Pro and Post did not affect operational taxonomic units (OTU) abundance (adjusted-P > 0.05) and diversity indexes (P > 0.05). Within CD, Pro and Post affected the relative abundances of 37 and 44 OTUs, respectively (adjusted-P < 0.05), with Post but not Pro affecting β-diversity indexes (P = 0.041 and 0.064 for Bray and Jaccard, respectively). Within CD, Post increased cecal acetate (21%; P = 0.007) and butyrate (41%; P = 0.002) concentration and affected the concentration of 2 metabolites (adjusted-P < 0.05), while Pro affected 240 metabolites (adjusted-P < 0.05). No diet-additive interactions were observed on serum Ig (P > 0.05), except for IgM at d14 (P = 0.004). Diet composition, but not the additives, affected immune status parameters. The Pro and Post affected cecal microbiota composition only under dietary challenging conditions as previously reported for growth.

The association between taurine concentrations and dog characteristics, clinical variables, and diet in English cocker spaniels: The Canine taURinE (CURE) project.

Occurrence of low blood taurine concentrations (B-TauC) and predisposing factors to taurine deficiency in English Cocker Spaniels (ECS) are incompletely understood. Investigate the occurrence of low B-TauC in a Swedish population of ECS and evaluate the association between B-TauC and dog characteristics, clinical variables, and diet composition. One-hundred eighty privately owned ECS. Dogs were prospectively recruited and underwent physical examination, blood analyses, and echocardiographic and ophthalmic examinations. Dogs with clinical signs of congestive heart failure (CHF) also underwent thoracic radiography. Taurine concentrations were analyzed in plasma (EDTA and heparin) and whole blood. Diets consumed by the dogs at the time of the examination were analyzed for dietary taurine- (D-TauC), cysteine- (D-CysC), and methionine concentrations (D-MetC). Fifty-three of 180 dogs (29%) had low B-TauC, of which 13 (25%) dogs had clinical and radiographic signs of CHF, increased echocardiographic left ventricular (LV) dimensions and volumes, and impaired LV systolic function. Five (9%) dogs with low B-TauC had retinal abnormalities. Dietary MetC, dietary animal protein source (red/white meat), and age were associated with B-TauC in the final multivariable regression model (P < .001, R2 adj = .39). Low B-TauC suggests that taurine deficiency may play a role in the development of myocardial failure and CHF in ECS. Low D-MetC and diets with red meat as the animal protein source were associated with low B-TauC. Dogs with B-TauC below the normal reference range were older than dogs with normal concentrations.

The analysis of natural forage of blue smimming crab (Portunus pelagicus Linnaeus, 1758) on the east coast of Pangandaran, West Java

Continuous use of blue swimming crab (Portunus pelagicus) without any control can cause population decline which leads to damage to the stability of the marine ecosystem, especially in East Coast Pangandaran, therefore cultivation is needed. In aquaculture, it is necessary to provide the right feed by knowing its natural diet. This study aimed to determine the natural diet of blue swimming crabs. The method used was descriptive analysis. The parameters observed were carapace width, gastric weight, the composition of natural diet. The relationship between the carapace width and gastric weight was analyzed by simple regression while the main type of natural diet was known by calculating the percentage of food composition. The relationship between carapace width and gastric weight was positive. Based on the composition found in crab gastric, there were 5 types of natural foods consisting of crustaceans (28.35%), meat (25.37%), mollusk (18.65%), fish (15.67%), and undefined material (UM) (4.47%). It is revealed that crabs are carnivores and scavengers, pose significant relationship between their size and gut content weight. It was also found that the composition of female crab feed was generally higher than that of males.

Natural Foraging Selection and Gut Microecology of Two Subterranean Rodents from the Eurasian Steppe in China.

As the most abundant group of mammals, rodents possess a very rich ecotype, which makes them ideal for studying the relationship between diet and host gut microecology. Zokors are specialized herbivorous rodents adapted to living underground. Unlike more generalized herbivorous rodents, they feed on the underground parts of grassland plants. There are two species of the genus Myospalax in the Eurasian steppes in China: one is Myospalax psilurus, which inhabits meadow grasslands and forest edge areas, and the other is M. aspalax, which inhabits typical grassland areas. How are the dietary choices of the two species adapted to long-term subterranean life, and what is the relationship of this diet with gut microbes? Are there unique indicator genera for their gut microbial communities? Relevant factors, such as the ability of both species to degrade cellulose, are not yet clear. In this study, we analyzed the gut bacterial communities and diet compositions of two species of zokors using 16S amplicon technology combined with macro-barcoding technology. We found that the diversity of gut microbial bacterial communities in M. psilurus was significantly higher than that in M. aspalax, and that the two species of zokors possessed different gut bacterial indicator genera. Differences in the feeding habits of the two species of zokors stem from food composition rather than diversity. Based on the results of Mantel analyses, the gut bacterial community of M. aspalax showed a significant positive correlation with the creeping-rooted type food, and there was a complementary relationship between the axis root-type-food- and the rhizome-type-food-dominated (containing bulb types and tuberous root types) food groups. Functional prediction based on KEGG found that M. psilurus possessed a stronger degradation ability in the same cellulose degradation pathway. Neutral modeling results show that the gut flora of the M. psilurus has a wider ecological niche compared to that of the M. aspalax. This provides a new perspective for understanding how rodents living underground in grassland areas respond to changes in food conditions.

Diet variation and trophic impact of weakfish, Cynoscion regalis, within multiple marine habitats of the eastern United States.

Weakfish (Cynoscion regalis) is not federally managed but feeds on species of management and ecological interest. We examined the trophic ecology of weakfish in Chesapeake Bay and the coastal and offshore waters of the eastern United States. For these areas, we determined the dominant prey of weakfish; identified how much diet variation was explained by the factors: season, size class, and year; and quantified prey biomass removed by weakfish from 2007 to 2019. In general, diet composition was mostly dominated by Engraulidae, Osteichthyes (bony fishes), and Mysidacea, and significantly varied by season and size class in Chesapeake Bay and coastal waters, although this was less dramatic in Chesapeake Bay. The total amount of variance explained by the three factors was 23.1% (Chesapeake Bay) and 14.7% (coastal waters), with year not being a significant factor in explaining weakfish diet variation for these areas. Weakfish total prey biomass removal occurred primarily in coastal waters in the fall and small size class (annual mean: approximately 41,038 t; maximum: approximately 63,793 t). Highly opportunistic feeders, weakfish cannibalism also played an essential part of their diet. These results have implications for fisheries and ecosystem management of weakfish when considering ecological interactions in regulatory approaches, such as recruitment and cannibalism, competition with federally managed fishes, and the natural mortality of their prey.

Dietary pattern and the corresponding gut microbiome in response to immunotherapy in Thai patients with advanced non-small cell lung cancer (NSCLC).

204 Background: Gut microbiota is considered a key player modulating the response to immune checkpoint inhibitors (ICI) in cancer. The effects of dietary pattern on this interaction is not well-studied. Methods: A prospective multicenter cohort of 95 patients with advanced non-small cell lung cancer (NSCLC) undergoing ICI therapy were enrolled. Stool shotgun metagenomic sequencing was performed. Three-day dietary patterns before ICI were assessed. Patients were categorized as hyperprogressive disease (HPD) if they exhibited a time to treatment failure of &lt;2 months. All others were categorized as non-hyperprogressive disease (non-HPD). The correlation between dietary patterns, gut microbiome, and response to ICI therapy was analyzed. Results: In the multivariate analysis, high abundance of Firmicutes unclassified and the Ruminococcaceae family correlated with significantly diminished progression-free survival (PFS) with HR of 2.40 [ P=0.006] and 4.30 [ P=0.005], respectively. More specifically, within the subset of NSCLC patients treated solely with ICI therapy, high abundance of Intestinimonas and the Enterobacteriaceae family were associated with reduced PFS with HR of 2.61 [ P=0.02] and HR 3.34 [ P=0.005], respectively. In dietary pattern analysis, HPD group showed increased consumption of cholesterol, sodium, and fats beyond recommended levels compared to non-HPD group. This group also displayed a tendency towards higher food pattern scores characterized by significant intake of fat and dairy products. Conclusions: Our study revealed distinct association between the gut microbiome composition and treatment outcomes. Based on these findings, the overall composition of diet may play a pivotal role in ICI therapeutic outcomes. [Table: see text]

In vitro bioaccessibility of inorganic and organic copper in different diets

In poultry diets, copper is an essential nutrient that is critical for various physiological functions. Although copper sulfate is commonly used due to its cost-effectiveness, organic copper sources are gaining popularity because of their superior production outcomes and environmental benefits. Nevertheless, understanding the distinct bioaccessibility of inorganic and organic copper in diverse dietary setting remains limited. This study investigated the bioaccessibility of copper sulfate, copper amino acid chelate, and copper proteinate in the intestine via in vitro digestion and in situ dialysis. The results showed significant differences in the molecular size distribution of compounds formed by different copper salts within the intestinal environment, thereby leading to varying bioaccessibility. Copper sulfate has a bioaccessibility of 47 % ± 4%, which is significantly lower than copper amino acid chelate and copper proteinate (63% ± 5%, and 60% ± 4%, respectively) in purified diet systems. Similarly, in whey protein systems, sulfate records 54% ± 10% bioaccessibility compared to 78% ± 9% and 76% ± 5% for copper amino acid chelate and copper proteinate. Coexisting feed ingredients have a significant impact on copper bioaccessibility. Copper sulfate forms precipitates, reducing its bioaccessibility to 34% ± 1% in sodium nitrate solution. The addition of digestive enzyme increases the bioaccessibility of copper sulfate to 81% ± 2% by providing organic ligands. Digestive enzyme also enhanced the bioaccessibility of copper proteinate from 36% ± 4% to 81% ± 4% by degrading its ligands. However, feed ingredients may decrease copper bioaccessibility by forming macromolecular complexes with copper, as all the organic ligands can competitively bind with copper in the intestine. These findings emphasize the importance of considering copper salt types and diet composition in animal nutrition practices.

Gut-derived appetite hormones do not explain energy intake differences in humans following low-carbohydrate versus low-fat diets.

The objective of this study was to explore how dietary macronutrient composition influences postprandial appetite hormone responses and subsequent energy intake. A total of 20 adults (mean [SEM], age 30 [1] years, BMI 27.8 [1.3] kg/m2, n = 8 with normal weight, n = 6 with overweight, n = 6 with obesity) consumed a low-fat (LF) diet (10% fat, 75% carbohydrate) and a low-carbohydrate (LC) diet (10% carbohydrate, 75% fat) for 2 weeks each in an inpatient randomized crossover design. At the end of each diet, participants consumed isocaloric macronutrient-representative breakfast test meals, and 6-h postprandial responses were measured. Ad libitum energy intake was measured for the rest of the day. The LC meal resulted in greater mean postprandial plasma active glucagon-like peptide-1 (GLP-1; LC: 6.44 [0.78] pg/mL, LF: 2.46 [0.26] pg/mL; p < 0.0001), total glucose-dependent insulinotropic polypeptide (GIP; LC: 578 [60] pg/mL, LF: 319 [37] pg/mL; p = 0.0004), and peptide YY (PYY; LC: 65.6 [5.6] pg/mL, LF: 50.7 [3.8] pg/mL; p = 0.02), whereas total ghrelin (LC: 184 [25] pg/mL, LF: 261 [47] pg/mL; p = 0.0009), active ghrelin (LC: 91 [9] pg/mL, LF: 232 [28] pg/mL; p < 0.0001), and leptin (LC: 26.9 [6.5] ng/mL, LF: 35.2 [7.5] ng/mL; p = 0.01) were lower compared with LF. Participants ate more during LC at lunch (244 [85] kcal; p = 0.01) and dinner (193 [86] kcal; p = 0.04), increasing total subsequent energy intake for the day compared with LF (551 [103] kcal; p < 0.0001). In the short term, endogenousgut-derived appetite hormones do not necessarily determine ad libitum energy intake.

Saugeye diets in southern reservoirs and insight for predatory control of stunted crappie

AbstractObjectiveSaugeye (Sauger Sander canadensis × Walleye S. vitreus) have been introduced in reservoirs for several purposes, including as a top‐down control to combat stunting in crappie Pomoxis spp. populations. However, no comprehensive diet evaluation has been completed in southern reservoirs. Our objectives were to assess variability in saugeye diet compositions, explore factors influencing crappie presence in saugeye diets, and investigate trends in prey size to inform management strategies regarding predatory control of crappie populations.MethodsWe collected 2638 saugeye diets from six Oklahoma reservoirs. We used permutational multivariate analysis of variance to test differences in diet compositions among saugeye lengths, study reservoirs, and seasons, and we used logistic regression models to correlate the presence of crappie in diets with saugeye size, season, crappie abundance, productivity, and turbidity. Finally, we used bivariate plots of diet indices and quantile regression to explore trends in prey importance and prey size relative to saugeye size.ResultSaugeye diet compositions were best explained by saugeye size, followed by study reservoir and season. Saugeye exhibited an ontogenetic shift from Inland Silverside Menidia beryllina to shad Dorosoma spp., and crappie were eaten infrequently in comparison. The presence of crappie prey in diets was most correlated with saugeye size (primarily large saugeye), followed by higher crappie abundance, lower reservoir productivity, and season (highest in fall). Saugeye consumed larger prey than most piscivores relative to predator size.ConclusionOur results indicated that dominant prey of saugeye transitioned from smaller‐bodied fishes to larger shad as they grew when both prey types were available, which may have implications for growth and recruitment. Ultimately, the low and variable use of crappie prey may lead to inconsistent predatory effects on crappie populations, and large saugeye may exert greater top‐down pressure on crappie in lakes with lower productivity or higher crappie abundance.

Evaluating the winter diet of elk using DNA metabarcoding analysis

North American elk Cervus canadensis inhabited portions of the eastern United States until extirpation in the mid‐1800s. From 2000 to 2008, 201 elk were reintroduced to the North Cumberland Wildlife Management Area (NCWMA), Tennessee. The stocking source was Elk Island National Park, Alberta Canada where there are two distinct genetic populations isolated from the north and south. This genetic structure has largely persisted in the population after translocation. Food habits were evaluated in the early stages of restoration, but the population has had approximately 20 years to adapt to the landscape, and current food habits are unknown. To assess diet composition using DNA metabarcoding, we collected fecal pellets of elk from 65 openings within the 79 318 ha NCWMA weekly from February to April of 2019. We targeted the ITS2 region of the nuclear ribosomal DNA to amplify vegetation sequences found in the internal portion of the elk feces. DNA metabarcoding of feces was linked to results from an accompanying elk population genetics study to investigate food habits between sexes from the two different genetic groups. The majority (80.298%) of sequences matched plants from 21 genera. The top genera (&gt; 5.000%) represented were Vaccinium (15.216%), Festuca (8.446%), Rosa (6.358%), Robinia (5.793%), and Eleagnus (5.186%). Elk heavily used woody plants before and after spring green‐up (&gt; 50% of diet). However, the quantity of forbs in their diet more than doubled after emergence in the spring. The sex‐genetic groups consumed similar vegetation in approximately proportionate amounts. Diversity analyses revealed a significant difference in plant genera sequence detection between males from the two genetic groups, although this finding is likely explained by limited sample size. NCWMA elk used a variety of forage in the winter and DNA metabarcoding analysis allows for a comprehensive analysis of food habits useful for monitoring how elk respond dietarily to habitat management.

Incorporating ecological heterogeneity and intraspecific variation differentiates complex interactions between apex predators and stocked fish

Ecological heterogeneity and intraspecific variation can impact energy flow from the base of the food web to top predators. We evaluated the effect of intraspecific variation on estimates of lake trout (Salvelinus namaycush) consumption of stocked kokanee (lacustrine sockeye salmon, Oncorhynchus nerka) in a 390 ha oligotrophic lake with two distinct basins. Lake trout stomach content analyses, stable isotope niche space, and catch rates indicated high intraspecific variation in resource use across habitats and basins. Intraspecific variation and ecological heterogeneity were incorporated into two bioenergetics modeling approaches; one lake-wide model, and one partitioned model that accounted for differences in lake trout diet composition and population size across habitats. The ecologically partitioned model highlighted that lake trout consumption was primarily in the epilimnion of one basin, while the lake-wide, unpartitioned model performed similarly but failed to provide ecological context for where that consumption occurred. Incorporating ecological heterogeneity and intraspecific variation into bioenergetic models can more accurately represent top predators foraging patterns across habitats and inform management actions to mitigate impacts to stocked fish.