Nutrient Excretion Research Articles

Marine protection and environmental forcing influence fish‐derived nutrient cycling in kelp forests

Abstract Animal consumers excrete dissolved inorganic nitrogen, an essential nutrient for regulating primary production and macroalgal growth in the ocean. Often overlooked in attempts to explain kelp forest productivity, relatively little is known about the role of consumers in nutrient cycling in temperate systems, such as the magnitude of nutrients excreted and the factors that influence spatial and temporal variability in consumer‐derived nutrients. To investigate the supply of ammonium (NH4+) excreted by the dominant members of the nearshore rocky reef fish community, we combined empirically‐measured relationships between excretion rate and body mass with data on fish density and size structure from visual SCUBA surveys conducted from 2005 to 2018 in the northern Channel Islands, California, USA. The fish community excreted a substantial amount of ammonium to the kelp forest (mean: 95.5–131.3 μmol·m−2·h−1), however excretion varied substantially among sites and over time (range: 23.1–247.9 μmol·m−2·h−1). The ammonium supply was influenced by the establishment of marine protected areas (MPAs) that restricted fishing activities and environmental characteristics that influenced geographic and temporal shifts in the overarching fish community structure. Fish‐derived ammonium excretion rates were 50%–80% greater inside MPAs compared to areas open to fishing, while environmental and habitat characteristics (e.g. habitat vertical relief, kelp biomass, wave exposure, chlorophyll a) explained 85% of the spatial variation in community excretion rates. In contrast, large‐scale oceanographic phenomena (e.g. North Pacific Gyre Oscillation index) and past patterns of fish recruitment explained 57% of the temporal variation in nutrient excretion over the 14‐year time series. Results suggest that fish‐derived ammonium may provide an important and underappreciated nutrient source to kelp beds, particularly during low‐nutrient periods (e.g. seasonal reductions in upwelling or El Niño‐Southern Oscillation events), and that fishing disrupts these nutrient cycling pathways. Fishes likely play a critical role in supporting the resiliency of kelp forest ecosystems by supplying a relatively constant source of reduced nitrogen that can be utilized by giant kelp and other macroalgae to fuel primary production of biogenic habitat. Read the free Plain Language Summary for this article on the Journal blog.

Renal Health Through Medicine-Food Homology: A Comprehensive Review of Botanical Micronutrients and Their Mechanisms.

As an ancient concept and practice, "food as medicine" or "medicine-food homology" is receiving more and more attention these days. It is a tradition in many regions to intake medicinal herbal food for potential health benefits to various organs and systems including the kidney. Kidney diseases usually lack targeted therapy and face irreversible loss of function, leading to dialysis dependence. As the most important organ for endogenous metabolite and exogenous nutrient excretion, the status of the kidney could be closely related to daily diet. Therefore, medicinal herbal food rich in antioxidative, anti-inflammation micronutrients are ideal supplements for kidney protection. Recent studies have also discovered its impact on the "gut-kidney" axis. Here, we review and highlight the kidney-protective effects of botanicals with medicine-food homology including the most frequently used Astragalus membranaceus and Angelica sinensis (Oliv.) Diels, concerning their micronutrients and mechanism, offering a basis and perspective for utilizing and exploring the key substances in medicinal herbal food to protect the kidney. The index for medicine-food homology in China contains mostly botanicals while many of them are also consumed by people in other regions. Micronutrients including flavonoids, polysaccharides and others present powerful activities towards renal diseases. Botanicals with medicine-food homology are widely speeded over multiple regions and incorporating these natural compounds into dietary habits or as supplements shows promising future for renal health.

Precision feeding as a tool to reduce the environmental footprint of pig production systems: a life-cycle assessment.

Nitrogen and phosphorus excretion are major sources of environmental contamination in growing-finishing pig operations. Nutrient excretion can be reduced by feeding pigs daily-tailored diets to their estimated nutrient requirements using individual precision feeding (IPF) techniques. This study modeled and evaluated the environmental impact of moving from conventional group 3-phase feeding (CGF) to IPF systems in Quebec, Canada, using life-cycle assessment with SimaPro software. The cradle-to-farm model included inputs and outputs of each subphase: raw materials/feedstuffs production, feed mill processing, transport, animal rearing, and manure management. The model was identical for both treatments in all aspects except for the production of feeds and barn and manure emissions in the growing-finishing phases. All feed ingredients originated from Quebec, simulating agricultural practices using real management data from an average farm in Quebec. Based on observed pig growth data, the CGF and IPF systems were compared in the growing-finishing phase. IPF diets were modeled as the blend of 2 feeds (i.e., A and B), while CGF diets were stablished according to the industry. The evaluated impact categories were global warming potential (GWP), eutrophication potential (EP), and acidification potential (AP). The functional unit was 1 t of feed at the feed mill gate and 1 t of finished pig live weight at the farm gate. A Monte Carlo analysis determined the uncertainty of the growth performance results. Feeding programs were compared using analysis of variance. Corn was associated with elevated GWP and AP impacts, leading to higher impacts for diets with higher corn content. Feed B, which contained 83% corn, resulted in impacts of 645kg of CO2-eq., 8.53kg SO2-eq., and 4.89kg PO4-eq. Diets with higher EP impact had a higher percentage of soybean meal. Feed A contained 25% of this ingredient and had an impact of 608kg CO2-eq., 6.98kg SO2-eq., and 5.57kg PO4-eq. CGF diets had environmental impacts between those of feeds A and B. Compared to CGF, applying IPF programs during the growing-finishing phase decreased GWP by 7.6%, AP by 16.2% and EP by 13.0%. IPF significantly reduced the environmental impact in all categories through the more efficient use of nutritional resources by pigs. IPF could help to improve the sustainability of growing-finishing pig operations in Quebec and likely other regions using corn and soybean-based diets.

Species identity and diversity of filter‐feeding bivalves impact green and brown food webs

Abstract In freshwater ecosystems, consumers can play large roles in nutrient cycling by modifying nutrient availability for autotrophic and heterotrophic microbes. Nutrients released by consumers directly support green food webs based on primary production and brown food webs based on decomposition. While much research has focused on impacts of consumer driven nutrient dynamics on green food webs, less attention has been given to studying the effects of these dynamics on brown food webs. Freshwater mussels (Bivalvia: Unionidae) can dominate benthic biomass in aquatic systems as they often occur in dense aggregations that create biogeochemical hotspots that can control ecosystem structure and function through nutrient release. However, despite functional similarities as filter‐feeders, mussels exhibit variation in nutrient excretion and tissue stoichiometry due in part to their phylogenetic origin. Here, we conducted a mesocosm experiment to evaluate how communities of three phylogenetically distinct species of mussels individually and collectively influence components of green and brown food webs. We predicted that the presence of mussels would elicit a positive response in both brown and green food webs by providing nutrients and energy via excretion and biodeposition to autotrophic and heterotrophic microbes. We also predicted that bottom‐up provisioning of nutrients would vary among treatments as a result of stoichiometric differences of species combinations, and that increasing species richness would lead to greater ecosystem functioning through complementarity resulting from greater trait diversity. Our results show that mussels affect the functioning of green and brown food webs through altering nutrient availability for both autotrophic and heterotrophic microbes. These effects are likely to be driven by phylogenetic constraints on tissue nutrient stoichiometry and consequential excretion stoichiometry, which can have functional effects on ecosystem processes. Our study highlights the importance of measuring multiple functional responses across a gradient of diversity in ecologically similar consumers to gain a more holistic view of aquatic food webs.

Life cycle assessment of the production of an extruded dog food in Brazil

Sustainability is the current focus of the scientific community, governments, and companies in various market segments, such as pet food. Pet food production has increased rapidly in recent years, with a trend toward the development of environmentally friendly products and processes. The first step in creating strategies for mitigating environmental impacts is to assess key points in manufacturing processes. Given this, this study aimed to perform a life cycle assessment (LCA) to estimate the environmental impacts associated with the formulation, production, and distribution phases of an extruded dog food produced in Brazil. System boundaries were from cradle-to-gate, encompassing extraction of raw materials, transportation, processing, production, packaging, and distribution. Estimates were based on the amount of food required to meet the energy requirements for maintenance of a 10 kg dog (functional unit = 2.59 MJ day−1, reference flow = 177.3 g day−1). Environmental impacts were calculated by the environmental footprint method (EF 3.0 v. 1.00) using SimaPro software (v. 9.1.1.1). Product ingredients and packaging materials were modeled under Brazilian conditions using ecoinvent 3.7.1 and Agri-footprint 5.0 databases. Data regarding transportation, processing, distribution, electric and thermal power generation, water usage, and waste generation were obtained from the company's records (2019–2020). In this study, as expected, formulation was the most relevant factor, accounting for 70%–90% of the total environmental impacts. The main impact categories were terrestrial and marine eutrophication, acidification, particulate matter, and climate change (80% of total impacts). Production of the evaluated dog food was associated with the emission of 88.73 kg CO2 eq year−1 or 1.37 kg CO2 eq kg−1 distributed food. The use of animal meals (poultry by-product meal and meat and bone meal) and vegetable by-products (wheat bran and rice bran) contributed to reducing environmental impacts. Therefore, in this study, ingredient selection was considered the most important factor in mitigating the environmental impacts of pet foods. As the overall impact of the formulation depends on data on the use stage, such as nutrient excretion after consumption, future studies should adopt a cradle-to-grave approach for a better comprehension of the feasibility of applying animal and vegetable by-products in the eco-design of pet food products.

PSVI-18 Low and high feed efficiency grower-finisher pigs fed three different levels of dietary crude protein showed no immediate difference in blood metabolomics profile

Abstract Improving feed efficiency (FE) of grower-finisher pigs is of great importance considering its impact on production economy, nutrient excretions as well as carbon-footprint. The biological background describing variation in FE between pen mates, is difficult to establish as feed intake (FI) and FE are not estimated on an individual level. In this study advanced feeding stations were used to estimate FI and further calculate feed conversion ratio (FCR) on individual level. The study aimed to investigate the possible difference in the blood metabolic profile between low and high FE grower-finisher pigs fed three different levels of dietary crude protein (CP). The study included 60 newly weaned gilts divided in two series, housed as 10 pigs/pen. The 30 pigs per series were distributed between three pens (10 pigs/pen) and were balanced by body weight and litter. Throughout the entire weaner period all pigs had ad libitum access to the same diet. Pigs were redistributed among the grower-finisher pens to balance FCR levels between dietary treatments (CP levels) and to reduce any carry over effect from the weaner to the grower-finisher pens. From 30-115 kg body weight (BW), pigs were fed either a low (L; 14.8% CP), standard (15.2% CP) or high (H; 15.8% CP) CP diet equal in energy, where BW, average weekly gain (AWG), and FCR were determined on weekly basis, while FI was estimated on daily basis. Three low FE (20% least) and three high FE (20% greatest) pigs were selected based on the final 4 wk of growth within station and CP level. On the final day of the experimental period all low-FE and high-FE pigs within each dietary treatment were euthanized and blood plasma was sampled and subjected to a nontargeted LC-MS metabolomics analysis. Growth performance and metabolite data were, respectively, analyzed in R and MetaboAnalyst 5.0 with FE and CP as fixed effects. High-FE and H-CP pigs continuously displayed numerically greater BW, while AWG and FCR were, respectively, numerically greater, and less in L-CP than H-CP group during last 2 wk of the experimental period. Principal Component Analysis (PCA) showed no grouping (P > 0.05) of metabolites and no specific pattern of the metabolic profile from either the two FE categories or the three dietary CP levels. Furthermore, no correlation (P >0.05) of metabolites to any other observation was found, and only little variation, measured by distance to model showing deviation of each pig to overall model, was observed. In conclusion, at first glance the metabolomics profile did not appear to present any specific pattern between low and high feed efficiency grower-finisher pigs or between pigs exposed to different levels of dietary CP in the grower finisher period.

PSVI-5 Extruded blend of Nannochloropsis oculata microalgae and flaxseed and its effects on ruminal fermentation and nutrient digestion

Abstract Omega-3 fatty acids are essential nutrients for mammals, and are required for cellular growth and synthesis of numerous cellular signaling molecules. NBO3 Technologies, LLC (Manhattan, KS) has developed an omega-3 supplement consisting of an extruded blend of flaxseed and Nannochloropsis oculata microalgae (GreatOplus; GOP). Our objective was to evaluate effects of GOP on dry matter intake (DMI), water intake (WI), ruminal metabolism, and apparent total tract nutrient disappearance in cannulated Holstein steers (n = 11; initial body weight 586.4 ± 49.7 kg). Treatments consisted of backgrounding diets (40% roughage, 60% concentrate) containing 0% (CON) or 10% GOP (dry basis). Feed and water intake were recorded using an Insentec Roughage and Water monitoring system (Hokofarm Group; Emmeloord, The Netherlands). Steers were utilized in a cross-over design with two 19-d periods. Each period consisted of a 15-d adaptation phase and a 4-d collection phase. Ruminal contents, duodenal digesta, and feces were collected at 8-h intervals for 4 d starting at 1000 h on d 16. The sampling schedule was advanced by 2 h with each subsequent sampling day, thus generating a 24-h profile at 2-h intervals post-feeding over the 4-d sampling phase. Titanium dioxide (15 g) was dispensed directly into the rumen of each steer 15 min before feeding and to estimate apparent ruminal flow and fecal excretion of nutrients. There was a Treatment X Day interaction for DMI (P < 0.001); DMI was greater for steers fed GOP some of the days during the adaptation phase compared with steers fed the control diet, but intakes were similar during the collection phase. Ruminal fluid pH, ruminal ammonia concentration, and WI were not affected by treatment (P > 0.10). As expected, ruminal outflows of total fatty acids (195.6 vs 338.1 g/d for CON and GOP, respectively) and α-linolenic acid (ALA; 1.6 vs 6.3 g/d, respectively) were greater for steers fed GOP compared with steers fed CON (P < 0.05); however, ruminal disappearance (i.e., biohydrogenation) of ALA was extensive, with only 8% and 4.7% of ALA intake exiting the rumen for CON and GOP, respectively. Apparent total tract digestion of organic matter was not impacted by diet (P > 0.20; 78.1 and 76.8% for CON and GOP, respectively). Supplementing an extruded blend of flaxseed and microalgae can effectively increase the amount of α-linolenic acid available for absorption in the small intestine, but overall recovery of dietary α-linolenic acid is relatively low due to extensive biohydrogenation by microbes within the rumen.

Can the use of phytase in feed improve the performance and health of broiler chickens?

This study aimed to evaluate the effect of phytase supplementation on feeds with reduced nutritional calcium and phosphorus on broiler chickens from 1 to 49 days of age. Chickens fed five experimental diets distributed in a completely randomized design, with eleven replicates of 20 chickens each, were used for evaluating performance, bone quality, and serum mineral levels. The diets consisted of one positive control (PC); one negative control (NC), with reduced levels of available phosphorus and calcium; and four diets consisting of NC feed supplemented with phytase at levels 0, 500, 1000, or 1500 U/kg. Supplementation with 1000 FU/kg of phytase in diets based on corn, and soybean meal is ideal for obtaining excellent performance and bird welfare results reducing nutrient excretion and improving digestion and absorption of nutrients by the animal.

Teaching Nutrient Cycling and Climate Change Concepts Using Excretion Experiments with Common Fish

Many high school students learn about nutrient cycling during biology, environmental science, and agriculture classes. These lessons often focus on soil and plants, and nutrient cycling is usually taught independently from climate change. Scientists know that animals, including fish, can have strong effects on nutrient cycling (i.e., nitrogen and phosphorus) in ecosystems. Additionally, research has shown that nitrogen and phosphorus excretion rates of animals increase with water temperatures. We worked with high school students to design and conduct nutrient excretion experiments using common fish (zebrafish) to explore the impact of climate change on nutrient cycling. This allowed students to have hands-on laboratory experience. In 2021, we worked with students participating in a residential summer program in Georgia. Meanwhile, in 2022, students enrolled in the local high school visited the university campus on two occasions to participate in the experiments, and we once again worked with students in Georgia. Students from all three groups showed an increased understanding of the role of animals in nutrient cycling and ways climate change may impact these processes, despite variable results from the excretion experiments. Students also showed increased understanding of science processes and were more likely to feel like part of the science community. We believe that these experiments can be done in high school classrooms to expand students’ understanding of the scientific process, nutrient cycling, and climate change.

4 Hands-On I: Building an Agent-Based Model in Anylogic

Abstract Livestock farming systems (LFS) have detrimental effects on the environment, associated mainly with feed production, enteric methane and emissions from manure. LFS are complex because they are structured by multiple interactions between biological and human-controlled processes, at various organizational levels. Their behavior and the extent to which feeding strategies can mitigate this environmental burden is not always easily predictable. Dynamic mechanistic models of LFS can simulate the effects of feeding strategies on both animal performance and the associated excretion of nutrients. These models are useful tools to produce the life cycle inventories needed in the second step of a life cycle assessment. In the pig-fattening unit, the effects of multiphase group feeding depend largely on the variability of growth potential among pigs and the farmer has decisions that can target either the group of pigs or each individual (e.g., when choosing pigs to deliver to slaughterhouse). Therefore, simulating the growth trajectory of each individual pig and events like deliveries to slaughterhouse makes it possible to estimate the response of the pig population rather than the average pig to feeding strategies. Individual-based models (IBM) are particularly adequate because they make it possible to simulate each individual and to build the response of the population from the aggregation of individuals. Agent-based models are IBM that rely on self-governing agents made of properties, behavioral rules and resources that allow each agent to make decisions upon the occurrence of an event, which can be triggered randomly or not. This hands-on will focus on a specific example dedicated to the simulation of the response (growth, nitrogen excretion and subsequent gaseous emissions from manure) of a population of fattening pigs to a multiphase feeding strategy. In a first step, we will develop a simplified individual-based model of a pig-fattening pen including pigs and the farmer as agents. In a second step, we will improve this model by introducing interactions between these agents. For both steps, we will work with python language using pre-developed jupyter notebooks.

247 In Vitro Characterization of Equine Fore- and Midgut Digestion

Abstract Considerable advancements can be made in the field of equine nutrition and diet formulation, by improved feed characterization and the development of nutritional models, including in vitro models, to describe nutrient degradation. Methodologically, literature values for in vitro small intestine incubation times are widely variable ranging from 2 to 18 h. While some incubation times are selected to represent approximate mean retention times, conversely, insufficient in vitro incubation times and sampling time points could prohibit or result in inaccuracies characterizing nutrient degradability characteristics, ultimately affecting both degradability and digestion values and their use. The objective of this trial was to assess whether macronutrient degradability plateaus when digested for 2 h in a simulated gastric environment plus 8, 12, or 16 h in a simulated small intestinal environment. To replicate in vivo digestion, a pepsin-pancreatin approach was selected. The first step of this method replicates the gastric environment. Ten g of each test ingredient are weighed into beakers containing 60 mL hydrochloric acid (HCl; 0.1 M) and 0.4 g pepsin (~2,500 U/g) solution. Beakers are then covered and incubated for 2 h at 39 ℃ under constant stirring. One mL aliquots of the digestion liquid are sampled at 0, 5, 10, 20, 30 60, 90 and 120 min after the start of the gastric simulation. Before replicating intestinal digestion, samples are neutralized with sodium hydroxide and the pH is increased to 7. The second step of this method replicates the small intestinal environment. Fifty mL of pancreatin-phosphate buffer (350 U/g protease, 6,000 FIP U/g lipase, 7,500 U/g amylase) is added to the beakers, which are then covered and incubated for either 8, 12, or 16 h at 39 ℃ under constant stirring. One mL aliquots of the digestion liquid are sampled at 0, 5, 10, 20, 30 60, 90, 120, 150, 180 min and thereafter hourly up until the end of digestion (480, 720, or 960 min). Aliquot samples are analyzed for starch via a glucose assay, protein via o-phthalaldehyde assay, and lipids via gas chromatography. A model will is fit to the time point data to determine degradation rates and degradable fractions of the digested samples. Results from these analyses go beyond estimating gross nutrient and digestible nutrient values and inform on the rate of degradation of nutrients of equine feedstuffs and the impact of in vitro methodology. The resulting degradability values will be used in a mechanistic model of equine digestion which will inform precision feeding. Ultimately this will improve how we feed horses to reduce nutrient excretion into the environment and reduce the risk of metabolic conditions such as laminitis.

50 Individual Precision Feeding can Greatly Reduce Global Warming, Eutrophication, and Acidification Environmental Impacts

Abstract Nitrogen and phosphorus excretion are among the primary potential sources of environmental contamination in growing-finishing pig operations. Nutrient excretion can be reduced by feeding pigs with daily tailored diets to their estimated nutrient requirements using individual precision feeding (IPF) techniques. The environmental impact of moving from conventional group 3-phase-feeding (CON) to IPF systems in Québec, Canada, was evaluated in this study using life-cycle analysis. A cradle-to-farm gate life-cycle analysis was conducted using Simapro software (v. 8.0.3.14; PRE Consultants, Amersfoort, The Netherlands). The model included inputs and outputs of each sub-phase: raw materials/feedstuffs production, feed mill processing transport, animal rearing (maternity, weaning, and fattening units), and manure spreading in all livestock productions. All feed ingredients originated from Quebec (Montérégie region) and agricultural practices were simulated using real management data from an average farm in Quebec. Based on observed pig growth data, the CON and IPF systems were compared in the growing-finishing phase (Andretta et al., 2016). The IPF diets were obtained by blending two feeds (i.e., A and B), while CON diets were formulated according to the ones used by the industry. The evaluated impact categories were global warming (GW), eutrophication (EU), and acidification (AC). The functional unit was 1 ton of feed at the feed mill gate, and 1 ton of pig live weight at the farm gate for finished pigs. A Monte Carlo analysis was performed to determine the uncertainty of the growth performance results. Feeding programs were compared with ANOVA. Corn was the ingredient with greater GW and AC impacts, therefore, diets with greater corn content were those with greater impacts in these categories. Feed B, which contained 83.2% of corn, resulted in impacts of 570 kg of CO2 eq., 8.21 kg SO2 eq. and 6,27 kg PO4 eq. Diets with greater EU impact were those with a greater percentage of soybean meal. Feed A contained 25.4% of this ingredient and impacted 554 kg of CO2 eq., 6,84 kg SO2 eq. and 7.05 kg PO4 eq. CON diets had environmental impacts between those of feeds A and B. Compared with CON, IPF decreased GW by 5.1%, AC by 14.2% and EU by 12.2%. IPF significantly reduced the environmental impact in all categories due to the more efficient use of nutritional resources. IPF is an effective alternative to improve the sustainability of growing-finishing pig operations in Québec and likely other regions using corn and soybean-based diets.

Consumer-driven nutrient recycling of freshwater decapods: Linking ecological theories and application in integrated multitrophic aquaculture.

The Metabolic Theory of Ecology (MTE) and the Ecological Stoichiometry Theory (EST) are central and complementary in the consumer-driven recycling conceptual basis. The understanding of physiological processes of organisms is essential to explore and predict nutrient recycling behavior, and to design integrated productive systems that efficiently use the nutrient inputs through an adjusted mass balance. We fed with fish-feed three species of decapods (prawn, anomuran, crab) from different families and with aquacultural potential to explore the animal-mediated nutrient dynamic and its applicability in productive systems. We tested whether body mass, body elemental content, and feeds predict N and P excretion rates and ratios within taxa. We also verified if body content scales allometrically with body mass within taxa. Finally, we compared the nutrient excretion rates and body elemental content among taxa. N excretion rates of prawns and anomurans were negatively related to body mass, emphasizing the importance of MTE. Feed interacted with body mass to explain P excretion of anomurans and N excretion of crabs. Body C:N content positively scaled with body mass in prawns and crabs. Among taxa, prawns mineralised more N and N:P, and less P, and exhibited higher N and C body content (and lower C:N) than the other decapods. Body P and N:P content were different among all species. Body content and body mass were the main factors that explained the differences among taxa and influence the role of crustaceans as nutrient recyclers. These features should be considered to select complementary species that efficiently use feed resources. Prawns need more protein in feed and might be integrated with fish of higher N-requirements, in contrast to crabs and anomurans. Our study contributed to the background of MTE and EST through empirical data obtained from decapods and it provided insightful information to achieve more efficient aquaculture integration systems.

Empirical measurements of ammonium excretion in kelp forest fishes: Effects of body size, taxonomy and trophic guild

Fishes and other consumers excrete metabolic waste products, including dissolved nutrients rich in nitrogen, which is an essential nutrient for primary production. Relatively little is known about the magnitude and variability of nutrients excreted by fishes in kelp forest ecosystems and whether consumer-derived nutrients are important for supporting kelp productivity. In this study, the supply of ammonium (NH4+) excreted by the dominant fishes (30 species representing ∼85% of total fish biomass) was investigated on nearshore rocky reefs in California. Using rapid field incubations, the amount of excreted dissolved ammonium was measured as a function of body size (n = 460 individuals) and predictive models were developed relating mass to excretion rates at the family-level. Mass-specific excretion rates ranged from 0.08 to 3.45 μmol·g−1·hr−1, and per capita ammonium excretion rates ranged from 5.9 to 2765 μmol·individual·hr−1. Ammonium excretion scaled with fish body mass to the ¾ power, as predicted by the metabolic theory of ecology; mass-specific excretion rates were higher in smaller fishes, but larger fishes contributed more ammonium per individual. When controlling for body size, ammonium excretion rates were greatest among surfperch (Embiotocidae), damselfish (Pomacentridae), and wrasses (Labridae), and the general trophic groups of planktivores and micro-carnivores. When body size differences were considered, the greatest mean excretion rates per individual were observed in larger-bodied species, such as California Sheephead (Semicossyphus pulcher) and Lingcod (Ophiodon elongatus). Empirical estimates of nutrient excretion by fishes, among the first measured in temperate kelp forests, were consistent with those in other aquatic systems. Ultimately, empirically derived excretion rates are the first step to quantifying the relative importance of consumers to nutrient cycling in kelp forest ecosystems.

Seasonal interactions between Quagga Mussel grazing and phytoplankton in western Lake Erie: The view from different measuring technologies

Abstract We measured Quagga Mussel grazing-induced changes in seston concentration in 20-L laboratory mesocosms containing lake water, during May-October, as part of a study to investigate the present role of mussel feeding and nutrient excretion in affecting phytoplankton composition. A variety of measuring methodologies including size-fractionated chlorophyll (< 2, 2-20, and >20 µm), phytoplankton groups by FluoroProbe, cyanobacterial genera by 16S rRNA gene sequencing, and particulate C, N, and P gave us different insights into seasonal phytoplankton dynamics and mussel selective feeding and assimilation. High clearance rates and/or high assimilation rates were seen during late May-early July across all size categories, with high rates seen particularly in cryptophytes and diatoms as revealed by FluoroProbe. Starting in late July cyanophytes dominated the phytoplankton and feeding rate on them was generally zero or low. Sequencing analyses suggested that there was a diverse cyanobacterial community present, with Microcystis, contrary to expectation, dominating only in late June. Cyanobium was the dominant genera at most times during summer-fall, and as expected, Microcystis was rejected by mussels relative to other cyanobacteria. Planktothrix, dominant in spring, was readily ingested as well as Anabaena in late June. We show that a combination of methods is helpful to make progress in understanding plankton succession and grazing. These methods were important adjuncts to microscopic analysis (Carrick et al, this issue). Our results support the hypothesis that dreissenid mussels, when abundant, can affect seasonal succession of phytoplankton shifting composition to cyanobacteria and even changes within the cyanobacterial community; however, impacts are likely modest now due low mussel biomass (Carter et al., this issue). Assimilation of C, N, and P was generally high, which is important for mussel population maintenance.

Optimizing Animal Nutrition and Sustainability Through Precision Feeding: A Mini Review of Emerging Strategies and Technologies

Abstract Precision feeding, a practice involving customized diets tailored to individual nutritional requirements, has emerged as a promising paradigm within animal production, underpinned by advanced technologies and data analytics. This mini review embarks on an exploration of the evolutionary trajectory of precision feeding and its profound ramifications on animal nutrition, environmental sustainability, and animal welfare. Prominent technological advancements, exemplified by sensors and automation, have wrought transformative change across various sectors, spanning from dairy farming to poultry production. These technological innovations facilitate real-time monitoring and data accrual, thereby augmenting feed efficiency and fostering animal well-being. Environmental sustainability assumes an integral role in the precision feeding paradigm. Through the reduction of feed wastage and the minimization of nutrient excretion, it serves as a potent mitigating solution against the environmental footprint synonymous with livestock production. This entails a noteworthy reduction in greenhouse gas emissions and the prevention of water pollution. The interplay between precision feeding and animal welfare is intricate and multifaceted. On one hand, it furnishes farmers with the capability to expeditiously monitor and address animal health issues. On the other hand, it poses challenges associated with social interactions and the fulfilment of individualized nutritional needs. The future trajectory of precision feeding is inherently tied to the resolution of imminent challenges, including the imperative for real-time monitoring, the development of cost-effective large-scale implementation, and comprehensive elucidation of long-term effects on animal health and welfare. The ensuing panorama portends promising prospects, encompassing the optimization of resource efficiency, diminution of environmental impacts, and the formulation of personalized nutritional strategies. In summation, precision feeding stands as a domain teeming with potential, poised to optimize both animal nutrition and the sustainability quotient within animal production. Realizing this potential hinge on the adept addressing of forthcoming challenges, coupled with the astute harnessing of emergent technologies, in our collective pursuit of a more sustainable and ethically principled agricultural landscape.

Fish and Black Soldier Fly Meals as Partial Replacements for Soybean Meal Can Affect Sustainability of Productive Performance, Blood Constituents, Gut Microbiota, and Nutrient Excretion of Broiler Chickens.

One hundred and twenty, one-day-old male broiler chicks were used to investigate the effects of supplementation with different dietary protein sources on their performance and immune systems. Chicks were randomly divided into four equal experimental groups (six replicates, each of five chicks). The first group served as a control and was fed a standard corn-soybean meal diet. The second, third, and fourth groups were fed diets in which the soybean meal (SBM) was partly replaced by fish meal (FM), black soldier fly larvae (BSFL), and black soldier fly prepupae (BSFP), respectively. Throughout 1-14 and 15-42 days of age, FM, BSFL, and BSFP were added at 3 and 5%, respectively. The feed conversion ratio (FCR) of the FM group was the best among the tested groups. Feeding BSFP decreased final body weight (BW), BW gain, feed intake, and impaired the FCR compared to the other treatments for the entire experimental period. The BSFP group had significantly lower cecal Salmonella counts compared to the control group and lower total bacterial counts compared to the other groups except for BSFL. BSFL can be fed to broiler chickens at 3% during the starter period and 5% during the grower-finisher periods without negative influences on growth performance, red blood cell characteristics, blood lipid profiles, and nutrient excretion, while BSFP can improve the chickens' gut ecosystem.

Enhancing the recovery of human-edible nutrients in milk and nitrogen efficiency throughout the lactation cycle by feeding fatty acid supplements

Dairy cows convert low-quality feedstuffs unsuitable for human consumption into milk, a high-quality protein source for humans. Even under grazing conditions of well-managed pastures, dietary energy limits the efficiency of animal production, contributing to the excretion of nutrients to the environment. Thus, our study aimed to assess the effect of supplying sources and levels of supplemental fat to grazing dairy cows during early lactation on nutrient excretion and recovery of human-edible (HE) nutrients in milk throughout the lactation cycle. Two experiments were conducted with grazing Jersey × Holstein dairy cows. In Experiment 1, five dairy cows were used in a 5 × 5 Latin Square design. Treatments were a control diet (concentrate without supplemental fat) or diets supplemented with calcium salts of either soybean fatty acids (CSSO) or palm fatty acids (CSPO) fed at two levels of supplementation (400 g/day or 700 g/day) for 24 days. In general, the level of supplemental fat had a minor effect on production parameters and methane emission and intensity. Feeding cows with CSPO increased milk yield by 8.1%, milk energy output by 20%, and milk fat yield by 35.2% compared with CSSO. A tendency was observed for CSPO to decrease methane per unit of milk energy compared with CSSO. In experiment 2, 24 dairy cows were used in a randomized block design. Treatments were a control diet or diets supplemented with calcium salts of either CSSO or CSPO fed at 400 g/day for 13 weeks. The carryover effect of the diets was evaluated until 42 weeks of lactation. During the supplementation period, feeding CSPO improved the recovery of HE energy, protein, and indispensable amino acids compared with control and CSSO. Interestingly, we demonstrated that feeding CSPO improved the recovery of HE energy, protein, and indispensable amino acids compared with control over the lactation cycle. Overall, our results suggested that the dose of supplemental fat used in our study had a minor influence on production and rumen fermentation parameters. We demonstrated that feeding dairy cows with a fatty acid source based on palm oil under tropical grazing conditions reduced nutrient excretion and improved the recovery of HE nutrients throughout the lactation cycle.

Environmental and Economic Responses to Precision Feed Management in Dairy Cattle Diets

The dairy industry is under pressure to reduce its environmental impact while producing more milk to meet society’s needs. Precision feed management (PFM) is one tool that can be used to meet this challenge. A simple definition of PFM is to provide adequate, but not excessive, nutrients to meet animal requirements. There has been an industry trend to decrease diet nitrogen (N) and phosphorus (P) in the last 20 years. New York herds lowered diet N by 10.8% between 1999 and 2019. Milk per cow increased by 40% during this time, while total manure N excretion decreased by 8.1%. Research results from on-farm trials have consistently indicated that lowering diet crude protein (CP) decreases manure N excretion while improving profitability; in a 3-year study with 8 herds, diet CP was decreased by 9.7%, while manure N excretion was 14% lower. Income over purchased feed cost increased by $137/cow/year. Carbon footprint (CF) has also decreased. A decrease of 19% between 2007 and 2017 was reported for the United States dairy industry. The dairy industry has already made significant strides in improving milk production while lowering its impact on the environment; however, there are additional opportunities to further reduce nutrient excretion and emissions into the environment and increase the efficiency of nutrient use.

118 Nutrient Cycling Potential from Manure from Heifers Fed Four Bermudagrass Cultivars

Abstract Maintenance of pastures for grazing accounts for $132.50/animal in the United States (23% of operating costs), and pasture nutrient input represents the single greatest influence in productivity per unit area. Cultivar differences in the forage offered to cattle have the potential to manifest differences in digestive efficiency, resulting in different nutrient excretion profiles. The objective of this study was to assess the growth potential and incorporation of N, P, and K into forage material from manure from cattle fed one of four bermudagrass (Cynodon dactylon [L.] Pers.) cultivars. Ruminally fistulated heifers (n = 4) were assigned randomly to one of four bermudagrass cultivars (Coastal, Russell, Tifton 44, or Tifton 85) for four 30-d in vivo periods (21-d adaptation and 9-d collection). On d 23, total fecal collections were subsampled from each heifer. As a hierarchical addition, a controlled greenhouse experiment was conducted for each period [15 pots per period; 5 manure treatments (four bermudagrass diets plus a negative control) × 3 replications]. Manure was added to 4.58 L pots based on stocking rate estimates for Central Alabama (1,110 kg/ha). The pots were seeded with bermudagrass (cv. Giant) as an indicator for forage nutrient uptake. At harvest (d 70), herbage, root, and soil samples were collected. Herbage and root samples were assayed for CP. Soil samples were assayed for pH, N, P, K, Mg, and Ca. Data were analyzed using SAS v. 9.4. There was no effect of manure treatment on herbage (P = 0.88) or root DM yield (P =.00;.54 and.73 g/pot, respectively). Similarly, there was no effect of manure treatment on soil pH (P = 0.18; 5.5), P (P = 0.78; 24.2 kg/ha), or K (P = 0.42;56.7 kg/ha). Results are interpreted to mean that, regardless of the cultivar effects on ruminal digestive dynamics, there is little to no effect of the resulting manure on subsequent forage production and nutrient uptake.