Characterization of hatchery residues for on farm implementation of circular waste management practices

The conventional management of hatchery residues is associated with greenhouse gas and unpleasant odor emissions, the presence of pathogens and high disposal costs for producers. To address these issues, on-farm alternatives like composting, fermentation, and insect valorization are promising approaches. This study aims to characterize hatchery residues and define critical quality thresholds to identify effective processes for their management. Hatchery residue samples were collected bi-monthly over a year (N = 24) and were analyzed for proximate composition (dry matter, ash, energy, crude protein, crude lipid, crude fiber, carbohydrates), pH, color (L*a*b*, Chroma) and microbiological loads (total aerobic mesophilic counts, coliforms, lactic acid bacteria). Volatile fatty acid composition was also measured (N = 8). Significant correlation coefficients were found between TAM and LAB loads and residue characterization (pH, chroma, crude fibers, carbohydrates, and temperature). On a dry matter basis, residues were high in energy (2498 to 5911 cal/g), proteins (21.3 to 49.4 %) and lipids (14.6 to 29.1 %), but low in carbohydrates (0 to 15.3 %) despite temporal fluctuations. Ash content varied widely (8.6 to 49.1 %, dry matter) and is influenced by eggshell content. Microbiological loads were high for total aerobic mesophilic bacteria (6.5 to 9.1 log cfu/g), coliforms (5.4 to 8.5 log cfu/g) and lactic acid bacteria (6.7 to 9.0 log cfu/g). Valorization of hatchery residues on the farm will depends on the optimization of effective upstream stabilization processes. The critical points are discussed according to the valorization potentials that could be implemented on the farm from composting to upcycling by insects.

Thermal tolerance and fish heart integrity: fatty acids profiles as predictors of species resilience

The cardiovascular system is a major limiting system in thermal adaptation, but the exact physiological mechanisms underlying responses to thermal stress are still not completely understood. Recent studies have uncovered the possible role of reactive oxygen species production rates of heart mitochondria in determining species' upper thermal limits. The present study examines the relationship between individual response to a thermal challenge test (CT_max), susceptibility to peroxidation of membrane lipids, heart fatty acid profiles and cardiac antioxidant enzyme activities in two salmonid species from different thermal habitats (Salvelinus alpinus, Salvelinus fontinalis) and their hybrids. The susceptibility to peroxidation of membranes in the heart was negatively correlated with individual thermal tolerance. The same relationship was found for arachidonic and eicosapentaenoic acid. Total H₂O₂ buffering activity of the heart muscle was higher for the group with high thermal resistance. These findings underline a potential general causative relationship between sensitivity to oxidative stress, specific fatty acids, antioxidant activity in the cardiac muscle and thermal tolerance in fish and likely other ectotherms. Heart fatty acid profile could be indicative of species resilience to global change, and more importantly the plasticity of this trait could predict the adaptability of fish species or populations to changes in environmental temperature.

Effects of Killing Methods on Lipid Oxidation, Colour and Microbial Load of Black Soldier Fly (Hermetia illucens) Larvae

Black soldier fly (BSF) larvae represent a promising alternative ingredient for animal feed. Post-production processing can, however, affect their quality. This project aimed to optimize larval killing by comparing the effects on the nutritional and microbiological quality of 10 methods, i.e., blanching (B = 40 s), desiccation (D = 60 °C, 30 min), freezing (F20 = -20 °C, 1 h; F40 = -40 °C, 1 h; N = liquid nitrogen, 40 s), high hydrostatic pressure (HHP = 3 min, 600 MPa), grinding (G = 2 min) and asphyxiation (CO2 = 120 h; N2 = 144 h; vacuum conditioning, V = 120 h). Some methods affected the pH (B, asphyxiation), total moisture (B, asphyxiation and D) and ash contents (B, p < 0.001). The lipid content (asphyxiation) and their oxidation levels (B, asphyxiation and D) were also affected (p < 0.001). Killing methods altered the larvae colour during freeze-drying and in the final product. Blanching appears to be the most appropriate strategy since it minimizes lipid oxidation (primary = 4.6 ± 0.7 mg cumen hydroperoxide (CHP) equivalents/kg; secondary = 1.0 ± 0.1 mg malondialdehyde/kg), reduces microbial contamination and initiates dehydration (water content = 78.1 ± 1.0%). We propose herein, an optimized protocol to kill BSF that meet the Canadian regulatory requirements of the insect production and processing industry.

Hybridization between char species (Salvelinus alpinus and Salvelinus fontinalis): a fast track for novel allometric trajectories

Hybridization between closely related species can generate genetic and phenotypic variation, providing valuable biological material to assess the physiological impact of the structural or functional variability of different organs. In the present study, we examined growth rates of various organs and whole body in brook char, Arctic char and their reciprocal hybrids over a period of 281 days. Parental species achieved significantly higher body mass than their hybrids. Hybridization significantly reduced the relative size of the heart, liver and spleen. The relative size of pyloric caeca did not differ among the four groups. The observed lower growth performance of the hybrids compared to parental species strongly suggests that divergence in the relative size of digestive organs, liver and heart partly dictate growth capacity. Our results also suggest that the increased variability achieved through hybridization may prove useful in a genetic selection program.

Thermal tolerance and thermal sensitivity of heart mitochondria: Mitochondrial integrity and ROS production

Cardiac mitochondrial metabolism provides 90% of the ATP necessary for the contractile exertion of the heart muscle. Mitochondria are therefore assumed to play a pivotal role in heart failure (HF), cardiovascular disease and ageing. Heat stress increases energy metabolism and oxygen demand in tissues throughout the body and imposes a major challenge on the heart, which is suspected of being the first organ to fail during heat stress. The underlying mechanisms inducing heart failure are still unclear. To pinpoint the processes implicated in HF during heat stress, we measured mitochondrial respiration rates and hydrogen peroxide production of isolated Arctic char (Salvelinus alpinus) heart mitochondria at 4 temperatures: 10°C (acclimation), 15°C, 20°C and 25°C (just over critical maximum). We found that at temperature ranges causing the loss of an organism's general homeostasis (between 20°C and 25°C) and with a substrate combination close to physiological conditions, the heat-induced increase in mitochondrial oxygen consumption levels off. More importantly, at the same state, hydrogen peroxide efflux increased by almost 50%. In addition, we found that individuals with low mitochondrial respiration rates produced more hydrogen peroxide at 10°C, 15°C and 20°C. This could indicate that individuals with cardiac mitochondria having a low respiratory capacity, have a more fragile heart and will be more prone to oxidative stress and HF, and less tolerant to temperature changes and other stressors. Our results show that, at temperatures close to the thermal limit, mitochondrial capacity is compromised and ROS production rates increase. This could potentially alter the performance of the cardiac muscle and lead to heat-induced HF underlining the important role that mitochondria play in setting thermal tolerance limits.

Establishment of a comprehensive reference transcriptome for vertebral bone tissue to study the impacts of nutritional phosphorus deficiency in rainbow trout (Oncorhynchus mykiss, Walbaum)

Reducing dietary phosphorus (P) is a common approach to reduce effluent P outputs. The potential resulting P-deficiency is known to negatively impact fish bone condition and might result in vertebral deformities. To date, no large-scale study involving deep sequencing of the bone transcriptome has been conducted in salmonids and vertebral molecular changes remain poorly described. This study aims to provide the first comprehensive vertebral transcriptome for rainbow trout (Oncorhynchus mykiss) to allow functional and quantitative expression studies. Fish weighing 60.8±1.6g, were fed for 27weeks using two practical diets having 0.29% (deficient) and 0.45% (sufficient) available phosphorus (P), respectively. Deep sequencing was conducted using HiSeq2000 Illumina 100 paired-end technology from pooled P-deficient and P-sufficient fish and individuals displaying vertebral deformities. Over 140 million trimmed paired-end reads were assembled de novo with Trinity and resulted in 679,869 transcripts with a mean length of 542.5bp. From these sequences, 340,747 matched with referenced ESTs from rainbow trout. Furthermore, 141,909 and 117,564 sequences were functionally annotated against Nr and Uniprot databases, respectively. Interestingly, we observed putative homologue sequences for most of the key components involved in bone formation and turnover in mammals.

Influences of dietary biotin and avidin on growth, survival, deficiency syndrome and hepatic gene expression of juvenile Nile tilapia Oreochromis niloticus

This study was undertaken to assess the interactive effects of dietary biotin and avidin on growth, feed conversion, survival and deficiency syndrome of tilapia and to determine the influence of dietary biotin deficiency on the expression of key genes related to biotin metabolism in tilapia. Six iso-nitrogenous and iso-energetic diets based on a common purified basal diet (vitamin-free casein as the protein source) were prepared for this study. The six dietary groups were 0 g avidin with 0 mg biotin (A0B0), 0 g avidin with 0.06 mg biotin/kg diet (A0B1), four avidin-supplemented diets incorporating at a incremental concentrations 0.25, 0.5, 1.0 and 2.0 g/kg diet with 0.06 mg biotin/kg diet (A15B1, A30B1, A60B1 and A120B1). Fish were hand-fed three times a day to apparent satiation for 12 weeks. Each diet was fed to three replicate groups of fish. Fish were kept in glass aquaria in a recirculating aquaculture system under standardized environmental conditions. Growth was significantly higher in fish that received the biotin-supplemented diet (A0B1), compared to diets lacking biotin or supplemented with avidin. Tilapia fed higher concentration of avidin-supplemented diets (A60B1 and A120B1) showed significant growth depression and displayed severe deficiency syndromes such as lethargy, anorexia, circular swimming and convulsions, which ultimately lead to death. There was a strong proportional linear relationship between the avidin content of the diet and feed conversion ratio, FCR (y = 0.43x + 0.135; r = 0.960; P < 0.001) and strong inverse relationship with protein efficiency ratio, PER (y = -0.309x + 2.195; r = 0.961; P < 0.0001). Elevated levels of biotinidase, pyruvate carboxylase, propionyl-CoA carboxylase-A and propionyl-CoA carboxylase-B transcripts were noted in fish fed all graded level of avidin-supplemented diets. A broken-line analysis indicated that feeding tilapia a diet with 44.5 times more avidin than the dietary biotin requirement can induce deficiency syndromes including retarded growth, when analyzing the data of percentage weight gain.

Production of BSA-loaded alginate microcapsules: Influence of spray dryer parameters on the microcapsule characteristics and BSA release

The aim of this study was to optimize the production of BSA-loaded alginate microcapsules by spray drying and to study the release of bovine serum albumin fraction V (BSA) under gastric simulated conditions. Microcapsule yield, BSA release, microcapsule size and size distribution were characterized following the application of different production parameters including inlet air temperature, inlet air pressure and liquid feed rate. The microcapsules were incubated in 0.1 N HCl and BSA release was quantified over time. The yields were higher with the pressure of 3 bar compared to 4 bar and with a feed rate of 0.45 vs. 0.2 ml s(-1). A high feed rate (0.45 vs. 0.2 ml s(-1)) allows one to obtain microcapsules with a low BSA release (p = 0.0327). The increase of the atomizer inlet temperature leads to microcapsules with a higher BSA release (p = 0.0230). A higher air pressure of 4 bar compared to 3 bar resulted in a lower microcapsule size (2.55 vs. 2.80 microm) and led to a narrower size distribution (0.92 vs. 1.07). In conclusion, the spray dryer parameters influenced the alginate microcapsule characteristics as well as subsequent protein release into a simulated gastric medium.

Oral vaccines for finfish: academic theory or commercial reality?

Aquaculture is the fastest growing food-producing sector, providing an acceptable supplement to and substitute for wild fish and plants. Increased production intensification, particularly in high-value species, involves substantial stress, which, as in other captive livestock species, has resulted in outbreaks of major diseases and related mortalities. Widespread use of antibiotics has led to the development of antibiotic-resistant bacteria and the accumulation of antibiotics in the environment and the flesh of fish. Thus, recently effort has been dedicated to vaccine development. Vaccination in fish is complicated by their aquatic environment. Individual injections are labor-intensive and stressful, since fish have to be removed from the water and anaesthetized. Some vaccines offer a limited duration of protection, and thus booster applications are required. In salmonid species, many commercial vaccines use oil-based adjuvants, resulting in a greatly improved duration of protection. However, oil-based adjuvants have been related to significant growth depression, internal adhesions and injection site melanization, resulting in carcass downgrading. Oral administration to aquatic species is by far the most appealing method of vaccine delivery: there is no handling of the fish, which reduces stress; and administration is easy and suitable for mass immunization. However, few oral vaccines have been commercialized, due in part to the increased quantity of antigen required to provoke an immune response, and the lack of an adequate duration of protection. For effective oral delivery, protective antigens must avoid digestive hydrolysis and be taken up in the hindgut in order to induce an effective protective immune response. Antigen encapsulation technologies have been used to protect antigen; however, such strategies can be expensive and are not always effective. Alternative approaches, currently under development, are discussed.

Factors affecting protein release from alginate-chitosan coacervate microcapsules during production and gastric/intestinal simulation

A series of experiments was performed to evaluate the influence of a number of physico-chemical factors on the diffusion of a model protein, bovine serum albumin (BSA), from dried chitosan-coated alginate microcapsules. Diffusion of BSA was quantified during the microcapsule manufacture processes (gelation, washing, rinsing) and during incubation in conditions simulating the pH encountered during the gastric (0.1 N HCl; pH 1.5) and intestinal (200 mM Tris-HCl; pH 7.5) phases of digestion. Factors tested included alginate and chitosan concentration, calcium chloride (CaCl2) concentration in the gelation medium, loading rate, chitosan molecular mass and pH of the gelation medium. Microcapsule size and gelation time were altered in order to determine their effects on protein retention. Alginate and chitosan concentration significantly influenced BSA retention during microcapsule manufacture and acid incubation, as did calcium chloride concentration in the gelation medium (P<0.05). BSA retention during manufacture was not significantly altered by protein loading rate or pH of the encapsulation medium, however, protein retention during acid incubation decreased significantly with increasing protein loading rate and encapsulation medium pH (P<0.05). Microcapsules that were washed with acetone following manufacture demonstrated significantly increased protein retention during acid incubation (P<0.05). In microcapsules that had been acetone-dried to a point whereby their mass was reduced to 10% of that immediately following encapsulation, protein retention was over 80% following 24-h acid incubation vs. only 20% protein retention from non acetone-dried microcapsules. The presence of calcium in the neutral buffer medium significantly reduced BSA diffusion in a concentration-dependent manner (P<0.05).

Evaluation of protein release from chitosan-alginate microcapsules produced using external or internal gelation

A series of experiments was undertaken to evaluate the diffusion of a model protein, i.e. bovine serum albumin (BSA), from chitosan-alginate microcapsules produced using either internal or external gelation. Diffusion of BSA was quantified during the microcapsule manufacture processes (gelation, washing, rinsing) and during incubation in conditions simulating the pH encountered during the gastric and intestinal phases of digestion. Encapsulation of an acid phosphmonoesterase permitted in situ protein localization, providing evidence to explain results obtained with BSA. There was significantly greater protein loss from internally versus externally-gelled chitosan-alginate microcapsules during the manufacture process (37.6% versus 4.7%, respectively). Similar trends were observed during 24 h incubation in 0.1 N hydrochloric acid. Increasing alginate concentration from 2-4% (w:v) did not significantly reduce losses from internally-gelled microcapsules. Addition of 0.25 M NaCl to the gelling medium significantly increased protein diffusing during microcapsule manufacture and acid incubation from externally gelled microcapsules. In situ protein localization revealed a higher level of protein near the surface of the microcapsules of externally gelled microcapsules versus internal gelation. The above data indicate that externally-gelled microcapsules are inhomogeneous with a higher concentration of alginate near the microcapsule surface, thus reducing the porosity of the resulting microcapsules. These results suggest that the porous nature of internally-gelled chitosan-alginate microcapsules may result in low encapsulation efficiency, depending on the nature of the product being encapsulated.