Innovative raw materials to be used in aquaculture fish species feeding and the importance of fish welfare to obtain a high nutritional quality and antibiotic-free product

The present PhD project had the aim to find strategies to increase the non-specific immune defences of farming fish avoiding the use of drug, in particular antibiotics, in order to obtain a high nutritional quality products as human food. Considering that animal health is crucial to improve food and nutrition security on one side and Public Health on the other side, fish welfare is an essential factor to improve and the constantly interaction between fish surface and aquatic environment must be considered. Improving fish health means also working on fish nutrition, topic strictly connected to aquatic sustainability, based on the characterization of new raw materials to be used as protein sources in partial substitution of fish meal

Sterol and Mineral Profiles of the Common Sea Snail Hinia Reticulata and the Long Sea Snail Nassarius Mutabilis (Gastropods) Collected from the Middle Adriatic Sea

Sea snails represent a common food in the world as a source of sterols, such as cholesterol and phytosterol, and minerals. Sterols play important roles in body functions and also minerals are important for human health, so the intake of these nutrients into human diets should be known. The aim of this study was to examine the sterol and mineral profiles of the long (Hinia reticulata) and the common (Nassarius mutabilis) sea snails. Samples of both species were collected at different catch times from November 2019 to March 2020 and transported to the University of Camerino (UNICAM) for the evaluation of their sterol and mineral profiles, including toxic elements (Cd, Cr, Pb). The results of the study showed that the average content of total lipid were 57 mg/100 g, 38 mg/100 g for cholesterol and 19 mg/100 g for phytosterol in the long sea snail, and the values were respectively 68, 48, and 20 mg/100 g in the common sea snail, without significant differences in the two examined sea snails. Additionally, the result of the mineral analysis showed that both species were significant sources of minerals, with negligible levels of toxic metals and metalloids. Therefore, the Long and the Common sea snail are suitable and safety sea products for human nutrition

Effect of a Guar Meal Protein Concentrate in Replacement of Conventional Feedstuffs on Productive Performances and Gut Health of Rainbow Trout (Oncorhynchus mykiss)

A trial was performed to investigate the effect of a proprietary guar protein concentrate, as a partial replacement of conventional protein sources, on the productive performances of rainbow trout through the growing phase. A total of 2700 rainbow trout were reared in 3 m3, 12 concrete tanks for 90 days. Three diets were formulated to contain a protein level of 43% and a lipid content of 25.3% by replacing 0% (CD), 5% (D5), and 15% (D15) of conventional protein sources with guar protein concentrate. The final mean weight was similar between D5 and CD, significantly higher than D15. The same trend was observed in weight gain and specific growth rate. The feed conversion rate had the most favourable performances in D5 and CD. Feed palatability was higher in CD and D5 than in D15. Histological intestinal score showed significant differences (p < 0.05) between the groups with the highest values in CD and the lowest in D15. Significant differences were observed for goblet cell hyperplasia with higher values in the CD group. Based on this trial, the 5% guar protein concentrate inclusion gave the best zootechnical results

Effects of stress conditions on plasma parameters and gene expression in the skin mucus of farmed rainbow trout (Oncorhynchus mykiss)

The aim of this study was to investigate the physiological response of rainbow trout (Oncorhynchus mykiss) before slaughtering in the last phase of farming analyzing skin mucus and plasma. Two groups of rainbow trout were considered: Group UN (“unstressed”), represented by fish randomly captured from raceways, in the last phase of a standard fattening cycle; Group S (“stressed”), collected at the end of the pre-slaughtering tank, soon after slaughtering. The fish skin mucus was swabbed from head to tail using a sterile plastic spatula and the blood was collected through an endocardial puncture. qRT-PCR was used to study the gene expression in skin mucus. The mRNA expression levels of the IL-6 and IgD genes were higher in the S than in the Group UN. The plasma analysis showed an only a decrease in the glucose plasma levels in the Group S when compared to the Group UN. The present results indicated that the procedures adopted after slaughtering only affected changes in plasma glucose and skin mucus activity in rainbow trout suggesting that management protocol was compatible with non-stressful farming conditions

Effects of Partial Substitution of Conventional Protein Sources with Duckweed (Lemna minor) Meal in the Feeding of Rainbow Trout (Oncorhynchus mykiss) on Growth Performances and the Quality Product

Duckweed (Lemna minor) meal was included in the formulation of three experimental feeds (L1, L2, L3) for rainbow trout at 10%, 20%, 28% of the protein source, respectively. Increasing the duckweed inclusion, the other protein sources were adjusted to get isonitrogenous (41%) and isolipidic (20%) diets, as the control diet (LC). 540 fish (mean body weight 124.5 ± 0.7 g) were randomly allocated in 12 tanks divided equally among the four different diets. After 90 days, fish were weighed and the most important productive performances, fillet quality and fatty acid profile were determined. The final body weight in L1 (340.53 g) and L2 (339.42 g) was not different from LC (348.80 g); L3 trout significantly (p < 0.05) exhibited the lowest one (302.16 g). Similar trends were found in final mean length, weight gain, specific growth rate, food conversion rate. Somatic indices were affected by duckweed inclusion. Diets had not significant effects on the proximate composition and fatty acids of the fillet in L1, L2, L3 respect to LC. Based on this study, duckweed meal derived from Lemna minor can be included in the feed for the rainbow trout without negative effects on the growth performances at 20% of the protein substitution

Improvement of the Water Quality in Rainbow Trout Farming by Means of the Feeding Type and Management over 10 Years (2009–2019)

Background: In Europe, rainbow trout is one of the main fresh water fish farmed in a constantly developing environment that requires innovative studies to improve farm management, fish welfare and environmental sustainability. The aim of this paper is to investigate the trend of water quality parameters over 10 years, after a feeding strategy change from pellet to extruded feed. Methods: The study was conducted on a farm in central Italy, based on parallel raceways. The cycle started from young rainbow trout (90 ± 2 g) that were grown until they reached market size. A water sample of 500 cm3 was collected monthly from 2009 to 2019 from the lagoon basin in order to investigate the trends of the total suspended solids (TSS), biochemical oxygen demand (BOD5), chemical oxygen demand (COD), nitrites (NO2-N), nitrates (NO3-N), total ammonia nitrogen (TAN), total phosphorus (TP) and pH. Results: All of the studied parameters (TSS, BOD5, COD, NO2-N, NO3-N, TAN and TP) showed a significant improvement from 2009 to 2019. The pH parameter did not display notable variation during the studied period. The feed conversion ratio (FCR) was also investigated and exhibited a significant improvement from 1.4 to 1.1. Conclusion: Based on the decrease of all the investigated parameters, it is possible to say that extrusion is currently an excellent processing feed technique in aquaculture with a good level of respect for the environment

Effects of Partial Substitution of Conventional Protein Sources with Duckweed (Lemna minor) Meal in the Feeding of Rainbow Trout (Oncorhynchus mykiss) on Growth Performances and the Quality Product

Duckweed (Lemna minor) meal was included in the formulation of three experimental feeds (L1, L2, L3) for rainbow trout at 10%, 20%, 28% of the protein source, respectively. Increasing the duckweed inclusion, the other protein sources were adjusted to get isonitrogenous (41%) and isolipidic (20%) diets, as the control diet (LC). 540 fish (mean body weight 124.5 ± 0.7 g) were randomly allocated in 12 tanks divided equally among the four different diets. After 90 days, fish were weighed and the most important productive performances, fillet quality and fatty acid profile were determined. The final body weight in L1 (340.53 g) and L2 (339.42 g) was not different from LC (348.80 g); L3 trout significantly (p < 0.05) exhibited the lowest one (302.16 g). Similar trends were found in final mean length, weight gain, specific growth rate, food conversion rate. Somatic indices were affected by duckweed inclusion. Diets had not significant effects on the proximate composition and fatty acids of the fillet in L1, L2, L3 respect to LC. Based on this study, duckweed meal derived from Lemna minor can be included in the feed for the rainbow trout without negative effects on the growth performances at 20% of the protein substitution

Evaluation of Long Sea Snail Hinia reticulata (Gastropod) from the Middle Adriatic Sea as a Possible Alternative for Human Consumption

: In mid Adriatic Sea the common sea snail is the habitual snail eaten, but over the years fishermen started to capture also the long sea snail, a possible alternative for human consumption. This study aims to compare the quality traits of the edible fraction in the common and long sea snails. In this study, common and long sea snail samples were provided by fishermen in November 2018 and March 2019. Total weight (meat and shell), fractions of meat and shell (after having extracted the edible part), fatty acid, elements in meat, and calcium content in shells were determined. Meat quality traits showed high nutritional value without significant differences between the two species. The fatty acid profile showed n3/n6 ratio significantly different both considering the season of sampling (November: 4.1; March: 2.38) and the species of sea snail (common: 4.98; long: 2.86). The long species showed a higher yield in the total body and calcium content concentrations. However, the long sea snail showed 50% lower meat yield compared with the common sea snail. In conclusion, the long sea snail can be used as an alternative to the common sea snail for human consumption

Effects of stress conditions on plasma parameters and gene expression in the skin mucus of farmed rainbow trout (Oncorhynchus mykiss)

The aim of this study was to investigate the physiological response of rainbow trout (Oncorhynchus mykiss) before slaughtering in the last phase of farming analyzing skin mucus and plasma. Two groups of rainbow trout were considered: Group UN ("unstressed"), represented by fish randomly captured from raceways, in the last phase of a standard fattening cycle; Group S ("stressed"), collected at the end of the pre-slaughtering tank, soon after slaughtering. The fish skin mucus was swabbed from head to tail using a sterile plastic spatula and the blood was collected through an endocardial puncture. qRT-PCR was used to study the gene expression in skin mucus. The mRNA expression levels of the IL-6 and IgD genes were higher in the S than in the Group UN. The plasma analysis showed an only a decrease in the glucose plasma levels in the Group S when compared to the Group UN. The present results indicated that the procedures adopted after slaughtering only affected changes in plasma glucose and skin mucus activity in rainbow trout suggesting that management protocol was compatible with non-stressful farming conditions