Effect of different stocking densities on growth, muscle development and fatty acid profile of Acipenser baerii larvae

Sturgeons, as well as paddlefishes, belong to the Acipenseriformes group, which is one of the most primordial 57 orders of the Osteichthyes that comprehends 25 species spread throughout Europe, Asia and North America. The present study aims at investigating muscle growth and development as well as fatty acid profile in Siberian sturgeon free-embryos when subjected to three different rearing densities. Fatty acids, in particular polyunsaturated fatty acids of n-3 series, are generally known as key nutrients in fish larvae.This study was approved by the Ethic Committee of the University of Milan (OPBA_22_2017). Siberian sturgeon larvae were reared at 18°C, at three stocking densities until complete yolk-sac absorption: low (LD, 30 larvae/l), mid (MD, 80 larvae/l) and high (HD, 150 larvae/l). Sampling timepoints were: hatching, schooling and complete yolk-sac absorption stage (YSA). Sacrificed larvae were weighed and histological analyses were performed in order to assess muscle development as described elsewhere ; fatty acid profile was determined by GC-FID analysis as described by Vasconi et al. (2015). Statistical analysis was performed with SAS software (v. 9.3, Cary Inc., NC).At the end of the experiment, LD larvae presented a higher weight than larvae reared at the other two densities (P<0.05). Within the schooling stage (Figure 1), Total Muscle Area was lower for HD larvae (P<0.05); red and white muscle areas in schooling and YSA were higher than at hatching (P<0.05), regardless the density. Concerning fatty acids, no statistical differences were recorded between different rearing densities, while during the development regardless the rearing density, there was a common pattern: linoleic and alfa linolenic acids, significantly decreased their relative content, while others, as arachidonic acid and DHA, significantly increased. Siberian sturgeon larvae reared at LD or MD reveal an anatomically normal muscle development, while in the HD it is possible to observe a slowdown.What the aquaculture industry requires is a set of guidelines that allows the development of a sustainable industry, so that we tried to develop guidelines for stocking density in the very early stage of farming. As a conclusion, it would seem that mid density could be more suitable for this species in this stage of development

Oxidative stress and lateral muscle development in Siberian Sturgeon (Acipenser baeri): preliminary observations.

Embryonic development in bony fish is strongly influenced by environmental factors, mainly by temperature and dissolved oxygen, but little is known about their influence on Sturgeons. Since 1998 the international trade of Sturgeons has been regulated under CITES due to depletion of wild stocks. Sturgeon aquaculture as well as larvae production is, therefore, important because it may contribute to the repopulation of the wild stocks (Bronzi et al., 2011; Di Giancamillo et al., 2012).The aim of this study is to monitor oxidative stress status and muscle development during embryonic and precocious larval phases in Siberian Sturgeon (Acipenser baeri), when subjected to different incubating temperatures (13°, 16° and 19°C).Siberian sturgeon eggs were subjected to different incubation temperatures. Data regarding water quality parameters were recorded, as well as mortalities, embryonic period length, and precocious larvae behavior. Sampling was performed in the same developmental stage for each temperature, at five time points: 48 hours post-fertilization, embryo movements, hatching, schooling and yolk-sac full absorption. The observed hatching rates were between 85.5% and 98.8% with significant differences concerning the different experimental temperatures (T19 vs T13 and T19 vs T16, p<0,05). Histological, histochemical and immunohistochemical analyses will be performed to assess ontogeny of the lateral muscle and stress biomarkers (Lushchak, 2011), and gene expression will be analyzed for muscle development (Johnston, 2006). The obtained results will be compared with those concerning teleosts and will possibly contribute to better rearing conditions of sturgeons.This study has been approved by the ethic committee of the Università degli Studi di Milano, with the following authorisation code: OPBA_20_2016.

Rearing temperature effect on the skeletal muscle fibres of Acipenser baerii yolk-sac larvae

Siberian sturgeon farming is important because it provides an alternative source of caviar and meat, but also for the conservation of the endangered natural stocks. Farmed fish is continuously subjected to stress factors, of which, water temperature is considered a major one (Schram et al., 2006). It has been demonstrated that physiological stress may have serious negative consequences on growth (Wendelaar Bonga, 1997) and that fish larvae appear less tolerant than adults to temperature variations (Stefanovich et al., 2016). The present study aims at investigating the stress response and development in precocious stages of siberian sturgeon when subjected to different rearing temperatures, by analysing ontogeny, growth and stress response of yolk-sac larvae. This study was approved by the Ethic Committee of the University of Milan (OPBA_20_2016). Fertilized Siberian sturgeon eggs were reared at 16°C, 19°C and 22°C until complete yolk-sac absorption. Sampling timepoints were: hatching, schooling and complete yolk-sac absorption stage. Water parameters and larvae development data were registered. Histological, histochemical and immunohistochemical analyses were performed in order to assess ontogeny and stress biomarkers and whole body cortisol was measured by a specific microtitre radioimmunoassay (RIA). Statistical analysis was performed with SAS software (v. 9.3, Cary Inc., NC). Larvae subjected to the highest water temperature showed a faster yolk-sac absorption and larvae body weight significantly increased from hatching onwards. Structural normal development considering the three different temperatures investigated from hatching until the end of the trial was observed. Significant differences were found between temperatures regarding body weight and cortisol levels (P<0.01). A qualitative stronger expression of stress markers was noticed in larvae subjected to the lower temperature. Even if this study indicates that lower rearing temperatures would appear more suitable for Siberian sturgeon rearing, further studies would be necessary to evaluate the temperature effect on a mid-long term basis

Stages of Gut Development as a Useful Tool to Prevent Gut Alterations in Piglets

During the prenatal, neonatal, and weaning periods, the porcine gastrointestinal tract undergoes several morpho-functional, changes together with substantial modification of the microbial ecosystem. Modifications of the overall structure of the small intestine also occur, as well as a rapid increase of the volume, mainly in the last period of gestation: intestinal villi, starting from jejunum, appears shortly before the sixth week of gestation, and towards the end of the third month, epithelial cells diversify into enterocytes, goblet cells, endocrine, and Paneth cells. Moreover, in the neonatal period, colostrum induces an increase in intestinal weight, absorptive area, and brush border enzyme activities: intestine doubles its weight and increases the length by 30% within three days of birth. During weaning, intestinal environment modifies drastically due to a replacement of highly digestible sow milk by solid feed: profound changes in histological parameters and enzymatic activity are associated with the weaning period, such as the atrophy of the villi and consequent restorative hypertrophy of the crypts. All these modifications are the result of a delicate and precise balance between the proliferation and the death of the cells that form the intestinal mucosa (i.e., mitosis and apoptosis) and the health conditions of the piglet. An in-depth knowledge of these phenomena and of how they can interfere with the correct intestinal function can represent a valid support to predict strategies to improve gut health in the long-term and to prevent weaning gut alterations; thus, reducing antimicrobial use

How Different Stocking Densities Affect Growth and Stress Status of Acipenser baerii Early Stage Larvae

In the present study, a multidisciplinary approach was used in order to evaluate growth, muscle development, and stress status in Siberian sturgeon Acipenser baerii larvae at schooling (T1) and complete yolk sac absorption (T2), reared at three stocking densities (low, medium, and high). Larvae growth, morphological muscle development, and whole-body cortisol levels were assessed. The expression of genes involved in the growth process (igf1 and igf2), in the myogenesis (myog), and in the regulation of cellular stress (glut1, glut2, glut4, and hsp70) was analyzed using a quantitative PCR. Larvae reared at lower densities showed a higher Specific Growth Rate and showed a physiological muscle development. Cortisol levels were low and did not differ significantly, both in different time sampling and across densities, suggesting that either the considered densities are not stressors in this species in the early stages of development or the hypothalamus-pituitary-adrenal (HPA) axis is not yet fully mature. Gene expression of glut1, igf1, and igf2 showed an up-regulation in both developmental stages at all the rearing densities considered, while myog significantly up-regulated at T1 at the highest density. Considering all of the results, it would seem that lower densities should be used in these stages of development, as these showed a higher growth rate, even if it is not economically feasible in commercial hatcheries. Therefore, choosing an intermediate stocking density could be a good compromise between larval performance and economical feasibilit

Rearing Environment during the Endogenous Feeding Stage of Acipenser baerii

The aim of this study was to evaluate behaviour, growth, lipid composition, muscle development, and stress status of Siberian sturgeon larvae reared with two types of substrate: Bioballs1 (BB1) and Bioballs2 (BB2), when compared to no substrate (CTR). Sampling points were: hatching (T0), schooling (T1), and yolk-sac full absorption (T2). BB1 larvae were less active and showed no schooling behaviour. At T1 and at T2, BB1 larvae showed a significantly higher weight and total length than larvae reared in either CTR or BB2 (p < 0.05). The lipid content of larvae decreased over time, with little relevant differences between groups. At T2, total muscle area, slow muscle area and fast muscle area were significantly higher in larvae reared in BB1 (p < 0.05). No significant differences in muscle proliferation were found between groups. Real Time PCR was used for evaluating the relative expression of a pool of genes: myod, myog, mrf4, igf2, hsp70, hsp90a, hsp90b, and glut2. The expression of these genes did not seem to be much affected by the type of rearing substrate, except for myog and hsp70 at T1, which was greater in BB2 larvae. Our data suggest that the presence of a substrate during this developmental period seems to have positive effects but further studies would be necessary during the exogenous feeding stage

How Do Alternative Protein Resources Affect the Intestine Morphology and Microbiota of Atlantic Salmon?

The availability and cost of fishmeal constitute a bottleneck in Atlantic salmon production expansion. Fishmeal is produced from wild fish species and constitutes the major feed ingredient in carnivorous species such as the Atlantic salmon. These natural stocks are at risk of depletion and it is therefore of major importance to find alternative protein sources that meet the nutritional requirements of the Atlantic salmon, without compromising the animals’ health. Terrestrial animal by-products have been used in aquaculture feed, but their use is limited by the lack of several essential amino acids and consumer acceptance. In the case of plant ingredients, it is necessary to take into account both their concentration and the extraction methodologies, since, if not dosed correctly, they can cause macro- and microscopic alterations of the structure of the gastrointestinal tract and can also negatively modulate the microbiota composition. These alterations may compromise the digestive functions, growth of the animal, and, ultimately, its well-being. An updated revision of alternative protein sources is provided, with the respective impact on the intestine health in terms of both morphology and microbiota composition. Such information may constitute the premise for the choice and development of Atlantic salmon feeds that guarantee fish health and growth performance without having a significant impact on the surrounding environment, both in terms of depletion of the fish’s natural stocks and in terms of pressure on the terrestrial agriculture. The sustainability of aquaculture should be a priority when choosing next-generation ingredients

Postnatal morpho-functional development of a dog’s meniscus

: This study evaluates the morpho-functional modifications that characterize meniscal development from neonatal to adult dogs. Even if menisci are recognized as essential structures for the knee joint, poor information is available about their morphogenesis, in particular in dog models. Menisci from a group of Dobermann Pinchers aged 0, 10, 30 days, and 4 years (T0, T10, T30, adult, respectively) were analyzed by SEM, histochemistry (Safranin O and Picro Sirius Red Staining analyzed under a polarized light microscope), immunofluorescences (collagen type I and II), biomechanical (compression) and biochemical analyses (glycosaminoglycans, GAGs, and DNA content). SEM analyses revealed that the T0 meniscus is a bulgy structure that during growth tends to flatten, firstly in the inner zone (T10) and then even in the outer zone (T30), until the achievement of the completely smooth adult final shape. These results were further supported by the histochemistry analyses in which the deposition of GAGs started from T30, and the presence of type I birefringent collagen fibers was observed from T0 to T30, while poorly refringent type III collagen fibers were observed in the adult dogs. Double immunofluorescence analyses also evidenced that the neonatal meniscus contains mainly type I collagen fibers, as well as the T10 meniscus, and demonstrated a more evident regionalization and crimping in the T30 and adult meniscus. Young's elastic modulus of the meniscus in T0 and T10 animals was lower than the T30 animals, and this last group was also lower than adult ones (T0-T10 vs T30 vs adult). Biochemical analysis confirmed that cellularity decreases over time from neonatal to adult (p < 0.01). The same decreasing trend was observed in GAGs deposition. These results may suggest that the postnatal development of canine meniscus may be related to the progressive functional locomotory development: after birth, the meniscus acquires its functionality over time, through movement, load, and growth itself