Red Vetchling (Lathyrus cicera L.), a Promising Crop for the Sustainable Replacement of Soybean Meal and Reducing the Carbon Footprint of European Aquafeeds.

In fish diets, soybean meal (SBM) is still positioned as the most widely used alternative to replace fishmeal. Red vetchling (Lathyrus cicera), a crop locally produced in Europe, is here evaluated as a substitute for SBM. Rainbow trout (Oncorhynchus mykiss) juveniles (10.34 ± 0.04 g) were fed for 90 days. Six experimental diets replacing the SBM content at 0, 8, 16, 33, 66, and 100% (Named Control, T8, T16, T33, T66, and T100) were tested. Growth performance and fish fillet amino acid composition were only significantly reduced in fish fed the T100 diet. Histopathological analysis showed that no major alterations were observed in the intestine, while T100 fish had a higher density of pyknotic nuclei in the hepatocytes than the Control, but similar hepatocyte surface coverage. Finally, postprandial levels of glucose and triglycerides in blood plasma decreased when red vetchling content was increased, but was only not fully restored after 24 h in the case of glucose in T66 and T100 fish. According to these results, red vetchling meal can replace up to 66% of the SBM without a negative effect on fish growth or physiology, representing a good alternative raw material for reducing European aquaculture's dependency on SBM imports and the carbon footprint of aquafeeds.

Specific Blood Plasma Circulating miRs Are Associated with the Physiological Impact of Total Fish Meal Replacement with Soybean Meal in Diets for Rainbow Trout (Oncorhynchus mykiss).

High dietary SBM content is known to induce important physiological alterations, hampering its use as a major FM alternative. Rainbow trout (Oncorhynchus mykiss) juveniles were fed two experimental diets during 9 weeks: (i) a FM diet containing 12% FM; and (ii) a vegetable meal (VM) diet totally devoid of FM and based on SBM (26%). Fish fed the VM diet did not show reduced growth performance when compared with fish fed the FM diet. Nevertheless, fish fed the VM diet had an increased viscerosomatic index, lower apparent fat digestibility, higher aminopeptidase enzyme activity and number of villi fusions, and lower α-amylase enzyme activity and brush border integrity. Small RNA-Seq analysis identified six miRs (omy-miR-730a-5p, omy-miR-135c-5p, omy-miR-93a-3p, omy-miR-152-5p, omy-miR-133a-5p, and omy-miR-196a-3p) with higher expression in blood plasma from fish fed the VM diet. Bioinformatic prediction of target mRNAs identified several overrepresented biological processes known to be associated with high dietary SBM content (e.g., lipid metabolism, epithelial integrity disruption, and bile acid status). The present research work increases our understanding of how SBM dietary content has a physiological impact in farmed fish and suggests circulating miRs might be suitable, integrative, and less invasive biomarkers in fish.

Changes in digestive enzyme activities during the early ontogeny of the South American cichlid (Cichlasoma dimerus).

Cichlasoma dimerus is a neotropical cichlid that has been used as a biological model for neuroendocrinology studies. However, its culture is problematic in terms of larval feeding to allow having enough fry quantity and quality. Larviculture requires full knowledge about the digestive system and nutrition; therefore, this study was intended to assess the digestive enzymes' changes at different ages during the early ontogeny. Acid protease activity was detectable from the first day after hatching (dah), increasing to its maximum peaks on 9 dah. In contrast, alkaline proteases had low activity in the first days of life but reached their maximum activity on 17 dah. Chymotrypsin, L-aminopeptidase, and carboxypeptidase A activities increased at 6 dah, while trypsin activity was first detected on 13 dah and reached its maximum activity on 17 dah. Lipase and α-amylase activity were detectable at low levels in the first days of life, but the activity fluctuated and reaching its maximum activity at 21 dah. Alkaline phosphatase continued to oscillate and had two maximum activity peaks, the first at 6 dah and the second at 19 dah. Zymograms of alkaline proteases on day 6 dah six revealed four activity bands with molecular weights from 16.1 to 77.7 kDa. On 13 dah, two more activity bands of 24.4 and 121.9 kDa were detected, having a total of six proteases. The enzymatic activity analyzes indicate the digestive system shows the low activity of some enzymes in the first days after hatching, registering significant increases on 6 dah and the maximum peaks of activities around at 17 dah. Therefore, we recommend replacing live food with dry feed and only providing dry feed after day 17 dah.

Skeletal Development and Deformities in Tench (Tinca tinca): From Basic knowledge to Regular Monitoring Procedure.

Skeletal deformities reduce fish viability, growth, wellbeing, and feed efficiency but also degrade the consumer's perception of aquaculture products. Herein, the skeletal development and the incidence of skeletal deformities in tench (Tinca tinca) reared in semi-extensive conditions has been described in detail for the first time. Larval skeletons were assessed through an acid-free double-staining procedure in 157 individuals, while 274 specimens at the juvenile stage were evaluated through X-ray analysis. The first skeletal structures to be formed were those related with breathing and feeding activities (e.g., Meckel's cartilage and opercula) and were visible in larvae of 4 mm of standard length (SL). The axial skeleton was fully ossified in larvae of 12-17 mm of SL, and the caudal fin complex in larvae with 17-26 mm of SL. At the larval stage, no upper-jaw or opercula deformities were observed, while a low incidence (1-9%) of other severe deformities in the heads of the fish (e.g., lower-jaw deformities) were reported. The incidence of vertebral deformities in tench reared in natural ponds was considerable in larvae (54%) and juveniles (52%). Vertebral deformities (fusion and compression) were the most common deformities found in tench larvae (approximately 30%) and vertebral shape deformity in juveniles (around 10%), being mainly located in the caudal region. Thus, a regular monitoring of the skeletal deformities in tench might help to identify better rearing protocols and improve product quality sold at markets. Characterizing the skeletal development not only in semi-extensive systems such as artificial and natural ponds but also under intensive rearing conditions, seems vital for a sustainable and profitable European tench aquaculture.

Effects and Safe Inclusion of Narbonne Vetch (Vicia narbonensis) in Rainbow Trout (Oncorhynchus mykiss) Diets: Towards a More Sustainable Aquaculture.

Aquaculture's sustainability deeply relies on the identification and inclusion of alternative raw materials. Although meals from insects and/or byproducts from different industries are being recently tested, the meal from terrestrial vegetable species is still the main substitution candidate for fish meal. Here the effects of 0% (Control), 10% (A10) and 30% (A30) inclusion of Narbonne vetch (Vicia narbonensis; ZV-156 strain) meal in rainbow trout (Oncorhynchus mykiss) diets was assessed in a 63-day feeding trial by means of growth performance, histopathological, nutritional value of the fish fillet and blood biochemistry analyses. A dose-response trial was conducted in triplicate with 25 rainbow trout juveniles (20 g average body weight) per 500 L tank. Narbonne vetch meal decreased total intestine protease activity in vitro (from 26.81% to 48% inhibition), although high temperature partially inhibited the action of antinutritional factors (ANFs). No differences in fish growth performance and no severe histopathological alterations on the proximal intestine were observed between 10% Narbonne vetch inclusion and Control groups. In contrast, high inclusion (30%) of Narbonne vetch led to poor growth performance (30% reduction on final growth) and severe histopathological alterations (e.g., loss of brush border integrity, high number of villi fusion, reduced goblet cells density as well as reduced width of submucosa, muscular and serosa layers). Furthermore, while the A30 diet decreased docosahexaenoic fatty acid (FA) content in fish fillets, the A10 diet improved monounsaturated FA content when compared to that of the Control group. No altered levels of cholesterol, glucose or triglycerides in blood plasma and/or histopathological effects on the liver were observed among fish fed the different experimental diets. Although further research efforts (e.g., identifying potential enzymatic treatments to decrease the action of ANFs from Narbonne vetch meal) might be required, present results show that a low inclusion (10%) of Narbonne vetch in rainbow trout diets is possible. The inclusion of locally produced legumes such a Narbonne vetch might be an interesting approach to reduce carbon footprint in European aquaculture and the dependency on other alternative raw materials such as soybean (Glycine max) imported from third countries.

Vitamin K in Vertebrates' Reproduction: Further Puzzling Pieces of Evidence from Teleost Fish Species.

Vitamin K (VK) is a fat-soluble vitamin that vertebrates have to acquire from the diet, since they are not able to de novo synthesize it. VK has been historically known to be required for the control of blood coagulation, and more recently, bone development and homeostasis. Our understanding of the VK metabolism and the VK-related molecular pathways has been also increased, and the two main VK-related pathways-the pregnane X receptor (PXR) transactivation and the co-factor role on the γ-glutamyl carboxylation of the VK dependent proteins-have been thoroughly investigated during the last decades. Although several studies evidenced how VK may have a broader VK biological function than previously thought, including the reproduction, little is known about the specific molecular pathways. In vertebrates, sex differentiation and gametogenesis are tightly regulated processes through a highly complex molecular, cellular and tissue crosstalk. Here, VK metabolism and related pathways, as well as how gametogenesis might be impacted by VK nutritional status, will be reviewed. Critical knowledge gaps and future perspectives on how the different VK-related pathways come into play on vertebrate's reproduction will be identified and proposed. The present review will pave the research progress to warrant a successful reproductive status through VK nutritional interventions as well as towards the establishment of reliable biomarkers for determining proper nutritional VK status in vertebrates.