Crayfish Diet Research Articles

Effects of yeast and willow extract in the diet on the survival and growth parameters of the crayfish (Cambarellus montezumae)

ABSTRACT The use of additives such as yeast or plant extracts in crayfish diets, even though are typically found in their natural habitats, has attracted recent attention due to the observed health, growth, and socio-economic benefits they offer. The presence of willow detritus in the stomach contents of free-living crayfish suggests its potential role in crayfish growth, even though it has not yet been demonstrated. This study aimed to evaluate the effect of yeast and willow extract as dietary additives on the growth of the crayfish Cambarellus montezumae. A total of 630 juvenile crayfish were collected, introduced into a recirculating aquaculture system, and randomly assigned to three treatment groups with three replicates each one (n = 70 per replicate): shrimp-balanced ration with yeast, shrimp-balanced ration with willow extract, and shrimp-balanced ration as the control. Throughout a 70-days period, the crayfish were weekly measured and weighed to assess various growth parameters and survival. Crayfish fed with the yeast ration showed improvements in weight, length, biomass, periodic absolute increase in weight and length, and relative growth rate in length compared with those in the willow and control groups. The incorporation of yeast into the ration demonstrates greater advantages to produce Cambarellus montezumae. The underlying mechanisms suggest efficient ration utilization and the potential for increased production which, has important implications for the aquaculture industry.

Influence of Different Feed Particle Sizes on the Growth Performance and Nutrition Composition in Crayfish, Procambarus clarkii Larvae.

A suitable feed size has a positive effect on animal feeding. For aquatic larvae, the correct feed size is very important for their growth. This experiment analyzed and compared the effect of different particle sizes of feed for larval stages on the growth performance, whole body composition, and muscle amino acid and fatty acid composition of crayfish. Five larval crayfish diets of different particle sizes, namely < 0.40 mm (Group A, control group), 0.40-0.50 mm (Group B), 0.71-0.85 mm (Group C), 0.90-1.00 mm (Group D) and 1.5 mm (Group E), were fed to 2000 crayfish (initial weight 0.0786 ± 0.0031 g) for 100 d. The results showed that as the particle size increased, final weight, weight gain (WG, p = 0.001) and specific growth rate (SGR, p = 0.000) of the crayfish tended to increase and then leveled off, with the control group being the lowest. The feed conversion ratio (FCR, p = 0.000) showed a decreasing and then equalizing trend with increasing particle size, but there was no significant difference between the groups except the control group. Broken-line regression analysis showed that the critical values for the appropriate particle feed size for crayfish larvae were 0.55 mm and 0.537 mm using SGR and FCR as indicators. Groups B, C and D had the highest crude protein content and were significantly higher than the control group (p = 0.001). Group E had the highest umami amino acid (UAA) and was significantly higher than the control group (p = 0.026). The content of isoleucine (Ile, p = 0.038) and phenylalanine (Phe, p = 0.038) was highest in group C and significantly higher than in the control group. Through principal component analysis, groups C and D were shown to contain leucine (Leu), glutamic (Glu), methionine (Met), valine (Val), histidine (His), Phe, and Ile levels significantly induced. The content of linoleic acid (C18:2n6, p = 0.000), linolenic acid (C18:3n3, p = 0.000), saturated fatty acid (SFA, p = 0.000), monounsaturated fatty acid (MUFA, p = 0.001), polyunsaturated fatty acid (PUFA, p = 0.000) and n-6 PUFA (p = 0.000) in group C was the highest and significantly higher than the control group. Principal component analysis showed that group C significantly induced the levels of C18:2n6, C18:3n3, DHA, EPA, n-3 PUFA and n-6 PUFA in muscle. Therefore, our results suggest that appropriate feed particle size can improve the growth performance and nutrient composition of crayfish. Based on the broken-line regression analysis of SGR and FCR, the critical values of optimal particle size for crayfish are 0.55 mm and 0.537 mm, and when the particle size exceeds these critical values (not more than 1.5 mm commercial feed), growth performance and FCR of the crayfish are no longer changed. Nevertheless, group C has high protein and low lipid content, as well as better nutrition with amino acids and fatty acids. Overall, combined with growth performance and nutrient composition, it is recommended that the particle size of the diet at the larval stage for crayfish is between 0.71 and 0.85 mm.

A study on the effects of replacing fishmeal with soybean meal in the feed of Procambarus clarkii: Assessing growth performance, immunity, and gut microbiota

The unstable supply and high cost of fishmeal have led to increased interest in low fish meal feed. As such, the present study aimed to investigate the effects of replacing fishmeal in feeds with soybean meal (SM) on the growth, immunity, and gut microbiota of crayfish. A total of 750 crayfish (4.00 g) were randomly divided into five groups (SS0, SS25, SS50, SS75, and SS100) with three replicates, and were fed diets with different levels of soybean meal substituted for fishmeal for six weeks. The results revealed that crayfish subjected to high SM diets experienced a significant decrease in the final body weight, weight gain rate, and specific growth rate (p<0.05), together with enzyme activities related to nutrient digestion and absorption. Of note, the groups with 25–50 % SM replacement exhibited decreased final body weight without significance compared to that in the SS0 group (p>0.05). Moreover, increasing SM inclusion exhibited the potential to impair the intestine, characterized by the increase in hemolymph LD content, decrease in the levels of TC content, T-AOC, and AKP, along with the observed edema of the lamina propria, and up-regulated mRNA expression levels of nfkb, alf, and tlr. Furthermore, high SM diets resulted in the emergence of new species and a shift in Firmicutes, Bacteroidota, Proteobacteria, and Fusobacteriota. Specifically, the abundance of lower Firmicutes and higher Proteobacteria was observed in the SS100 group, which was closely correlated with genus-level Candidatus Bacilloplasma, and RsaHf231 abundance alterations. MENAs demonstrated that the high SM diets led to a more complex, yet fragile and unstable microbial network. The global network further indicated that the microbes contributing more to crayfish were in module eigen 4, in which 9 OTUs were identified as major biomarkers and mainly classified into Proteobacteria. Taken above, SM could replace 25 % of fishmeal in crayfish diets without negatively affecting growth performance, nutrient utilization, immunity, and antioxidant capacity. Excessive SM levels contributed to gut dysfunction and weakened the immune system of crayfish.

BODY WEIGHT OF CHERAX QUADRICARINATUS AND INDICATORS OF HS-GROUPS IN THEIR LIVER AFTER INCLUSION OF DIFFERENT DOSES OF VERMICULTURE BIOMASS IN THE DIETS

Crustacean products have a positive dynamic demand among the population of the country. Crayfish meat is an effective source of essential amino acids and other biologically active substances for the human body. An important element in the technology of crayfish farming is their feeding. The growth rate of crayfish Сherax quadricarinatus depends on the content and origin of protein in their diets. An effective source of protein for crayfish can be the biomass of a hybrid of red California worms. However, the issue of determining the effectiveness of using vermiculture biomass grown on a substrate containing broiler manure fermented with active aeration in crayfish diets remains unexplored. The aim of the study is to investigate the effect of the optimal content of vermiculture biomass in diets on the growth of crayfish and the content of HS groups in their liver. To achieve the planned goal, in the conditions of the experimental farm of the Bila Tserkva National Agrarian University, crayfish from the I, II and III experimental groups were fed standard diets containing 10.0, 15.0 and 20.0 % of California worm biomass. Crayfish from the control group were fed standard diets (complete feed + oak leaves). The content of sulfhydryl groups in the homogenate from the liver of Cherax quadricarinatus was determined using the method of Ellman G.L. It was proved that feeding diets containing 20.0 % of vermiculture biomass increased the body weight of crayfish by 7.0 % compared to the control. The highest body weight of Cherax quadricarinatus at the end of the experiment was found in the group where the diet containing 15.0 % of California worm biomass was used. The difference with the control was 8.2 %. An increase in the preservation of crayfish by 8.0 % was found when feeding them 15.0 and 20.0 % of vermiculture biomass. The use of worm biomass increases the average daily and absolute growth of crayfish and does not cause a decrease in the content of sulfhydryl groups in their liver. The study of the chemical composition of muscle tissue of crayfish when fed diets containing vermiculture biomass is promising.

Effects of l-ascorbic acid on growth, non-specific immunity, antioxidant capacity, and intestinal and hepatopancreatic histology of red swamp crayfish, Procambarus clarkii

This study investigated the dietary effects of coated l-ascorbic acid (LA) on growth, feed utilization, survival, serum biochemical indices, immunity, antioxidant capacity, and intestinal and hepatopancreatic histology of the pre-adult red swamp crayfish. Four isoproteinous and isolipidic diets were formulated to contain several LA levels as 0, 1300, 1600, and 1900 mg/kg and designated as control (LA0), LA13, LA16, and LA19, respectively. However, the analyzed LA concentrations in diets were 0.00, 199.57, 360.45, and 487.50 mg/kg in LA0, LA13, LA16, and LA19, respectively. Triplicate treatments of crayfish (21.60 ± 0.14 g) were fed the test diets and reared in fiberglass tanks with a density of 20 individuals per each for eight weeks. Results revealed that all LA treatments had significantly enhanced growth performance compared to the control. Of interest, the LA16 treatment recorded the highest final tank biomass, biomass gain, total feed intake, condition factor, and muscle yield among the other treatments. The tank feed conversion ratio was significantly decreased in LA treatments compared to the control. Moreover, dietary LA16 and LA19 had significantly higher survival rates (93.3%) compared to (85.0%) in the LA0 group. All dietary doses of LA significantly increased serum parameters (total protein, albumin, globulin, lysozyme activity) and respiratory burst activity compared to the LA0 treatment. Dietary LA16 significantly boosted the hepatopancreatic antioxidant capacity, manifested by decreased malondialdehyde concentrations, increased catalase, superoxide dismutase, and glutathione peroxidase enzyme activities, and reduced glutathione content compared to the LA-free diet. A normal histoarchitecture of the hepatopancreatic tubules was found in all LA treatments except with some minor degenerative changes in the tubular lumen, and hepatopancreatic cells associated with enlarged nuclei were found in the LA19. However, normal intestinal histoarchitecture was found in all treatments with no recorded intestinal lesions. Of interest, the polynomial regression performed on the analyzed LA concentrations suggested that 380 mg/kg would be suitable to provide maximal biomass gain for pre-adult crayfish. In conclusion, results revealed that coated LA could enhance the growth, immunity, and antioxidant capacity of pre-adult red swamp crayfish, suggesting its potential as a functional and necessary micronutrient for crayfish diets.

Saccharomyces cerevisiae additions normalized hemocyte differential genes expression and regulated crayfish (Procambarus clarkii) oxidative damage under cadmium stress

Because China produces the most crayfish in the world, safe solutions must be improved to mitigate the risks of ongoing heavy metal stressors accumulation. This study aimed to use Saccharomyces cerevisiae as a bioremediation agent to counteract the harmful effect of cadmium (Cd) on crayfish (Procambarus clarkia). Our study used three concentrations of S. cerevisiae on crayfish feed to assess their Cd toxicity remediation effect by measuring total antioxidant capacity (TAC) and the biomarkers related to oxidative stress like malondialdehyde (MDA), protein carbonyl derivates (PCO), and DNA–protein crosslink (DPC). A graphite furnace atomic absorption spectroscopy device was used to determine Cd contents in crayfish. Furthermore, the mRNA expression levels of lysozyme (LSZ), metallothionein (MT), and prophenoloxidase (proPO) were evaluated before and following the addition of S. cerevisiae. The results indicated that S. cerevisae at 5% supplemented in fundamental feed exhibited the best removal effect, and Cd removal rates at days 4th, 8th, 12th, and 21st were 12, 19, 29.7, and 66.45%, respectively, which were significantly higher than the basal diet of crayfish. The addition of S. cerevisiae increased TAC levels. On the other hand, it decreased MDA, PCO, and DPC, which had risen due to Cd exposure. Furthermore, it increased the expression of proPO, which was reduced by Cd exposure, and decreased the expression of LSZ and MT, acting in the opposite direction of Cd exposure alone. These findings demonstrated that feeding S. cerevisiae effectively reduces the Cd from crayfish and could be used to develop Cd-free crayfish-based foods.

Microcystin profiles in European noble crayfish Astacus astacus and water in Lake Steinsfjorden, Norway

Lake Steinsfjorden, an important noble crayfish (Astacus astacus) habitat, is often affected by blooms of Planktothrix spp. that produce microcystins (MCs). A poor correlation between MCs by ELISA in the water and in crayfish tissue in a study in 2015 prompted further investigation by LC–HRMS. LC–HRMS analyses of filters from water samples and on selected crayfish tissue extracts from the 2015 study revealed the presence of known and previously unreported MCs. Crayfish samples from May and June 2015 were dominated by MCs from the Planktothrix bloom, whereas in September novel MCs that appeared to be metabolites of MC-LR were dominant, even though neither these nor MC-LR were detected in the water in 2015. A water sample from October 2016 also showed MCs typical of Planktothrix (i.e., [d-Asp3]- and [d-Asp3,Dhb7]MC-RR and -LR), but low levels of MC-RR and MC-LR were detected in the lake water for the first time. In late summer and autumn, the MC profiles of crayfish were dominated by the homonorvaline (Hnv) variant MC-LHnv, a putative metabolite of MC-LR. Taken together, ELISA, LC–HRMS and previous PCR analyses showed that although Planktothrix was part of the crayfish diet, it was not the sole source of MCs in the crayfish. Possibly, crayfish in Lake Steinsfjorden may be ingesting MCs from benthic cyanobacteria or from contaminated prey. Therefore, information on the cyanobacterial or MC content in the water column cannot safely be used to make predictions about MC concentrations in the crayfish in Lake Steinsfjorden. Interestingly, the results also show that targeted LC–MS analysis of the crayfish would at times have underestimated their MC content by nearly an order of magnitude, even if all previously reported MC variants had been included in the analysis.

Effects of different fertilization patterns on the dietary composition of Procambarus clarkii in a rice-crayfish coculture system

As an omnivorous species, crayfish (Procambarus clarkii) have varying feeding habits in different environments. However, little is known about the diet of crayfish under different fertilization patterns in rice-crayfish cocultures. In this study, we investigated the effect of fertilization on the growth performance, dietary composition and isotopic niche of crayfish in a rice-crayfish coculture system. Four experimental treatments were established: no fertilizer (CK), slow-release fertilizer (HS), crayfish rice fertilizer (XD) and compound fertilizer (FH). The results showed that HS and FH could significantly promote crayfish growth, and the growth of crayfish treated with HS was the best. Fertilization patterns had significant effects on the dietary composition of crayfish. The food source of unfertilized crayfish was relatively balanced. However, in the HS, XD and FH treatments, particulate organic matter increased with contribution rates of 34.04%, 56.89% and 42.86%, respectively. In addition, the artificial feed intake of crayfish in the FH group was the lowest. The isotopic niche revealed that crayfish in the HS group significantly increased in the direction of the δ15N axis. Based on routine economic indicators, slow-release fertilizer was suitable for the rice-crayfish coculture system. These findings could provide scientific guidance for the selection of fertilization modes in rice-crayfish coculture systems and the exploration of healthy crayfish culture models.

Effects of formulated Nigerian yellow maize, soybean, and crayfish blends on some growth performance and physiological status

In order to develop adequate complementary foods (CFs) to improve infant and young child feeding, the inclusion of animal source foods (ASFs) into plant-based foods (PBFs) is paramount. Unfortunately, the incorporation of ASFs into PBFs to formulate adequate CFs was infrequent in the developing countries, especially Nigeria. Yet, few CFs that were formulated by this strategy lacked adequate studies. This study investigated the compositional quality of CFs formulated from Nigerian yellow maize flour (MF), yellow maize + soybean flour (MSF), yellow maize + soybean + crayfish flour (MSCF), and commercial fortified wheat milk flour (FWMF) and their impact on the growth performance and physiological status of Sprague Dawley rats (SDRs). Compositional quality of CFs and their effects on the health status of SDRs were assessed. MSCF had higher protein and ash contents, its sulphur amino acids content was about 132% higher than that of MSF and astaxanthin was detected only in it. Determined antinutrients much reduced in MSCF compared with other CFs. The body weight gain (23.75 g) in yellow maize + soybean + crayfish diet (MSCD) group was significantly higher than other diet groups, whilst the value of protein efficiency ratio (2.59), feed efficiency ratio (0.30) in MSCD group was nominally higher compared with other groups. Better improvement in some of the biochemical and haematological parameters were observed in MSCD group compared with other groups, but no signs of illness, infection, and organ damage were seen in all the groups. The current study proved that crayfish could be used in a dietary modification to produce an adequate CF that potentiates improved growth performance and positive health outcomes in animals.Graphical

Reduced protein intake in Procambarus clarkii fed diets containing graded levels of purslane: Effects on growth and quality

AbstractIn this study, 144 red swamp crayfish (Procambarus clarkii, initial mean weight 3.9 ± 0.3 g) juveniles were fed diets containing graded levels of purslane (Portulaca oleracea), with a decreasing percentage of proteins (from 17.3% to 1.0%) for 10 weeks. Six diets were administered: four fishmeal diets containing 5%, 15%, 25%, and 50% purslane, a diet with 100% purslane, and a commercial diet. Growth performance and the amounts of fatty acids and carotenoids were measured. Crayfish fed 25% and 50% purslane diets showed optimal contents in fatty acids (FAs) and astaxanthin, and their growth was comparable to that of the control group. Significant differences in FA content of the crayfish groups were observed for saturated FAs, monounsaturated FAs (MUFAs), and polyunsaturated FAs (PUFAs). The highest levels of n − 3 α‐linolenic acid (ALA) and n − 6 linoleic acid (LA) were found in the groups fed 25%, 50%, and 100% purslane diets. This study shows that the best purslane content to be included in the crayfish diet should range between 25% and 50%. Although the nutritional value of purslane is low, its inclusion at up to 50% in crayfish diets seems to improve the carotenoid content and FA quality, while reducing the daily intake of animal protein, without affecting growth performance, thus contributing to the goal of more sustainable crustacean aquaculture.

Evaluation of the protein-sparing effects of carbohydrates in the diet of the crayfish, Procambarus clarkii

To explore the effects of dietary protein (P)/carbohydrate (C) ratios on the growth performance, body composition, immunity, and metabolism of red swamp crayfish (Procambarus clarkii), soybean meal, peanut meal, and cottonseed meal were used to adjust the P content of the feed, and corn starch was used to adjust the C content. Five groups of crayfish were fed diets with different P/C ratios (P25%/C39%, P28%/C36%, P31%/C33%, P34%/C30%, and P37%/C27%) for 8 weeks. The growth performance, body composition, and immunity of the crayfish, as well as the enzyme activities and expression of genes in the hepatopancreas, were assessed at the end of the feeding period. While the P/C ratio had no significant effect on growth performance, immunity, or body composition, a decrease in the P/C ratio resulted in a significant increase in the expression of glucose transporter 1 (GLUT1), as well as gradual increases in the activities and expression of hexokinase and pyruvate kinase in the hepatopancreas. There were significant differences in these values between the highest P/C ratio group (P37%/C27%) and the lowest P/C ratio group (P25%/C39%). However, the activities of the glycolytic enzymes glucose-6-phosphatase (G6P) and pyruvate carboxylase (PC) showed the opposite trend, indicating that a decrease in the P/C ratio inhibited gluconeogenesis. Increases in the dietary P/C ratio were associated with increases in aspartate aminotransferase (AST) and alanine aminotransferase (ALT) activities, which correlated with increases in the expression of AST, ALT, and glutamate dehydrogenase (GDH). An increase in dietary P content was also associated with significant increases in expression of the mechanistic target of rapamycin (mTOR) and 4E binding protein 1 (4EBP1) genes, which promote protein deposition. By contrast, while increasing C content decreased and then increased hepatopancreatic malondialdehyde content, it increased and then decreased superoxide dismutase and glutathione peroxidase activities. There were no significant differences in circulating acid phosphatase, alkaline phosphatase, AST, and ALT activities among the groups. Thus, the addition of carbohydrate to crayfish diets has a protein-sparing effect, and a diet containing 31% P and 33% C is optimal for maintaining antioxidative capacity, while a diet with a 25%P/39%C ratio results in maximum cost saving.

Effects ofPortulaca oleraceawhole diet on pigments and fatty acids profiles of juvenile red swamp crayfish (Procambarus clarkiiGirard, 1852) under laboratory conditions

A 10-week feeding trial was carried out to emphasize the effects of purslane weed (Portulaca oleracea) whole diet on pigmentation and fatty acids profile of juvenile freshwater red swamp crayfish Procambarus clarkii. Purslane weed is an annual succulent herb easily found in tropical and temperate regions showing a high-quality PUFA profile and carotenoid content. Crayfish fed with P. oleracea were compared with two groups fed with aquatic macrophytes control diets. At the end of the experiment, each group showed a distinct fatty acid composition, with crayfish feeding P. oleracea that exhibited significantly higher n-3 PUFA content (1.01 mg × 100 g−1) and total carotenoids (mainly astaxanthin) concentration (72.2 mg × kg−1). In natural conditions, plants are not used as primary foodstuff by crayfish, but in extensive and semi-intensive aquaculture, they could bring supplementary nutrition benefits to crayfish without affecting growth performance. P. oleracea could represent a promising ingredient in crayfish diets, or in new artificial feeds, given its added values in terms of carotenoids and polyunsaturated fatty acids. The results of this study might encourage further research aimed at defining the optimal percentages of P. oleracea inclusion in sustainable crayfish diets.

Effects of Two Different Macroalgae (Ulva lactuca and Jania rubens) Species on Growth and Survival of Red Swamp Crayfish (Procambarus clarkii) as Feed Additive

The effects of dietary supplementation of two different macroalgae Ulva lactuca and Jania rubens on the growth performance, survival and feed conversion ratio of juvenile red swamp crayfish juvenile (Procambarus clarkii) were investigated. Red swamp crayfish with an average total length of 56.2±6.67 mm and an average weight of 3.77±0.2 g were placed at tanks (10 crayfish at each tank) and offered diets 8 weeks. Different levels of macroalgae were added to commercial sea bass feed, and no seaweed was used as a control group. It was observed that crayfish fed with 10% feed had higher growth performance (in terms of length and weight) than those fed with 15% diet and control group (P&amp;lt;0.05). The lowest feed conversion rate was observed in juvenile crayfish fed with 15% feed (P&amp;lt;0.05). The highest survival rate was 50.0% at group fed with 15% feed, followed by 46.66% (control group) and 43.33% (10% diet groups), respectively. This study showed that there was no statistical difference in survival rate among treatment groups (P&amp;gt;0.05). However, the frequency of molting was mostly observed in the group fed with 10% diet. Therefore, the results showed that seaweed (Ulva lactuca and Jania rubens) could be used as a supplement for red swamp crayfish diet (Procambarus clarkii) at 10% to improve growth performance with no adverse effects on feed efficiency or survival rate.

Quantitative analysis of density dependent resource utilization, cannibalism, and competition of the red swamp crayfish (Procambarus clarkii) in rice-crayfish cocultures without supplementary food

A 90-day, integrated rice-crayfish coculture experiment using net enclosures (8 m × 10 m each) was performed to determine resource utilization, cannibalism, and inter-sexual competition in the red swamp crayfish (Procambarus clarkii) at four stocking densities (4 ind/m2, 6 ind/m2, 9 ind/m2, and 12 ind/m2). The results were as follows: (1) With increasing stocking density of crayfish, the relative contribution of animal feed sources to male and female crayfish diets initially decreased and then increased, whereas the contributions of plant feed sources and detritus as a feed source initially increased and then decreased. There was no significant difference in the diets of female and male crayfish between 4 ind/m2 and 12 ind/m2; plants (> 50%) were predominant, followed by animal feed (> 20%), cannibalism (~ 18%), and detritus (> 6%). At 6 ind/m2 and 9 ind/m2, the contributions of feed sources for both male and female diets were as follows: plants (> 60%), animal feed (> 15%), detritus (> 10%), and cannibalism (< 8%). The trophic and spatial niche area per individual unit (SEA/density, SEA·m2/ind) of female and male crayfish decreased as stocking density increased. (2) With increasing stocking density, the contribution of cannibalized feed sources to crayfish initially decreased (from 4 ind/m2 to 6 ind/m2) and then increased (from 6 ind/m2 to 12 ind/m2). The SEA f,m (representing the similarity of diets between female and male crayfish and, therefore, the potential for inter-sexual competition) initially increased with stocking density (from 4 ind/m2 to 9 ind/m2) and then decreased (from 9 ind/m2 to 12 ind/m2). This indicated that cannibalism might reduce the competition between sexes for natural resources. (3) Based on the high trophic and spatial niche area per individual unit (SEA·m2/ind; female = 0.37 and male = 0.88), low contributions of cannibalized feed sources (female = 5.88 ± 2.62% and male = 7.97 ± 3.44%), and low degree of inter-sexual competition (SEA f,m = 0.25), 6 ind/m2 (crayfish tail weight 9.60 g) was identified as the optimal stocking density for P. clarkii in rice fields without supplementary artificial feed.

Comparative evaluation of fish, crayfish waste, meat and blood meal for broiler production

The effect of different animal protein sources in broiler production was investigated. 300 seven-day old broilers of equal average initial weight were randomly allotted into five treatment groups with three replications of 20 birds each and at the end of 28 days, birds were weighed again and re-randomized to the five treatment groups with three replicates of 16 birds each. The diets consisted of four animal proteins. Treatment 1 (Control) had no animal protein while diet 2, 3, 4 and 5 had 4% fish meal, 4% crayfish waste meal, 4% blood meal and 4% meat meal, respectively. The study was conducted for 56 days with 28days starter phase and 28days finisher phase. Parameters evaluated were proximate composition of test ingredients, growth performance of experimental animals, nutrient digestibility and economic analysis. The results showed blood meal had the highest (P&lt;0.05) crude protein level (77.68%) followed by fish meal (54.53%), crayfish waste (48.08%) and meat meal (41.67%). Cray fish waste meal had the highest (P&lt;0.05) crude fibre (6.07%) while blood meal had the least (2.98%). Fish meal had the highest ether extract (5.99%) followed by crayfish waste meal (4.03%), meat meal (3.67%) and blood meal (3.93%). There were nonsignificant (P&lt;0.05) differences in feed intake during both starter and finisher phases across the treatment groups. Blood meal significantly (P&lt;0.05) depressed final live weight, weight gain, feed conversion ratio and protein efficiency ratio while other ingredients showed (P&gt;0.05) similarities in the above parameters apart from in protein efficiency ratio for which meat meal only showed significant (P&lt;0.05) depression. The least cost per kg feed and least cost per kg weight gain (naira) were observed with birds on crayfish diets. There was better (P&lt;0.05) digestibility of crude protein by birds on treatment diets 1 and 2 followed by 3 and 4 while birds than on treatment diet5 had the least value (58.10%). Conclusively, the use of crayfish waste meal in broiler starter diets and combined proteins in broiler fisher diets should be encouraged.

Skin Pigmentation in Gilthead Seabream (Sparus aurata L.) Fed Conventional and Novel Protein Sources in Diets Deprived of Fish Meal.

Simple SummaryIntensive farming of carnivorous fish species relies on the use of feeds, where fish meals have represented, for a long while, ideal sources of protein to ensure optimal growth, health and quality to cultured fish. Due to the gap between the demand for these commodities by the growing aquaculture industry and the unsustainability of further exploitation of the alieutic resources, their levels of inclusion in fish feeds have been mostly replaced by terrestrial plant protein-rich derivatives and conventional animal processed proteins. Recently, novel ingredients (i.e., insects and microalgae) have been proposed to this end. While the impact of different alternative proteins on fish growth and health has been studied, limited information exists on the effects of such dietary changes on quality traits of cultured fish such as skin pigmentation. The present study was aimed at assessing the pattern of yellow pigmentation of the skin in gilthead seabream fed various alternative protein sources (vegetable ingredients, insects, poultry by-product meal, red swamp crayfish and marine microalgae) included in different proportions in fishmeal-free diets, in order to evaluate new feed formulations on the basis of their coloring capacity, as intense skin coloration have been associated with high-quality of farmed fish products.The pattern of yellowish pigmentation of the skin was assessed in gilthead seabream (Sparus aurata) fed for 12 weeks iso-proteic (45%) and iso-lipidic (20%) diets deprived of fish meal and containing either a blend of vegetable protein-rich ingredients or where graded levels of the vegetable protein blend were replaced by insect (Hermetia illucens—10%, 20% or 40%) pupae meal, poultry by-product meal (20%, 30% or 40%), red swamp crayfish meal (10%) and marine microalgae (Tisochrysis lutea and Tetraselmis suecica—10%) dried biomass. Digital images of fish fed diets differing in protein sources were analyzed by means of an automatic and non-invasive image analysis tool, in order to determine the number of yellow pixels and their dispersion on the frontal and lateral sides of the fish. The relationship between the total carotenoid concentration in the diet and the number of yellow pixels was investigated. Test diets differently affected gilthead seabream skin pigmentation both in the forefront and the operculum, due to their carotenoid content. The highest yellow pixels’ number was observed with the diet containing microalgae. Fish fed poultry by-product meal were characterized by the lowest yellow pixels’ number, diets containing insect meal had an intermediate coloring capacity. The vegetable control, the microalgae mix diet and the crayfish diet had significantly higher values of yellow pixels at both inspected skin sites.

The crayfish distribution, feeding plasticity, seasonal isotopic variation and trophic role across ontogeny and habitat in a canyon-shaped reservoir

Man-made reservoirs are important freshwater ecosystems as they are globally common and share features of both standing and running waters. In streams and lakes, crayfish are an important component of freshwater ecosystems due to their habitat-modifying behaviour, substantial size, omnivorous feeding and often high abundance; however, their trophic role in reservoirs is not known. We evaluated the distribution and diet of noble crayfish (Astacus astacus) in the canyon-shaped, oligotrophic Nýrsko reservoir in West Bohemia region, Czech Republic. Using stable isotope analysis, we quantified the trophic level of all major components of the reservoir food web and investigated seasonal isotopic variation and how the trophic role of noble crayfish varied with habitat and ontogeny. Crayfish were an important food source for both predatory and omnivorous fish and consumed food sources from multiple trophic levels, including detritus, algae, zoobenthos and other crayfish. Throughout ontogeny, crayfish had similar levels of carnivory, but cannibalism was more prevalent in adult crayfish, while juveniles and sub-adults fed more on other zoobenthos. Moreover, crayfish had high feeding plasticity in time, as the relative importance of dominant food sources varied with season. Their feeding plasticity was especially evident in crayfish populations from different habitats, which adapted their feeding strategy to local resources. In addition, pelagic source usage increased with the depth as detritus and algae usage decreased. Proportion of females increased with the depth, while population density showed a unimodal response to the depth gradient. These findings indicate that crayfish are indeed ecologically important species with both direct and indirect roles in the trophic web of this reservoir ecosystem.

Microcystins in European Noble Crayfish Astacus astacus in Lake Steinsfjorden, a Planktothrix-Dominated Lake.

Lake Steinsfjorden, an important Norwegian location for noble crayfish (Astacus astacus), is often affected by cyanobacterial blooms caused by microcystin (MC)-producing Planktothrix spp. The impact of MCs on noble crayfish as a food source and crayfish health is largely unknown. We investigated the quantities and correlations of MCs in noble crayfish and lake water during and after a cyanobacterial bloom peaking in June–July 2015. Noble crayfish and water samples were collected monthly from June to October 2015 and in October 2016. The content of MCs was analysed by ELISA from tail muscle, intestine, stomach and hepatopancreas. PCR analysis for Planktothrix gene markers was performed on crayfish stomach content. Water samples were analysed for phytoplankton composition, biomass and MCs. PCR-positive stomach contents indicated Planktothrix to be part of the noble crayfish diet. Concentrations of MCs were highest in the hepatopancreas, stomach and intestine, peaking in August–September. Tail muscle contained low concentrations of MCs. Similar levels of MCs were found in crayfish from 2016. Except in September 2015, a normal portion of boiled noble crayfish tails was below the tolerable daily intake (TDI) for MCs for humans. Removing the intestine more than halved the content of MCs and seems a reasonable precautionary measure for noble crayfish consumers.

Dietary lipid sources modulate the intestinal transport of fatty acids in the red swamp crayfish Procambarus clarkii

The optimization of feed formulations is an effective strategy to increase the growth of aquatic animals, but the effects of dietary lipid sources other than fish oil are not well established in most of crustacean. In this study, we investigated how different dietary lipid sources influence fatty acid absorption, synthesis, and transport in the red swamp crayfish (Procambarus clarkii). Six isonitrogenous and isocaloric diets were formulated with the following lipid sources: fish oil (FO), corn oil (CO), rapeseed oil (RO), soybean oil (SO), palm oil (PaO), and beef tallow (BT). The crayfish fed FO, SO, or BT exhibited a significantly higher weight gain rate (WGR) and specific growth rate (SGR) and a lower feed conversion ratio (FCR) than those of crayfish fed PaO. Polyunsaturated fatty acid (PUFA) profiles in the hepatopancreas and muscle tissues closely mirrored those in the diets. Low total triglyceride (TG) and total cholesterol (TC) contents were observed in the hemolymph and hepatopancreas of crayfish fed FO or BT diet. In the lipid anabolism pathway, fatty acid synthase (fas), sterol regulatory element-binding protein 1 (srebp1), and retinoid X receptor (rxr) were down-regulated by dietary FO but up-regulated by some vegetable oils. A gene involved in fatty acid (FA) uptake and transport, fatty acid binding protein (fabp), was up-regulated by CO in the hepatopancreas and by BT in muscle tissues. With respect to intestinal fatty acid transporters, fatty acid transport protein 4 (FATP4) was up-regulated in the BT diet, diacylglycerol transferase1 (DGAT1) was down-regulated in the FO or BT diet, and Niemann-Pick C1-like 1 (NPC1L1) was down-regulated in the SO diet. Apolipoprotein B-48 (Apo B-48) and fatty acid translocase (FAT/CD36) were not influenced by dietary lipid sources. According to the observed results, BT is the more suitable candidate for FO replacement in crayfish diets, whereas PaO is not recommended.

Effect of dietary Antarctic krill Euphausia superba on the growth performance and nonspecific immunity of red swamp crayfish Procambarus clarkia

This study aims to investigate the effects of replacing different proportions of fishmeal with Antarctic krill (AK) on the growth performance, body composition and nonspecific immunity index of red swamp crayfish Procambarus clarkia. AK was used to replace 0 (control), 25%, 50% and 100% of the fishmeal in the basic diet of crayfish to formulate four test feeds with basically equivalent nitrogen and lipid contents; these feeds were denoted AK0, AK25, AK50 and AK100, respectively. Compared with the control group, crayfish fed diets with AK replacement showed increased body weight gain; feed efficiency; survival rate; body protein content; phenoloxidase, superoxide dismutase and glutathione peroxidase activities; total haemocyte counts; number of hyaline, semigranular and granular cells; and disease resistance against Aeromonas hydrophila. Conversely, the body lipid level of these crayfish decreased relative to that of the control. However, a high AK level (AK100) does not show improvements in efficiency compared with a moderate AK level (AK50). Based on the efficiency of AK in enhancing the growth performance and nonspecific immunity of crayfish, the optimum replacement proportion of fishmeal with AK was 50%. These results confirm that AK can promote the growth of crayfish and improve their disease resistance.