Plasma and tissue transferrin and ferritin, and gene expression of ferritin, transferrin, and transferrin receptors I and II in channel catfish Ictalurus punctatus fed diets with different concentrations of inorganic or organic iron.

Ferritin, transferrin, and transferrin receptors I and II play a vital role in iron metabolism, health, and indication of iron deficiency anaemia in fish. To evaluate the use of high-iron diets to prevent or reverse channel catfish (Ictalurus punctatus) anaemia of unknown causes, we investigated the expression of these iron-regulatory genes and proteins in channel catfish fed plant-based diets. Catfish fingerlings were fed five diets supplemented with 0 (basal), 125, and 250 mg/kg of either inorganic iron or organic iron for 2 weeks. Ferritin, transferrin, and transferrin receptor I and II mRNA and protein expression levels in fish tissues (liver, intestine, trunk kidney, and head kidney) and plasma were determined. Transferrin (iron transporter) and TfR (I and II) genes were generally highly expressed in fish fed the basal diet compared to those fed the iron-supplemented diets. In contrast, ferritin (iron storage) genes were more expressed in the trunk kidney of fish fed the iron-supplemented diets than in those fed the basal diet. Our results demonstrate that supplementing channel catfish plant-based diets with iron from either organic or inorganic iron sources affected the expression of the iron-regulatory genes and increased body iron status in the fish.

Digestibility of Conventional and Novel Dietary Lipids in Channel Catfish Ictalurus punctatus.

Lipid and fatty acid digestibility is presumably high in Channel Catfish, but data is lacking. We determined the lipid and fatty acid digestibility of traditional and alternative dietary lipids in Channel Catfish to inform lipid choice for commercial diets. Six diets contained 4% of different lipids: soybean oil (SBO), soybean oil containing conjugated linoleic acids (CLA-SBO), catfish offal oil (COO), flaxseed oil (FXO), menhaden fish oil (MFO) and poultry fat (PF). Diets were fed to Channel Catfish (150-200 g) maintained at 26.5 °C in each of six 110 L aquaria. Six hours post-prandial, feces were collected for analysis. Total lipid, crude protein and fatty acids of lyophilized feces were analyzed, and apparent digestibility coefficients (ADCs) were calculated. ADCs of lipid, saturated and monounsaturated fatty acids, linoleic acid and protein digestibility were similar among diets. CLA isomers (cis-9, trans-11 (84.1%) and trans-10, cis-12 (90%)) in the CLA-SBO diet were highly digestible. Oleic acid digestibility was highest in the PF diet. ADC was high for α-linolenic acid in the FXO diet, and for arachidonic acid and n-3 LC-PUFA in the MFO diet. Overall, total lipid digestibility was high, but ADCs of individual fatty acids differed by source.

Elevated concentrations of organic and inorganic forms of iron in plant-based diets for channel catfish prevent anemia but damage liver and intestine, respectively, without impacting growth performance.

We compared the effects of using inorganic and organic forms of iron in plant-based diets on catfish performance in a feeding trial with 6-g catfish fingerlings. The objective was to determine whether dietary iron in excess of known requirements negatively affected the fish. Five diets supplemented with 0 (basal), 125, 250 mg Fe/kg of either FeSO4 or iron methionine were formulated. Weight gain, feed conversion ratio, hepatosomatic index, and survival were similar among diets. Plasma and intestine iron concentration was similar among diets. Whole-body total lipid, protein, and dry matter were similar among diets, while ash content was higher in fish fed the basal diet. Total liver iron concentration was higher in fish fed diets supplemented with 250 mg Fe/kg in both iron forms than other diets. Hematological parameters were similar among treatments. Liver necrosis, inflammation, and vacuolization were highest in fish fed the diet supplemented with 250 mg Fe/kg from organic iron, followed by those fed diets with 250 mg Fe/kg from inorganic iron. Inorganic iron-supplemented diets caused more intestinal inflammation (increased inflammatory cells, villi swelling, thicker lamina propria) than the organic iron-supplemented diets or basal diet. Organic iron at 250 mg/kg resulted in a $0.143/kg increase in feed cost. Latent iron deficiency and initial signs of anemia developed in catfish fed the basal diet. Supplemental iron from either form prevented iron deficiency. Organic iron at 125 mg/kg optimized fish performance at a cost comparable to that of fish fed other diets, but without overt negative effects.

Effects of Different Feeding Regimes on Growth Rates and Fatty Acid Composition of Largemouth Bass Micropterus nigricans at High Water Temperatures.

As the northern Largemouth bass (LMB) (Micropterus nigricans) industry shifts toward fingerling production, implementing practical feeding strategies to ensure efficient growth during high water temperatures is paramount. Twenty (12.7 ± 0.2 g) (Trial 1) and fifteen (7.2 ± 0.1 g) (Trial 2) LMB fingerlings were stocked in two recirculating systems (each containing nine tanks), acclimated to 30 °C, with one system fed daily rations of 3, 5 and 7% body weight (Trial 1), and the second system fed to satiation daily, every second day, or every third day (Trial 2), for 28 days each. All treatments were triplicated. Multiple growth metrics and lipid composition were analyzed. The 3% treatment yielded the lowest final average weight (36.05 g) and FCR (0.83), with no difference in final biomass in Trial 1 treatments. Fish fed to satiation daily and every second day produced FCRs and biomasses of 0.83 and 356.78 g, and 0.93 and 272.26 g, respectively. There were no differences in total lipid concentration, however, fatty acid profiles differed significantly between all treatments within their respective trials. Feeding LMB fingerlings 3% of total body weight or feeding daily to satiation allows for efficient growth at 30 °C and implements cost-effective feeding strategies.

Physio-biochemical, metabolic nitrogen excretion and ion-regulatory assessment in largemouth bass (Micropterus salmoides) following exposure to high environmental iron.

Iron overload is a significant water quality issue in many parts of the world. Therefore, we evaluated the potential toxic effects of waterborne elevated iron on largemouth bass (Micropterus salmoides), a highly valued sport and aquaculture fish species. First, a 96 h-LC50 toxicity assay was performed to understand the tolerance limit of this species to iron; and was determined to be 22.07 mg/L (as Fe3+). Thereafter, to get a better insight on the fish survival during long-term exposure to high environmental iron (HEI) (5.52 mg/L, 25% of the determined 96 h-LC50 value), a suite of physio-biochemical, nitrogenous metabolic and ion-regulatory compensatory responses were examined at 7, 14, 21 and 28 days. Results showed that oxygen consumption dropped significantly at 21 and 28 days of HEI exposure. Ammonia excretion rate (Jamm) was significantly inhibited from day 14 and remained suppressed until the last exposure period. The transcript concentration of Rhesus glycoproteins Rhcg2 declined; likely diminishing ammonia efflux out of gills. These changes were also reflected by a parallel increment in plasma ammonia levels. Under HEI exposure, ion-balance was negatively affected, manifested by reduced plasma [Na+] and parallel inhibition in branchial Na+/K+-ATPase activity. Muscle water content was elevated in HEI-exposed fish, signifying an osmo-regulatory compromise. HEI exposure also increased iron burden in plasma and gills. The iron accumulation pattern in gills was significantly correlated with a suppression of Jamm, branchial Rhcg2 expression and Na+/K+-ATPase activity. There was also a decline in the glycogen, protein and lipid reserves in the hepatic tissue from 14 days, 28 days and 21 days, respectively. Overall, we conclude that sub-lethal chronic iron exposure can impair normal physio-biochemical and ion-regulatory functions in largemouth bass. Moreover, this data set can be applied in assessing the environmental risk posed by a waterborne iron overload on aquatic life.

Physiological insights into largemouth bass (Micropterus salmoides) survival during long-term exposure to high environmental ammonia.

Waterborne ammonia is an environmental pollutant that is toxic to all aquatic animals. However, ammonia induced toxicity as well as compensatory mechanisms to defend against high environmental ammonia (HEA) are not well documented at present for largemouth bass (Micropterus salmoides), a high value fish for culture and sport fisheries in the United States. To provide primary information on the sensitivity of this species to ammonia toxicity, a 96 h-LC50 test was conducted. Thereafter, responses at physiological, ion-regulatory and transcript levels were determined to get insights into the underlying adaptive strategies to ammonia toxicity. For this purpose, fish were progressively exposed to HEA (8.31 mg/L representing 25% of 96 h-LC50) for 3, 7, 14, 21 and 28 days. Temporal effects of HEA on oxygen consumption rate (MO2), ammonia and urea dynamics, plasma ions (Na+, Cl- and K+), branchial Na+/K+-ATPase (NKA) and H+-ATPase activity, muscle water content (MWC), energy store (glycogen, lipid and protein) as well as branchial mRNA expression of Rhesus (Rh) glycoproteins were assessed. Probit analysis showed that 96 h-LC50 of (total) ammonia (as NH4HCO3) at 25 °C and pH 7.8 was 33.24 mg/L. Results from sub-lethal end-points shows that ammonia excretion rate (Jamm) was strongly inhibited after 7 days of HEA, but was unaffected at 3, 14 and 21 days. At 28 days fish were able to increase Jamm efficiently and concurrently, plasma ammonia re-established to the basal level. Urea production was increased as evidenced by a considerable elevation of plasma urea, but urea excretion rate remained unaltered. Expression of Rhcg isoform (Rhcg2) mRNA was up-regulated in parallel with restored or increased Jamm, suggesting its ammonia excreting role in largemouth bass. Exposure to HEA also displayed pronounced augmentations in NKA activity, exemplified by a rise in plasma [Na+]. Furthermore, [K+], [Cl-] and MWC homeostasis were disrupted followed by recovery to the control levels. H+-ATPase activity was elevated but NKA did not appear to function preferentially as a Na+/NH4+-ATPase. From 14 days onwards MO2 was depressed, potentially an attempt towards minimizing catabolism. Glycogen content in liver and muscle were temporarily depleted, whereas a remarkable increment in protein was evident at the last exposure period. Overall, these data suggest that ammonia induced toxicity can disturb several biological processes in largemouth bass, however, it can adapt to the long-term sub-lethal ammonia concentrations by activating various components of ammonia excretory, ion-regulatory and metabolic pathways.

An environmentally friendly approach for mitigating cyanobacterial bloom and their toxins in hypereutrophic ponds: Potentiality of a newly developed granular hydrogen peroxide-based compound.

Cyanobacterial blooms and their associated toxins are growing issues for many aquatic resources, and pose a major threat to human health and ecological welfare. To control cyanobacterial blooms and their toxins, the efficacy of a newly developed granular compound (sodium carbonate peroxyhydrate 'SCP', trade name 'PAK® 27' algaecide) containing hydrogen peroxide (H2O2) as the active ingredient was investigated. First, the dose efficacy of the SCP that corresponded to 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 5.0 and 8.0 mg/L H2O2 was tested for 10 days in small-scale tanks installed in 0.1-acre experimental hypereutrophic ponds dominated by blooms of the toxic cyanobacterium Planktothrix sp. SCP ranging from 2.5-4.0 mg/L H2O2 selectively killed Planktothrix sp. without major impacts on either eukaryotic phytoplankton (e.g., diatom Synedra sp., green algae Spirogyra sp. and Cladophora sp.) or zooplankton (e.g., rotifers Brachionus sp. and cladocerans Daphnia sp.). Based on these results, SCP at 2.5 mg/L and 4.0 mg/L H2O2 were homogeneously introduced into entire water volume of the experimental ponds in parallel with untreated control ponds. The dynamics of cyanobacterium Planktothrix sp., microcystins (commonly occurring cyanotoxins), eukaryotic phytoplankton, zooplankton, and water quality parameters were measured daily for 10 days and followed by a weekly sampling for 6 weeks. Temporal analysis indicated that Planktothrix sp. blooms collapsed remarkably in both 2.5 mg/L and 4.0 mg/L H2O2 treatments. Both treatments also were accompanied by an overall reduction in the total microcystin concentration. At 2.5 mg/L H2O2, the growth of eukaryotic phytoplankton (Synedra and Cladophora sp.) increased, but these populations along with zooplankton (Brachionus and Daphnia sp.) were suppressed at 4.0 mg/L H2O2. The longevity of 2.5 and 4.0 mg/L H2O2 treatment effects were up to 5 weeks. In addition, the added granular algaecide degraded within a few days, thereby leaving no long-term traces of H2O2 in the environment.

Effects of dietary sweet potato leaf meal on the growth, non-specific immune responses, total phenols and antioxidant capacity in channel catfish (Ictalurus punctatus).

BACKGROUND: Traditional energy sources in catfish diets have become costly, and economical alternatives are needed. Sweet potato leaves are underutilised agricultural by-products that provide energy and substantial amounts of phenols, which affect animal and human health. There is little information on the effects of these compounds on catfish, or the capacity of catfish to accumulate dietary phenols. Catfish enriched with phenols have marketing potential as functional foods. This study investigated the effects of diets with sweet potato leaf meal (SPLM) on growth performance, health and total phenolic compounds in catfish. RESULTS: SPLM was substituted for wheat middlings in three diets fed to groups of juvenile catfish for 10 weeks. Weight gain, feed conversion, survival, alternative complement activity and lysozyme activity were similar among diets. Haematocrit was lower in fish fed diets with SPLM, but within the normal range. Total phenols and antioxidant capacity in the whole body were similar among treatments. CONCLUSION: SPLM was an effective energy source for catfish up to the maximum level tested (230 g kg(-1) diet). SPLM did not enhance total phenols in catfish, but there were no apparent antinutritional effects of the meal on catfish growth, health or survival.

Alternative complement activity and resistance to heat stress in golden shiners (Notemigonus crysoleucas) are increased by dietary vitamin C levels in excess of requirements for prevention of deficiency signs.

Golden shiners (Notemigonus crysoleucas) require a dietary source of ascorbic acid (AA) for growth or survival, depending on diet composition. However, no quantitative requirements of golden shiners for AA for growth, health or survival have been determined, and specific deficiency signs have not been observed. The purpose of this study was to determine the effects of different dietary levels of AA on the growth and health of golden shiners fed diets containing 0-218.5 mg AA/kg diet for 10-16 wk. Weight gain, survival and gross deformities were assessed at 10 wk. The remaining fish were fed the same diets from wk 11-16; hematology and alternative complement activity were then assessed and a subset of live fish from each tank was exposed to elevated temperature. Gross deformities appeared in fish fed 0 mg AA/kg diet at 9 wk. The 19.5 mg AA/kg diet was sufficient to prevent the deformities and optimize survival, whereas growth did not differ among treatments. Fish fed 40.3 mg of AA/kg diet had a higher survival rate than fish fed 0 or 19.5 mg AA/kg diet after exposure to elevated temperatures (34-35.5 degrees C). Alternative complement activity and visceral AA concentrations were greater in fish fed diets with 218.5 mg AA/kg than in all other groups. The results indicate that the dietary requirement of AA for golden shiners increases in response to heat stress, and that the alternative complement activity (one index of immune competence) was strongly enhanced in fish fed a diet with approximately 10 times the amount of AA required to prevent deficiency signs.