Marine microalgae commercial production improves sustainability of global fisheries and aquaculture

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The Effect of Using Low-Phytate Cereal Varieties on Phosphorus Digestibility and Selected Production Indices

The pollution of surface waters by excessive biogenic elements, especially phosphorus, is a highly topical subject. Fishery management on ponds may be one of the potential sources of phosphorus in waters. Cyprinid fish generally have a very poor digestion of the phosphorus contained in the plant-based components of feeds. In them, phosphorus is deposited in the form of phytic acid which is almost indigestible for cyprinids. The conducted testing was focused on affecting the digestibility of phosphorus contained in plant-based feeds. Two of the cereals most frequently grown in the Czech Republic were tested, namely, wheat and barley. Control feeds were varieties commonly grown in our country, i.e. Vánek and Bojos. Furthermore, we used special cereal mutant lines with a decreased content of the phytic acid, JS-12/IDO 563 and M955. The test results showed that when using the low-phytate wheat line, the digestibility of phosphorus was increased by up to 11.21 % (P < 0.01); and by 5.89 % (P < 0.05) in the case of barley. Both low-phytate lines of the cereals used significantly affect phosphorus digestibility and decrease the loading of the environment with phosphorus. When using the low-phytate wheat line, a significant effect (P < 0.05) was found on the fat content in the fish body compared to the control variety but also compared to the low-phytate barley line. No significant effect was found comparing both control varieties and comparing the barley varieties mutually.O

Used of microbial phytase to replace inorganic phosphorus in sex-reversed red tilapia: 1 dose response

Sex-reversed red tilapia of average initial body weight 5.5 g were fed seven practical diets containing 0, 500, 1,000, 2,000 and 4,000 units of microbial phytase/kg and two diets containing 0.2 and 0.3% feed grade dicalcium phosphate (DCP) (but no microbial phytase), respectively. The experiment was carried out in 235- l glass aquaria filled with 180 l water and attached with a closed-recirculating water system with 0.8 l/min flow rate. The experimental period was 10 weeks. All experimental diets were formulated with plant-based protein of 30% and 6% fat. Results indicated an improvement in apparent digestibility coefficient of phosphorus (ADCP) in fish given phytase supplemented feed. There was no difference in ADCP when 1,000 unit phytase/kg diet or higher phytase levels (2,000 and 4,000 unit phytase/kg diet) or 0.2 and 0.3% DCP were supplemented. A significant increase was noted for hemoglobin in tilapia that received 1,000 unit phytase/kg diet or higher levels compared to the control. Serum phosphorus ma kedly increased when the fish were given feeds with 1,000 unit phytase/kg diet and over, while the supplementation of 500 unit phytase/kg diet and over increased serum zinc level. Higher levels of phosphorus were retained in bone whereas lower levels of phosphorus presented in the feces of tilapia fed feeds supplemented with phytase. Growth performance was markedly influenced when the fish were given feed with 4,000 unit phytase/kg diet

Wutiporn Phromkunthong

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Effects of Spirulina sp. on growth performance and antibody levels in hybrid catfish, Clarias macrocephalus x Clarias gariepinus (Burchell)

A 8-wk feeding trial was carried out for hybrid catfish with an initial average weight of 7 g in 235-l glass tanks attached to closed-recirculating system with 0.8 l/min flow rate. Feeds containing varying percentages of dry Spirulina sp. 0, 5, 10, 15, 20, 25 and 30% were tested with three replications for each treatment. All the feeds were formulated to contain dietary requirement for the catfish i.e. 30% protein, 7% fat and 360 kcal gross energy/ 100 g feed. The results showed that the feed with 10% Spirulina sp. achieved the best performance on weight gain, specific growth rate, feed conversion ratio, apparent net protein utilization and development of antibody levels against bacteria Aeromonas hydrophila. The total carotenoid contents in fish flesh increased with the level of Spirulina sp. supplemented. The supplementation of Spirulina sp. resulted in no changes of blood parameters or histology

The supplementation of phytase RONOZYME P on the growth and the utilisation of phosphorus by sex-reversed red tilapia (Oreochromis niloticus Linn.)

The effect of phytase supplementation to a low fish meal based diet on growth performance and phosphorus utilisation was investigated in sex-reversed red tilapia. Diets were prepared without phytase or inorganic phosphorus supplementation, with phytase, with supplemented inorganic phosphorus and with both phytase and supplemental inorganic phosphorus. Available phosphorus was set below requirement and the total phosphorus set to meet requirement for tilapia. After 8 weeks, there were significant differences in weight gain and protein utilisation between diets. There was an effect of phytase addition and inorganic phosphorus supplementation on bone phosphorus and whole-body phosphorus (p<0.05). A significant effect was also observed on phosphorus digestibility, phosphorus retention efficiency and phosphorus load of the water. Phosphorus digestibility and retention efficiency were significantly (p<0.05) higher, and phosphorus load of the water was significantly (p<0.05) lower in fish fed the phytase supplemented diet compared with diets containing supplemental inorganic phosphorus and the basal diet. In conclusion, phytase increased phosphorus availability, therefore reducing the need to add inorganic phosphorus and reducing phosphorus waste from low fish meal based diets for tilapia

The supplementation of phytase RONOZYME P on the growth and the utilisation of phosphorus by sex-reversed red tilapia (Oreochromis niloticus Linn.)

Abstract The effect of phytase supplementation to a low fish meal based diet on growth performance and phosphorus utilisation was investigated in sex-reversed red tilapia. Diets were prepared without phytase or inorganic phosphorus supplementation, with phytase, with supplemented inorganic phosphorus and with both phytase and supplemental inorganic phosphorus. Available phosphorus was set below requirement and the total phosphorus set to meet requirement for tilapia. After 8 weeks, there were significant differences in weight gain and protein utilisation between diets. There was an effect of phytase addition and inorganic phosphorus supplementation on bone phosphorus and whole-body phosphorus (p&lt;0.05). A significant effect was also observed on phosphorus digestibility, phosphorus retention efficiency and phosphorus load of the water. Phosphorus digestibility and retention efficiency were significantly (p&lt;0.05) higher, and phosphorus load of the water was significantly (p&lt;0.05) lower in fish fed the phytase supplemented diet compared with diets containing supplemental inorganic phosphorus and the basal diet. In conclusion, phytase increased phosphorus availability, therefore reducing the need to add inorganic phosphorus and reducing phosphorus waste from low fish meal based diets for tilapia

Effects of mycotoxin T-2 and zearalenone on histopathological changes in black tiger shrimp (Penaeus monodon Fabricius)

The effects of T-2 toxin and zearalenone were studied in black tiger shrimp (Penaeus monodon Fabricius). In the experiment, black tiger shrimp were fed with different concentrations of T-2 toxin, i.e. 0, 0.1, 1.0 and 2.0 ppm and zearalenone, i.e. 0, 0.1. 0.5 and 1.0 ppm. Shrimp with initial average weight of 4.7 g were experimented for a-10-wk period. Supplementation of 0, 0.1 and 1.0 ppm T-2 produced no histological changes in hepatopancreatic, hemopoietic tissue or lymphoid cell while at higher concentration of 2.0 ppm atrophy, severe necrosis and degeneration of hepatopancreatic tubules, loose contact of hemopoietic tissue and lymphoid organ occurred. Similar observations were noted for the treatments with 0.5 and 1.0 ppm zearalenone - supplemented feed. Histological changes were, however, observed in hepatopancreatic tissue. The scale of histological changes correlated with feeding period and concentrations of zearalenone shrimp received

Dietary exposure to melamine and cyanuric acid induced growth reduction, oxidative stress and pathological changes of hepatopancreas in Pacific white shrimp

Abstract This study examined the effects of dietary melamine (MEL) and cyanuric acid (CYA) singly and in combination on growth, nutrient utilization, immunological responses, oxidative stress, and histological changes in Pacific white shrimp. Seven experimental isonitrogenous (35%) and isolipidic (8%) diets were formulated, namely diet 1 (a control diet without MEL and CYA); diets 2–5 (with MEL and CYA at 2.5 + 2.5, 5 + 5, 7.5 + 7.5 and 10 + 10 g kg−1 diet); diet 6 (with only MEL at 10 g kg−1 diet) and diet 7 (with CYA alone at 10 g kg−1 diet). The shrimp with initial body weight 2.37 ± 0.02 g were fed with these diets for 10 weeks. The results indicate that all the diets with MEL and CYA singly or in combination had adverse effects on growth and nutrient utilization relative to the control diet (p < 0.05). Total protease and trypsin activities were significantly lowered by all diets containing MEL (p < 0.05). Haemolymph parameters, including total hemocyte count, phenoloxidase (PO) activity, respiratory burst, and lysozyme activity, were significantly decreased (p < 0.05) in shrimp receiving MEL alone (10 g kg−1 diet) and at high combination dosages (10 + 10 g kg−1 diet). Moreover, MEL and CYA induced oxidative stress, damaged hepatopancreas, decreased antioxidant responses, increased lipid peroxidation, and caused abnormality of hepatocytes

Replacing palm kernel cake for fishmeal in sex-reversed red tilapia (Oreochromis niloticus Linn.) feed

Five isonitrogeneous and isocaloric feeds containing various levels of palm kernel cake (0, 10, 20, 30 and 40%) as a replacement for fishmeal were fed to four replicate groups of sex-reversed red tilapia (Oreochromis niloticus Linn.) fingerlings, mean initial weight 3.02-3.03 g, in 235-l aquaria fitted with a closed recirculation system for 10 weeks. The results showed declines in growth, feed utilization and digestibility coefficient with increases in the levels of supplemented palm kernel cake. The maximum growth was achieved in the fish given the feed with 10% palm kernel cake and was different from that when the basal feed (formula 1) was used. Satisfactory results of feed utilization, (feed conversion ratio, protein efficiency ratio, apparent net protein utilization) and digestibility coefficient were noted in the fish groups given the feed with a maximum of 20% palm kernel cake in their feeds. The supplementation of palm kernel cake at any levels in the feeds had no effects on fish’s blood parameters or hepatosomatic index. It was concluded that the maximum of 20% palm kernel cake could be supplemented in the feed for sex-reversed red tilapia while maintaining satisfactory growth, feed utilization, digestibility coefficient and normal fish physiology. Besides, the feed cost was kept minimum compared to the supplementation of other levels of palm kernel cake in their feeds