Tilapia Strains Research Articles

Identification of a Novel QTL on LG16 Associated with Acute Salt Tolerance in Red Tilapia (Oreochromis spp.) Using GWAS.

Culturing saline tilapia has become a new trend in the aquaculture due to the scarcity of freshwater resources. In this study, the genetic basis controlling for salt tolerance were investigated by using a ddRAD-seq-based GWAS in 288 individuals with extreme salt tolerant traits from half-sib families of red tilapia. 12 genome-wide significant SNPs and 6 chromosome-wide significant SNPs associated with acute salt tolerance were identified. Two QTLs on LG18:25,593,701-7009020 and on LG16:19,735,164-21,231,391 were defined. It is noteworthy that the QTL on LG16 is a novel QTL associated with acute salt stress. Near the significant SNP sites, we identified candidate genes sik1, ltb4r2b, pnp5b and kirrel1b with differential transcript expression under salt stress. Furthermore, significant physiological differences in serum osmolality and ion concentrations were confirmed between the tolerant group and sensitive group under 4.5h of 22 ppt stress. The sensitive group had much higher serum osmolality (osmolality: 642.20 ± 6.30mOsm/kg) and higher concentrations of sodium and chloride ions (sodium: 317.67 ± 5.03mmol/L and chloride: 316.43 ± 8.28mmol/L) than the tolerant group (547.60 ± 15.44mOsm/kg, p osmolality = 0.0002; sodium: 280.53 ± 9.13 mmol/L, p sodium < 0.0242; chloride: 266.00 ± 12.00 mmol/L, p chloride < 0.0184). However, the lowest bicarbonate concentration was detected in the sensitive group at 22 ppt (2.53 ± 0.30mmol/L), which was significantly different from both the sensitive group at 0 ppt (p = 0.0008) and the tolerant group at 22 ppt (p = 0.0164). Our research laid the foundation for exploring the genetic mechanisms of acute salt tolerance and osmoregulation in red tilapia and for developing strains of red tilapia adapted to saltwater.

A comparative study of the genetically improved Abbassa Nile tilapia strain (GIANT-G9) and a commercial strain in Egypt: growth vs. stress response

Selective breeding is a potent method for developing strains with enhanced traits. This study compared the growth performance and stress responses of the genetically improved Abbassa Nile tilapia strain (G9; GIANT-G9) with a local commercial strain over 12 weeks, followed by exposure to stressors including high ammonia (10 mg TAN/L), elevated temperature (37 °C), and both for three days. The GIANT-G9 showed superior growth, including greater weight gain, final weight, length gain, specific growth rate, and protein efficiency ratio, as well as a lower feed conversion ratio and condition factor compared to the commercial strain. The expression of growth hormone in the brain of the GIANT‐G9 increased significantly after 6 weeks, although it slightly decreased after 12 weeks. Growth hormone receptor 1 expression also increased significantly after 6 weeks. Muscle insulin-like growth factors (igf1 and igf2) levels up-regulated significantly only after 12 weeks in the GIANT‐G9. Under stress, serum enzymes (alanine aminotransferase, aspartate aminotransferase, and alkaline phosphatase (ALP)) were significantly higher in the GIANT‐G9, while the commercial strain had lower levels. No significant changes were observed in liver ALP activity among stressed strains. Under stress, the GIANT‐G9 exhibited marked upregulation of splenic Toll-like receptors (tlr2, tlr9, tlr21), myeloid differentiation primary response protein 88 (myd88), nuclear factor kappa B (nf-κB), interleukin (il) 1β, and il6. Notably, il6 expression was higher than il1β in the spleen, with the opposite pattern in the head kidney. In response to immune stimulation, globulin levels significantly increased in the GIANT‐G9 but with similar values to the stressed commercial strain. Myostatin expression increased in the spleen of the stressed GIANT‐G9. The commercial strain exhibited the best liver catalase and superoxide dismutase activities under stress, while the GIANT‐G9 showed increased liver glutathione-S-transferase (GST) activity after exposure to ammonia and temperature stress. Serum lysozyme activity increased in the stressed commercial strain and under temperature stress in the GIANT‐G9 but decreased under other stress conditions. Overall, the stressed commercial strain demonstrated higher survivability than the stressed GIANT‐G9. The study revealed significant interactions between strains and stress factors. The GIANT‐G9 exhibited higher growth rates but lower antioxidant and immune capacities compared to the commercial strain at the juvenile stage of life and production cycle.

Mapping QTLs associated with resistance to Streptococcus agalactiae infection in the GIFT strain of Nile tilapia (Oreochromis niloticus) by QTLseq and methyl-QTLseq

Mapping QTLs associated with resistance to Streptococcus agalactiae infection in the GIFT strain of Nile tilapia (Oreochromis niloticus) by QTLseq and methyl-QTLseq

Sensory evaluation of four red hybrid tilapia (Oreochromis Sp.) strains among fish consumers

The viability of tilapia in the aquaculture industry is due to the market demands that consumers decide. Since every aquaculture species had distinct sensory attributes, a hedonic sensory evaluation was performed to assess the sensory characteristics of the flesh of four red hybrid tilapia strains: (i) ?O.niloticus x ?O.niloticus (A)(MF280061), ?O.mossambicus x ?O.mossambicus (B) (MF509596), ?O.niloticus x ?O.mossambicus (C)(MF509597) and ?O.mossambicus x ?O. niloticus (D)(MF509598). Hedonic and ranking tests were carried out by 120 participants who assessed each strain's 25 g steamed flesh. The sensory analysis was carried out by using five hedonic scales. They participated through a volunteer invitation. The surveyed population participated by 62.50% and 37.50% females and males, respectively. Participants were asked to complete the questionnaires, including demographic questions hedonic scores, and rank according to their preferences. Means of sensory attributes were analysed using the Kruskal-Wallis test at p&lt;0.05. No significant differences (p&gt;0.05) exist between strains in the sensory attributes related to taste, odour, and juiciness. Strain D had the highest scores in all sensory attributes compared to other strains. However, only the texture (3.97±0.71) attribute was found to be significantly different (p&lt;0.05). Overall acceptability by participants demonstrated that the variations between strains were not statistically different (p&gt;0.05). Nevertheless, strain D (141.00) was ranked significantly higher compared to other strains. Thus, the participant's distinct, undistinguishable sensory attributes revealed that all strains could be commercialised as table fish.

Identification of the effects of hypoxia on the liver tissues of Nile tilapia Oreochromis Niloticus

BackgroundHypoxia stress resulted in mortality during the fish aquaculture program, affecting the sustainable development of the aquaculture industry. The Egyptian strain of O. niloticus showed a strong ability to hypoxia. In this study, a Nile tilapia strain that was kept and selected for 45 years by the author’s team was used to elucidate the mechanism of the hypoxia response in the liver, including the identification of metabolic pathways and genes, involved in the hypoxia response of this strain.ResultsThe effects of hypoxia stress were detected at 0-hour, 6-hour, and 72-hour time points (0 h, 6 h, 72 h) on tilapia liver at 1 mg/L dissolved oxygen conditions. The blood triglyceride, blood glucose and cholesterol values exhibited significantly different change trends, but the hemoglobin content showed no significant differences between 0 h, 6 h and 72 h (P > 0.05). The activities of catalase (CAT), glutathione peroxidase (GSH-PX), total antioxidant capacity (T-AOC), lactate dehydrogenase (LDH), and acid phosphatase (ACP) in the liver tissue gradually increased at 0 h, 6 h and 72 h (P < 0.05). Histological analyses revealed structural changes in intracellular lipid droplets, nuclear migration and dissolution, and cell vacuolization in liver tissues. Six pathways were identified as the main enriched metabolic pathways according to the transcriptome profiling analysis, which were protein processing in endoplasmic reticulum, steroid biosynthesis, peroxisome, PPAR signaling pathway, glycolysis/gluconeogenesis and Insulin signaling pathway. The expressions of the important differentially expressed genes were verified by qPCR analysis, including erola, LOC100692144, sqle, cratb, pipox, cpt1a2b, hik and acss2l, ehhadh, prkcz, fasn and plaa, which showed the same expressions trends as those of RNA-Seq.ConclusionsThe Nile tilapia strain improves the abilities of hypoxia response through energy metabolism. Antioxidant enzyme measurements in the liver indicate that these five antioxidant enzymes play important roles in protecting the body from hypoxic damage. The histological changes in liver cells indicate that the damage caused by hypoxia stress. The immune-related metabolic pathways and energy metabolism-related pathways were obtained by transcriptome profiling, and these metabolic pathways and the differentially expressed genes selected from these metabolic pathways may be involved in the mechanism of hypoxia tolerance in this strain. These findings provide a better understanding of the hypoxia response mechanism of fish, and represent a useful resource for the genetic breeding of O. niloticus.

SUSTAINABLE AQUACULTURE; ORGANIC INNOVATIONS FOR DISEASE PREVENTION AND HEALTH MANAGEMENT IN NILE TILAPIA (OREOCHROMIS NILOTICUS)

Sustainable aquaculture has become imperative in guaranteeing the enduring prosperity of aquatic farming, specifically for the Nile tilapia (Oreochromis niloticus), one of the most extensively farmed fish species. This study examines organic developments in Nile tilapia farming focused on eco-friendly practices that reduce the use of artificial chemicals and antibiotics to avoid sickness and maintain health. Integrating natural probiotics, probiotics, and immunostimulants into fish meals is one of the most critical tactics for strengthening the immune system and boosting the resistance of Nile tilapia against parasitic, bacterial, and viral infections. By maintaining the fish's natural defenses and promoting intestinal health, these natural additions lessen the need for conventional antibiotics. Moreover, the employment of beneficial microorganisms and biofiltration systems are two sustainable water management strategies that are essential for limiting the spread of illness in aquaculture settings. By emphasizing water quality through natural filtration processes, organic pond systems create a more balanced environment, lowering stress levels and disease susceptibility. By minimizing nutrient run-off, organic feed formulations using plant-based components, essential oils, and herbal extracts improve fish health and reduce the environmental effects of aquaculture techniques. This analysis also assesses these organic systems' economic viability, emphasizing how cost-effective and scalable they are compared to conventional aquaculture techniques. The aquaculture sector may minimize ecological impact while increasing fish health, producing better results, and adding to global food security through sustainable methods in Nile tilapia cultivation. To further advance sustainable aquaculture in the future, more studies are required to maximize these advances under various environmental circumstances and tilapia strains.

Comparative growth, survival, and feed conversion factor of the F1 generation of two new strains of tilapia Oreochromis niloticus produced by mass selection

Growth, survival, and use of feed of the F1 generation of two new strains of tilapia Oreochromis niloticus (GenBank Strain Y = OK078792 to OK078796 and Strain A = OK078797 to OK078807) produced by mass selection was compared with a known fast-growing commercial strain in Mexico (GenBank Strain Q = OR744820 to OR744838), during a grow-out phase of 165 days. Genetic variability including observed (Ho) and expected (He) heterozygosity, inbreeding coefficient (Fis), and paired comparisons of strain fixation index (Fst) of the three strains were also compared, and an additional analysis of molecular variance (AMOVA) was performed. Twelve hapas of 8.2 m3 (four for each strain) were stocked at a density of 25 org m−3 of 4.58 ± 0.67 g, which were fed with 45 to 25% crude protein feed under a dynamic feeding scheme of 8 to 3% live weight. Growth was estimated by growth rates in weight and length, and by the weight-specific growth rate (SGR). The use of feed was estimated by the total feed consumption rate and the feed conversion factor (FCF). Results indicate no significant differences (P > 0.05) in growth parameters of the three strains, except in SGR which was significantly higher in the control strain (Q) (2.75% day−1) as compared with strains Y and A (2.51 and 2.59% day−1 respectively). The average final weight and size of the fish were 314.6 ± 11.8 g and 25.5 ± 0.4 cm respectively. No significant differences (P > 0.05) were found in survival and feed utilisation among strains, with average values of 96.4% survival, feed consumption of 3.91 g day−1, and FCF of 2.08. Results of genetic diversity indicate that there were no significant differences (P > 0.05) in Ho and He of the three strains, with average values of 0.310 and 0.280 respectively. Fis values were negative and similar for the three strains, with a mean value of −0.109 which indicates no consanguinity in their populations. Finally, the paired comparisons of Fst were significantly different (P < 0.001), showing relatively low values but different from 0 (Y vs. A = 0.025, A vs. Q = 0.041 and Y vs. Q = 0.055), indicating slight but significant population differentiation between strains. In conclusion, the performance and genetic variability of the F1 generation of the two new strains suggest that valuable broodstock is now available for mass production of fry, with similar performance as to one of the best strains of tilapia in Mexico.

Effect of Crossbreeding on Fecundity, Growth Performance, and Heterosis of Black Tilapia, Red Tilapia, and Mozambique Tilapia Reared in Earthen Ponds in West Java, Indonesia

Graphical Abstract Highlight Research The crossbred performance of the four tilapia strains showed diverse heterosis values, with some being better, worse, or the same as their parents. Crossbred of black tilapia produced the best growth and fecundity performance. A hybrid of Mozambique tilapia and black tilapia showed the highest mid-parent heterosis value on growth traits but produced negative heterosis on fecundity, biomass, and survival traits. Crossbred of black tilapia and Mozambique tilapia have the potential to be used as candidates for cultivation and performance improvement through selection, although there are depressions and crossover advantages that are not prominent. Abstract Increased tilapia production is challenged by genetic decline. Hybridization efforts for performance improvement through a selection of the best parent and strain pairs were a promising option. The objective of this study was to evaluate the crossing of black tilapia, red tilapia, and Mozambique tilapia against the performance of fecundity, growth, and survival and estimate the value of heterosis. The experimental design used a completely randomized design with 3 replications with the treatment of different populations of crosses. The rearing activities were carried out in earthen ponds for 150 days with a stocking density of 10 fish/m2. The parameters observed included egg fecundity, growth, survival, and the value of heterosis. The results showed that the fecundity and growth values of crossbred black tilapia were significantly higher than others (p&lt;0.05). The highest survival rate was shown by crossing pure strains of red tilapia. The hybrid of Mozambique tilapia and black tilapia (♀ MJ x ♂ NW) showed the highest mid-parent heterosis value on growth characters but produced negative heterosis on characters, fecundity, biomass, and survival. Overall, the crossbred of black tilapia (♀BS x ♂ NW) performed better than the inbred strains, with positive mid-parent heterosis in all characters measured. These results indicate that crossbreeding has the potential to be used as a candidate for cultivation and performance improvement through selection, although there were depressions, and the superiority of the crosses was not prominent.

Zootechnical parameters and hepatosomatic index of two genetic strains of Nile tilapia fed with β-Glucan + Mannan oligosaccharide (βG+MOS)

The increasing expansion and the rising demand for food require a greater intensification in the production of Nile tilapia (Oreochromis niloticus), and genetic improvement programs are essential to achieve this goal. In managing these programs, new genetic material is introduced after several generations of selections to reduce inbreeding and enhance genetic diversity. In this sense, analyzing the zootechnical parameters of these introductions, with an emphasis on the use of nutritional additives, is of great importance for understanding their impact on breeding programs. Thus, the aim of this study was to evaluate the zootechnical parameters and hepatosomatic index of two genetic strains of Nile tilapia from the genetic improvement program fed with β-Glucan + Mannan oligosaccharide (βG+MOS). This study utilized a 2 × 2 factorial design containing two genetic groups and two treatments with βG+MOS (Control, 0.2%). The groups were formed from the 12th generation of the Tilamax genetic improvement program (TILAMAX) and by crossing Tilamax with an introduced test strain (CBTILAMAX). In total, 96 tilapias (31.1 ± 5.73 g) were distributed into 16 aquariums, with 6 fish per aquarium, 24 per group, and four repetitions. The experimental period lasted for 41 days, and the water parameters were measured daily and maintained under ideal conditions. The condition factor and hepatosomatic index were analyzed. Final weight, total length, and standard length were measured, and other zootechnical parameters were calculated based on these data. The condition factor showed that the fish in both groups exhibited adequate health and growth during the experiment, with no differences in strain or use of additives. Similarly, the hepatosomatic index did not differ between the groups, indicating that liver size was proportional to fish body size. Similarly, no significant differences (P&gt;0.05) were observed for the other zootechnical parameters evaluated (initial and final total and standard lengths, final weight, total weight gain, condition factor using total and standard lengths, and specific growth rate). Based on these results, it is concluded that there were no differences between TILAMAX and CBTILAMAX related to performance and health under the effect of feeding with βG+MOS. This result is positive regarding the introduction of the test strain into the Tilamax genetic improvement program and establishes a starting point for further research that may provide greater clarity on its future effects.

Genotyping of red tilapia strains in Central Luzon Philippines targeting ESR1 gene

Tilapia is an economically important commodity worldwide. Marker-assisted selection (MAS) has been practiced in livestock culture to ensure the selection of a specific trait that will benefit the culture system. This study assessed the allelic variation in six red tilapia strains in Central Luzon, Philippines. Polymerase Chain Reaction-Restriction Fragment Length Polymorphism (PCR-RFLP) was done to evaluate the genotypes of six strains of red tilapia using intron one portion of the chromosome one of the estrogen receptor 1 (ESR1) gene. The target gene was amplified using primers designed in previous study and then subjected to RFLP using PvuII restriction enzyme. Single Nucleotide Polymorphisms (SNPs) were also evaluated in six DNA sequences. Results showed that 18 red tilapia samples were found to be of the AA genotype. Aligned sequences of the 122 bp ESR1 gene revealed that among six red tilapia strains, there are 117 identical pairs, three transversional pairs, and three transitional pairs. The SNPs observed can be used to identify restriction enzymes that discriminate different genotypes in the target gene. Association studies can be done to determine the genotypes that are linked to specific traits in cultured animals.

Resistance of Indonesian tilapia strains, Oreochromis niloticus to Tilapia Lake Virus Disease (TiLVD)

This study aims to evaluate the resistance of six Indonesian tilapia strains to TiLV disease and assess the impact of mimicked daily water temperature fluctuations on the disease severity. Six widely cultured Indonesian tilapia (Oreochromis niloticus) strains were evaluated for resistance to tilapia lake virus disease (TiLVD). Resistance to TiLVD was assessed using two artificial infection methods, cohabitation and intraperitoneal (IP) injection. Fish infected with TiLVD exhibited behavioural, clinical and mortality patterns associated with TiLV disease. Virus presence was also confirmed molecularly. All six tilapia strains were susceptible to TiLV infection, causing disease and mortality. The range of mortality for cohabitation was 1.67% - 28.33% and for IP injection was 16.67% - 61.67%. The most resistant tilapia strain to TiLV disease was Gesit, followed by Best, Red/Albino, Nirwana, Non-specific and Srikandi. Daily temperature variation results in higher significant virus-induced mortality pattern among tilapia strains. These findings can be used to guide the selection of appropriate tilapia strain and temperature control to mitigate the adverse effects of TiLV associated disease.

Comparative Study of Growth Performance of Three Tilapia Strain in Intensive Culture System

High stocking density is an important factor in cultivation to increase the eficency if fish farming for nutrition requirements. High stocking density generally impact on fish physiology and growth performance. However, many studies on individual fish have different growth perfromance from different strain. Some technology had been developed to optimize tilapia production in high stocking density. This study aimed to determine the growth performance of three different strain of tilapia (red tilapia, nirwana tilapia, and jatimbulan tilapia) reared in 20 m3 of round tarpaulin with additional of microbubble generator. This study used an intensive system with 100 fish/m3 of stocking density. The results showed that the microbubble generator was able to increase the carrying capacity of water quality such as increasing dissolved oxygen in the waters, temperature and pH. The high content of dissolved oxygen in the water significantly increasing the growth of tilapia. The highest weight was found in red tilapia with a final weight of 199.56 ± 0.05 gr, followed by Nirwana tilapia with 176.59 ± 0.10 gr, and Jatimbulan tilapia with 153.91 ± 0.06 gr. In addition, the high content of dissolved oxygen in the waters also affect the rearing period of tilapia.

Survival, Growth, Meristic and Morphometric Characteristics of Hybrids Between Black and White Nile Tilapia Strains

Survival, Growth, Meristic and Morphometric Characteristics of Hybrids Between Black and White Nile Tilapia Strains

Comparative analysis of quantitative phosphoproteomics between two tilapias (Oreochromis niloticus and Oreochromis aureus) under low-temperature stress.

As an important farmed fish, tilapia has poor tolerance to low-temperatures. At the same time, different tilapia strains have apparent differences in low-temperature tolerance. In this study, using the iTRAQ method, the phosphorylated proteomics of two tilapia strains (Oreochromis niloticus and Oreochromis aureus) with different tolerances to low-temperature stress were quantitatively and comparatively analyzed, to clarify the physiological mechanism of tilapia's response to low-temperature stress. Through the GO and IPR analyses of differentially phosphorylated proteins, a number of similarities in physiological activities and regulatory effects were found between the two tilapias in response to low-temperature stress. Many differentially phosphorylated proteins are mainly involved in lipid metabolism, cell proliferation and apoptosis. However, the difference in endurance of low temperature of these two tilapias might be related to the differences in categories, expression and modification level of genetic products which were involved in the aforementioned physiological processes. And meanwhile, the enrichment results of KEGG showed the changes of multiple immune-related and growth-related phosphorylated proteins in the cytokine-cytokine receptor interaction pathway in O. aureus are more prominent. Furthermore, the significantly enriched pathway of carbohydrate digestion and absorption in O. niloticus may indicate that low-temperature stress exerts a more severe impact on energy metabolism. The relative results would help elucidating the molecular mechanism by which tilapia responds to low-temperature stress, and developing culture of tilapia species.

Acute hyperthermia and hypoxia tolerance of two improved strains of nile tilapia (Oreochromis niloticus)

Tilapia production in Ghana has been hit with episodes of stress and pathogen-induced mass fish kills which have anecdotally been linked to the culture of illegally imported Genetically Improved Farmed Tilapia (GIFT) strains of Nile tilapia, Oreochromis niloticus. This study was thus set up to comprehensively assess the stress tolerance of the GIFT strain and a native strain of Nile tilapia (the Akosombo strain) following exposures to hyperthermic and hypoxic stressors. In a series of experiments, oxygen consumption (MO2), aquatic surface respiration (ASR), thermal limits and hypoxia tolerance were assessed. The effects of these stressors on haematological parameters were also assessed. The GIFT strain was less tolerant of hypoxia and performed ASR at higher O2 levels than the Akosombo strain. Under progressive hypoxia, the GIFT strain exhibited higher gill ventilations frequencies (fV) than the Akosombo strain. The thermal tolerance trial indicated that the Akosombo strain of O. niloticus has higher thermotolerance than the GIFT strain and this was reflective in the higher LT50 (45.1℃) and LTmax (48℃), compared to LT50 and LTmax of 41.5℃ and 46℃ respectively. These results imply that it is crucial to consider how the GIFT strain performs under various environmental conditions and changes during culture. Particularly, raising the GIFT strain of Nile tilapia in earthen ponds rich in phytoplankton and subject to protracted episodes of extreme hypoxia may have a detrimental physiological impact on its growth and welfare.

Streptococcosis on Nile tilapia (Oreochromis niloticus) in Indonesian freshwater aquaculture

This review aimed to provide the current status of streptococcosis in freshwater aquaculture in Indonesia. So far, this disease has been mostly reported in tilapia aquaculture, and there have been no serious reports of this disease in other species of freshwater aquaculture. The disease is mostly encountered during the dry season or the transition period from the dry season to the rainy season or vice versa. Initially, the disease was mostly reported in tilapia larger than 250 grams, but in its development, it was also reported in smaller fish. The Ministry of Marine Affairs and Fisheries (MMAF) has classified this disease as a major disease in tilapia in Indonesia since 2014. Based on the characteristics of Streptococcus agalactiae isolates collected from diseased tilapia from various regions in Indonesia, two biotypes were found consisting of ?-hemolytic S. agalactiae (biotype I) and non-hemolytic S. agalactiae (biotype II). Biotype I cause disease with acute mortality patterns, while biotype II causes disease with chronic and persistent mortality patterns. Based on susceptibility to S. agalactiae during artificial infection testing, it is known that all tilapia strains that have been released to the public for aquaculture purposes are susceptible to infection with the bacteria; although each strain has a different level of susceptibility. Fish health management strategies that are based on preventive measures and relevant to sustainable aquaculture programs should be based on ecological-biological approaches such as the implementation of biosecurity systems, the use of vaccines for endemic diseases, probiotics, essential herbs, and the development of more disease-resistant populations.Keywords: health management, streptococcosis, Streptococcus agalactiae, tilapia

Comparative estimation of the lysine requirements in two generations of improved strain of Nile tilapia (Oreochromis niloticus) at the grow-out stage

A 3 × 2 factorial experiment was conducted to investigate the effects of dietary lysine on growth performance, body indices, feed intake, feed efficiency, whole body nutrient composition and amino acid deposition in two successive generations (16th and 17th) of GIFT (Oreochromis niloticus). Three diets containing different levels of lysine at 1.16%, 1.56% and 2.41% were prepared for the feeding trial. Triplicate groups of fish with an initial body weight of 155 g were fed to apparent satiation for 10 weeks in a recirculating aquaculture system. Apparent digestibility coefficients (ADC) of dry matter, crude protein, crude lipids, and total carbohydrates were measured in the experimental diets. At the end of the experiment, no interactions between dietary lysine levels in diet and fish generation were observed on all parameters except for the condition factor (CF) and ADC of crude protein. However, dietary lysine level significantly affected the final weight, weight gain, thermal unit growth coefficient (TGC), protein efficiency ratio (PER) and ADC of dry matter regardless of the fish generation. Final weight, weight gain and TGC of fish were the highest in fish fed 2.41% dietary lysine in diet or 6.52% lysine in the protein. PER was the lowest in fish fed 1.16% dietary lysine. The final weight and the body's accumulation of isoleucine, phenylalanine, and alanine were significantly affected by the fish generation, with the 17th generation having the best performance. Increase growth and higher lysine requirement observed in the improved generation (17th) compared to the (16th) generation at grow out phase indicating that genetic improvement may have changed the dietary lysine requirement.

Evaluating the inclusion of phytase sources to phosphorus-free diets for GIFT tilapia (Oreochromis niloticus): Growth performance, intestinal morphometry, immune-antioxidant responses, and phosphorus utilization

The current study aimed at evaluating the growth performance, phosphorus (P) retention, and welfare status of GIFT strain of Nile tilapia (Oreochromis niloticus) fed on P-free diets containing fungal phytase (FPhyt) and/or a novel hybrid bacterial phytase (HB-Phyt). The control reference diet (T1) was supplemented with dicalcium phosphate (DCP; 8.7 g total P/kg). Other five low-P (with no DCP; 5.9 g total P/kg feed) diets were supplemented with 500, 1000 FTU/g of FPhyt (T2-T3) or 500, 1000 FTU/g of HB-Phyt (T4 – T5), while T6 contained 1000 and 1000 FTU/g of both phytase sources. Each diet was allocated randomly to three 100-L tanks stocked with GIFT tilapia (n = 15 fish per tank, initial mean weight, 2.38 ± 0.22 g). Fish were fed on experimental diets up to satiation thrice a day for 60 days. Fish in T1, T3, T5, and T6 recorded highest growth performance; meanwhile, highest values of villi length/width and absorption area were observed in T3, T5, and T6 fish groups as compared with other groups. Highest values of hematological indices (red blood cell, hemoglobin, packed cell volume, white blood cell, and lymphocytes %) and immune-antioxidant biomarkers (superoxide dismutase, catalase, lysozyme, and respiratory burst activity) were highest in the case of fish in T3, T5, and T6 with no significant difference among them. Meanwhile, feeding fish on diets with 500 FPhytase (T2) or 500HB-Phyt (T4) showed lowest values of immune-antioxidant indices accompanied with highest value of malondialdehyde as compared with other treatments. Compared with other treatments, highest values of bone-P were observed in T3, T5, and T6, while highest whole-body P values were detected in T5 and T6 only, with no significant difference among them. The present study revealed much lower feed input per unit production accompanied with higher return on investment in GIFT fed on diets supplemented with 500 FTU/g of HB-Phyt than 1000 FTU/g of either FPhyt or HB-Phyt. Hence, the present study showed that the dietary inorganic P could be compensated by adding 1000 FTU/g of either FPhyt or HB-Phyt to fish diets. The growth and immune-antioxidant indices in fish fed with HB-Phyt were superior to FPhyt treatments. No synergetic effects of using both of FPhyt and HB-Phyt were detected in this study.

Effects of dietary copper (Cu) on growth performance, body composition, mineral content, hepatic histology and Cu transport of the GIFT strain of Nile tilapia (Oreochromis niloticus)

This study determined the influence of dietary copper (Cu) levels on growth and feed utilization, body composition, mineral content, liver histology and intestinal Cu transport, and identify dietary Cu requirement of the GIFT strain of Nile tilapia (Oreochromis niloticus). Six diets were prepared with Cu sulfate addition at levels of 0 (control), 5, 10, 20, 40, and 80 mg/kg, respectively. Analytical dietary Cu contents were 1.55, 2.97, 4.51, 7.25, 11.30, and 19.24 mg Cu/kg diet, respectively. Each experimental diet was fed to three replicates of GIFT tilapia (25 fish per tank, initial body weight 4.34 ± 0.01 g) in a recirculating freshwater system for eight weeks. GIFT tilapia fed 4.51 mg Cu/kg diet had higher growth performance and feed utilization. Cu contents in the whole-body, the liver and intestinal tract increased with dietary Cu levels. Moreover, dietary Cu addition also affected whole-body Mg content significantly, but did not affect whole body crude protein, lipid, zinc (Zn), iron (Fe), and calcium (Ca) content. GIFT tilapia fed with 4.51 mg Cu/kg diet had lower liver vacuoles relative area. Furthermore, dietary Cu addition also significantly influenced mRNA expression of genes involved in intestinal Cu transport, such as copper transporter 1 (ctr1), copper transporter 2 (ctr2), antioxidant 1 copper chaperone (atox1), cytochrome c oxidase copper chaperone (cox17) and copper-transporting ATPase alpha (atp7a). The regression analysis of weight gain and whole-body Cu retention against the dietary Cu levels suggested that 4.23 to 4.57 mg Cu/kg diet was optimal for GIFT tilapia. Statement of relevanceOur study determined the optimal dietary Cu requirement of GIFT strain of tilapia, which provided good references for dietary Cu addition for the fish species, and accordingly was helpful for its feed formulation and aquaculture production. Our study also demonstrated that dietary Cu addition influenced mRNA expression of genes involved in Cu transport, which provides a good basis for exploring Cu metabolism in fish.

Effect of Pulsed Feeding of GIFT Strain of Tilapia in Biofloc System Using Inland Saline Water

Feed is one of the major inputs in aquaculture system and constitutes 60%–80% of total production costs of tilapia. Inappropriate selection of feed quality and the feeding strategy affects the feed utilization resulting in high food conversion ratio (FCR). A 60 days experiment was conducted to evaluate the growth performance and immuno-physiological responses of GIFT tilapia, (Oreochromis niloticus) by pulsed feeding under biofloc culture system in inland saline water. For the experiment, feeding pattern in pulsed was followed viz., in situ biofloc with daily feeding (T1), in situ biofloc with alternate day feeding (T2), in situ biofloc with every third day feeding (T3), in situ biofloc with no feeding (T4), and clear water control with daily feeding (C) each in triplicates. Biofloc based treatment receiving daily feeding (T1) resulted in significantly (P&lt;0.05) higher average body weight, weight gain, and specific growth rate (SGR) compared to control. T1 and C showed a significantly similar feed conversion ratio (FCR) and protein efficiency ratio (PER). Fish maintained in T4 grew the least and survival was lowest (85%). The immunological parameters showed a significant difference (P&lt;0.05) for nitroblue tetrazolium (NBT) and myeloperoxidase content whereas no significant difference (P&gt;0.05) for lysozyme activity was observed. Higher NBT activity was observed in biofloc based treatments compared to control. Activity of superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx) activity were considerably higher (P&lt;0.05) in biofloc based treatments than control. Among biofloc based treatments the antioxidant activities were lower in T1. The carbohydrate metabolism enzymes lactate dehydrogenase (LDH) and malate dehydrogenase (MDH) were lower in T1, T2, and T3 compared to control and T4. In conclusion, in-situ biofloc with daily feeding is found to be effective in growth improvement and to elicit immune-physiological responses in GIFT tilapia under pulsed feeding using biofloc based system.