Thermal-unit Growth Coefficient Research Articles

Black Soldier Fly Larvae Meal vs. Soy Protein Concentrate Meal: A Comparative Digestibility Study in Barramundi (Lates calcarifer)

Black soldier fly larvae meal (BSFM) from Hermetia illucens has emerged as a dependable protein source in aquaculture. This study aimed to assess BSFM’s digestibility in barramundi juveniles and compare it to soy protein concentrate meal (SPCM). Four diets (control, 30% BSFM; 30% SPCM; and commercial feed control) were tested on 1,800 barramundi juveniles (weight: 71.1 g) over 51 days in a recirculating aquaculture system (RAS). The final body weight (FBW) of fish fed with BSFM reached 222.2 (± 8.7), with a thermal-unit growth coefficient (TGC) of 4.33 (± 0.15) and a feed conversion ratio (FCR) of 1.04 (± 0.01). While BSFM and SPCM inclusion did not significantly impact FBW, body weight gain (BWG), TGC, or survival rates (P >0.05), FCR increased. BSFM significantly raised total feed intake (P<0.05) but did not affect daily feed intake (P >0.05). Importantly, BSFM and SPCM inclusion did not alter diet apparent digestibility coefficient (ADC) for any nutrient groups (P >0.05), with BSFM showing high ADC for dry matter (76.8%), crude protein (93.2%), and gross energy (83.9%). No significant difference (P >0.05) was observed in these ADCs between BSFM and SPCM. The high digestibility of BSFM in warm seawater RAS (29.4°C) under high stocking density (33.7 kg m−3) supports its efficacy in contemporary barramundi farming.

Utilization of an insect-based diet by a herbivorous fish (Oreochromis mossambicus) and an opportunistic predator (Clarias gariepinus)

An 8-week feeding trial was conducted to evaluate the effect of Alates termite (Macrotermes falciger) based diet in a herbivorous (Oreochromis mossambicus) and an opportunistic predator (Clarias gariepinus). Five diets were formulated to replace fishmeal at 0, 10, 30, 50, and 70 % and were denoted D1, D2, D3, D4, and D5, respectively. Clarias gariepinus sub-adults (209.24 ± 2.41 g/fish) were stocked at 5 fish per tank in recirculating fibreglass tanks (400 L) in triplicates. Oreochromis mossambicus juveniles (7.4 ± 4.78 g/fish) were randomly stocked at 10 fish per tank in recirculating fibreglass tanks (400 L) in triplicates. Fish were fed their allocated diets, twice a day to apparent satiation. Growth performance indices (specific growth rate, thermal-unit growth coefficient) were lowest at inclusion level above 50 % in both species (P < 0.05). The nutrient utilization indices (feed intake, protein efficiency ratio) were lowest at inclusion level above 50 % in both species. The organosomatic indices (condition factor, hepato-somatic index, viscero-somatic index) were not influenced by the inclusion of Alates termite meal in both species. The aspartate aminotransferase (AST) and alanine aminotransferase (ALT) were not influenced by Alates termite meal in O. mossambicus (P > 0.05). However, AST and ALT levels significantly increased at inclusion levels above 50 % in C. gariepinus (P < 0.05). The triglyceride, cholesterol, and glucose levels showed no significant difference across diets in both fish species (P > 0.05). The study showed that both species may utilize an insect-based diet up to 50 % inclusion levels without adverse effects on growth performance and nutrient utilization.

Relationships between the specific growth rate and the thermal-unit growth coefficient applied to cultured juvenile fish

The growth of cultured juvenile fish is usually quantified by two indexes, the specific growth rate or SGR, and the thermal-unit growth coefficient or TGC. The SGR is a relative growth index based on logarithms of body weights, and it decreases with body weight. The classical TGC is based on one-third powers of body weights and the summation of temperature over time. It can also depend on body weight, but it is possible to release this dependency by empirically adjusting the power function in its mathematical definition. These two indexes are usually presented in the same article to compare the growth attained by different groups of fish subjected to different experimental treatments. However, no formal framework linking both indexes is available for researchers up to the moment, the meanings of SGR and TGC remaining unrelated. The present work shows that the TGC of a group of fish growing at a given temperature can be expressed as a function of the SGR. In addition, the relationship between SGR and TGC here reported provides the basis to re-defined the TGC as a size-independent index with application to fish culture.

Growth models in aquaculture for hybrid and natural groupers based on early development stage

Grouper has been highlighted as current hot species for marine aquaculture in China, so it is vital to master its growth performance in early development stage and understand growth trend of it. However, there are few detailed reports on the growth model and biological parameters in the early growth of grouper. The aim of this study is to discuss and compare the applicability of growth indexes and 10 biological growth models in larval and juvenile stage of hybrid and natural groupers, then to evaluate the optimum model. Pearl gentian grouper (PG) and kelp grouper (KG) were selected. The growth data of grouper larvae and juvenile were chosen. Absolute growth (AG), relative growth rate (RGR) and specific growth rate (SGR), and the thermal-unit growth coefficient (TGC) were calculated. Ten nonlinear models, such as Logistic, Gompertz,Von Bertalanffy, Generalized Weibull, Janoschek, Schnute and et al., were used to fit growth. Models were evaluated and selected by Akaike information criterion (AIC) method, the values of RMSE, MAE and R2, parameter significance level and iterations. Fitting results showed that compared with AG, RGR and SGR, TGC has higher fitting degree, especially for fitting weight (R2 > 0.99). In larval stage, Schnute model had the highest best fit ratio (75%), and minimum number of iterations (< 71), with more than two significant parameters (P < 0.001). In juvenile stage, the beat fitting ratio of Janoschek model evaluated by AIC was 25%, and that by RMSE, MAE and R2 was 50%, which was higher than other models. It also had low iteration times and high significant level (P < 0.05). For model evaluation, best fitting result evaluated by AIC method was different from that evaluated by RMSE, MAE and R2. It is more reliable to combine the two methods for model evaluation. The growth curves generated by optimum models showed that the growth characteristics of larvae is exponential, and in juvenile stage, PG maintained accelerated growth but the growth rate of KG gradually decreased. In summary, the optimum model of larval stage was Schnute model and that of juvenile stage was Janoschek model; 4-parameter models have high robustness and accuracy for fitting growth; Compared with KG, PG grows faster and is more suitable for aquaculture.

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.

Estimating stocking weights for Atlantic salmon to grow to market size at novel aquaculture sites with extreme temperatures

Land-based hatcheries are now capable of growing large Atlantic salmon (Salmo salar) post-smolts (approximately 150 – 1000 g), which means that marine net-pens can be stocked with substantially larger fish compared to traditional stocking sizes (&amp;lt; 150 g). This stocking strategy typically aims to reduce the time required for fish to grow to market size in the marine environment and limit risks (e.g., exposure to pathogens and diseases, opportunities for escapes). This study investigates another potential application of this strategy: the use of novel sites in areas previously considered unsuitable for aquaculture due to seasonally cold temperatures. The thermal-unit growth coefficient (TGC) model was applied to estimate the stocking weight needed to reach a harvest size of 5.5 kg, based on observed degree days for three sites. High resolution, depth-partitioned temperature time series from coastal locations in Atlantic Canada were used to represent a short, medium, and long growing season, as constrained by seasonal temperature extremes. Growing days for model inputs were defined as temperatures &amp;gt; 4 °C and trending up for stocking, &amp;lt; 18 °C to account for heat stress, and &amp;gt; -0.7 °C to avoid superchill conditions. Different TGC values were applied to simulate remedial, average, and elite growth performance. There was a range of model stocking weight estimates for each site (1.5 – 2.5 kg, 0.94 – 2.8 kg, and &amp;lt; 0.1 – 0.52 kg, for the short, medium, and long season sites, respectively). Results were sensitive to the number of degree days, heat stress threshold, and TGC value. At the two sites where season length was constrained by superchill, fish with a stocking weight of approximately 1.5 kg could grow to market size in shallow water depths (&amp;lt; 15 m), assuming elite growth performance. This investigation suggests that with appropriate growth performance assumptions and high-resolution temperature data, large post-smolt stocking strategies could enable the use of novel sites in coastal areas previously considered unsuitable for aquaculture.

Indispensable and dispensable amino acid supplementation in diets offered to Nile tilapia Oreochromis niloticus

The objectives of this study were to further optimize balance of dietary amino acids (AA) offered to Nile tilapia by investigating the role of dispensable AA (DAA) across the range of indispensable AA (IAA) intakes. The possible limitation of IAA intake in fish consuming diets with high inclusion of crystalline AA (CAA) supplemented to the diets was also confirmed. The basal diet was formulated to contain 22.2% intact protein in which IAA were adjusted to reach 100%, 110% and 120% of NRC requirements with or without DAA supplementation. Glycine and glutamic acid were used as DAA sources at 1:1 and 2:2 ratio to assign 2 levels of DAA at 2% and 4% of the diet. Fish were hand sorted to a uniform size then randomly stocked into 44 aquaria with 15 fish per/tank. Fish were fed 4 times a day to near satiation over a 10-week period. To evaluate feeding regimes on CAA utilization diets with 100% IAA without DAA supplements and 110% IAA with 4% DAA supplements were paired and fed to fish using 2 and 4 feedings per day. Results confirmed that DAA contribute to meeting the nitrogen requirement of fish in which fish fed diets with DAA supplementation had significantly higher growth rates (thermal-unit growth coefficient, TGC) and lower FCR compared to fish fed diets without DAA supplementation. Growth of fish fed diets without DAA supplementation was not comparable to fish fed diets supplemented with DAA irrespective of IAA supplements up to 120% NRC requirement. Fish fed diets with DAA supplements at 4% exhibited superior growth compared to fish fed diets with 0% and 2% DAA supplements. The supplementation of IAA at 110% NRC requirement helped the fish have better growth compared to fish fed diets formulated to 100% NRC. However, no further benefit was observed on growth performance of fish fed diets with IAA supplements up to 120%. Fish fed diets with IAA supplements at 110% NRC and 4% DAA supplements exhibited the best response. The results of this study indicated that although DAA provided benefits in balancing AA profiles of feed, limitation of IAA intake at 100% NRC might cause impaired growth of Nile tilapia. In addition to this, no influence of feeding frequency was obtained on growth performance of fish feed, suggesting that fish can be fed successfully two times per day regardless of high inclusion levels of CAA.

Soğuk, dondurulmuş veya ortam koşullarında depolanan yemlerin gökkuşağı alabalığı (Oncorhynchus mykiss) yavrularında büyüme performansı ve yem tüketimi üzerindeki etkileri hakkında bir ön çalışma

The storage of commercial feeds in a cool and dry place is a prerequisite management strategy to minimize the deterioration of commercial feeds. This study investigated the effects of feed storage conditions on feed intake and growth performances of juvenile rainbow trout (Oncorhynchus mykiss). A total of 240 juvenile rainbow trout, weighing 8.7–10.5 g, were randomly distributed into four groups. Each group was further subdivided into three replicates with 20 fish in each. The experimental fish were fed to apparent satiation twice daily over a 35-days period using four commercial feeds previously kept at different storage conditions, i.e., room temperature storage (20.8°C), cold storage (10°C), or frozen storages (-1.1°C and -15°C). The feed utilization was assessed by relative feed intake (RFI%) and feed conversion rate (FCR), while growth performance was evaluated by the thermal-unit growth coefficient (TGC) and specific growth rate (SGR). The preliminary findings suggest that the food storage conditions did not significantly affect feed intake and growth performance in juvenile rainbow trout. The findings provide practical information for fish farmers in the management of feed storage, which covers a remarkable proportion of the total production costs in aquaculture facilities.

The effect of dietary fish meal replacement with blood meal on growth performance, metabolic activities, antioxidant and innate immune responses of fingerlings black carp, Mylopharyngodon piceus

This study was focused on evaluating the effect of dietary fish meal replacement with blood meal on growth performance, metabolic activities, antioxidant and innate immune responses of fingerlings black carp, Mylopharyngodon piceus. Six iso-nitrogenous and iso-caloric diets were formulated with varied blood meal (BM) inclusion levels to replace fish meal at 0%, 20%, 40%, 60%, 80% and 100% (designed as BM0, BM20, BM40, BM60, BM80 and BM100 respectively). Triplicate groups of 25 fish/tank (28.62 ± 0.06 g) were fed one of six experimental diets for 8 weeks. No significant differences were observed in the growth performance including weight gain, specific growth rate, thermal unit growth coefficient and survival among experimental groups. Growth performance was decreased with increasing dietary BM content but BM40 was little higher than BM20, BM60 and BM80 groups and no fish died in this group compared to others. The activity of intestine trypsin was significantly decreased with increasing dietary BM levels, and lower amylase was significantly observed in fish fed diets BM40 and BM100 than other dietary groups (p < .05). There were no significant differences observed among treatments for lipase, pepsin and chymotrypsin. The activities of hepatic catalase, glutathione peroxidase, the levels of total antioxidant capacity and glutathione were significantly higher in fish fed diets BM0, BM20 and BM40 than other dietary groups. The activity of hepatic superoxide dismutase was significantly lower in fingerlings black carp fed diets BM20 and BM60 than other dietary groups (p < .05). Hepatic glutathione s-transferase did not show any significant difference among all dietary treatments (p > .05). Higher malondialdehyde was significantly observed in fish fed diets BM60 and BM80 than BM0 and BM100 (p < .05). Serum lysozyme was significantly higher in fish fed diet BM0 than other dietary groups (p < .05); however, no significant differences were observed for complement C3 and C4. No significant differences were observed on the kidney mRNA expression levels of natural resistance-associated macrophage protein, interferon-α, lysozyme and complement C9 among fingerlings black carp fed all experimental diets (p > .05). Briefly, the results of this research were shown that a suitable level of fish meal replacement with blood meal could be around 40% in the diets of fingerlings black carp without reducing growth performance and innate immune responses.

Site selection for finfish cage farming using spatial multi-criteria evaluation and their validation at field in the Bay of Souahlia (Algeria)

The development of marine fish farming on the Algerian coast is facing a number of environmental and logistical constraints. In a multi-disciplinary approach, based on aquaculture activity planning and field validation, the aim of this study is to target suitable areas for the setting of floating cages for Sparus aurata breeding at the Bay of Souahlia, Algeria. Multi-criteria evaluation via GIS was applied, combining 3 sub-models (environmental, socioeconomic, and constraint sub-models). The field verification was carried out on El Mokretar Aqua farm, by comparing its position with the result of the multi-criteria evaluation and by studying the growth performance indicators, thermal unit growth coefficient, specific growth rate, and feed conversion ratio and biomass. The regeneration of the final suitability map allowed for the delimitation of the favorable area for the implantation of the floating cages, which corresponds to 32% of the total area, with 3 classes of suitability. The El Mokretar Aqua farm is located at station S11, with a significant relevance index of 0.69. The gilthead seabream reflects a good growth performance. It grows with an average weight of 5 to 305 g over a 306-day rearing period, due to the environmental conditions and the good management of the farm.

Efficacy of reduced protein diets and the effects of indispensable amino acid supplements for Nile tilapia Oreochromis niloticus

The study was conducted to evaluate the production performance of Nile tilapia Oreochromis niloticus fed graded levels of protein with or without indispensable AA (IAA) supplemented in practical diets. A control diet containing 32 % intact protein was modified to meet the respective requirements of IAA based upon NRC recommendations for Nile tilapia. From this diet, two series of diets were formulated to confirm the efficacy of crystalline AA (CAA) used as supplements in the practical diets of fish by applying “ideal protein concept”. In the first series of diets, intact protein was reduced gradually from 32 to 24 % of the diet without IAA supplementation. In the second series of diets, the same dietary protein levels were formulated; however, the IAA profiles of these diets were modified to meet the respective requirement of Nile tilapia (NRC, 2011). Five commercially-available AAs, including methionine, lysine, tryptophan, histidine and valine, were supplemented if necessary to attain the targeted AA profile. The supplementation of all deficient IAAs was obtained in the last diet to evaluate if there is further benefit of using IAAs other than commercial AAs to balance the AA profiles of diets. Four groups of Nile tilapia (12.7 ± 0.2 g) were fed each diet four times daily to near satiation. The results obtained after eight weeks indicated that fish fed diets with IAA supplementation had significantly higher weight gain compared to fish fed diets without IAA supplementation. Fish fed intact protein levels above 27.2 % with the supplementation of IAA up to the reported requirement (NRC, 2011) showed comparable performance to fish fed the control diet. The reduction of intact protein further than that, however, resulted in reduced growth rate (thermal-unit growth coefficient) of fish even though the IAA profiles of these diets met the reported requirement of tilapia for optimal growth (NRC, 2011). Based on the data obtained from this study, it can be concluded that ideal protein concept can be applied in formulating the diets for Nile tilapia to optimize AA profile of the diets. Well-balanced IAA profile can be used to reduce the intact protein levels of feed (32 to 27.2 %) without causing impaired growth of fish.

Cholesterol requirement and phytosterols efficiency in semi‐purified diets of juvenile Pacific white shrimp Litopenaeus vannamei

Studies pertaining to cholesterol requirement are limited based on the levels evaluated and statistical analysis. Two trials were conducted to refine cholesterol requirement in Pacific white shrimp Litopenaeus vannamei feeds. The basal diet was supplemented with graded levels of cholesterol (ranging from 0.48 to 1.85 g/kg) in trial 1. Since the shrimp (initial weight: 0.24 g) growth response was very linear without reaching a plateau, it was not clear whether the requirement was met. Hence, a second trial was designed using eight diets designed with an increased range of cholesterol levels from 0.45 to 4.57 g/kg of diets. The shrimp (0.38 g initial weight) reached a final weight of (4.31–7.43 g) or per cent weight gain from 1,014%–1,874% (n = 4) after 6 weeks. Saturation kinetic model and broken‐line models with linear or quadratic ascending portions were used to evaluate dose–response relationships of feed efficiency (FE), thermal‐unit growth coefficient (TGC), whole‐body cholesterol (CHOL) and cholesterol deposition (CHOLD) against dietary cholesterol. The cholesterol requirement of shrimp was estimated at 1.9 (1.1–4.3) g/kg, 1.7 (1.1–3.4) g/kg, 2.5 (2.3–2.9) g/kg and 2.7 (2.4–3.1) g/kg of shrimp diet for FE, TGC, CHOL and CHOLD, respectively. Additionally, based on improved growth, the inclusion of phytosterol can serve as a partial replacement for cholesterol.

Feed requirement determination of grass carp (Ctenopharyngodon idella) using a hybrid method of bioenergetics factorial model and fuzzy logic control technology under outdoor pond culturing systems

In outdoor pond culturing systems, formulated feed is the most main nutrition source and expenditure. Improving the feeding management efficiency is of great significance for reducing economic losses and alleviate ecological environmental pollution. In recent years, with the development of precision agriculture and animal welfare rearing, providing appropriate feed quantity based on the nutrient requirements of fish has become an important developing trend. In this study, a hybrid method, combining the bioenergetics factorial model with fuzzy logic control technology, was proposed to predict the feed requirement of grass carp and construct a precision feeding control (PC) system in outdoor pond culturing conditions. First, prediction of the growth parameter of grass carp using the calibrated TGC (the thermal-unit growth coefficient) model in different growth stanzas; then, prediction of energy and nutrition demands based on the model of the bioenergetics factorial; and then, determination of the feed requirement and feed rate daily according to the nutrient composition of feed and apparent digestibility coefficient (ADC) of grass carp; finally, determination of the proportion of each feeding time in per day using fuzzy logic control technology (FLC) based on dissolved oxygen (DO) and water temperature (WT). In addition, the performance of the PC system and traditional feeding control (TC) system was evaluated by the Nash-Sutcliffe efficiency coefficient (NS), the root mean squared error (RMSE), the water quality parameters, and fish growth parameters, respectively. The results indicated that the PC system was superior to that of the TC treatment for forecasting feed decisions, the NS was promoted 0.534 to 0.936 and the RMSE was reduced 22.512 to 10.973, respectively. Meanwhile, Compared the growth parameters of fish with TC treatment, it did not affect the growth performance of fish but promote it to a certain extent, and the feed conversion rate (FCR) of fish was decreased by 12.24% (P < .05). Moreover, the mean of ammonium concentration and turbidity of water in ponds decreased by 25.51% and 5.8 cm, respectively. Therefore, application of the hybrid method to develop feeding system can significantly improve economic and environment efficiency of aquaculture, and may can guide to develop the new feeding equipment or control systems in some outdoor culture systems of other freshwater fish species.

Growth performance and nutrient utilization of growth hormone transgenic female triploid Atlantic salmon (Salmo salar) reared at three temperatures in a land-based freshwater recirculating aquaculture system (RAS)

This study examined the effect of rearing temperature on growth performance and nutrient utilization of AquAdvantage Salmon (growth hormone transgenic female triploid Atlantic salmon) reared in a land-based freshwater recirculating aquaculture system (RAS) at three temperatures (10.5 °C, 13.5 °C, 16.5 °C) from first-feeding to 1500 g. All fish were fed the same commercial diets, which were analyzed for proximate, amino acid, fatty acid and mineral composition, and daily feed consumption was recorded for the calculation of feed conversion ratios (FCRs). Whole-body samples were collected at 300, 500, 800 and 1500 g for proximate composition, and fillet samples were collected at 500, 800 and 1500 g for amino acid, fatty acid, and mineral composition. Fillet yield, astaxanthin concentration and DSM SalmoFan™ colour were determined at 1500 g. Results indicated that fish reared at 16.5 °C required more feed per unit of biomass gain, and were less efficient at depositing important nutrients such as omega-3 fatty acids, compared to salmon reared at 10.5 °C and 13.5 °C. With higher viscerosomatic index (VSI) and condition factor (K) scores at 16.5 °C, these fish also diverted more dietary energy to lipid deposition in the viscera instead of muscle tissue compared to the lower temperature treatments. Fish reared at 16.5 °C had lighter fillet colouration compared to salmon reared at 13.5 °C, and exhibited lower fillet yields than the colder temperature groups. Fish reared at 16.5 °C reached the end target weight (1500 g) in 36 fewer days compared to 13.5 °C and 93 fewer days in contrast to 10.5 °C. However, thermal-unit growth coefficient (TGC) results indicated that growth rate was higher in fish reared at 10.5 °C compared to 16.5 °C for the majority of the trial. Collectively, these results suggest that it is preferable to rear AquAdvantage Salmon at either 10.5 °C or 13.5 °C in freshwater RAS. The information generated from this study is the first to provide insight into the relationships between rearing temperature and nutrient utilization in AquAdvantage Salmon for commercial application.

Growth trajectory analysis of Pacific whiteleg shrimp ( Litopenaeus vannamei ): Comparison of the specific growth rate, the thermal‐unit growth coefficient and its adaptations

Empirical growth models have widespread application in the field of aquaculture. These models allow estimates of harvest size and waste outputs in addition to nutrient and feed requirements. In an effort to increase the ability to predict shrimp growth, the specific growth rate (SGR) and thermal-unit growth coefficient (TGC) models were fitted to 15 datasets encompassing growth of Pacific whiteleg shrimp (Litopenaeus vannamei). Shrimp were reared under commercial conditions in Southeast Asia with weights ranging from 0.01 g to 34 g. Growth rates were regressed against body weights to identify changes in growth pattern across life stages. Analysis identified two distinct patterns of growth, with a break point between stanzas at 7.5 g. The body weight exponent of the TGC model, traditionally assumed to be (1 − b) = 1/3, was solved for iteratively in each identified growth stanza in an effort to improve the goodness of fit of the TGC model. Average body weight exponents in the first and second stanzas were 0.416 and 0.952 respectively. Projected growth trajectories using these exponents resulted in significantly better fits in comparison to the traditional TGC and the SGR on the basis of statistical measures of goodness of fit.

Dietary taurine supplementation to a plant protein source‐based diet improved the growth and intestinal immune function of young grass carp (Ctenopharyngodon idella)

The effects of taurine supplementation on the growth and intestinal immune function in young grass carp (Ctenopharyngodon idella) were investigated in this study. A total of 540 fish (initial average weights of 255.74 +/- 0.65 g) were fed one fish-meal diet and five all-plant protein source-based diets with graded levels of taurine (0 to 1.98g/kg diet) for 60 days, and then challenged with Aeromonas hydrophila for 14 days. First, the results showed that the taurine supplementation improved growth (PWG, TGC, FI and FE), enteritis resistance, intestinal antimicrobial compounds (LZ, ACP, C3, C4, IgM, hepcidin, LEAP-2A, LEAP-2B, beta-defensin-1 and MUC2) and attenuated intestinal inflammation in young grass carp under the all-plant protein sourcebased diet. Second, the taurine supplementation attenuated intestinal inflammation partially referring to nuclear factor kappa B (NF-kappa B) and target of rapamycin ( TOR) signallings. Finally, under the all-plant protein source-based diet, the comparable level of taurine supplementation based on growth and ability against enteritis relative to fishmeal diet was established as 0.50 g/kg diet, and the optimal levels of taurine supplementation based on thermal-unit growth coefficient (TGC), ability against enteritis and acid phosphatase (ACP) activity were established as 0.97, 1.08 and 1.21 g/kg diet, respectively.

Effect of the probiotic, Lactobacillus plantarum on growth performance and haematological indices of rainbow trout (Oncorhynchus mykiss) immunized with bivalent streptococcosis / lactococcosis vaccine

The present study evaluated the effect of Lactobacillus plantarum as a probiotic on the growth performance and haematological parameters of juvenile rainbow trout (O. mykiss) weighing 29.6±1.8 g immunized with streptococcus/lactococcus vaccine. Fish were randomly allocated into 4 equal groups consisting of fish fed with the probiotic supplemented in diet (group P), fish immunized with streptococcosis / lactococcosis vaccine and fed with a normal diet (group V), fish immunized with streptococcosis / lactococcosis vaccine and fed with probiotic supplemented in diet (group P+V) and unimmunized fish fed (group C). The probiotic (108cells/g) was used at 1 g ∕ kg feed. Results showed that weight gain, final weight, condition factor and thermal-unit growth coefficient were improved in P+V group compared to the control one (P 0.05) was found in MCH, MCHC and MCV levels among the different experimental groups. Hence, application of probiotic can be considered as a beneficial dietary probiotic for improvement of growth performance and some haematological parameters in trout vaccinated against streptococcosis / lactococcosis.

Dietary supplementation with low molecular weight sodium alginate improves growth, haematology, immune reactions and resistance againstAeromonas hydrophilainClarias gariepinus

A few studies have illustrated the effects of sodium salt derived from alginic acid on different fish species. However, little is known about the effect of sodium alginate on catfish (Clarias gariepinus). Therefore, this study was performed to assess the use of low molecular weight sodium alginate (LMWSA) in C. gariepinus. A total of 180 apparently healthy C. gariepinus with a mean body weight of 45 g were randomly divided into three equal groups (D1, D2 and D3). D1 the control group received a control diet, while D2 and D3 received 1% and 3% LMWSA, respectively, for 8 weeks. A challenge test against Aeromonas hydrophila was performed on 15 randomly selected catfish for 15 days. At the end of the experiment, catfish in D3 that received a diet of 3% LMWSA showed significant increases in the final body weight, weight gain and thermal-unit growth coefficient compared with those in D2 and D1. There was a significant decrease in the erythrogram in D1 after the 4-day pathogen challenge. A leucogram revealed leucocytosis, heterophilia and lymphocytosis in catfish in D2 and D3 compared with those in D1. After the 4-day challenge, the following changes took place: lysozyme, nitric oxide, phagocytic activity and the respiratory burst were significantly elevated in catfish that received LMWSA and were more pronounced in D3 than in D1. The mortalities of catfish have been stopped after pathogen challenge from 8-day in D1 and D2 where at 6-day in D3. Thus, administration of 1% and 3% LMWSA enhances the growth, immune response and resistance of C. gariepinus against A. hydrophila.

The effects of naturally occurring or purified deoxynivalenol (DON) on growth performance, nutrient utilization and histopathology of rainbow trout (Oncorhynchus mykiss)

It has been previously established that rainbow trout are extremely sensitive to the ubiquitous Fusarium mycotoxin deoxynivalenol (DON); however, the contribution of co-occurring mycotoxins and/or their potential interactions with DON have not been discounted. Concurrently, there have been few systematic efforts to characterize the pathological basis of the sensitivity of rainbow trout to DON. This study was conducted to investigate these outstanding issues. Triplicate groups of rainbow trout (initial average body weight = 50.3 g/fish) were fed eight diets containing graded levels of purified DON (0, 0.7, 1.4 and 2.1 ppm) or DON from naturally contaminated corn (0, 2.1, 4.1 and 5.9 ppm) for eight weeks. Fish experienced significant linear decreases in weight gain (P < .0001), thermal-unit growth coefficient (TGC; P < .0001) and feed intake (P < .0001) regardless of the source of DON. Similarly, significant linear and/or quadratic decreases (P < .01) in feed efficiency (FE), whole body crude protein (CP) content, retained nitrogen (RN), recovered energy (RE) and nitrogen retention efficiency (NRE) were observed in fish fed the diets containing either purified or naturally occurring DON. There were no significant differences (P > .025) in the above mentioned parameters between fish fed the diets contaminated with the same level of purified or naturally occurring DON (2.1 ppm). In general, bi-weekly sampling (6 fish/treatment/sampling) revealed significant linear or quadratic increases in dead (apoptotic/necrotic) cells in the pyloric caeca and significant linear or quadratic decreases in mitotic cells in the pyloric caeca and liver with increasing dietary levels of purified DON or DON from naturally contaminated corn without any distinct histopathological abnormalities (i.e. lesions). These cellular changes are in agreement with the known ability of DON to activate mitogen-activated protein kinases (MAPKs) indicating that the mechanism of action of DON in rainbow trout is consistent with that described in other species. Comparison of the response of fish fed the diet containing 2.1 ppm purified DON and 2.1 ppm DON from naturally contaminated corn suggested that decreased growth performance and nutrient utilization efficiency of rainbow trout exposed to grains naturally contaminated with Fusarium mycotoxins was most probably associated mainly with DON; however, continued research involving multiple levels of purified and naturally occurring DON is necessary to verify this finding.

A comparative investigation of the effects of feed-borne deoxynivalenol (DON) on growth performance, nutrient utilization and metabolism of detoxification in rainbow trout (Oncorhynchus mykiss) and Nile tilapia (Oreochromis niloticus) fed diets containing different levels of digestible carbohydrates

Increasing evidence suggests that variability in hepatic glucuronidation is a critical determinant of mammalian species-specific sensitivity to the Fusarium mycotoxin deoxynivalenol (DON). Concurrently, ongoing work regarding the effects of DON on fish has led to broad classifications concerning species-specific sensitivity (e.g. rainbow trout are highly sensitive to DON and channel catfish are highly tolerant to DON). This study was designed to determine if sensitivity to DON in fish is related to inherent differences in UDP-glucuronosyltransferase (UDPGT) activity and to evaluate if increased dietary digestible starch content could be an effective strategy to increase glucuronidation capacity. Rainbow trout or Nile tilapia (initial average body weight = 21.9 and 8.1 g/fish, respectively) were fed two series (12 or 24% digestible starch) of three diets containing graded levels of naturally occurring DON (0.1, 0.7 and 1.3 ppm) for 10 weeks. Significant linear decreases in weight gain, thermal-unit growth coefficient (TGC, P ≤ .05), feed efficiency (P < .001), whole body crude protein (CP) content (P < .001), retained nitrogen (RN, P ≤ .05) and nitrogen retention efficiency (NRE, P < .01) were associated with increasing levels of DON in rainbow trout regardless of the dietary digestible starch content. There were no significant effects of DON on any of these parameters in Nile tilapia (P > .05) with the exception of a quadratic increase in NRE (P < .01) in fish fed the diets containing 24% digestible starch. The effect of DON on growth performance and nutrient utilization was not altered by the digestible starch content of the diet (P > .05, DON × digestible starch). A significant quadratic decrease (P ≤ .05) in UDPGT activity was associated with increasing levels of DON in rainbow trout fed the diet containing 12% digestible starch, whereas trout and tilapia fed the diet containing 24% digestible starch experienced significant quadratic or linear increases (P ≤ .05) in UDPGT activity, respectively. However, UDPGT activity was approximately 10-fold higher in rainbow trout than in Nile tilapia. This suggests that UDPGT activity is not responsible for the observed species-specific sensitivity to DON or it is not an appropriate biomarker of DON glucuronidation. A significantly higher relative fold expression of CYP1A in tilapia compared to trout (P = .0001) may offer potential opportunity for future study. We demonstrate for the first time that Nile tilapia are unaffected by practically relevant levels of DON which are detrimental to rainbow trout. This study also extends the current knowledge of DON metabolism and represents an important contribution to the development of efficacious nutritional mycotoxin mitigation strategies.