Impact of high dietary cornstarch level on growth, antioxidant response, and immune status in GIFT tilapia Oreochromis niloticus

This study was conducted to investigate the relationship between different cornstarch levels in tilapia diet and immune function. All test fish were fed with three cornstarch levels: low-cornstarch (0, LS), medium-cornstarch (18%, MS) and high-cornstarch (36%, HS) diets. Three hundred and sixty fish (initial mean body weight 31.73 ± 1.36 g) were randomly allocated into twelve water-circulated tanks, and thirty fish per tank. Compared with the low and medium cornstarch diets, the results of growth showed that the high cornstarch diet significantly decreased the FBW, WGR, and SGR, and increased the FCR of tilapia (P < 0.05). The high cornstarch diet significantly decreased the content of crude protein and increased the content of crude lipid in whole body composition (P < 0.05). Moreover, the VSI and CF in HS diet were significantly higher than those of LS diet (P < 0.05). The results of blood biochemical index exhibited that the HS diet significantly increased the content of blood glucose, and liver/muscle glycogen (P < 0.05). The results of antioxidant experiments demonstrated that the content of SOD and T-AOC in MS diet were significantly higher than those of HS diet (P < 0.05). Meanwhile, the content of MDA in MS diet was significantly lower than that of HS diet (P < 0.05). The results of immune index test showed that the lysozyme activities in the serum, liver, and gill, and the phagocytic activity and index in MS diet were significantly higher than those of HS diet (P < 0.05). The challenge assay results revealed that the mortality rate of HS diet was higher than those of LS and MS diets, but the difference was not significant (P > 0.05). In conclusion, the overall results suggested that the 36% cornstarch diet reduced not only the growth performance, but also body immunity. Under this experimental condition, GIFT tilapia could tolerate 18% cornstarch, but not 36% cornstarch.

Digestibility of Local Feed Ingredients in Tilapia Oreochromis niloticus Juveniles, Determined on Faeces Collected by Siphoning or Stripping

Eight locally available protein source ingredients in Tanzania were selected for assessment of apparent digestibility (AD) in tilapia Oreochromis niloticus, using faeces samples collected by siphoning or stripping. The selected protein source ingredients were Lake Victoria sardines (FM), brewers spent yeast (BSY), moringa leaves (ML), freshwater shrimp (FSH), marine shrimp (MSH), cattle blood (CB), duckweed (DW) and fish frames (FF). The AD (%) of dry matter (DM), organic matter (OM) and crude protein (CP) was unaffected (p > 0.782–0.901) by the faeces collection method (i.e., siphoning or stripping), with correlation coefficient (r) of 0.98, 0.99 and 0.93 between AD values for DM, OM and CP, respectively, following siphoning and stripping. The AD (%) of DM, OM, CP and gross energy (GE) in the test ingredients differed (p < 0.0001). The AD (%) of DM and OM was lowest in BSY and DW, followed in increasing order by ML, MSH, FF, FSH and CB. In general, the AD (%) of CP was high (>76%), but with a low value (46%) for DW. The AD (%) of GE was closely correlated (r = 0.96) with the AD of OM. In conclusion, FSH, MSH, CB, FF, BSY and ML have acceptable protein digestibility to be used in tilapia diet formulation.

Digestibility and gastrointestinal transit of Ulva fasciata seaweed meal in tilapia (Oreochromis niloticus) juveniles: basis for the inclusion of a sustainable ingredient in aquafeeds

The seaweed Ulva fasciata has many features favorable to integrated multi-trophic aquaculture (IMTA). It is efficient at biofiltering, shows high biomass production, and is rich in many nutrients useful in aquatic animal diets. We evaluated the digestibility of the seaweed meal of U. fasciata produced in IMTA and its effects on gastrointestinal transit time in tilapia (Oreochromis niloticus) juveniles. Juveniles (6.30 ± 1.80 g initial weight, and 5.5 ± 0.61 cm initial length) were cultivated in six tanks (50 individuals per tank) in a closed recirculating aquaculture system. The digestibility of Ulva meal was 57.92 ± 5.21% for dry material, 78.59 ± 1.91% for protein, and 69.87 ± 3.72% for energy. The inclusion of 10% seaweed meal did not alter the gastrointestinal transit time in tilapia juveniles as compared to controls. The earliest colored feces were observed four hours after first feeding in both treatments (feed diets with [10%] and without seaweed); all fecal material was colored after ten hours. The digestibility of seaweed meal was satisfactory for dry material, protein, and gross energy, and the inclusion of 10% of that meal did not change gastrointestinal transit time - indicating that the inclusion of 10% seaweed meal in tilapia diet is safe and without any nutritional use losses.

Growth evaluation of Oreochromis niloticus fed different concentrations of choline and methionine

A 12-week research was conducted to determine the effects of choline and methionine supplementation on the growth performance of Nile tilapia (Oreochromis niloticus). Three diets, P2-P4 with 0.04; 0.08; 0.12 % of choline; P6-P8 with same levels choline plus methionine (0.15 %); a diet with only 0.15 % methionine (P5); and control without any supplementation (P1) were fed to tilapia (initial weight ±21.05 g) for 12 weeks. Final weight (FW), Body Weight Gain (BWG), Average Daily Gain (ADG), Specific Growth Rate (SGR), and Protein Efficiency Ratio (PER), Feed Efficiency (FE), Feed Intake (FI), Feed Conversion Rate (FCR), Survival Rate (SR), crude protein and lipid of fish fed various levels of choline and methionine were also measured. The results showed that tilapia fed 0.04 % choline (P2) had significantly better growth parameters and feed efficiency than other groups. Meanwhile, SR of tilapia was not affected by any supplementation of choline and methionine. The tilapia fed 0.08% choline (P3) showed the highest crude protein (52.50 ± 0.98 %) in the carcass proximate but low lipid (19.03 ± 0.10 %). This finding demonstrated the benefits of choline (0.04-0.08 %) supplementation in the tilapia diet in term of growth and carcass proximate.

Comparative evaluation of Hermetia illucens larvae reared on different substrates for red tilapia diet: effect on growth and body composition

Black soldier fly larvae (BSFL; Hermetia illucens) can be a very beneficial source of protein to replace fishmeal for fish feed, but little is known about the impact of their growing substrate on the performance and nutritional composition of the fish consuming them. In this study, BSFL were reared on two different substrates; palm oil decanter cake (DC) and coconut pulp (CP) for 35 days before processing and including them in tilapia diet with 50% inclusion level. The weight and length of the BSFL as well as waste reduction efficiency was observed. The fish were assigned to three different diets, namely DC50 (50% BSFL from DC), CP50 (50% BSFL from CP) while 100FM (100% fishmeal) is treated as a control. The fish performance, feed efficiency and nutritional composition of their body after 4-weeks of feeding trial were observed. The results indicate that BSFL cultured in DC obtained higher body weight gain but less efficient in reducing waste compared to those cultured in CP. The utilisation of 50% inclusion level of BSFL cultured in DC for tilapia diet improves growth and feed efficiency. However, the inclusion of all experimental diets has a less pronounced effect on protein and ash body composition; although fish fed with CP50 has the least lipid body composition compared to other treatments. The experiment demonstrated that replacement of fishmeal by BSFL cultured in different substrates would influence the performance of fish consuming it. Results of the present study will offer an optimal solution, especially for large-scale commercial BSFL cultivation.