Significance of extrinsic factors for the optimization of dietary cobalt supplementation in Tor putitora fingerlings.

Extrinsic factors play a significant role during aquaculture feed manufacturing practices. Herein, a 90-day feeding trial was designed in triplicate under controlled environmental conditions to evaluate the efficiency of different chemical forms of dietary cobalt at different dosage levels on growth performance, hematological, and immunological indices of Tor putitora fingerlings. Firstly, cobalt chloride nanoparticles (Co-NPs) and cobalt methionine chelated complex (Co-Met) were synthesized via physical and chemical methods respectively and then characterized for their size, surface morphology, and elemental composition analysis by using X-rays diffraction spectroscopy (XRD), scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS). Results indicated the crystalline nature of Co-NPs with spherical shape having an average size < 20 nm while Co-Met appeared as an amorphous complex with a honey-comb-like octahedral structure with an average size of 82.69 nm. Afterward, a feeding experiment was executed and fish were divided into three groups, i.e., control group (CG; fed 40% crude protein diet with no mineral added), while the other two groups were fed graded levels (0.5-3 mg/kg; increment of 0.5 mg Co/group) of Co-NPs and Co-Met supplemented diets. Statistical analysis of results by using two-way ANOVA indicated significant (P < 0.001) effect of both chemical forms, dosage levels, and their interaction level on fish indicating a dose-dependent significant effect of different chemical forms of dietary cobalt on fish. Additionally, Co-Met supplemented group of fish at supplementation level of 3 mg/kg diet showed highest growth performance, and improved hemato-immunological as compared to other experimental and control group of fish.

Dietary cobalt supplementation improves growth and body composition and induces the expression of growth and stress response genes in Tor putitora.

A 90-day randomized feeding experiment was performed to assess the effects of dietary cobalt (Co) supplementation on the growth performance, muscle composition, status of iron and manganese in the muscle as well as the expression of growth-related genes in the muscle (myoblast determination protein 1 homolog (MyoD) and myogenin) and the stress-related gene heat shock protein 70 KDa (Hsp-70) in the liver of mahseer (Tor putitora). Feeding trial was conducted in triplicate under controlled semi-static conditions, and graded levels of dietary cobalt (0.5-3 mg/kg) were fed to six groups of advanced fry of T. putitora. The results obtained indicated a curvilinear relationship of dietary Co levels with body crude protein content and weight gain (%). A positive correlation was observed with up to 2 mg Co/kg diet. However, a decreasing trend was found with values over 2 mg Co/kg diet. The expression of muscle growth biomarkers MyoD and myogenin showed a similar response, upregulation up to 2 mg Co/kg diet and decreased expression at 3 mg Co/kg diet. Indeed, the highest dietary Co supplementation increased the expression of Hsp-70, a key gene expressed in response to stress. Moreover, the muscle content of iron and manganese showed an inverse relationship with the dietary Co supplementation. Our findings suggest that 2 mg/kg Co dietary supplementation stimulates myogenesis and optimize muscle growth and body composition, while higher levels enhanced the expression of stress response genes and impaired growth of T. putitora.

Dietary administration of the commercially available probiotics enhanced the survival, growth, and innate immune responses in Mori (Cirrhinus mrigala) in a natural earthen polyculture system.

The use of probiotics is considered effective for survival, growth and enhanced immune response in aquaculture. In the current study, effects of commercially available probiotic (Magic Plus) was investigated on survival, growth and immune response of Mori (Cirrhinus mrigala) in a polyculture system. The experiment was conducted for 90 days on 1200 fingerlings in two groups i.e. control and probiotic supplemented groups each having 600 fingerlings. Control group was fed with 35% protein basal diet without any supplements and the other group was supplemented with commercially available probiotic at the rate of (1012 CFU kg-1 diet). After 90 days, probiotic supplemented group was characterized with significant increase (p < 0.05) in growth parameters like, total weight, total length, %weight gain, specific growth rate and survival growth rate. Immunological indices like, lysozyme activity, white blood cells, total plasma protein level and immunoglobulin (IgM) of supplemented group were also significantly (p < 0.05) enhanced. Moreover, digestive enzymes i.e. cellulase, protease and amylase were also found to be significantly (p < 0.05) hyper-active in probiotic supplemented groups. Haematological parameters like, RBCs, Hb, Hct, MCH and MCHC were also significantly (p < 0.05) increased. Thus, the current study strongly suggests that a commercially available probiotic Magic plus may serve as a healthy and immunostimulating feed additive in C. mrigala culture.