Enhancement of Monosex Hybrid Red Tilapia,Oreochromis mossambicus × O. niloticusProduction in Portable Canvas Tanks Through Mixed-Feeding Strategies

Abstract

The viability of mixed-feeding schedules utilizing low-and high-protein diets for the production of monosex hybrid red tilapia, Oreochromis mossambicus × O. niloticuswas evaluated. Male red tilapia juveniles (mean initial weight 16.8±0.08 g) stocked at a rate of 159 fish/m³ in canvas tanks (3.05m × 0.92m × 1.22m) were grown under five different feeding schedules for 24 weeks. Two schedules, using low (25%, A) and high (35%, B) dietary protein were designated as control. Three mixed-feeding schedules tested were: the feeding of 1 day of low protein diet followed by 3 days of high-protein diet (1A/3B); 2 days of low-protein diet followed by 3 days of high-protein diet (2A/3B); and 3 days of low-protein diet followed by 3 days of high-protein diet (3A/ 3B). Results showed that growth performance parameters, such as specific growth rate (% SGR), percent gain, and weight gain were significantly higher (P < 0.05) for fish maintained on the feeding schedule of 3A/3B. Similarly, the feed conversion ratio, protein efficiency ratio, and protein retention values were also significantly better for fish grown under this schedule. In terms of production, the 3A/3B feeding schedule also resulted in the highest total yield (kg/m³) and yield above 250 g. The 3A/3B feeding schedule resulted in a 10.1% protein saving relative to Diet B. These results suggest that a 3A/3B feeding schedule be adopted for the best biological and economical performance of red tilapia.     

Replacement of Marine Feedstuffs with Stabilized Poultry Protein Meal and Fat in Practical Diets for Sunshine Bass,Morone chrysops × M. saxatilis

We evaluated production performance and fillet composition of sunshine bass fed increasing levels of stabilized poultry protein meal (PM) and poultry fat (PO) to replace menhaden fish meal (FM) and/or oil (FO) in diets. The control diet included 200 g/kg (dry matter basis) FM and 98 g/kg FO. In eight treatment diets, 50% or 100% of the FM and/or FO were replaced with PM and PO. Each diet was fed to four replicate tanks of juvenile sunshine bass for 10 wks. Survival, food conversion ratio, and liposomatic index were unaffected by dietary treatment, although consumption, growth, and HSI were reduced with complete FM replacement. Fillet lipid content and athero- and thrombogenicity indices differed with lipid source; substitution of FO with PO resulted in marked increases in dietary and fillet monoenes and n-6 fatty acids. Consistent with this, dietary and fillet n-3 and highly unsaturated fatty acids were reduced in fish fed more PO. FM replacement similarly affected fillet fatty acid profile, though to a lesser degree. Our data suggests little to no interaction between FM, FO, and their alternatives in diets for sunshine bass, except with respect to the effect of FO and residual lipids in FM on tissue fatty acid composition.     

Sacha inchi meal as a fish-meal replacer in red hybrid tilapia (Oreochromis niloticus × O. mossambicus) feeds: effects on dietary digestibility,growth metrics,hematology, and liver and intestinal histology

Aquaculture International - The utilization of sustainable and innovative raw materials to substitute for traditional fishmeal (FM) ingredients is required for the aquaculture sector. Sacha inchi...     

The effects of gonadal development and sex steroids on growth hormone secretion in the male tilapia hybrid (Oreochromis niloticus × O. aureus)

Profiles of plasma growth hormone (GH) in male tilapia hybrid (Oreochromis niloticus x O. aureus) were measured and compared at different times of the year. The profiles did not appear to be repetitive, however, differences in their nature were observed at the different seasons; the most erratic profiles were seen in the height of the reproductive season (July), while the peaks were more subdued in the spring and disappeared in the autumn. Peaks in male fish were more prominent than in the females when measured in July. Perifused pituitary fragments from fish with a high GSI responded to salmon gonadotropin-releasing hormone (sGnRH) analog (10 nM-1 M), while those from fish with a low GSI barely responded to even the highest dose. Exposure of perifused pituitary fragments from sexually-regressed fish to carp growth hormone-releasing hormone (cGHRH; 0.1 M) or sGnRH (I M) stimulated GH release only after injection of the fish with methyl testosterone (MT; 3 injections of 0.4 mg kg ¹). The same MT pretreatment did not alter the response to dopamine (DA; 1 or 10 M). GH pituitary content in MT-treated fish was lower than in control fish, which may be explained by the higher circulating GH levels in these fish, but does not account for the increased response to the releasing hormones. Castration abolished the response of cultured pituitary cells to sGnRH (I fM-100 nM) without altering either their basal rate of secretion or circulating GH levels. Addition of steroids to the culture medium (MT or estradiol at 10 nM for 2 days) enabled a GH response to sGnRH stimulation in cells from sexually regressed fish. Pituitary cells which had not been exposed to steroids failed to respond to sGnRH, although their response to forskolin or TPA was similar to that of steroid-exposed cells. It would appear, therefore, that at least one of the effects of the sex steroids on the response to GnRH is exerted proximally to the formation of cAMP, or PKC, presumably at the level of the receptor. An increase in the number of receptors to the GH-releasing hormones, following steroid exposure, would explain also the changing nature of the GH secretory profile in different stages of the reproductive season.