Effects of feeding rates on growth and production of Nile tilapia, common carp and silver carp polycultured in fertilized ponds

Abstract In an attempt to identify appropriate feeding rates for multispecies of fish raised in fertilized earthen ponds, the present work was conducted over a 19‐week experimental period to establish the growth performance, production and body composition of Nile tilapia, common carp and silver carp fed 0.0%, 0.5%, 1.0%, 3.0%, 5.0% biomass and to apparent satiation (treatments). Twelve ponds were stocked with a similar number and weight of each fish species. Two ponds were assigned to each of the treatments, and a 25% protein pelleted fish feed was used to feed fish at the specified rate of feeding. At the end of the experiment, growth, weight gain, survival, yield and body composition of fish groups were affected by the treatments. The economic effectiveness also varied among treatments. The most conspicuous attribute of the feeding rates was its lack of influence on growth (g day^?1), weight gain (g per fish), yield (kg ha^?1) or body composition of silver carp. The results of whole‐body proximate analysis indicated that various feeding rates had either an irregular pattern or no effects on the protein and ash gain per 100 g of fish body weight (bw) gain. The most notable exceptions were significant (P < 0.05) increases in body fat and gross energy gains in Nile tilapia, common carp and silver carp accompanied by decreases in percentages of moisture (but not in silver carp) as feeding rate increased. Among the six different feeding levels, feeding to apparent satiation (feed amount was equivalent to 2.67% of fish bw day^?1) appeared to be optimal, as it significantly (P < 0.05) supported the highest fish production, income and net profit compared with all other treatments except for the 3% feeding level, for which the differences in those measurements were comparable.     

Partial and complete replacement of fish meal with gambusia meal in diets for red tilapia 'Oreochromis niloticus × O. mossambicus'

A 12‐week experiment was conducted to evaluate the suitability of gambusia (Gambusia affinis) fish meal (GFM) as a partial and complete substitute for the protein supplied by herring fish meal (HFM) in diets for red tilapia fingerlings (mean weight 0.42 g). Seven isonitrogenous (35% crude protein), isolipidic (9% fat) and isoenergetic (15.9 kJ DE‐g^?1 diets were formulated in which GFM replaced 0.0, 10, 25, 50, 75, 90 and 100% of the protein supplied by HFM. In general, GFM exhibited good potential as a substitute for HFM in red tilapia diets with no adverse effects on growth, feed efficiency, body composition, blood parameters or apparent digestibility of dry matter, protein and gross energy compared with the HFM‐based control diet. Growth performance (in terms of final weight, weight gain, per cent increase in weight and growth rate) of fish fed diets containing GFM at 25 or 50% level of replacement for HFM‐protein (diets 3 and 4) was statistically higher than for fish fed diets containing GFM at replacement levels >50%. Diet 4 had the best economic efficiency of fish weight gain. Partial or complete substitution of GFM for HFM did not affect feed utilization efficiency (in terms of FCR, FER, PER and APU) or digestibility coefficients of dry matter, protein and gross energy compared with those of the HFM‐based diet. Apparent protein digestibility varied little between diets, ranging from 84.2 to 87.3% with no significant differences. Survival of fish fed all the experimental diets (except for fish fed GFM at 90 or 100% level of replacement for HFM‐protein) was comparable with that of fish fed the control diet and ranged from 91.7 to 98.3%.     

Appropriate Timing of Supplemental Feeding for Production of Nile Tilapia, Silver Carp, and Common Carp in Fertilized Polyculture Ponds

In an attempt to identify appropriate times for initial application of supplemental feed in polyculture fertilized fish production earthen ponds, a study was conducted for 19 wk to establish the growth performance, yield, survival, and body composition of Nile tilapia, common carp, and silver carp as influenced by four different feeding regimens (treatments). The four treatments were: 1) supplemental feeding beginning at onset of the experiment (T-I) (control treatment); 2) 6-wk delay of feeding after fish stocking (T-II); 3) 13-wk delay of feeding after fish stocking (T-III), and 4) no supplemental feed application (T-IV). Two ponds were assigned to each treatment and each pond was stocked with a similar number and weight of each fish species. A commercial pelleted fish feed (25% protein) was used to feed fish in T-I, T-II, and T-III at 3% of their body weight, twice a day. At the end of the experiment, fish species (except for silver carp) in T-II showed weight gain, growth rates, and yields significantly higher than fish in T-III or T-IV. Also, the total fish production and net profit in T-II were significantly higher than in T-III or T-IV. Fish species in T-II showed weight gain, growth rates, survival rates, and yields similar to those of T-I (control treatment) with no significant differences. The amount of feed consumed by fish in T-II was reduced by approximately 7.3% compared to that consumed by fish at T-I. Moreover, there was increase in th net profit in T-II by 4.8% over that achieved in T-I. Therefore, T-II appears to be the most appropriate among the tested feeding treatments and recommended for use in order to achieve the best growth, production, and net profit.     

Antioxidant capacity and phenolic content of <Emphasis Type="Italic">Rumex dentatus</Emphasis> L. Grown in Egypt

Rumex dentatus L. (Family: Polygonaceae) is a weedy plant widely distributed in many countries including Egypt. It has been used in the Mediterranean diet as a leafy vegetable and its leaves and roots exhibited various biological activities. In our study, total phenolics, antioxidant capacities assayed by 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical scavenging and β-carotene bleaching methods and reducing power were evaluated in different extracts/fractions of leaves and roots of R. dentatus grown in Egypt. In addition, their phenolic compositions were determined by GC-MS and HPLC. The results showed that total phenolic content in the ethyl acetate fractions of leaves and roots were high and measured at 169.5 and 257.4 mg gallic acid equivalent per g extract, respectively. The ethyl acetate fractions of leaves and roots exhibited strong DPPH activity and the DPPH IC₅₀ values were 0.021 and 0.012 mg mL⁻¹ of leaves and roots, respectively. Furthermore, the ethyl acetate fractions of leaves and roots showed high reducing power and antioxidant activity assayed by β-carotene bleaching method. GC-MS and HPLC analyses indicated that these fractions contained a variety of phenolic compounds including p-hydroxybenzoic acid, syringic acid, vanillin, benzoic acid, ferulic acid, and cinnamic acid. Our study verified that the ethyl acetate fractions of leaves and roots of R. dentatus have strong antioxidant activities which are correlated with its high levels of phenolic compounds and therefore, they could be utilized as a natural source of antioxidant in food industry.     

Growth Response of Nile Tilapia Oreochromis niloticus to Dietary L-Ascorbic Acid, L-Ascorbyl-2-Sulfate, and L-Ascorbyl-2-Polyphosphate

Abstract.— Purified diets were formulated and fed to seven groups of Nile tilapia Oreochromis niloricus fingerlings for 12 weeks. Six of the formulated diets contained 5 or 50 mg/kg of ascorbic acid equivalent supplied either by L-ascorbic acid (AA), L-ascorbyl-2-sulfate (AS) or L-ascorbyl-2-polyphosphate (APP). The seventh basal diet was ascorbate-free and served as the control. The study indicated that APP or AS was more effectively utilized as a source of vitamin C than equimolar AA in promoting growth, improving food conversion, and preventing scurvy in Nile tilapia. Fish fed the ascorbate-free diet and the diet containing 5 mg AA/kg exhibited external signs of scurvy at 10 weeks. Diets containing 5 mg/kg of ascorbic acid from AS or APP provided some growth with no overt signs of scurvy indicating that this concentration of AS and APP might be near the minimum requirements for the species. The best growth, food conversion ratio, survival rate, and ascorbic acid content in liver were obtained with the diet containing 50 mg ascorbate equivalent/kg diet from APP followed by the diet containing 50 mg ascorbate equivalent/kg diet from AS. Fish fed diets with 50 mg ascorbic acidkg diet from AS and APP gained 27.9% and 36.2% more weight, respectively, than fish fed diets with 50 mg ascorbic acidkg diet from AA. These results indicated nearly equal ascorbic acid activity from AS and APP.     

Effect of Milk Proteins on Physical and Chemical Characteristics of Crispy Puff Snacks

Dairy proteins included sweet whey solids （SWS）, whey protein concentrate （WPC）, milk protein concentrate （MPC） or sodium caseinate （SC） at level of 10% by weight were extruded with corn, rice, oat flour and other ingredients in a twin screw extruder. The functional properties and textural of crispy balls snacks （CBS） have been studied. The results showed that different protein types were significantly affected on functional and chemical properties of extrudate. The bulk density of CBS-SC was the lowest due to the highest expansion, while CBS-WPC retained the most water in the product, whereas, the maximum value of water solubility index was obtained in the CBS-CWP. Results also showed that protein digestibility value of extrudates had higher than non-extruded products. Color analysis of CBS-SC and CBS-SWS products had the highest AE values （P ≤ 0.05）, whereas CBS-SWS was statistically higher than CBS-SC in rank. Also, it was noticed that CBS-SWS had the highest value of browning index. The hardness of all extrudates products was desirable for expanded crispy where ranged from 17.3 N to 12.18 N. Generally, MPC and SC incorporated with cereal flour had acceptable quality characteristics and improved significantly the functional and texture properties of crispy balls products.     

Feed efficiency, nutrient retention and body composition of Nile tilapia, Oreochromis niloticus L., fed diets containing L-ascorbic acid, L-ascorbyl-2-sulphate or L-ascorbyl-2-polyphosphate

Seven purified diets were formulated and fed to seven groups of Nile tilapia, Oreochromis niloticus L., fingerlings for 12 weeks. Six of the formulated diets contained 5 or 50 mg kg^?1 of ascorbic acid equivalent supplied by either L-ascorbic acid (AA), L-ascorbyl-2-sulphate (AS) or L-ascorbyl-2-polyphosphate (APP). The seventh basal diet was ascorbate-free and served as the control. The results of diet analysis for ascorbic acid showed that it was not detected or negligible in the control diet and in the diets containing AA at the end of the experiment, whereas there was no loss of ascorbic acid from diets prepared with AS or APP. The results demonstrated that the feed efficiency and growth parameters in fish fed APP-5, AS-5, AA-5 or AA-50 diets were statistically similar to the same parameters in fish fed the control diet. The study indicated that diets supplemented with 5 or 50 mg kg^?1 ascorbic acid in the form of APP or AS were more effectively utilized as sources of vitamin C than equimolar AA in promoting growth, improving food efficiency, increasing nutrient retention and preventing scurvy in Nile tilapia. Fish fed the ascorbate-free diet and the diet containing 5 mg AA kg^?1 exhibited external signs of scurvy during the last growth period of the experiment. Diets containing 5 mg kg^?1 of ascorbic acid from AS or APP provided some growth with no overt signs of scurvy, indicating that this concentration of AS and APP might be near the minimum requirement for the species. The APP-50 diet was the most efficient, and significantly (P < 0.05), had the lowest value of the amount of dietary protein necessary for 100 g weight gain (dietary protein index, DPI), the highest values of feed conversion efficiency (FCE) and the highest values of nutrient retention, i.e. protein (PRV), fat (FRV), ash (ARV) and gross energy (ERV) compared to the other diets. Fish that received the APP-50 diet had a significantly (P < 0.05) higher weight and protein gains in tissues than the other fish groups. The increase in the feed efficiency and growth parameter values in fish receiving the APP-50 diet compared with the values for the same parameters in the AA-50 diet were calculated as percentages, and the results were: weight gain, 36.2%; protein gain, 40.9%; FCE, 53.3%; PRV, 58.1%; FRV, 34.9%; ARV, 57.4%; and ERV, 51.9%. The diet containing APP-50 was followed in order by the AS-50 diet. The AS-50 diet had statistically comparable (P > 0.05) values of weight gain, protein gain and FRV to the APP-50 diet. The increased feed efficiency and growth parameters values of fish receiving the AS-50 diet compared with the AA-50 diet were calculated as percentages, and the results were: weight gain, 2 7.9%; protein gain, 27.9%; FCE, 18.2%; PRV, 17.9%; FRV, 19.2%; ARV, 8.9%; and ERV, 18.2%. There were no significant (P > 0.05) differences between the groups in the percentages of moisture, protein and ash in whole fish at the end of the study, whereas lipid percentages were significantly (P < 0.05) lower in all the tested groups in comparison with the control fish. Increasing the level of ascorbic acid equivalent from 5 to 50 mg kg^?1 diet from APP, AS or AA reduced the percentage of fat in Nile tilapia bodies. These results indicate that all the tested vitamin C sources were effective in inducing lipolysis in Nile tilapia tissues.