K.F. Shim

Interactions of varying dietary protein and lipid levels in young red tilapia: Evidence of protein sparing

A 12-week feeding trial was carried out with young red tilapia, a hybrid of Oreochromis mossambicus and O. niloticus, with a mean weight of 1.185 g. Three series of isocaloric, experimental diets of 15%, 20% and 30% protein content (by dry weight) and for each series, four diets of 6%, 12%, 18% and 24% lipid content were tested. At all three protein levels the best growth was obtained with diets of 18% lipid. Daily consumption (in mg/g fish day−1) was correlated negatively to the digestible energy content of the diets, and overall rate of growth positively to the mean daily protein consumption (per g fish per day). The food conversion ratio ranged from 1.10 (P30L24) to 2.32 (P15L12), the protein efficiency ratio from 2.18 (P30L6) to 3.56 (P20L18) and apparent net protein utilization from 19.9% (P15L6) to 42.95% (P30L18), where P and L refer to dietary protein and lipid, and the subscripts to the approximate percentage. The carcass lipid and protein reflected the dietary regimes. The study indicates the protein-sparing capabilities of young red tilapia. The protein-sparing capability increased with increasing dietary lipid content up to 18% and decreased thereafter.

The influence of replacing fish meal partially in the diet with soybean meal on growth and body composition of juvenile tin foil barb (Barbodes altus)

Juvenile Barbodes altus (0.90±0.02 g body weight) were fed 42% crude protein diets in which dietary protein was supplied by brown fish meal (FM) (60% crude protein) or an isonitrogenous mixture of soybean (defatted, with hulls, 44% crude protein) and FM. Diet 1 was a control diet containing 73% FM (100% fish meal protein (FP)) as a protein source and without any soybean meal (SP). Diets 2–4 contained 27%, 37%, and 52% SBM with FM (ratios of FP to soybean meal protein (SBM) were 3:1, 2:1, and 1:1, respectively). Fish fed the diet containing FP/SP ratio of 1:1 had significantly (P<0.05) lower weight gain and feed efficiency than fish fed with the other diets. There was no significant difference in body weights of fish fed with the other three diets. When compared to the control (Diet 1), fish fed with the other three diets did not show any significant difference in body protein content. However, body fat content was significantly higher in fish fed with the control diet than the fish fed with diets containing FP/SP ratios of 2:1 and 1:1. Whole-body ash content was significantly lower in fish fed with a diet containing fish-protein/soy-protein ratio of 1:1 than in those fed the other diets. The results of the present study indicate that SBM may be included in the diet up to 37% as a substitute for FM, replacing about 33% of FP.

Effect of dietary protein level on puberty, oocyte growth and egg chemical composition in the tilapia, Oreochromis niloticus (L.)

Abstract Oreochromis niloticus were maintained on 5 isocaloric diets of different dietary protein levels (10, 17, 25, 32 and 40%). In Expt. 1, O. niloticus (initial mean weight approximately 0.3 g) maintained on diets of 10 and 17% protein levels showed lower growth rates compared to those on the higher protein levels and none reached puberty. In Expt. 2 (initial mean weight approximately 3 g), only those receiving 10% dietary protein level gave similar results; fish fed 17% reached puberty. Fish fed higher protein levels (32 and 40%) reached puberty at an earlier age, with oocytes growing and maturing faster, than those fed lower levels (≤ 25%). The former also showed higher growth rates, lower food conversion ratios and higher survival rates. When the onset of puberty and the rate of oocyte maturation were evaluated in relation to size (regardless of age), there were no significant differences among the treatments, suggesting that dietary protein may have influenced oocyte growth and puberty by its effect on growth. The chemical composition of post-vitellogenic oocytes, expressed as percent protein, lipid, moisture, and essential amino acids (mg in 100 mg protein), was not significantly different among the different dietary treatments.

Qualitative requirements of essential fatty acids for juvenile Penaeus monodon

Abstract The requirements of essential n − 3 and n − 6 fatty acids (EFA) for juvenile Penaeus monodon were assessed qualitatively in terms of weight and survival responses by feeding diets excluding each fatty acid separately. Purified diets contained 5% lipid mixture of 16:0 and 18:1 n − 9 (conditioning/control diet), 5% cod liver oil (reference diet) or 4.2% lipid mixture of 16:0 and 18:1 n − 9 and 0.8% mixture of four fatty acids of the five EFAs; 18:2 n − 6, 18:3 n − 3, 20:4 n − 6, 20:5 n − 3 and 22:6 n − 3. In a separate experiment, shrimp were fed diets with 1% 20:5 n − 3, 1% 22:6 n − 3 or 1% mixture of 20:5 n − 3 and 22:6 n − 3 added to a 4% mixture of 16:0 and 18:1 n − 9 as dietary lipid. In both experiments, feeding the reference diet with 5% cod liver oil resulted in higher growth than diets supplemented with pure polyunsaturated fatty acids (PUFAs). In Experiment 1, weight gain of shrimp fed diets without supplements of 18:2 n − 6, 20:4 n − 6 and 20:5 n − 3 ranged from 275 to 301%. A requirement for pre-formed 18:3 n − 3 and 22:6 n − 3 was indicated by the significant declines ( P n − 3 as dietary EFA, weight gain of shrimp (359%) was significantly ( P n − 3. However, the addition of 22:6 n − 3 to 20:5 n − 3 significantly ( P n − 3 and n − 6 PUFAs supplemented into diets. Tissue levels of saturates and monounsaturates decreased with the supplementation of n − 3 and n − 6 PUFAs. No de novo synthesis of 18:3 n − 3 was evident. The chain elongation and desaturation of 20:5 n − 3 to 22:6 n − 3 and the retroconversion of 22:6 n − 3 to 20:5 n − 3 occurred. These results showed differences in the qualitative requirements of EFA and bioconversion capabilities of P. monodon as compared with other penaeids.

Effect of dietary protein level on spawning performance and amino acid composition of eggs of Nile tilapia, Oreochromis niloticus

Abstract Oreochromis niloticus were maintained on three purified, isocalorific diets of different dietary protein levels (10, 20 and 35%), with casein and gelatin as protein sources. The dietary protein influence on spawning interval, fecundity, relative fecundity (number of eggs per unit weight) and egg size at four successive spawnings was investigated. The protein, moisture, free and bound amino acid composition of the spawned eggs were determined. O. niloticus females fed 20 and 35% protein levels maintained their spawning cycle, whereas at 10% spawning intervals were prolonged after about 4 months of feeding. Females fed 20 and 35% protein diets produced a higher number of eggs per spawn than those fed 10%, especially at later spawnings. But relative fecundity and egg size did not differ significantly between the treatments. The amount of protein in eggs of females maintained on 35% protein diet was significantly higher than in others. However, the moisture content of the eggs did not vary among the diets. Of the free amino acids, methionine, valine, tyrosine, serine, glycine and proline were influenced by the dietary regime. The total (free + protein bound) individual amino acids in the eggs were not affected by dietary protein level. However, the total overall amino acid pool of eggs in the 35% protein level was higher than in the others.

Influence of protein content of broodstock diets on larval quality and performance in Nile tilapia, Oreochromis niloticus (L.)

Abstract Performance of mature Nile tilapia females reared on three isocaloric, purified, diets of 10, 20 and 35% crude protein (CP), for a minimum period of 4 months, in relation to fertilizability, hatchability and larval quality was investigated. Care was taken to minimize the influence of males on egg and larval quality, and to ensure that the results reflect the nutritional history of the brooding females. The eggs of females reared on the 10% CP diet were not fertilized. The means of the number of eggs per spawn, egg diameter and percent fertilizability were 359 ± 31 and 398 ± 39, 2.29 ± 0.05 and 2.31 ± 0.05 mm, and 79.8 ± 4.2 and 83.8 ± 3.9 for females fed on 20 and 35% CP diets, respectively. The differences between the diets for the above parameters were not significant. However, the percent hatchability (20% CP 41.7 ± 5.1; 35% CP 68.7 ± 3.6) of the eggs and the percentage of normal larvae (20% CP 41.8 ± 4.4; 35% CP 59.8 ± 2.8) from the females on 35% CP diet were higher ( P Significant differences were, however, observed in the free amino acid content of larvae from the two groups of females, but not in other chemical traits such as total protein or moisture content. A relationship was evident between fertilizability and hatchability of eggs to their free amino acid content.

Influence of dietary protein content on the distribution of amino acids in oocytes, serum and muscle of Nile tilapia, Oreochromis niloticus (L.)

In this paper changes in the physical and chemical characteristics including the amino acid content of mature oocytes (Stage 4; pear-shaped; > 2.4 mm diameter) of Oreochromis niloticus females in relation to dietary protein content of 10, 20 and 35% are presented. Corresponding changes in amino acid content of dorsal muscle and serum (18 h post-prandial) were also investigated in the females sampled. The amount of protein in oocytes of females maintained on the 10% protein diet was significantly lower (P < 0.05) than the others. However, the gonadosomatic index of females and the diameter, mean weight and moisture content of oocytes were not affected significantly by the dietary protein levels. Diet related changes were observed in total (protein-bound + free) amino acid patterns in oocytes and muscle. Total essential amino acid patterns of muscle and oocytes were positively and significantly correlated to those of the diets, but with respect to the total non-essential amino acids, only the dietary amino acid patterns for the 20 and 35% protein diets were correlated to that of muscle. Serum and oocyte free essential and non-essential amino acid patterns were also highly correlated with dietary amino acids at all three dietary levels. The significance of these observations is discussed in light of possible ‘maternal compensation’, whereby the female attempts to channel essential nutrients to developing oocytes even when her nutrition is sub-optimal.

Growth response of juvenile Barbodes altus fed isocaloric diets with variable protein levels

An experiment was carried out to determine the dietary protein requirement of the cyprinid fish Barbodes altus cultured under controlled conditions. Seven approximately isoenergetic purified diets were formulated with protein levels ranging from 20 to 50%, in increments of 5%, and fed to young B. altus (0.8 ± 0.012 g body weight and 4.27 ± 0.10 cm total length). The feeding trial was conducted for 10 weeks with triplicate groups in each treatment and the fish were fed at 5% body weight daily. Weight gain was proportional to protein levels up to an incorporation rate of 40%; beyond this level, it was significantly (P 0.05) affected by various dietary protein levels.

Magnesium requirement of the guppy (Poecilia reticulata Peters)

The requirement of the guppy (Poecilia reticulata Peters) for dietary magnesium was investigated by feeding diets containing levels of magnesium (0.0, 0.18, 0.36, 0.54, 0.72, 0.90 g/kg of dry diet) for about 3.5 months. Poor growth, low feed efficiency, and high mortality were demonstrated in magnesium-deficient guppies. Magnesium, calcium, sodium and potassium content of the kidney, heart, liver, muscle and bone were determined. Most of the organs in magnesium-deficient fish tended to have low magnesium and potassium but high calcium and sodium concentrations. The level of magnesium required for optimal growth was found to be 0.54 g/kg of diet.

Apparent digestibility of lipid and fatty acids in residual lipids of meals by adult Penaeus monodon

Abstract The apparent digestibilities of total lipid, lipid classes and individual fatty acids in the residual lipids from full fat soya, fish, squid, squid liver and fish liver meals were determined to assess the nutritive value of these meals to 20 g Penaeus monodon . Test ingredients were incorporated at 15% substitution levels into a reference diet. Chromic oxide was used as the inert marker. Residual lipids of these meals contained much higher levels of polyunsaturated fatty acids, especially n − 3 type fatty acids, than equivalent oils. Triacylglycerols comprised 86.72% of total lipid in full fat soya as compared to 17.38 to 40.02% in the marine meals. Dry matter and total lipid digestibilities were highest with fish liver and squid liver meals. Triacylglycerols were fully digested (range 96.09–99.75%) in all meal lipids. The variability in apparent digestibility coefficients was high for free sterols (33.67–75.99%), steryl esters (23.23–93.95%) and free fatty acids (5.72–73.82%), but comparatively low for total phospholipids (60.19 to 94.12%). Mean values for individual fatty acids ranged from 53.79 to 99.94%. With the exception of squid meal lipid, the digestibilities of eicosapentaenoic and docosahexaenoic were not significantly different ( P > 0.05) within meals.