Thêmis Sakaguti Graciano

Digestible lysine requirement of Nile tilapia fingerlings fed arginine-tolysine-balanced diets

This study was conducted to determine the digestible lysine requirements of Nile tilapia fingerlings. Fish (n = 300; average initial weight = 1.44 g) were distributed 15 300-L aquariums, in a completely randomized design with five treatments and three replicates, and fed extruded diets containing 11.3, 13.7, 16.1, 18.4 or 20.8 g/kg of digestible lysine. The arginine:lysine ratio was maintained at 1.3:1. All fish were fed diets containing 281 g/kg of digestible protein and 3,372 kcal digestible energy/kg, hand-fed until apparent satiation. There was no effect of the dietary lysine levels on survival rate, or protein and ash body rates. With increasing levels of lysine in the diet, a quadratic effect on weight gain, feed conversion, protein efficiency ratio, protein deposition rate, deposition rate of fat, body moisture and body lipids was observed, where the best values of the variables were estimated at 15.96, 16.4, 14.35, 15.21, 15.87, 15.21 and 16.29 g/kg of lysine, respectively. The digestible lysine requirement of Nile tilapia fingerlings is 15.21 g/kg (5.41 g/100 g of digestible protein), in diets balanced for the arginine:lysine ratio.

Digestible methionine + cystine requirement for Nile tilapia from 550 to 700 g

This trial was conducted to determine the dietary digestible methionine + cystine requirement of Nile tilapia (550 to 700 g) based on the ideal protein concept. Six hundred fish were distributed in a completely randomized design with five treatments and four replicates, with 30 fish per experimental unit. The fish were fed diets containing approximately 262 g of digestible protein/kg, 3,040 kcal of digestible energy/kg and 7.90, 9.40, 10.90, 12.40 or 13.90 g of methionine + cystine/kg. The fish were hand-fed three times a day until apparent satiation for 30 days. No effects of dietary methionine + cystine on feed conversion ratio, daily protein deposition, whole body moisture, fillet moisture, crude protein, ether extract and ash, plasmatic HDL and LDL cholesterol were observed. Dietary methionine resulted in a linear increase in whole body protein and linear reduction in lipid deposition rate, hepatosomatic index, whole body ether extract and ash, plasmatic total cholesterol, plasmatic total lipids and plasmatic triglycerides. According to the Linear Response Plateau, the daily weight gain and fillet yield increased up to a level of 9.00 and 9.90 g methionine + cystine/kg of diet, respectively. The digestible methionine + cystine requirement of Nile tilapia is 9.00 g/kg for weight gain and 9.90 g/kg for fillet yield, corresponding to methionine + cystine:lysine ratios of 0.60 and 0.66, respectively.

Redução da proteína em dietas para tilápias-do-nilo por meio da suplementação de aminoácidos com base no conceito de proteína ideal

The objective of this work was to evaluate the effects of reduction of protein in diets for Nile tilapia by supplementation of synthetic amino acids on performance, digestibility and diameter of muscle fiber of Nile tilapias. The amino acids (lysine, methionine, threonine and arginine) were supplemented to keep the profile of amino acids in the reference diet. It was used 160 fish with initial live weight of 105.7 ± 2.5 g, distributed in 16 tanks (1 m3 each tank) fed diets containing 26.74; 25.82; 23.09 or 22.16% of digestible protein for 110 days. It was not observed any effects of protein levels in the diets on daily weight gain, hepatosomatic index, visceral fat, fillet yield, carcass humidity, crude protein and ash, fillet ash, survival rate and on the white muscle fiber diameter. A linear decrease on apparent digestibility coefficients, gross energy, crude protein, ether extract and phosphorus was observed when protein levels in the diet were reduced. There was a quadratic effect on feed conversion ratio, protein efficiency rate, nitrogen retention, nitrogen excretion, fillet humidity, carcass and fillet fat and fillet protein, in which the best-fit responses were estimated with 24.53, 24.25, 24.04, 25.15, 24.67, 24.14, 24.34 and 25.11% of digestible protein, respectively. It is possible to reduce the dietary protein level from 26.74 to 24.53% for Nile tilapia 100 to 500-g phase.

Mathematical modeling for digestible protein in animal feeds for tilapia

The objective of this study was to formulate a mathematical model to estimate digestible energy in animal feeds for tilapia. Literature results were used of the proximate composition of crude protein, ether extract, mineral matter and gross energy, as well as digestible energy obtained in biological assays. The data were subjected to stepwise backward multiple linear regression. Path analysis was performed to measure the direct and indirect effects of each independent variable on the dependent one. To validate the model, data from independent studies and values obtained from a digestibility trial with juvenile Nile tilapia testing five meat and bone meals (MBM) were used, using the Guelph feces collecting system and chromium oxide (III) as an indicator. The obtained model is described below and cannot estimate digestible energy (DE) of animal origin: 775