Thiago Archangelo Freato

Efeito do peso de abate nos rendimentos do processamento da piracanjuba (Brycon orbignyanus, Valenciennes, 1849)

Objetivou-se, com o presente trabalho, avaliar o efeito do peso de abate sobre os rendimentos do processamento do peixe teleosteo piracanjuba (Brycon orbignyanus, Valenciennes, 1849). Inicialmente, alevinos com peso medio de 12 g, oriundos da Estacao Experimental da Usina Hidreletrica de Itutinga, foram estocados e cultivados em um viveiro de terra na Estacao de Piscicultura do Departamento de Zootecnia da Universidade Federal de Lavras. Ao final de 18 meses de cultivo, 121 peixes foram insensibilizados, abatidos, pesados e dissecados, para a determinacao das porcentagens de cabeca (%CAB), nadadeiras (%NAD), visceras (%VIS), pele com escamas (%PE), e residuos da filetacao (%RF) e dos rendimentos de carcaca (RCAR) e de file sem pele (RFSP), em relacao ao peso de abate. Para as analises de variância, os dados obtidos foram agrupados em 4 classes de peso (CP1=515 g a 629 g; CP2=630 g a 744 g; CP3=745 g a 859 g; e CP4=860 g a 975 g) e as equacoes de regressao estimadas em funcao do peso medio de cada classe. Nao foi constatado (P>0,05) efeito de classe de peso sobre RCAR, %NAD e %PE. Por outro lado, observaram-se efeito linear do peso de abate sobre %CAB (P<0,01), %RF (P<0,01) e RFSP (P<0,09), e efeito quadratico sobre %VIS (P<0,05). As variaveis %CAB e %RF diminuiram, ao passo que o RFSP e %VIS aumentaram, com o aumento do peso de abate. Pode-se concluir que, nas condicoes em que o experimento foi realizado, piracanjubas com maiores pesos de abate proporcionam maior RFSP e menores %CAB e %RF. Entretanto, a reducao da %CAB nao foi suficiente para aumentar o RCAR como seria esperado, em razao provavelmente de um maior aumento da %VIS.

Rendimento do processamento de linhagens de tilápias (Oreochromis niloticus) em função do peso corporal

With the objective of evaluating the yield processing of tilapia strains in function of body weight, an experiment was carried out at the Fish Culture of the Animal Sciences Department, Federal University of Lavras, M.G. - Brazil. A total 93 fish of the Chitralada strain and 78 of the Supreme strain, weighting between 150 and 790 g were used. The fish were cultivated in two tanks of 40 m2, fed with commercial ration supplied according to the biomass and water temperature. The water temperature and oxygen were evaluated every day, at the early morning and at the late afternoon, and the pH checked weekly. During the fish growth, random samples were taken. After 24 hours of fasting, the fish were insensibilized (thermal shock), slaughtered (anoxia), weighted and dissected. The regression analysis showed that in higher weight, the Chitralada strain presented higher head percentage and skin yield. The Supreme strain presented higher carcass, fillet and residue weights, being more expressive in body weights superior to 500 g and smaller limiting value for the percentage of viscera. It was concluded that the two strains have growth of body parts proportional to the increase of the body weight, and this increase does not modify the parts yield. The Supreme strain showed more carcass and fillet yield than Chitralada, and is should be indicated for production and commercialization of heavier fillet.

Evaluation of Nile tilapia strains cultivated in cages under different feeding programmes

The objective of this study was to evaluate the performance of three Nile tilapia Oreochromis niloticus strains cultivated in cages and subjected to different feeding programmes. Initially, 31,200 Nile tilapia juveniles with an average weight of 61.15 g were distributed in 48 cages. Two genetically improved strains were used together with one from the Fish Culture Section of Universidade Federal de Lavras (UFLA). The fish were subjected to four feeding programmes, consisting of different levels of crude protein (CP) in diets provided at different stages of cultivation. There was no interaction effect of the strain and feeding programme for most variables. The UFLA strain presented the highest weight gain, but with greatest lack of uniformity at the end of cultivation. The feeding programme with diets containing 36%, 32% and 28% CP, consecutively, promoted the highest weight gain and highest final biomass. The UFLA strain has great growth potential, justifying the development of a breeding programme for this strain. Crude protein levels below 36% for tilapias between 60 and 170 g and below 32% for tilapias between 170 and 700 g worsen fish performance.

Desempenho produtivo de Brycon orthotaenia em tanques-rede sob diferentes densidades de estocagem

The objective of this study was to determine the stocking density of matrinxa (Brycon orthotaenia) in cages, considering the productive performance. Juvenile Brycon orthotaenia (n = 5280) were distributed in 16 cages of 4m³ at densities of 45, 70, 95 and 120 fish m -3. The fish were fed with commercial feed with 40% crude protein during all experimental period. Data were subjected to analysis of variance and linear regression to estimate the best fit using 5% probability. The production parameters such as survival, initial weight, final weight, feed conversion and specific growth rate were not influenced by stocking density, as well as the parameters of water quality. However, final biomass, biomass gain and feed intake showed a positive linear relationship with stocking density. Evaluating these results, it was concluded that the stocking density of matrinxa (Brycon orthotaenia) up to 120 fish m -3 represent the best productive performance.

Desempenho produtivo e digestibilidade pela tilápia do NILO (Oreochromis niloticus Linnaeus, 1758) alimentada com dietas suplementadas com níveis crescentes de silagem ácida de pescado

The experiments were carried out in order to evaluate the apparent digestibility coefficients of the nutrients and gross energy of acid silage of filetage residues of the Nile tilapia. The treatments were based on the increasing levels (0, 10, 20, 30, 40%) of the acid silage by substitution of fish meal in the diets. In the digestibility assay a total of 200 sexually inverted juveniles were used. The average weight was 2.0 g and were kept in 40 liter aquariums. Feces collect was made during seven subsequent days and the apparent digestibility coefficients and apparent digestible energy were determined by indirect method, using 1.0% of Cr203 as an indicator. In the performance assay 2000 sexually inverted juveniles were used, with average weight of 0.45g, kept in 1m2 hapas, in a fish crawl. The analyzed variables were: final weight (FWG), total feed intake (TFI), apparent feed conversion (AFC) and length increase (LI). The randomized outline was used with five treatments and four repetitions. The values for apparent digestibility were: apparent digestibility coefficient of dry matter, 95.49%; apparent digestibility coefficient of gross protein, 96.66%; apparent digestibility coefficient of ether extract, 97.18%; apparent digestibility coeficient of gross energy, 95.44%. There was no significant difference (P>0.05) for total feed intake (TFI). One observed a quadratic effect (P<0.01) in the final weight (FWG), apparent feed conversion (AFC) and length increase. One concluded that the acid silage of filetage residues should be efficiently used by the Nile tilapia.