The aim of this work was to evaluate the feed management (feed percentage and feeding frequency) of pacu (Piaractus mesopotamicus) juveniles bred in net cages. To evaluate the feed percentage 2,000 juveniles (12.12±0.51 g) were randomly distributed in 20 cages of 1 m3 (0.8 m3 of useful volume). The fish were fed four times a day (8:00 a.m.; 11:00 a.m.; 2:00 p.m.; and 5:00 p.m.) with 4, 7, 10, 13, and 16% of feed. To evaluate feeding frequency, another 2,000 juveniles (9.56±0.56 g) were randomly distributed in 20 cages of 0.8 m3 of useful volume. The fish were fed one, two, three and four times a day. Due to the feed percentage, significant effects (P<0.05) were observed for the parameters of weight gain, final length, final biomass, specific growth rate, and apparent feed conversion. The performance parameters, centesimal composition, and blood biochemistry were not influenced (P>0.05) by the feeding frequency. Considering the weight gain and apparent feed conversion of pacu juveniles cultivated in net cages, 8% of feed is recommended regardless of the feeding frequency adopted.

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ABSTRACT. This work evaluated five classes of weight of bullfrog (Lithobates catesbeianus) seeking to define the ideal slaughter weight for the species. We used 79 bullfrogs, distributed in a completely randomized design (class 1 < 100 g (n = 10); class 2 from 101 to 150 g (n = 17); class 3 from 151 to 200 g (n = 24); class 4 from 201 to 250 g (n = 14); and class 5 >251 g (n = 14)), which were euthanized, weighted and gutted. For the carcass yield, we weighed the clean torso, thighs, liver, skin and head. The clean torso was subjected to chemical composition analysis. The carcass yield was, on average, 49% with no difference between weight classes (p > 0.05). The yield of posterior thighs was significantly higher for the lower weight class, which also presented higher percentage of paws (28.37 ± 0.63 and 9.33 ± 0.21, respectively) (p < 0.05). The percentages of visceral fat and skin showed a progressive increase along with the weight of the animals; the class with individuals weighing 201-250 grams showed the higher values (p < 0.05). The chemical composition indicated that individuals above 251 grams showed lower values of ether extract and higher values of crude protein (0.99 ± 0.14 and 15.80 ± 0.64, respectively) (p < 0.05). So, it is recommended the slaughter of bullfrogs weighing more than 201 grams, because of better yield and meat quality.Keywords: exotic species, meat processing, raniculture. Rendimento de carcaça e composição centesimal da rã-touro (Lithobates catesbeianus)RESUMO. O objetivo do trabalho foi comparar cinco diferentes classes de peso de rã-touro (Lithobates catesbeianus), buscando definir o peso ideal de abate para a espécie. Foram utilizados 79 exemplares de rãs-touro, distribuídas em um delineamento inteiramente casualizado (classe 1 <100 g (n = 10); classe 2 de 101 a 150 g (n = 17); classe 3 de 151 a 200 g (n = 24); classe 4 de 200 a 250 g (n = 14), e classe 5 > 251 g (n = 14)), que foram eutanaziados, pesados e eviscerados. Para o rendimento da carcaça foram pesados: tronco limpo, coxas, fígado, patas, pele e cabeça. O tronco limpo foi submetido à análise de composição centesimal. O rendimento de corpo limpo foi em média 49%, sem diferença entre classes (p > 0,05). O rendimento das coxas posteriores foi significativamente maior para a menor classe de peso, e essa classe também apresentou maior porcentual de patas (28,37 ± 0,63 e 9,33 ± 0,21, respectivamente) (p < 0,05). As porcentagens de gordura visceral e pele apresentaram um aumento progressivo concomitante ao peso dos animais, sendo que a classe com indivíduos de 201 a 250 g apresentou os maiores índices (p < 0,05). Na composição centesimal observou-se que indivíduos acima de 251 g, apresentaram menores valores de extrato etéreo e maior valor de proteína (0,99 ± 0,14 e 15,80 ± 0,64, respectivamente) (p < 0,05). Para melhor aproveitamento é recomendado que rãs-touro sejam abatidas com peso superior a 201 g, pois apresentam melhores rendimentos e características da carne.Palavras chave: espécie exótica, processamento de carne, ranic...

Aim of study: To evaluate if dietary restriction influence muscle and intestinal morphology as well as the production performance of juvenile Nile tilapia (Oreochromis niloticus).Area of study: State University of Western Paraná (Universidade Estadual do Oeste do Paraná – Unioeste), Toledo Campus, Brazil.Material and methods: The experimental design was completely randomized with four treatments and five replicates. The treatments were: 7:0 (fed daily; control); 6:1 (fed 6 consecutive days followed by 1 day of fasting); 5:2 (fed 5 consecutive days followed by 2 days of fasting); and 1:1 (fed 1 day followed by 1 day of fasting). A commercial ration with 33.70% crude protein and 4.60% lipid was used, and fish were fed four times daily until apparent satiety for 60 days.Main results: The following parameters were found to have differences among treatments (p<0.05): final weight, weight gain, final length, hepatosomatic index, visceral fat, intestinal quotient, protein efficiency rate, protein retention, ash, and frequency of muscle fiber diameters within the classes of<20 μm and between 20 and 50 μm. The intestinal villi height and hepatic glycogen content did not differ (p>0.05) among treatments. The cost of food and partial net revenue were higher in the 7:0 treatment compared to the experimental treatments.Research highlights: Dietary restriction for Nile tilapia in the juvenile phase negatively influences productive performance, centesimal composition, and muscle growth, which demonstrates that this practice is economically unfeasible for commercial production.

Aiming to assess organic soybean meal (OSM) for Nile tilapia, two studies were carried out: Study I - digestibility of OSM compared to conventional soybean meal (CSM) for Nile tilapia; and Study II - effect of OSM and CSM, supplemented or not with fish meal (FM) on the performance of Nile tilapia fingerlings. The apparent digestibility coefficients of the protein were 88.24 and 88.10%, resulting in 39.91 and 39.87% digestible protein for OSM and CSM, respectively. The apparent digestibility coefficients of energy were 75.92 and 70.48%, resulting in 3579.46 and 3141.44 kcal kg-1 of digestible energy for OSM and CSM, respectively. The diet containing CSM+FM presented the best results for final weight and weight gain. However, the highest levels of crude protein in the fish carcass were observed in the animals fed with the OSM + FM diet. The OSM diet presented the best results for total protein and albumin in the blood. The OSM diet has good apparent digestibility coefficients and its use in tilapia feeding presents a satisfactory productive performance and a higher deposition of protein in the carcass when supplemented with 20% of fish meal.