RESUMO -Avaliaram-se os efeitos da utilização de ciclos alternados de restrição alimentar e realimentação no crescimento do pacu, durante o período de engorda, e a viabilidade desta prática na produção comercial da espécie. Juvenis foram distribuídos em três tanques e submetidos a diferentes manejos alimentares, constituindo os tratamentos: A (alimentado ad libitum), B (restrição alimentar de 4 semanas, realimentado por 9 semanas) e C (6 semanas de restrição alimentar, realimentado por 7 semanas), em um total de 13 semanas por ciclo (4 ciclos experimentais). No final de cada ciclo alimentar, 20 peixes de cada tratamento foram amostrados e os dados biométricos registrados. Os valores obtidos para peso, comprimento total e fator de condição (K) foram submetidos a ANOVA e as médias comparadas pelo teste de Duncan. Os resultados mostraram que o tratamento C é o mais indicado somente para outono/inverno, promovendo maior crescimento, menor custo com ração, baixa conversão alimentar e maior receita líquida parcial. Entretanto, durante as estações mais quentes do ano (primavera/verão) outros programas de alimentação devem ser testados, utilizando-se períodos mais curtos de restrição alimentar. Quando se tratou da produção anual, o tratamento A respondeu melhor em termos de biomassa produzida, apesar do maior gasto com alimentação, visto que, com o aumento da temperatura, o crescimento dos peixes dos demais tratamentos ficou prejudicado.Palavras-chave: avaliação econômica, ciclos de restrição alimentar e realimentação, crescimento, custos com alimentação Evaluation of the Growth and Feeding Costs of Pacu (Piaractus mesopotamicus) Submitted to Alternate Cycles of Feeding Restriction and RefeedingABSTRACT -The present study evaluated the effects of alternating food restriction and refeeding cycles on the growth of pacu, during the growout phase and the viability of this practice in the commercial production of the species. Juvenile fish were distributed in 3 tanks and submitted to different feeding strategies: group A (fed ad libitum daily), B (food restricted to 4 weeks and refed for 9 weeks) and C (food restricted to 6 weeks and refed for 7 weeks) totalizing 13 weeks per cycle (4 experimental cycles). At the end of each feeding cycle, 20 fish per treatment were sampled and the biometric data were registered. Values of weight, total length and condition factor (K) were submitted to ANOVA and the averages were compared by Duncan test. The results showed that the treatment C presented better results only in autumn/winter periods, promoting better growth, lower cost ration, lower food conversion and better partial net income. Otherwise, during the warmer periods of the year (spring/summer) other feeding strategies must be tested, utilizing shorter periods of food restriction. Regarding to the annual production, the treatment A showed higher biomass, although higher feeding costs. With the increase in the temperature, the growth of the fish from the other treatments was delayed.

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This study compared the larval performance of matrinxa ì , Brycon amazonicus, after maternal triiodothyronine (T 3 ) injection or egg immersion of T 3 . In the ¢rst experiment, three groups of females (n 5 4) induced to spawning received pituitary extract (CPE) and a corn oil injection (control), or CPE plus 10 mg or 20 mg kg À 1 bw T 3 dissolved in corn oil (experimental). Larvae were sampled for body weight and length measurement at hatching (0 h) and12, 24, 36, 48 and 60 h thereafter. Hatching time, hatching success and abnormal development were monitored. In the second experiment, fertilized eggs from four females were immersed inT 3 solutions (0,0.01,0.05 and 0.10 mg L À 1 ) and larvae were sampled at hatching (0 h) and 6, 18, 30, 42, 54, 126 and 198 h thereafter. Hatching time was not a¡ected by either means of hormone treatment. Abnormalities decreased as the T 3 concentration increased in larvae from T 3 -treated brood¢sh but the number of dead larvae increased proportionally. Larvae from T 3 -injected females had higher weight from 24 h after hatching and greater length from hatching, while the weight of larvae produced from T 3 -immersed eggs changed at 198 h and length from 126 h of rearing. Both routes of T 3 administration a¡ected the early growth of matrinxa ì but the e¡ect was observed earlier when broodstock females were injected.

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Mathematical models are important tools to estimate nutritional requirements and animal growth. Very few calf models generated from other countries with different feeding programs, environment and production systems have been evaluated. The objective of this paper is to evaluate two calf models: (i) the National Research Council (NRC) in 2001 and (ii) the updates published by Van Amburgh and Drackley in 2005 and inputted into Agricultural Modeling and Training Systems (AMTS, version 3.5.8). Data from 16 previous studies involving 51 diets for dairy calves under tropical conditions (n = 485 calves, initial BW 37.5 ± 4.35 kg and weaning weight of 62.0 ± 10.16 kg) were used. The calves were fed with whole milk, milk replacer or fermented colostrum, plus starter (20.9 ± 1.78% of CP). The accuracy of the average daily gain (ADG) prediction was evaluated by mean bias, mean square prediction error (MSPE), concordance correlation coefficient, bias correction factor (Cb), and regression between the observed and predicted values. The ADG observed from birth to weaning was 0.452 ± 0.121 kg/day. Calves fed with whole milk had greater ADG compared with calves fed milk replacer (0.477 v. 0.379 kg/day) during the milk-feeding period. When all data were pooled (n = 51 diets), predictions had a mean bias of −0.019 and 0.068 kg/day for energy-allowable gain using NRC and AMTS models, respectively. The regression equation between observed and predicted values obtained from energy of diets showed an intercept different from zero ( P < 0.0001) and slope that differed from unity ( P < 0.0001). In a second evaluation, when calves were fed only milk replacer, the energy-allowable gain from AMTS showed the lowest mean bias (0.008 kg/day) and 82.1% of the MSPE value originated from random errors. The lowest MSPE, the higher Cb value and no significant slope bias ( P > 0.05) indicate that the AMTS growth model resulted in accurate predictions for calves fed with milk replacer. However, within these latter two approaches, the goodness of fit ( R 2 ) was low, representing low precision. The weight gain estimated by the energy available from the diet was overestimated by 19 g/day when calculated by the NRC and underestimated by 68 g/day when calculated by AMTS. The reasons for this discrepancy need to be understood, for only then new models could be developed and parameterized to estimate animal performance in tropical conditions more accurately and precisely.Keywords: calf models, cross-bred calves, growth, meta-analysis, prediction ImplicationsThe development of an accurate calf model has been challenging because several factors affect growth such as breed, colostrum and feeding programs, facilities and environmental conditions. Because of the conventional feeding system (e.g. 4 l/calf at each of two daily feedings) and tropical conditions, the animals evaluated in this study showed poor weight gains. The low energy to protein ratio likely reduced calf growth rates. Currently available calf models can be used to predict calf growth during ...

Alevinos de tilápia foram criados nas densidades de 90, 120 e 150 peixes em tanques circulares (0,5m³), submetidos a duas trocas totais de água (30 e 60 minutos), no sistema "raceway". Avaliaram-se os custos, a lucratividade e o desempenho produtivo. A incidência de custo (IC) aumentou com o aumento da densidade de estocagem dos peixes, na troca de água feita em 60 minutos (R$0,98 a R$1,07/kg); a melhor IC foi obtida com 120 peixes/m³ na troca de água em 30 minutos (R$0,90/kg). A renda líquida parcial (RLP) variou de R$11,11 a R$22,65, respectivamente, para a troca de água em 60 minutos/90 peixes e para a troca de água em 30 minutos/120 peixes. A maior RLP foi de R$90,60/m³ por ano, extrapolando-se para duas produções/ano. O melhor desempenho econômico ocorreu no tratamento com 120 peixes/m³ e troca de água em 30 minutos, que apresentou também o melhor desempenho produtivo. Palavras-chave: alto fluxo de água, custo parcial, lucratividade parcial, Oreochromis niloticus, taxa de lotação. ABSTRACT. Economic and productive performance of tilapia (Oreochromis niloticus) in raceway system. Tilapia fingerlings were reared at densities of 90, 120 and 150 fish in circular tanks (0.5m³), submitted to two full water exchanges (0 and 60 minutes), in a raceway system. Costs, profitability and productive performance were evaluated. The incidence of costs (IC) increased with fish stocking density increase, for water exchange in 60 minutes

Avaliou-se o desempenho produtivo dos alevinos de tilápia do Nilo, (Oreochromis niloticus L.) (Perciformes Cichlidae) estocados nas densidades de 90, 120 e 150 peixes/tanque, em 24 tanques circulares com 0,5 m³, em duas trocas totais de água (30 e 60 minutos), no sistema "raceway". Utilizou-se o delineamento inteiramente casualizado, em esquema fatorial 3x2, para análise dos dados. Após 128 dias, o peso final e o ganho de peso foram superiores na maior troca de água e menor densidade; a conversão alimentar não alterou significativamente; a biomassa total aumentou com o aumento da renovação de água e densidade de estocagem de 120 e 150 peixes/m³; a taxa de crescimento específico aumentou na maior renovação da água; os rendimentos de filé e de carcaça diminuíram com a menor troca de água nas maiores densidades de estocagem. Os melhores resultados ocorreram com troca total de água em 30 minutos, nas densidades de estocagem de 120 e 150 peixes/m³. Palavras-chave: produção, alto fluxo de água, taxa de lotação, Oreochromis niloticus.

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