Desempenho da cioba, Lutjanus analis, alimentada com rações contendo fontes protéicas vegetais em substituição a ingredientes de origem marinha

Abstract

Snappers belong to the Lutjanidae family, found in tropical and sub-tropical waters worldwide, and are considered potential candidates for aquaculture. Among the several species, the mutton snapper (Lutjanus analis) is one of the best options for culture due to its high market value, adaptability to confined conditions and acceptance to artificial food. The present study evaluated the growth of juvenile snappers [18,4 ± 4,6 g mean body weight (n= 300)] fed four isoenergetic and isonitrogenous diets over 95 days. Diets were formulated to contain the following ratios of marine animal versus plant protein (P): 2.02:1.00 (diet M:P_2.0), 1.03:1.00 (diet M:P_1.0), 0.51:1.00 (diet M:P_0.5) and 0.27:1.00 (diet M:P_0.3). Soybean protein concentrate (SPC) was the main replacer of fish meal (FM). The work was divided into two stages. The first stage evaluated fish growth performance while the second analyzed diet attractiveness and palatability. The replacement percentages of FM for SPC led to a negative impact over fish performance, particularly when marine animal and plant protein corresponded to 62.9% and 17.1% of the total diet protein content, respectively (diet M:P_0.3). At harvest, fish fed diet M:P_0.3 attained 54.9 ± 13.2 g mean body weight significantly lower when compared to 76.5 ± 14.0 g, 73.9 ± 13.8 g and 70.5 ± 14.0 g achieved with fish fed diets M:P_2.0, M:P_1.0 and M:P_0.5, respectively (P < 0.05). Fish fed the latter diets achieved a similar performance (P > 0.05). Similarly, fish yield dropped significantly, from 891 ± 36 under treatment M:P_0.3 to an average of 1,099 ± 111 g/m3 for remainder diets (P < 0.05). In the end of the study, the mutton snapper achieved a maximum body weight gain of 0.60 ± 0.05 g/day and a maximum specific growth rate of 1.47 ± 0.07 %/day when fed diet M:P_2.0. Apparent feed intake (AFI) reduced as replacement of marine animal for plant protein increased in diets. Statistical differences in AFI were only observed when diet M:P_0.3 was compared to diets M:P_2.0 and M:P_1.0 (P < 0.05). However, proportionally the mutton snapper fed more on diet M:P_2.0 compared to the others, as AFI was 6, 15 and 33% higher for M:P_2.0 in relation to M:P_1.0, M:P_0.5 and M:P_0.3, respectively. There was no significant statistical difference for food conversion ratio (FCR) and rate of protein retention among the different diets (P > 0.05; mean of 1.85 ± 0.06 and 1.47 ± 0.07%/day, respectively). Data on diet attractiveness and palatability revealed that the loss in growth performance when fish were fed high plant protein levels were the result of a decline in feed intake led by reduced diet palatability. Diets M:P_0.5 and M:P_0.3 containing 52.2 and 62.9% of plant protein, respectively, recorded the lowest number of pellets consumed and frequency of visits to feeding trays, parameters indicative of diet. In general, diets with up to 52.2% (diet M:P_0.5) plant protein relative total diet protein contribution fed to mutton snapper stocked at 15 animals/m³ allowed a growth performance near to other works conducted with the same species.