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PD/A CRSP Aquanews-Winter 2003

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Native Peruvian Plants as Ingredients for Practical Diets in Juvenile Pacu

by Maria Esther Palacios, Kyeong-Jun Lee, Mary Ann G. Abiado, and Konrad Dabrowski, The Ohio State University

mong the interesting aspects of nutritional studies on frugivorous fishes in the Amazon is the potential of native Peruvian plants to supplement diet formulations. Other than being good sources of protein and vitamins, these plants contain phytochemicals, such as catechins and flavonoids, that could improve nutrient utilization, prevent degradation of vitamins and lipids, and enhance the general health condition of the fish.

The Ohio State University (OhSU) Aquaculture Laboratory recently hosted Maria Esther Palacios from Universidad Nacional de San Marcos (UNSM), Lima, Peru, as a visiting scholar to study the effects of dietary supplementation with Peruvian plants, such as maca (Lepidium meyenii), camu-camu (Myrciaria dubia), and aguaje (Mauritia flexuosa). Parameters of interest include the enhancement of food acceptance, growth, and metabolic efficiency of the Amazon River fish, pacu (Piaractus brachypomus).

Maria Esther Palacios samples pacu for biochemical and histological analyses.

Photo by Mary Ann Abiado

At UNSM, Palacios had worked previously on determining the effects of diet containing maca meal on maturation and gamete quality of rainbow trout (Oncorhynchus mykiss). This research, completed in field conditions on a farm in El Ingenio, Huancayo Province, explored the potential for maca meal use in aquaculture. Therefore, Palacios has an excellent background to continue her work on nutrition of native Peruvian fish. She is currently working on her master’s degree dissertation at UNSM: "Conditioning, management, and optimization of reproductive and nutritional characteristics using native traditional feed ingredients for Colossoma macropomum," supervised by Professor Guillermo Alvarez. In addition to her involvement with academics, Palacios has also established contacts with the private sector, including the Peruvian Maca Producers Association. Because of Palacios’ academic experience and connection with the private sector, scientists at OhSU are delighted that she will play a key role in promoting the economic viability of the aquaculture and maca industries in Peru.

Juvenile pacu (ruler units are centimeters).

Photo by Mary Ann Abiado

Briefly, the experiment at OhSU involved replicated tank systems stocked at a density of 20 fish per tank. Three tanks were randomly assigned to one of four diets. Diets contained the identical protein source (casein-gelatin) and were supplemented with 15% wheat meal (diet 1 as a control), 15% freeze-dried camu-camu meal (diet 2); 15% freeze-dried aguaje mesocarp (diet 3); and 15% pulverized and dried maca root (diet 4). The fish (2 g initial weight) were fed experimental diets three times per day, seven days per week, at a decreasing rate, with feeding restricted from 4 to 2.6% body weight.

Recirculating tank system used for the pacu feeding experiment.

Photo by Mary Ann Abiado

After eight weeks of feeding and over ten-fold body weight increase, the growth rate was significantly higher in the fish fed the diet supplemented with maca meal. Growth rate increased by 35.3%. Voluntary food intake increased by 91.8% when fish were fed maca meal compared with the control diet. This result suggests that diets supplemented with maca meal can increase growth rate and feed utilization in pacu and could potentially improve utilization of other plant ingredients in order to replace fish meal. Other non-CRSP funded studies conducted in our Aquaculture Laboratory (Lee and Dabrowski, in preparation) support this conclusion as first-feeding larval rainbow trout also showed enhanced growth when fed maca meal. This is an important finding for the Peruvian aquaculture industry, considering that over 50% of production costs in fish farming is for feeds because of the soaring cost of fish-based feeds. Use of the new plant-based feed will also open new markets for the Peruvian maca meal industry.

The positive effects of maca meal need to be explored further in other frugivorous fishes of the Amazon rainforest. We are also working on physiological and biochemical basis of the effects of maca meal supplement. This promising field of research could have broad practical applications to the aquaculture and maca industries in Peru.

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