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PD/A CRSP Aquanews-Summer 2002

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Peru Project: Broodstock Diets and Spawning of Colossoma macropomum and/or Piaractus brachypomus Research Update

by Rebecca Lochmann, University of Arkansas at Pine Bluff

ne of the objectives of this Tenth Work Plan project is to determine the effect of improved broodstock nutrition on maturation and spawning performance of Colossoma macropomum and/or Piaractus brachypomus, species native to the Peruvian Amazon and locally known as tambaqui and pacu. Ideally, optimal broodstock diets will be formulated using nutrient sources that are cost effective and readily available in the Amazon region.

Assessment of the diets used previously for Characid broodstock revealed that they contain very low levels of xanthophyll (about 17 mg/kg) but no other carotenoids. Carotenoids are known to influence reproduction in some fish (red sea bream, yellowtail, Atlantic salmon). Furthermore, the natural diets of Characids are rich in carotenoids. Pijuayo (Bactris gasipaes) is a locally available fruit with a deep orange-red color. The fruit is similar to corn in its percentages of protein and lipids, but pijuayo contains mostly beta-carotene and corn contains xanthophyll. Previous research (Mori-Pinedo et al., 1999) has shown that pijuayo and corn could be used interchangeably for growth and body composition in tambaqui fingerlings. In addition, pijuayo is being used indiets for ornamental fishes at Fondepes, a government fish production facility in Peruvian Amazon city of Iquitos.

Assuming pijuayo has no negative effects on pacu growth, health, or
Pijuayo and other produce at the mercado in Iquitos, Peru.
survival, it should be safe to include in broodstock diets to determine the effects of carotenoid enhancement on spawning success. Therefore, we conducted a small feeding trial with juvenile pacu to determine whether or not pijuayo and corn can be used interchangeably to support normal growth without producing negative effects. Whole ripe pijuayo (including the seed, skin, and flesh) fruits were finely minced and dried in an oven at 40oC overnight at the CRSPs Peru research site, the Instituto de Investigaciones de la Amazonia Peruana, in Iquitos, Peru. The drying step destroys the trypsin inhibitor in pijuayo and makes it suitable for grinding to a flour. The flour was used in a feeding trial with pacu in a recirculating system at the University of Arkansas at Pine Bluff (UAPB). There were two diets that contained 20% fish meal, 34% soybean meal, 24% wheat flour, 2% vitamin/mineral mix, 4% soybean oil, and 16% either corn or pijuayo. Fish in triplicate 110-L tanks per treatment were fed to satiation three times daily for six weeks. Survival was 100%, and there were no significant differences in growth between treatments.

Therefore, pijuayo can be substituted for corn at 16% of the diet without sacrificing growth or health of pacu. Mori-Pinedo et al. (1999) showed that pijuayo or corn could be used up to 55% of the diet for comparable growth and body composition in tambaqui fingerlings. The next step is to determine whether substitution of corn with pijuayo confers any benefits to broodstock Characids in terms of spawning success.

Other work in progress at UAPB indicates additional changes to consider for pacu (broodstock and fingerling) diets. Apparent digestible energy coefficients determined recently for common feed–stuffs in pacu indicate that the available energy content of wheat bran is about half that of fish meal, soybean meal, or corn (Fernandes and Lochmann, unpublished). Apparent protein and lipid digestibility coefficients are also being determined for these feedstuffs in pacu.

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