ULVA MEAL Ulva pertussa AS A SUBSTITUTE FOR SOYBEAN MEAL IN PRACTICAL DIETS FOR PACIFIC WHITE SHRIMP Litopenaeus vannamei

As shrimp culture has become an expanded and intensified economic activity, the demand for more cost-effective and sustainable protein sources continues to increase. Macro-algae can use metabolic residues of aquatic animals as nutrients, absorb CO₂ and produce O₂ for the environment. The inclusion of macro-algae that contain high protein content in aquaculture feeds would be an alternative strategy to reduce the reliance on fish meal (FM) and terrestrial plant protein source such as soybean meal (SBM). Unfortunately, results from a previous trial in our lab indicated that Ulva pertussa (Batch 1) was a poor replacement for FM in diets for Pacific white shrimp Litopenaeus vannamei. Ingredient digestibility results indicated that apparent protein, energy, and amino acids digestibility of Ulva meal were significantly lower than FM and SBM. In order to confirm the utility of Ulva meal, two additional trials are being conducted using additional samples of Ulva meal. The first trial evaluated nine test diets formulated on equal protein and lipid basis (35% protein and 8% lipid). The first seven diets utilized increasing levels of Ulva meal (0, 5, 10, 15, 20, 25, and 30%) to replace SBM. Diet 8 and Diet 9 utilized high inclusion of Ulva meal from first and third batch to replace SBM compared to 20% inclusion of second batch Ulva. At the end of the growth trial, significant reductions of biomass, mean weight, weight gain as well as survival of the shrimp were observed (Table 1). The second trial evaluated four diets supplemented with high inclusion of three batches Ulva meal formulated on equal digestible protein basis. Significant decreased growth and survival were detected in the treatment contain Ulva meal from second batch. The results of this work indicate that besides low nutrient availability other problems such as high mineral contents, anti-nutritional factors as well as processing methods of Ulva meal may result in poor replacement for FM and SBM by Ulva meal.