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APARENT DIGESTIBILITY OF SELECTED FEED INGREDIENTS IN FORMULATED DIETS FOR JUVENILE TOTOABA Totoaba macdonaldi

 Jorge Madrid* and J. P. Lazo
 
Centro de Investigación Científica y de Educación Superior de Ensenada, B.C.  
Carretera Tijuana-Ensenada. Numero 3918. Zona playitas. C.P. 22860
jmadrid@cicese.edu.mx

The Totoaba (Totoaba macdonaldi) is the largest member of the Sciaenidae family, reaching lengths of up to 2 meters and weights over 100 kilos. It is an endemic species from the Gulf of California that has been over-fished to the brink of extinction. It is considered a good candidate for aquaculture due to its high growth rate, good survival and high commercial value. Several farms in the North of Mexico are currently evaluating the potential of this species under commercial conditions.

To date very little information has been published evaluating Totoaba's nutritional requirements. Recent studies suggest high protein (>50% P) with low lipid (<10% L) requirement and an adequate E:P ratio (9.46 kcal / g protein). However, to develop sustainable aquaculture of this species it is necessary to lower the feed costs and develop efficient feeds, utilizing renewable low cost ingredients, and formulating feeds to meet the requirement of the species of interest.

Proteins are the most important nutrient in aquatic feeds because they provide the essential amino acids needed for many vital metabolic processes and muscle growth. Additionally, proteins dramatically impact final production costs due to their high price and the relatively high protein requirement of marine fish. There are several biological and chemical indices to evaluate the quality of potential protein sources. Amino acid profile and digestibility are among the most important. Currently several methods are commonly used to evaluate protein digestibility, were the most reliable is to determine the digestibility in vivo.

Therefore, the objectives of the present study were to evaluate the apparent dry matter, protein and amino acid digestibility coefficients of several protein sources. High quality fish meal, soy-protein concentrate, soybean meal, high and low quality poultry by product meal, feather meal, meat and bone meal and corn meal. A reference diet was formulated to contain 45% protein and 10% lipid using fish meal as the main protein source. Seven test diets were formulated by substituting 30% of the reference diet with each of the protein sources. Three replicate tanks were used for each protein source evaluated. Five juvenile totoaba with mean weight 530 g were stock in each of experimental tanks. Feces collection was done by siphoning the feces after 2 h of each feeding period. Acid-insoluble ash was used as the indirect marker to determine digestibility values of the diets and ingredients. Preliminary results suggest protein sources have good digestibility values in this species with significant differences among them. Final results will be presented and discussed.

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