Digestive Enzyme Activity and Assimilation Efficiency in Pleoticus muelleri (Bate)

FENUCCI, JORGE LINO; FERNÁNDEZ GIMENEZ, ANALIA VERÓNICA; DÍAZ, ANA CRISTINA; VELURTAS, SUSANA MARIA

Veracruz, México

Congreso; World Aquaculture 2009; 2009

World Aquaculture Society

DIGESTIVE ENZYME ACTIVITY AND ASSIMILATION EFFICIENCY IN PLEOTICUS MUELLERI (BATE)                           Fenucci, J.L.*, Fernández Gimenez, A.V., Díaz, A.C. and Velurtas, S.M.   Facultad de Ciencias Exactas y Naturales, Universidad Nacional de Mar del Plata, CONICET, Funes 3350, B7602AYL, Mar del Plata, Argentina. jfenucci@mdp.edu.ar   The red shrimp Pleoticus muelleri has aroused great interest on account of its potential use in culture in temperate areas. The main obstacles to culture this penaeoid species are the nutritional requirements and selection of an appropriate protein source for cost reduction. The relationship between protein source, size, digestibility, and proteinase enzyme activity of shrimp P. muelleri were evaluated under experimental conditions. Two isoproteic formulated feeds were designed with different protein sources and 0.25% chromic oxide: D1 containing 48% fish meal and D2 with meat and bone meal partially replacing fish meal. Two size groups (3g and 8g) were obtained from a commercial fisherman and held in 150 l glass aquaria (33‰ salinity, 18°C, pH 7, 11:14 h photoperiod). Each feed was tested in three replicate groups of 8 prawns during three weeks. To determine the apparent digestibility for crude protein, feces were collected by siphoning. The chromic oxide levels in diets and feces were analyzed using a colorimetric method. At the end of experiment midgut glands were dissected and pooled for treatment. The protein content and specific proteinase activity were determined using three replicates of enzyme extracts. To evaluate the contribution of individual proteinases to the total activity, each sample was incubated with specific inhibitors and the residual activity was evaluated. Classes of proteinase were identified by SDS-PAGE, specific inhibitors for trypsin (TLCK), chymotrypsin (PMSF) and serin proteinases (SBTI) were used. Shrimp fed D1 exhibited higher protein digestibility and lower specific proteinase activity than shrimp fed D2 in both sizes. Small size showed better protein digestibility of D1. Proteinase activity in all samples was inhibited, without significant differences (Table I). Protein and activity bands were compared by SDS-PAGE and common patterns were observed. Five active bands distributed from 17.46 to 21.9 kDa were detected; three trypsins (17.4, 19.1, 20.0 kDa) and one chymotrypsin (21.9 kDa) were found. TABLE I. Digestibility coefficient, protein content, specific activity and effects of inhibitors in midgut gland of P. muelleri. Treatment Digestibility coefficient* Protein content** Specific activity*** Percentage inhibition*         TLCK SBTI PMSF Wild   1.6±0.69a 0.7±0.56a 54.0±17.0a 63.0±0.83a 42.0±0.01a D1-3g 92.6±0.27a 1.6±0.38a 2.5±0.37b 50.1±6.20a 50.0±5.90a 47.0±0.01a D2-3g 47.8±3.78b 0.4±0.17a 3.6±1.12c 70.4±17.2a 80.0±0.01a 43.0±17.6a D1-8g 69.9±3.61c 2.7±1.25a 1.2±0.16d 39.0±2.10a 46.0±7.30a 60.0±0.01a D2-8g 47.5±1.13b 0.7±0.01a 3.6±0.54c 77.9±6.90a 54.0±4.70a 38.0±7.60a Values are means ± standard error of triplicates. Percentages with similar superscripts are not significantly different (P<0.05). *%: **mg/ml; ***Abs/min/mg protein According to these results shrimp weighing more than 8g could be fed diets containing meat and bone meal thereby reducing feed costs in the later stages of intensive culture. More research is needed to determine the optimal inclusion level of this protein source in feed, and to assess their effect on shrimp survival and growth.