In vitro digestibility of locally available feedstuffs for white shrimp Penaeus indicus

An in vitro method of determining protein digestibility was modified for application in white shrimps. The protein digestibility of 21 locally available feedstuffs were determined. Vitamin-free casein was used as reference protein. To verify in vitro results, a feeding experiment was conducted using 300 shrimps with average initial weight of 0.075 g. The shrimps were fed isonitrogenous and isocaloric diets containing test ingredients with high (27.6% -33.7%) and low (4.0%-10.5%) digestibility for 61 days. Seawater temperature ranged from 26 to 29°C and salinity from 30 to 33 ppt. Defatted soybean meal (27.2% digestibility) was used as control. Growth and survival were determined. Animal proteins (40.9%-90.9%) were more digestible than plant proteins (0.0%-33.7%), although digestibility of papaya leaf meal (33.7%) was comparable with those of shrimp head meal (40.9%) and Peruvian fish meal (40.7%). Green mungbean meal was most digestible (27.6%) among the legumes. Protein digestibility of defatted soybean meal (27.2%) was significantly higher than that of unprocessed soybean meal (9.4%). Black cowpea meal and ricebean meal were not digestible. Results also showed that white shrimps given a diet containing cassava leaves performed best with weight gain, specific growth rate, and survival (706.4%, 3.44 and 49%) comparable with white cowpea meal (701.3%, 3.35 and 40%) and defatted soybean meal (726.8%,3.50 and 33%), followed by papaya leaf meal (505%, 3.02 and 38%). Shrimps fed a diet containing green mungbean meal showed the poorest response (344.2%, 2.46 and 18%). These results indicate that in vitro protein digestibility is not correlated with growth and survival. The amino acid pattern, anti-nutritional factors, and palatibility of the diets are other important factors that may influence the growth of P. indicus.