Apparent digestibility of differently processed grain legumes, cow pea and mung bean in black tiger shrimp, Penaeus monodon Fabricius and associated histological anomalies in hepatopancreas and midgut

Experiments were conducted to test the effect different treatment process like dehulling, soaking, autoclaving, germination and germination in combination with autoclaving on proximate composition and antinutritional factors (ANFs) of legume seeds, cow pea and mung bean. An in vivo digestibility trial was conducted in black tiger shrimp Penaeus monodon to determine the coefficient of total tract apparent digestibility (CTTAD) of differently processed legume seeds. The CTTADs were determined by comparing the concentrations of digestibility marker (Cr2O3) in the feed and faeces of the juvenile shrimp (4 ± 0.5 g). Seeds processed by germination in combination with autoclaving were low in ANFs and higher in proximate composition with increased protein contents of 18.3 and 15.6% in cow pea and mung bean, respectively. Though trypsin inhibitor activity was significantly (P<0.05) high in germinated seeds, there was a significant reduction by 83.3 and 81.21% on germination followed by autoclaving. Due to unexpected mortality of shrimp, dietary treatments containing raw, soaked, and germinated cow pea and mung bean were removed from the trial. There was a significant difference (P<0.05) in the CTTAD values between the feedstuffs and various treatment processes made. Higher CTTAD dry matter (DM), crude protein (CP) and nitrogen free extract (NFE) were obtained with seeds processed with germination in combination with autoclaving and the trend is similar in both the seeds tested. CTTAD for DM, CP and crude lipid of the grain legumes ranged between 0.683–0.885, 0.684–0.834 and 0.704–1.302, respectively. Histological examinations on hepatopancreas and midgut of shrimp sampled at slaughter revealed some common anomalies. With the exception of the shrimp fed dehulled cowpea, histology was normal in all the shrimps sampled at the end of the digestibility trial.