Effect of different processing techniques on the nutritive value of grass pea, Lathyrus sativus L., seed meal in compound diets for Indian major carp rohu, Labeo rohita (Hamilton), fingerlings

Abstract

Six isonitrogenous (35% crude protein approximately) and isocaloric (16.73 kJ g-1 approximately) diets incorporating processed grass pea, Lathyrus sativus L., seed meal at a 30% level by weight into a fish meal – based control diet were fed to rohu, Labeo rohita (Hamilton) fingerlings (average initial body weight 3.18 ± 0.11 g) in triplicate treatments at the rate of 3% of body weight daily for 80 days, and fish performance was studied. Four processing methods, namely fermentation, extrusion, autoclaving, and germination, were employed prior to the incorporation of the grass pea seed meal into the diets. The fermentation of grass pea seed meal was effective in significantly reducing the anti-nutritional factors, tannins, phytic acid, and the neurotoxin â-ODAP (â-oxalyl-diaminopropionic acid). The extrusion of grass pea seed was effective in significantly reducing tannins, trypsin inhibitor, and the neurotoxin â-ODAP. Autoclaving the grass pea seed meal resulted in the reduction of tannins but was not effective in reducing other anti-nutritional factors. The level of trypsin inhibitor was reduced to non-detectable limits in germinated grass pea seeds. The tannin content was also reduced considerably in the germinated grass pea seed meal. In terms of growth response, feed conversion ratio, and protein efficiency ratio, 30% fermented, extruded, and germinated grass pea seed meal incorporated diets resulted in significantly (P < 0.05) the best performance of rohu fingerlings. The apparent protein digestibility (APD) values obtained with processed grass pea seed meal were significantly higher as compared to those with raw seed meal incorporated diets (P < 0.05). The accumulation of carcass protein was comparatively higher in the groups of fish reared on diets containing 30% autoclaved, germinated, and extruded grass pea seed meal. The results of this study indicate that processing grass pea seed meal is effective in improving the nutritive value of L. sativus seed meal and that the processed grass pea seed meal can be incorporated into rohu diets up to a 30% level without any adverse effect.

CORRESPONDING AUTHOR:

Arun Kumar Ray, Fisheries Laboratory, Department of Zoology, Visva-Bharati University, Santiniketan 731 235, West Bengal, India, Tel./Fax: +91 3463 261268; e-mail: arun_ray1@rediffmail.com