Comparative study of in vivo and in vitro methods in determining protein digestibility of feeds for bagrid catfish, mystus nemurus
Loading...
Date
2008-04
Authors
Syed Muhammad, Sharifah Rahmah
Journal Title
Journal ISSN
Volume Title
Publisher
Abstract
The reliability study of the in vitro methods in relation to the in vivo method was
conducted to assess the protein digestibility of experimental diets formulated at 35%
protein and 15% lipid with 0 to 60% increasing protein substitution of fishmeal by
soybean meal for bagrid catfish, Mystus nemurus. As a part of this study, biochemical
assays showed optimum protease activity at pH 2.0 and 9.0 in the stomach and
intestiness respectively. Protease activity of post feeding study in the stomach and
intestines were highest at 2 and 5 hours accordingly. Pepsin was observed in the
stomach while serine proteases were more dominant in the intestines, followed by
trypsin, metalloproteases and chymotrypsin. Characterization of crude intestinal extract
of M nemurus via SDS-PAGE using commercial specific protease inhibitors revealed
eight alkaline proteases with molecular weights between 8.4 and 56.9 kDa. Prior to
formulation of experimental diets, in vitro protein digestibility of feedstuffs was
assessed using pH stat, pH drop, spectrophotometric assay and SDS-PAGE methods. pH
stat and pH drop methods revealed a decreasing order of respective Degree of
Hydrolysis (DH) and Relative Protein Digestibility (RPD) with fishmeal (FM) >
soybean meal (SBM) > squid meal (SM) > raw soybean meal (RSBM) using all enzyme
systems. However, RPD for pH drop method using Lazo 1-enzyme system showed FM
> SM > SBM > RSBM. Saterlee 4-enzyme system revealed the highest DH and RPD
values for all feedstuffs followed by the crude intestinal enzyme extract of M nemurus,
Hsu 3-enzyme and Lazo 1-enzyme system. In vitro spectrophotometric assay and SDSPAGE
demonstrated that crude intestinal enzyme extracts of M nemurus were inhibited
the highest by RSBM followed by SM, SBM and FM. Zymogram from SDS-PAGE
showed that preincubation of RSBM with crude intestinal enzyme extract of M
nemurus resulted in 3 reduced and 5 disappeared protease bands. Overall, protein
digestibility of experimental diets using in vivo and in vitro methods decreased as SBM
protein substitution level increased while percentage of inhibition increased as SBM
protein substitution level increased. The highest tolerance level of SBM protein
substitution for M nemurus was up to 1 0% which was determined using the in vivo
method. pH stat and pH drop methods showed the highest DH and RPD using Saterlee
4-enzyme system followed by crude intestinal enzyme extract of M nemurus, Hsu 3-
enzyme and Lazo 1-enzyme system. The highest correlation of the in vitro methods with
the in vivo method was obtained using spectrophotometric assay followed by pH stat,
SDS-PAGE and pH drop although no significant differences were observed among the
in vitro methods.
Description
Keywords
Determining protein digestibility , Bagrid catfish, mystus nemurus