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)
D. Lemos et al.rAquaculture 186 (2000 89–105 99

Fig. 5. Digestive proteinases from the hepatopancreas of some penaeid species in substrate-SDS-PAGE.
1sMolecular weight markers, 2s F. californiensis,3s L. Õannamei,4s F. paulensis, and 5s L. schmitti.

southern Brazil has decreased drastically because of the lack of adequate feeds to sustain
profitable production ŽBeltrame, personal communication .
.
Nutritional background is an important issue for the choice of shrimp feeds ŽAkiyama
et al., 1992; Lee and Lawrence, 1997 .. Some regionally available feed ingredients as
plant seed and fish meals may be an inexpensive source of protein for diet formulation.
However, these ingredients may contain antinutritional factors that inhibit digestive
˜
enzyme activity, decreasing growth rates ŽGarcia-Carreno, 1996 , or may be of poor
.
˜
quality because of the handling and processing of the raw material ŽGarcia-Carreno,
1998 .. The proteinaceous proteinase inhibitor from soybean soybean trypsin inhibitor
Ž
wSBTI x. can be detected and characterized by substrate-SDS-PAGE Fig. 6 . The
Ž
.
inhibition of trypsin activity seems to be proportional to the amount of SBTI assayed.
This inhibitor can reduce trypsin activity and weight gain in the Atlantic salmon in a
dose-dependent manner ŽOlli et al., 1994 . Meals made from some legume seeds also
.
seem to inhibit the degree of protein hydrolysis by the digestive gland extract of F.
californiensis and L. Õannamei ŽGarcia-Carreno et al., 1997 . Measuring the DH by the
˜
.
digestive enzymes helps to assess the potential digestibility of a particular feedstuff
ŽDimes et al., 1994 . The in vitro results of DH should positively correlate with in vivo
.
measurements of APD in order to validate the method ŽLee and Lawrence, 1997;
Ezquerra et al., 1998 .. The DH by the pH-stat method of some feed ingredients by L.
Õannamei digestive gland extract may vary from 23.2% Žtuna waste meal to 33.99%
.
Ždeboned white fish meal Table 2 . The low digestibility of some fish meals has been
. Ž
.
attributed to excessive heat treatment which reduces the nutritional value of dietary
˜
protein by causing cross-linking reactions or amino acid racemization ŽGarcia-Carreno,
1996, 1998; Ezquerra et al., 1997b .. In vitro measurements of the DH of some prepared