Ž .
Aquaculture 194 2001 161–171 www.elsevier.nlrlocateraqua-online
Influence of dietary recombinant microbial lipase on performance and quality characteristics of
rainbow trout, Oncorhynchus mykiss
Troels Samuelsen
a
, Mai Isaksen
b
, Ewen McLean
a,
a
Aalborg UniÕersity, Aquaculture Section, SohngaardsholmsÕej 57, DK-9000 Aalborg, Denmark
b
Danisco Cultor, Edwin Rahrs Vej 38, DK-8220 Brabrand, Denmark Received 26 April 2000; received in revised form 11 September 2000; accepted 11 September 2000
Abstract
In order to assess whether supplementary lipase affected growth and body composition of trout, Ž .
Ž
y1
. Ž . Ž
four diets were produced, consisting of A feed containing high 2083 mg kg , B low 208.3
y1
. Ž .
Ž .
Ž
y1
. Ž .
mg kg concentrations of lipase, C heat-treated inactivated lipase 2083 mg kg
, and D a Ž
basal control diet. Rainbow trout n s 40rtank; initial wt. 23.22 4.81 g; length 124.7 6.35 .
mm were fed, according to commercial feed tables, 6 daysrweek for 202 days. Retained activity Ž
. of supplemental lipase was verified by monitoring free fatty acid appearance FAA , which was
Ž .
Ž .
significantly higher P - 0.05 in treated feed and oil. Lipase addition had no effect P 0.05 on growth, fillet proximate composition, hepatosomatic, cardiac, or gut indices, and carcass percent-
age. However, lipase supplementation influenced the mono-unsaturated fatty acid profiles of the Ž
. fillet P - 0.05 . q 2001 Elsevier Science B.V. All rights reserved.
Keywords: Diet; Fillet composition; Lipase; Trout; Quality
1. Introduction
Ž .
Contemporary diets, augmented with hydrolytic exo enzymes assist digestion and absorption of low-grade ingredients, permit earlier weaning, and enhance growth and
Corresponding author. Present address: Department of Fisheries Science and Technology, College of Agriculture, Sultan Qaboos University, P.O. Box 34, Al-Khod 123, Sultanate of Oman. Tel.: q968-51-51-91;
fax: q968-51-34-18. Ž
. E-mail address: mcleansqu.edu.om E. McLean .
0044-8486r01r - see front matter q 2001 Elsevier Science B.V. All rights reserved. Ž
. PII: S 0 0 4 4 - 8 4 8 6 0 0 0 0 5 1 9 - 6
Ž . Ž
. feed conversion ratios FCR
Conneely, 1992; Lyons, 1992; Ritz et al., 1995 . Addition Ž .
of phytase to monogastric feeds has led to improvements in FCR and phosphorus P Ž
utilization and, hence, to a reduction in environmental pollution Cantor and Perney, .
1992; Walsh et al., 1993 . Since similar production and environmental concerns are associated with aquaculture, a natural progression in the field of dietary enzyme
supplementation will likely follow with aquafeeds. A number of studies have already been undertaken in this field. Two areas of particular interest to aquaculture include the
use of exoenzymes in larval feeds to assist weaning, and addition of phytase to plant protein-based grower diets in efforts to enhance P availability and reduce environmental
loading.
Several other enzymes have been used experimentally as additives in aquafeeds. Ž
. Although without success, Rodger et al. 1995 incorporated mammalian pancreatic
Ž .
enzymes 4 grkg into Atlantic salmon diets in an attempt to treat fish for pancreas Ž
disease. Addition of a-amylase to salmon diets did not improve performance Carter et .
al., 1992 , but mixed proteasercarbohydrase preparations, when added to a soybean Ž
. meal-based diet, increased appetite and growth and enhanced FCR Carter et al., 1994 .
Enzymatic pre-treatment of feeds has also been evaluated as a strategy for enhancing FCR and growth. Thus, exposure of soybean residue to papain was reported to improve
Ž .
growth of common carp Wong et al., 1996 , while increased growth and whole body protein levels were recorded in fingerlings fed diets treated with a mixture of enzymes
Žamylase, protease, b-glucanase, b-glucosidase and cellulase: 1.5 grkg; Bogut et al., .
1994 . Acyl hydrolases or lipases are present in various fish tissues, including the gut
Ž .
Smith, 1989 . In rainbow trout, lipases express fatty acid specificity, hydrolysing Ž
triacylglycerols containing C18:1 n y 9 in preference to C16:0 Henderson and Tocher, .
1987 . In fish, no correlation or adaptive response to lipase activity appears to exist with Ž
. feed lipid content or increased lipid intake Kuz’mina and Gelman, 1997 . This latter
observation is of relevance since lipid levels in currently available aquafeeds, especially those for salmonids, have increased dramatically over the last five years. Commonly,
lipids represent 30 of salmonid diets, with approximately 80 in the form of
Ž .
triglycerides, with 1–2 being free fatty acids Rasmussen et al., 2000 . Even though these so-called ‘high energy’ aquafeeds are associated with deterioration in flesh quality
Ž .
Andersen et al., 1997; Bell et al., 1998; Eckhoff et al., 1998 their use will likely increase due to the benefits they provide, including enhanced FCR and decreased P
Ž .
loading Alsted, 1991 . Methods that might neutralize the negative aspects of high-en- ergy feeds, or enhance their utility are, thus, deserved of attention. Only one study has
Ž .
examined the effect of adding lipase to aquafeed. Koven et al. 1993 considered the effects of supplemental lecithin and lipase on tissue fatty acid incorporation in gilthead
sea bream as a function of age. These authors reported a marked effect of lecithinrlipase supplementation upon tissue fatty acid profiles in animals of - 32 days post-hatch. The
study of Koven et al., therefore, indicates that lipase addition might modify the kinetics of lipid absorption and utilization in teleosts. However, their findings need to be
confirmed in larger animals. Accordingly, the objective of the present study was to examine whether pre-treatment of high-energy diets with lipase altered production and
performance characteristics of rainbow trout.
2. Materials and methods
