697
includes natural plant products, immunostimulants, vitamins and micro-organisms.
The outcome of the work, which has been summarized, in earlier chapters, is that
the addition of comparatively small amounts of these products to fi sh feed leads to
statistically signifi cant improvements in growth, including feed conversions, nonspecifi c immunostimulation particularly of innate and cellular immune parameters,
e.g. increases in phagocytic activity, and health benefi ts in terms of protection
against challenge by specifi ed pathogens within a fairly small timespan, i.e. positive
effects may be observed within 1–2 weeks of the fi rst application of the product. In
addition, there have been indications of non-specifi c health benefi ts, such as an
increase in vigour and an absence of background levels of fi n/tail rot. For example,
ß-glucans, which may be obtained from the yeast Saccharomyces cerevisiae , when
administered to carp led to signifi cantly increased leucocyte populations, enhanced
proportions of neutrophils and monocytes, and elevated superoxide anion production by kidney macrophages (Selvaraj et al. 2005 ). Moreover, spray-dried, heterotrophically grown preparations of the unicellular alga Tetraselmis suecica have been
accredited with antimicrobial activity and possibly immunostimulatory activity
when used as dietary supplements (Austin et al. 1992a ). Similarly, the yeast
Debaryomyces hansenii was immunostimulatory when fed for 4 weeks at 10
6 CFU/g
to leopard grouper ( Mycteroperca rosacea ) (Reyes-Becerril et al. 2008 ).
The list of immunostimulatory compounds is extensive, and includes those
which have often been applied by i.p. injection, i.e. Batpamum, chitin, dimerised
lysozyme, ß-1,3 glucans, killed cells of mycobacteria, laminaran, sulphated laminaran, lactoferrin, levamisole, LPS, oligosaccharides, Prolactin and synthetic peptides
(Dalmo and Seljelid 1995 ; Yoshida et al. 1995 ; Ortega et al. 1996 ; Siwicki et al.
1998 ; Sakai 1999 ). Initially, Olivier et al. ( 1985a , b ) observed that administration of
killed cells of mycobacteria enhanced resistance in coho salmon to various bacteria.
However, considerable interest has been directed towards the potential for ß-1,3
glucans, which are often included as one of the ingredients in fi sh feed. An extensive literature points to the success of glucans in preventing disease (Yano et al.
1989 ; Raa et al. 1990 ; Robertsen et al. 1990 ; Nikl et al. 1991 ; Matsuyama et al.
1992 ; Chen and Ainsworth 1992 ). Thus, it has been recognised that ß-glucans
enhance the non-specifi c resistance to disease, including pasteurellosis (Couso et al.
2003 ), ERM, Hitra disease and vibriosis, by immunostimulation (Robertsen et al.
1990 ; Kumari and Sahoo 2006 ). Matsuyama et al. ( 1992 ) used the glucans schizophyllan and scleroglucan to protect against streptococci. Thus, 2–10 mg of glucans/
kg of fi sh when administered by i.p. injection, enhanced resistance of yellowtail to
streptococcicosis. In particular, there was an elevation of serum complement and
lysozyme, and an increase in phagocytic activity of pronephros cells. Initially, success only appeared to result from injection of the glucans into fi sh. Yet, claims have
now been made that application via food also meets with success (Onarheim 1992 ).
Also, resistance to streptococcicosis and vibriosis has been enhanced following the
oral administration of peptidoglycan from Bifi dobacterium (Itami et al. 1996 ) and
Cl. butyricum (Sakai et al. 1995 ), respectively.
Farmed Fish
includes natural plant products, immunostimulants, vitamins and micro-organisms.
The outcome of the work, which has been summarized, in earlier chapters, is that
the addition of comparatively small amounts of these products to fi sh feed leads to
statistically signifi cant improvements in growth, including feed conversions, nonspecifi c immunostimulation particularly of innate and cellular immune parameters,
e.g. increases in phagocytic activity, and health benefi ts in terms of protection
against challenge by specifi ed pathogens within a fairly small timespan, i.e. positive
effects may be observed within 1–2 weeks of the fi rst application of the product. In
addition, there have been indications of non-specifi c health benefi ts, such as an
increase in vigour and an absence of background levels of fi n/tail rot. For example,
ß-glucans, which may be obtained from the yeast Saccharomyces cerevisiae , when
administered to carp led to signifi cantly increased leucocyte populations, enhanced
proportions of neutrophils and monocytes, and elevated superoxide anion production by kidney macrophages (Selvaraj et al. 2005 ). Moreover, spray-dried, heterotrophically grown preparations of the unicellular alga Tetraselmis suecica have been
accredited with antimicrobial activity and possibly immunostimulatory activity
when used as dietary supplements (Austin et al. 1992a ). Similarly, the yeast
Debaryomyces hansenii was immunostimulatory when fed for 4 weeks at 10
6 CFU/g
to leopard grouper ( Mycteroperca rosacea ) (Reyes-Becerril et al. 2008 ).
The list of immunostimulatory compounds is extensive, and includes those
which have often been applied by i.p. injection, i.e. Batpamum, chitin, dimerised
lysozyme, ß-1,3 glucans, killed cells of mycobacteria, laminaran, sulphated laminaran, lactoferrin, levamisole, LPS, oligosaccharides, Prolactin and synthetic peptides
(Dalmo and Seljelid 1995 ; Yoshida et al. 1995 ; Ortega et al. 1996 ; Siwicki et al.
1998 ; Sakai 1999 ). Initially, Olivier et al. ( 1985a , b ) observed that administration of
killed cells of mycobacteria enhanced resistance in coho salmon to various bacteria.
However, considerable interest has been directed towards the potential for ß-1,3
glucans, which are often included as one of the ingredients in fi sh feed. An extensive literature points to the success of glucans in preventing disease (Yano et al.
1989 ; Raa et al. 1990 ; Robertsen et al. 1990 ; Nikl et al. 1991 ; Matsuyama et al.
1992 ; Chen and Ainsworth 1992 ). Thus, it has been recognised that ß-glucans
enhance the non-specifi c resistance to disease, including pasteurellosis (Couso et al.
2003 ), ERM, Hitra disease and vibriosis, by immunostimulation (Robertsen et al.
1990 ; Kumari and Sahoo 2006 ). Matsuyama et al. ( 1992 ) used the glucans schizophyllan and scleroglucan to protect against streptococci. Thus, 2–10 mg of glucans/
kg of fi sh when administered by i.p. injection, enhanced resistance of yellowtail to
streptococcicosis. In particular, there was an elevation of serum complement and
lysozyme, and an increase in phagocytic activity of pronephros cells. Initially, success only appeared to result from injection of the glucans into fi sh. Yet, claims have
now been made that application via food also meets with success (Onarheim 1992 ).
Also, resistance to streptococcicosis and vibriosis has been enhanced following the
oral administration of peptidoglycan from Bifi dobacterium (Itami et al. 1996 ) and
Cl. butyricum (Sakai et al. 1995 ), respectively.
Farmed Fish