Correlation
between dietary lipid:protein ratios and plasma growth and thyroid hormone
levels in juvenile Arctic charr, Salvelinus alpinus (Linnaeus)
C. Cameron, R. Gurure, K. Reddy, R.
Moccia, J. Leatherland-2002
Aquaculture
Research, 33(6):
383-394
Abstract:
Sexually immature Arctic charr, Salvelinus
alpinus (Linnaeus), were fed one of five isoenergetic practical diets of
differing lipid:protein ratios (0.98, 0.67, 0.41, 0.26, 0.19) for an 84-day
period to examine the influence of diet composition on growth, and growth
hormone (GH) and thyroid hormone physiology. All five diets supported growth
at approximately the same rate, but the diet with a lipid:protein ratio of
0.98 had the lowest weight gain and highest food conversion ratios. A GH
enzyme-linked immunosorbent assay (ELISA), developed for use with
oncorhynchid fishes, was validated for use with Arctic charr. Plasma GH
concentrations were significantly higher in fish fed the diet with a
lipid:protein ratio of 0.98, and there were significant direct and inverse
correlations between plasma GH levels and dietary lipid and protein content
respectively. There were no significant differences in pre- and
post-prandial plasma GH concentrations for any group. There were significant
post-prandial elevations of plasma triiodothyronine (T3) and
thyroxine (T4) for fish fed the lower lipid:protein ratio diets,
but there were no differences related to the diets. The results are
discussed in terms of GH as a factor in the regulation of lipid and protein
homeostasis in fishes.
(Department of Biomedical Sciences,
Ontario Veterinary College, University of Guelph, Guelph, ON, N1G 2W1,
Canada. E-mail of J.F. Leatherland: jleather@ovc.uoguelph.ca)