Thyroidal compensation in rainbow trout (Salmo gairdneri) fed canola meal
- 41 Downloads
Rainbow trout (Salmo gairdneri Richardson) were fed either a soybean mealbased (SM) or canola meal-based (CM) diet for up to 20 weeks. Plasma thyroxine (T4) and triiodothryonine (T3) levels were significantly lower in the CM-fed fish sampled after 12 weeks. However, there appeared to be some compensation after 12 and 20 weeks in that the thyroid hormone levels in trout fed the CM were not significantly different from those of the SM-fed fish. Nevertheless, there was marked thyroid hyperplasia and hypertrophy in the CM-fed fish sampled at 12, 16 and 20 weeks after commencement of the experiment. Moreover, the growth rate was significantly lower in the CM-fed fish in comparison to the SM-fed fish throughout the 20 week study period.
Plasma T4 levels were similar in SM-fed fish sampled 12, 16 and 20 weeks after commencement of the experiment, but plasma T3 levels progressively increased over this period, as did the apparent activity of the thyroid tissue based on histological criteria.
Fasting for up to 8 weeks resulted in the arrested growth of the SM-fed fish, and a loss in body weight of the CM-fed animals over the 8 week period of the fast. In addition, the plasma thyroid hormone levels in the fasted fish tended to be lower than in fish fed both the SM and CM diets prior to fasting, and there was histological evidence indicating a reduced activity of the pituitary-thyroid axis. However, thyroid hyperplasia and hypertrophy were still evident in the fasted fish previously fed the CM diet indicating that the adverse affects of CM diets are not completely reversible after 8 weeks.
In fish fed the CM diet for 12 weeks and then the SM diet for up to a further 8 weeks (diet C-S) there was a compensatory increase in plasma thyroid hormone levels evident within 4 weeks after the change in diet, but no apparent decrease in thyroid hyperplasia or hypertrophy. In addition, in the fish fed the C-S diet there was a marked compensatory growth rate, and an increased feed: gain ratio; body weights of this group of fish were not significantly different from those of the SM-fed animals after 20 weeks of study, indicating a considerably higher growth rate over the last 8 week period.
Keywordscanola meal rainbow trout glucosinolates thyroid hormones growth thyroid histology adaptation compensatory growth
Unable to display preview. Download preview PDF.
- Dabrowski, K., Evans, R., Czarnocki, J. and Kozlowska, H. 1982. Rapeseed meal in the diet of common carp reared in heated waters. IV. Iodide (125I) accumulation and thyroid histology. Z. Tierphysiol. Tierern. Furterm. 48: 1–9.Google Scholar
- Eales, J.G. 1979. Thyroid functions in cyclostomes and fishesIn Hormones and Evolution, Vol. 1. pp. 341–346. Edited by E.J.W. Barrington, Academic Press, New York.Google Scholar
- Eales, J.G. 1985. The peripheral metabolism of thyroid hormones and regulation of thyroidal status in poikilotherms. Can. J. Zool. 63: 1217–1231.Google Scholar
- Hardy, R.W. and Sullivan, C.V. 1983. Canola meal in rainbow trout (Salmo gairdneri) production diets. Can J. Fish. Aquat. Sci. 40: 281–286.Google Scholar
- Higgs, D.A., Fagerlund, U.H.M., McBride, J.R., Plotnikoff, M.D., Dosanjh, B.S., Markert, J.R. and Davidson, B.J. 1983. Protein quality of Altex canola meal for juvenile chinook salmon (Oncorhynchus tshawytscha) considering dietary protein and 3,5,3′-triiodo-L-thyronine content. Aquaculture 34: 213–238.Google Scholar
- Hilton, J.W. and Slinger, S.J. 1981. Nutrition and feeding of rainbow trout. Can. Spec. Pub. Fish. Aq. Sci. 55: 1–15.Google Scholar
- Hilton, J.W. and Slinger, S.J. 1986. The digestibility and utilization of canola meal in practical-type diets for rainbow trout. Can. J. Fish. Aquat. Sci. 43: 1149–1155.Google Scholar
- Horwitz, W. 1980. Official Methods of Analysis of the Association of Analytical Chemists. Thirteenth Edition. AOAC, Washington, D.C. 20044Google Scholar
- Leatherland, J.F. 1985. Studies of the correlation between stress-response, osmoregulation and thyroid physiology in rainbow trout,Salmo gairdneri (Richardson). Comp. Biochem. Physiol. 80A: 523–531.Google Scholar
- Leatherland, J.F. and Sonstegard, R.A. 1980. Seasonal changes in thyroid hyperplasia, serum thyroid hormone and lipid concentrations, and pituitary gland structure in Lake Ontario coho salmon,Oncorhynchus kisutch Walbaum and a comparison with coho salmon from Lakes Michigan and Eric. J. Fish Biol. 16: 539–562.Google Scholar
- Leatherland, J.F., Hilton J.W. and Slinger, S.J. 1987. Effects of thyroid hormone supplementation of canola-meal based diets on growth, and interrenal and thyroid physiology of rainbow trout (Salmo gairdneri) Fish Physiol. Biochem. 3: 73–82.Google Scholar
- Steel, R.G.D. and Torrie, J.H. 1980. Principles and Procedures of Statistics. McGraw-Hill, Toronto.Google Scholar
- Yurkowski, M., Bailey, J.K., Evans, R.E., Tabachek, J.A.L. and Ayles, G.B. 1978. Acceptability of rapeseed proteins in diets of rainbow trout (Salmo gairdneri). J. Fish. Res. Board. Can. 35: 951–962.Google Scholar