Response of the somatotropic axis of juvenile coho salmon to alterations in plane of nutrition with an analysis of the relationships among growth rate and circulating IGF-I and 41 kDa IGFBP.
The effect of different feeding levels on plasma levels of insulin-like growth factor-I (IGF-I), 41 kDa insulin-like growth factor binding protein (41 kDa IGFBP), and growth hormone (GH) were assessed in post-smolt coho salmon. Fish were fed at either stable (1 and 2% body weight/day) or varying (1-0.5-1%, 2-0.5-2% body weight/day) feeding rates and plasma was sampled from 10 fish/treatment at 2-3 week intervals over five dates from June to September, resulting in a total of 200 samples. Fish fed at higher rates grew faster and had higher plasma IGF-I and 41 kDa IGFBP levels. Plasma GH levels were variable but generally showed an inverse relationship to feeding rate. Both plasma IGF-I and 41 kDa IGFBP increased seasonally, average IGF-I levels doubled from June to September, regardless of feeding rate. On any one date both IGF-I and 41 kDa IGFBP were highly related to growth rate with regression coefficients ranging from 0.36 to 0.68 (IGF-I) and from 0.33 to 0.70 (41 kDa IGFBP). No relationship was found between IGF-I:41 kDa IGFBP ratio and individual growth rate. Overall, both feeding rate and date were important in explaining variation in IGF-I and 41 kDa IGFBP levels.
Beckman
Brian R
BR
F/NWC2, Integrative Fish Biology Program, National Marine Fisheries Service, Seattle, WA 98112, USA. Brian.Beckman@noaa.gov
Shimizu
Munetaka
M
Gadberry
Brad A
BA
Cooper
Kathleen A
KA
D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D001699:Biometry; D005260:Female; D013006:Growth Hormone / Q000097:blood / Q000378:metabolism*; D018972:Insulin-Like Growth Factor Binding Protein 3 / Q000097:blood / Q000378:metabolism*; D007334:Insulin-Like Growth Factor I / Q000032:analysis / Q000378:metabolism*; D008297:Male; D017684:Oncorhynchus kisutch / Q000033:anatomy & histology / Q000254:growth & development* / Q000378:metabolism; D012044:Regression Analysis; D012737:Sex Factors; D013997:Time Factors
D018972:Insulin-Like Growth Factor Binding Protein 3; D007334:Insulin-Like Growth Factor I; D013006:Growth Hormone