title: Effects of methionine deficiencies on plasma levels of thyroid hormones, insulin-like growth factors-I and -II, liver and body weights, and feed intake in growing chickens.
abstract: We showed previously that Met deficiency at 0.25% of the diet causes elevations in plasma triiodothyronine (T3) in broilers. In the present study, plasma levels of thyroid hormones as well as insulin-like growth factors (IGF)-I and -II were measured in chicks fed 3 deficient levels of total Met. Control (0.5%) and Met-deficient diets (0.4, 0.3, and 0.2%) were fed to male broilers from 8 to 22 d of age. Additional groups of control chicks were pair-fed with the Met-deficient ones. Chicks receiving 0.4% Met increased feed intake by 10% with no significant change in body weight. The more severe Met deficiencies of 0.3 and 0.2% caused graded reductions in feed intake and weight gain. However, corresponding pair-fed control chicks were significantly heavier. These changes suggest more marked alterations in metabolic processes with 0.3 and 0.2% Met than with 0.4% Met. Liver weights were heavier in chicks fed 0.3 and 0.2% Met but not 0.4%. Plasma T3 was higher in all deficient chicks compared with the free-fed control, which was significant only with 0.3% Met. However, with 0.3 and 0.2% Met, plasma T3 was significantly elevated compared to pair-fed controls. Plasma thyroxine (T4) was lower in all deficient groups, which was significant only with 0.2% Met, whereas no significant differences occurred between deficient chicks and their pair-fed controls. Plasma IGF-I levels were not significantly different, but they were consistently lower in deficient chicks and deserve further study. Plasma IGF-II was significantly less in chicks fed 0.2% Met compared to pair-fed controls suggesting that Met deficiency interferes with IGF-II metabolism. We concluded that a deficit of dietary Met altered plasma T3 and IGF-II levels, but the effect was dependent on the degree of deficiency.
authors.affiliation: Department of Animal Science, University of Vermont, Burlington, Vermont 05405, USA. lyndon.carew@uvm.edu
authors.forename: L B
authors.initials: LB
authors.lastname: Carew
authors.forename: J P
authors.initials: JP
authors.lastname: McMurtry
authors.forename: F A
authors.initials: FA
authors.lastname: Alster
mesh_terms: D000818:Animals; D001835:Body Weight; D002645:Chickens / Q000097:blood / Q000254:growth & development* / Q000502:physiology; D004435:Eating; D007334:Insulin-Like Growth Factor I / Q000032:analysis*; D007335:Insulin-Like Growth Factor II / Q000032:analysis*; D008099:Liver / Q000254:growth & development*; D008297:Male; D008715:Methionine / Q000008:administration & dosage / Q000172:deficiency*; D009929:Organ Size; D013963:Thyroid Hormones / Q000097:blood*; D013974:Thyroxine / Q000097:blood; D014284:Triiodothyronine / Q000097:blood; D015430:Weight Gain
chemical_list: D013963:Thyroid Hormones; D014284:Triiodothyronine; D007334:Insulin-Like Growth Factor I; D007335:Insulin-Like Growth Factor II; D008715:Methionine; D013974:Thyroxine