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.

Reevaluation of Methionine Requirement Based on Performance and Immune Responses in Broiler Breeder Hens

“…Methionine requirements for settable eggs and EC were 494 and 554 mg/d, respectively. These values also were near to those reported by Cave et al (1990).…”

“…Mal-development of lymphoid organs due to the deficiency of methionine in the diet negatively influenced their normal function (Konashi et al, 2000;Carew et al, 2003). In the present study, humoral immunity was evaluated by antibody responses against SRBC (IgG＋IgM), NDV and BD.…”

“…In addition, recommended daily protein requirement was lower (20.6 g vs. 23.4 g) in compared with earlier studies. It was reported that 33-44 weeks old broiler breeders with 3.5 kg body weight and fed the diet containing 24.8 g/d protein showed the maximum egg mass production (50.3 g/d) with the consumption of 528 mg/d methionine and 960 mg/d TSAA (Cave et al, 1990). Second, inconsistency in the amount of dietary cystine, because the actual methionine requirement needs to be determine with adequate dietary cystine.…”

Dietary methionine effects on IGF-I and GHR mRNA expression in broilers

“…The concentration of IGF-I is affected not only by the restriction of methionine, but is also dependent on the level of deficiency of this amino acid (Carew et al, 2003). Thus, IGF-I mRNA transcription is also influenced by the amount and available source of methionine.…”

Expressão gênica de IGF-I e GHR no fígado e no músculo do peito de codornas de corte suplementadas com diferentes níveis de metionina em duas gerações sucessivas

“…Alguns estudos mostram que aves recebendo dieta deficiente em metionina apresentaram menor crescimento (Carew et al, 2003). Muitos autores têm mostrado relação entre administração de aminoácidos como a metionina e a secreção de GH (Groschl et al, 2003;Collier et al, 2005), e, ainda, que o desempenho mediado pela ação do IGF-I também pode ser influenciado pela suplementação da metionina. Neste estudo, como se pode observar na Tab.…”