Methionine is the first limiting amino acid in broiler diets. A study was undertaken to investigate the mechanism underlying the regulatory effect of this amino acid on broiler growth.

A total of 192 one-day-old broilers were housed in three-layer cages in a temperature-controlled room with continuous lighting. Cages were randomly allocated to two dietary treatments with six replicates (eight males and eight females per cage) per treatment. Control starter and finisher diets contained 0.50 and 0.43 percent methionine, respectively, with values for +methionine treatments being 0.60 and 0.53 percent, respectively.


The birds receiving the +methionine diets improved feed efficiency index throughout the experiment. Diets with extra methionine increased the relative weight of breast muscle and the concentrations of uric acid and triglyceride in serum at 42 days of age, whereas other serum measurements were not affected.

In conclusion, broilers fed the +methionine diets experienced increased breast muscle growth that was attributed to the expected expression of myostatin, Myf5 and MEF2B genes.