Abstract
The purpose of this 42-day study was to investigate the effects of methionine (Met) deficiency on immune function by determining the relative weight, morphological and ultrastructural changes of bursae of Fabricius, cell cycle, and apoptosis of bursa cells. One hundred and twenty one-day-old avian broilers were randomly divided into two groups and fed on a control diet (starter diet, Met 0.50%; grower diet, Met 0.40%) and Met-deficient diet (starter diet, Met 0.26%; grower diet, Met 0.28%) for six weeks. The relative weight of bursae was decreased with Met deficiency when compared to that of the control group. Lesions were also observed in the Met-deficient group. Histopathologically, the numbers of lymphocytes in the follicles were decreased. Ultrastructurally, the mitochondria of lymphocytes were swollen in the Met-deficient group. As measured by flow cytometry, bursal cells in the G0G1 phase were significantly higher (P < 0.01), and bursal cells in the S, G2M phases and proliferating index were obviously lower (P < 0.01) with Met deficiency than in the control group. Moreover, the percentage of apoptotic cells in the bursae were significantly increased in Met-deficient birds (P < 0.01). It was concluded that Met deficiency restrained the development of the bursae of Fabricius and affected the humoral immunity of the chickens.
Highlights
Methionine (Met) is the first limiting essential amino acid and can improve growth performance and carcass quality of poultry [1,2,3]
One essential function of Met in neurulation may be as precursor for S-adenosylmethionine (SAM) and the methyl donor in transmethylation reactions [7], which plays a main role as the biological methyl donor for the methylation of DNA, RNA, and protein [8]
Related weight (RW) of bursae was calculated by the following formula: RW = organ weight/body weight (g/kg)
Summary
Methionine (Met) is the first limiting essential amino acid and can improve growth performance and carcass quality of poultry [1,2,3]. It has been shown to prevent lipid accumulation in the liver [9,10] Apart from these functions, Met is involved in avian immune functions. Dietary Met can promote antibody production and cell-mediated immune responses in broilers [11,12,13]. The experiment was conducted with the objective of examining the effects of Met deficiency on the bursa, including lesions, the cell cycle, and apoptosis of bursae, before evaluating the immune function of chickens by methods of experimental pathology, flow cytometry (FCM) and immunohistological methods, in order to provide helpful materials for similar studies in both human and other animals in the future
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