The objective of this study was to investigate the effect of 5-aminolevulinic acid (5-ALA) as a dietary supplement on milk yield and composition as well as iron status and immune response in lactating dairy cows. In this study 13 lactating Holstein cows were randomly assigned to either a control group or a treatment group supplemented with 10 mg of 5-ALA per kilogram of dry matter. During feeding, 5-ALA was mixed with a small amount of the total mixed ration and top-dressed. The experiments followed a crossover design with 2 periods. Each period consisted of an adaptation period of 12 d and a test period of 2 d. Dairy cows fed the diet supplemented with 5-ALA exhibited increased counts of white blood cells and granulocytes compared with the control group. The rate of phagocytosis and mitogen-induced proliferation of peripheral blood mononuclear cells in cows fed 5-ALA were higher than in cows fed a basal diet. However, 5-ALA did not affect iron status or plasma biochemical composition. Supplementation with 5-ALA improved milk protein and milk casein contents; however, it had no effect on milk production, milk fat, lactose, total solids, or solids-not-fat, compared with the control. We conclude that dietary supplementation of 5-ALA to lactating dairy cows may have a positive effect on milk protein synthesis and the immune response.
Keywords: aminolevulinic acid; dairy cow; immunomodulator; iron status.
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