The effect of feed supplementation with zinc glycine chelate and zinc sulphate on hepatic proteome profiles in chickens

Abstract

One of the most important factors influencing production outcomes in poultry farming is optimal balancing of the feed ration in terms of macro- and micronutrients. Zinc is an essential trace element that increases metabolic processes. The natural components of poultry feed do not contain sufficient zinc, or even contain numerous factors limiting its absorption, which necessitates supplementation of feed with this element. The purpose of the study was to identify proteins synthesized in the liver of chickens fed a diet supplemented with zinc in the form of sulphates and a glycine chelate; to determine differences in the expression of these proteins; and to describe the peptide profile of hepatocytes in chickens. A total of 900 1-day-old male Ross 308 chickens, assigned to 5 dietary treatments, were used in the experiment. The experimental groups received a basal diet + zinc in inorganic and organic form and a phytase supplement. The material for analysis comprised samples of liver and serum. The zinc concentration in serum and tissues was determined by flame atomic absorption spectrometry. The liver lipid profile was estimated by the gravimetric method. A complete proteomic analysis of liver samples included protein separation by two-dimensional electrophoresis, plotting of a protein map illustrating the proteome of the liver, statistical analysis, and identification of statistically significant proteins by MALDI-TOF mass spectrometry. The results of the study demonstrate that organic and inorganic forms of zinc used as feed additives for chickens not only affect the concentration of this element in the liver, but also have a systemic effect by altering the expression of proteins. A complete proteomic analysis of liver samples made it possible to identify eight proteins whose expression depended on the type of supplement added to the feed. The results clearly indicate that bioavailable zinc administered in the form of glycine chelates affects processes stimulating synthesis of ApoA-I, β2-MG, protein-disulphide-isomerase, neuroblast differentiation-associated protein AHNAK, and alpha-N-acetylgalactosaminide alpha-2,6-sialyltransferase 1 in the tissues of chickens. Supplementation of poultry feed with zinc in both sulphate and chelated form caused changes in the expression of the protein yippee-like 4 and histone H1.1. A high concentration of prolyl endopeptidase protein in the liver of birds receiving zinc sulphate was also observed. In conclusion, supplementation of poultry feed with zinc chelates modifies the expression profiles of proteins involved in intracellular transport, the cell cycle, metabolism, and the immune response.