Resposta imunológica, metabolismo mitocondrial de frangos de corte que receberam dieta suplementada com zinco

Abstract

Zinc (Zn2+) is a trace element that is involved in several biological functions it is a cofactor of a large number of enzymes. This micromineral has an antioxidant effect and is essential for the development of the immune system. In broilers, the immune response can be influenced by nutritional levels or dietary ingredients. The objective was to evaluate the effect of a diet supplemented with different sources of zinc on the cellular and humoral responses and on the mitochondrial metabolism of these animals. Eight hundred and thirty-two one-day-old male Cobb-500 broilers were used, distributed in a completely randomized design with 4 treatments containing different sources and levels of zinc (1-Control (basal diet without zinc supplementation); 2- ZnO-100 (basal diet + 100mg of ZnO/kg of feed); 3 - Gl-Zn-25 (basal diet + 25mg of zinc glycinate/kg of feed) and 4- Gl-Zn-100 (basal diet + 100mg of zinc glycinate/kg of feed) in 8 repetitions with 26 birds per pen (10.11 birds/m2. At 12 days of age, blood was collected for peripheral blood mononuclear cell (PBMC) culture to verify the production of nitric oxide and cell proliferation. The humoral immune response was evaluated through antibody titers in response to inoculation of 10% sheep red blood cell suspension (SRBC). Inoculations were performed in 32 birds (8 birds/ treatment) with 0.25 mL of 10% SRBC at 7 and 21 days of age. Blood samples were collected one week after the last inoculation to obtain serum and perform a hemagglutination inhibition test. Cell-mediated immunity was assessed by measuring cutaneous basophil (CBH) activity to the intradermal phytohemagglutinin-P test at 28 days of age. In addition, the leukocyte population and the heterophil/lymphocyte ratio were evaluated on blood smears at 37 days of age. We also evaluated the weight of lymphoid organs, histomorphometric analysis of intestinal segments, evaluation of oxygen consumption of isolated liver mitochondria and evaluation of performance characteristics such as feed intake, weight gain and feed conversion in all phases. from creation. Data were evaluated by analysis of variance followed by Tukey's test to identify differences between treatments. In the group of birds that received 25mg of Zn glycinate/kg of feed, an increase in cell proliferation and a lower production of nitric oxide was observed in the PBMC culture (p <0.05), in addition to an increase in the depth of intestinal crypts. There was no significant difference in the response of skin basophils to phytohemagglutinin-P, nor in the titers of anti-SRBC 10% antibodies, as well as in the proportion between heterophils and lymphocytes. There was a decrease in the relative weight of the cloacal pouch in birds that received 100mg of Zn glycinate/kg of feed (p<0.05). There was no (p<0.05) effect of supplementation with different sources of zinc on oxygen consumption in stage 3 of cellular respiration or on the respiratory control rate (RCR), however, it was possible to observe a difference (p<0. 05) in relation to oxygen consumption in stages 2 and 4 of respiration in birds that received the ZnO-100 treatment. The results presented suggest that zinc glycinate at a concentration of 25 mg/kg of feed provided a better immune response in birds, which was reflected in greater cell proliferation and lower production of nitric oxide in the PBMC, in addition to greater depth of intestinal crypts and a greater body weight gain considering the total study period.