Development of innate immune response in healthy Holstein calves from birth until weaning

• Ano de defesa: 2020
• Autor(a) principal: Morita, Laila Miyuri
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: eng
• Instituição de defesa: Biblioteca Digitais de Teses e Dissertações da USP
• Palavras-chave em Português: Espécies Reativas do Oxigênio (EROs); Fagocitose; Hemácias; Leucócitos; Neutrófilos; Neutrophils; Phagocytosis; Reactive oxygen species (ROS); Red blood cells; White blood cells
• Link de acesso: https://www.teses.usp.br/teses/disponiveis/10/10136/tde-12052020-090340/

The general aim of this research was to evaluate the hematological and innate immune profile in Holstein calves naturally exposed to microorganisms during pre-weaning phase. It was performed a transversal study including 175 dairy calves distributed in three age groups: Group 1 - 1 to 7 days of life (n=65), Group 2 - 30 to 40 days of life (n=52) and Group 3 - 60 to 89 days of life (n=58) and also distributed in 2 subgroups, healthy and unhealthy, according to clinical examination findings. Blood samples were harvested in tubes with and without EDTA anticoagulant and heparin for Red Blood Cells (RBC) and White Blood Cell (WBC) count determination by using ADVIA 2120 system, biochemical markers and for immune response assays. The flow cytometry technique was used to assess polymorphonuclear (PMN) and mononuclear (MN) cells phagocytosis of pre labeled Escherichia coli, Staphylococcus aureus and Mannheimia haemolytica. Production of Reactive Oxygen Species (ROS) was assessed in leucocytes by use of the fluorescent dye dihydrorhodamine 123 and then the response ratio (RR) was calculated to compare data between the groups/subgroups. The predominant disease detected in unhealthy neonate calves (G1) was diarrhea (46%), while Bovine Respiratory Disease (BRD) was the most important illness in G2 (63%) and G3 (59%). Regard to age physiological response, the most differences were observed contrasting G1 with G2 and G3 observing in neonates a decrease trend of RBC and serum iron also a pro inflammatory profile under natural challenges. Most of phagocytosis parameters (MN and PMN) were independent of age or healthy groups, although the amount of ROS (AFU) decreased through advance of age. G1 unhealthy subgroup presented low concentration of total solids and total protein associated with low number of RBC and leukocytosis due to neutrophilia and lymphopenia compared with healthy subgroup. Production of ROS (AFU) for M. haemolytica was higher in unhealthy than healthy neonates. G2 unhealthy subgroup presented subtle changes in hematological and innate immune response, however the concentration of total solids, protein and ROS production and RR for all antigens were lower in the unhealthy group. G3 unhealthy animals presented increase of MN cells in WBC count, and both MN and PMN cells were more phagocytic responsive for all antigens, especially M. haemolytica, also in ROS assay, compared with healthy calves. This research has evidences that neonate had a high innate immune response intensity against natural exposition to pathogens, while the intermediate heifers (G2) presented immunologically less responsive to antigens associated with the high rate of BRD. G3 group seen to be more prepared to face the challenges presented during pre-weaning phase as the immune response was more effective against the antigens. The assumption is that the differences reported are associated with the concentration of colostrum maternal factors that act enhancing the innate immune response of neonate calves, with a gradual decrease of immune response in animals with 30 to 40 days of life (G2) and subsequently development of the active adaptative response in G3.