Basso Silva, Paula Regina2016-12-192016-12-192016-10https://hdl.handle.net/11299/183397University of Minnesota Ph.D. dissertation. October 2016. Major: Animal Sciences. Advisors: Ricardo Chebel, Marcia Endres. 1 computer file (PDF); xiii, 255 pages.Excessive fatty acids release from the adipose tissue of periparturient cows may result in hyperketonemia and hepatic lipidosis, which are known to compromise liver and damage immune cells. Immunosuppression in transition cows is a result of shortage in energy, nutrients and calcium impairing immune cells’ metabolism. Thereafter, immunosuppressed periparturient cows are at higher risks for developing infectious and non-infectious health disorders. Strategies that improve metabolism and immune function of periparturient dairy cows may reduce incidence of diseases. Six experiments were performed to test two main strategies: the use of recombinant bovine somatotropin (rbST) during the peripartum period and the reduction of prepartum pens’ stocking density (SD) from 100 to 80% of headlocks. The specific objectives of these experiments were to evaluate the effects of treating peripartum dairy cows with rbST on immune, inflammatory, and metabolic responses, incidences of postpartum diseases, performance, and hepatic and leukocyte gene expression; and to evaluate the effects of two prepartum SD (80 vs. 100%) on milk yield, concentration of metabolites, health and reproductive parameters, innate and adaptive leukocyte responses, and serum and hair cortisol concentrations. Results demonstrated that treatment of dairy cows with 125 mg of rbST improved innate immune responses and IgG concentration, with limited effects on metabolism, decreased the incidence of uterine disorders in Holstein and Jersey cows and increased yield of energy corrected milk during the first 30 DIM in Holstein cows. Administration of rbST during the periparturient period may improve liver function and health by increasing hepatic capacity for gluconeogenesis and lipid transport and by reducing inflammation and oxidative stress. Treatment of dairy cows with 125 mg of rbST during the periparturient period may improve leukocyte functions by upregulating mRNA expression of genes involved in glycolysis, pathogen recognition, phagocytosis and oxidative burst, antimicrobial peptides, and antibody production. Finally, in herds with weekly or twice weekly movement of new cows to the prepartum pen and separate housing of nulliparous and parous animals, 100% SD of headlocks on the day of movement does not affect health, metabolic, reproductive, and productive parameters and 80% did not improve leukocyte responses compared with 100% target SD.endairy cowhealthimmunitymetabolismsomatotropinstocking densityThesis or Dissertation