This thesis describes an evaluation of the impact of administering recombinant bovine somatotropin (rbST) before calving on health, milk production, reproductive performance and dry matter intake (DMI) of lactating dairy cows. In addition, this thesis includes an evaluation of the cost of subclinical ketosis (SCK), economic value of using Rumensin® Controlled Release Capsules (CRC) for disease prevention and the economic value of using propylene glycol (PG) for treatment of SCK after being diagnosed with different cow-side tests. One randomized clinical trial was conducted on 4 commercial dairy herds in Southern Ontario and at the University of Guelph where rbST was administered every other week starting at 28-22 days before calving until cows calved. The key finding of this study was that pre-partum rbST administration had no significant clinical impact on health and performance of dairy cows after calving. A spreadsheet was constructed to perform the economic analysis of ketosis cost and treatment. It was estimated that one case of SCK can cost up to $350. The economic value of using CRC to reduce ketosis depends on the prevalence of ketosis-related diseases in a herd. Using a cow-side test with high sensitivity and specificity to diagnose SCK pays off through minimizing the losses by classifying fewer cows as false negatives and therefore treating more sick cows and mitigating the negative impact of SCK. Results presented in this thesis highlight the insufficiency of rbST administration in the pre-partum period only, to improve health in the transition period and to improve cow performance after calving. Results of an economic analysis highlight the high cost impact of SCK and the importance of reducing its incidence through implementing management during the transition period.