The periparturient period places extreme metabolic stress on cows. Our lab has previously demonstrated that infusions with a serotonin precursor, 5-hydroxy-L-tryptophan (5-HTP), increases circulating glucose and nonesterified fatty acids (NEFAs) while concurrently decreasing β-hydroxybutyrate (b-HB). These results indicate that treatment with 5-HTP may be able to increase the cow’s ability to deal with negative energy balance due to calving. It is unknown whether feeding a negative DCAD diet alters the relationship between 5-HTP and metabolic stress. The main objective of this study was to determine whether feeding a negative DCAD diet before calving in conjunction with 5-HTP treatment could mitigate metabolic stress due to calving. This study utilized a randomized complete block design with a 2 × 2 factorial arrangement. Holsteins were fed either a positive (+130 mEq/kg) or negative (−130 mEq/kg) DCAD diet 21 d before calving and were also treated daily with saline or 5-HTP (1 mg/kg) IV beginning 7 d before estimated calving date. 32 multiparous Holstein cows, blocked by parity, were randomly assigned to 1 of 4 treatment groups in a 2 × 2 factorial arrangement: (1) positive DCAD plus saline; (2) positive DCAD diet plus 5-HTP; (3) negative DCAD plus saline; and (4) negative DCAD plus 5-HTP. This resulted in an n = 8 per group. Plasma glucose, blood urea nitrogen (BUN), insulin, and adiponectin were measured. Serum was used to measure NEFAs and BHB. Preliminary results suggest that neither pre or post-calving insulin, leptin, or glucose were significantly affected by either DCAD or 5-HTP treatment. However, both pre and post calving BUN were significantly elevated in cows treated with saline versus 5-HTP (P = 0.0184 and 0.005, respectively). This suggests that serotonin may have a significant impact on protein turnover during the transition period, regardless of DCAD level. Future experiments should be targeted at understanding the effects serotonin may have on protein turnover in the transition period.