The aim of this study was to investigate an AY (Saccharomyces cerevisiae) supplemented in high starch lactation diets and its effect on blood metabolites, in particular inflammatory biomarkers. Fifteen rumen-cannulated Holstein cows were assigned to 1 of 5 treatments in a replicated 5 × 5 Latin square design balanced to measure carryover effects. Treatments were: low starch diet without AY (LS0; control), high starch diet without AY (HS0), high starch diet with either 15 g (HS15), 30 g (HS30), or 45 g (HS45) of AY supplementation. The period of 21 d was divided into the adaptation phase (d 1 to 14) and a measurement phase (d 15 to 21). Blood was sampled from the coccygeal artery or vein at 0600 h on d 15, 18, and 21(n = 3) of each period from each cow. Data collected were analyzed using the MIXED procedure of SAS. Orthogonal contrasts were used. Contrasts; CONT1 = LS0 compared with HS0; CONT2 = HS0 compared with the average of the 3 AY treatments (HS0, HS15, HS45) and linear and quadratic treatment effects (HS0, HS15, HS30, and HS45). NEFA (93.69 vs. 82.71 ± 4.08 μEq/L; P = 0.04) was greater in cows fed LS0; insulin (0.93 vs. 0.74 ± 0.10 μg/L; P = 0.04) concentration was greater in cows fed HS0. Plasma gamma-glutamyl transferase (GGT; 26.09 vs. 24.94 ± 3.57 U/L; P = 0.05), and mineral phosphorus (5.86 vs. 5.38 ± 0.15 mg/dL; P = 0.005) concentrations were greater in HS0 compared with LS0. However, the LS0 diet had greater total protein (7.60 vs. 7.43 ± 0.42 g/dL; P = 0.03), and bilirubin (0.14 vs. 0.12 ± 0.008 mg/dL; P = 0.03) when compared with cows fed HS0. Supplementing AY to cows had greater plasma total protein (P = 0.008), globulin (P = 0.008), serum amyloid A (SAA; P = 0.02), but lower albumin:globulin (P = 0.03), and tendency for lower superoxide dismutase activity (SOD; P = 0.07; CONT2). Linear treatments effects for plasma BHB (0.52 ± 0.03 mmol/L; P = 0.08) was higher at HS15. In conclusion, cows in HS0 had lower insulin, total bilirubin and protein compared with LS0 but greater concentrations of albumin:globulin, and tendency for SOD compared with treatments with added AY (CONT2).