A data set was compiled from published research (n = 85) that tested the effect of supplemental dietary sugar. Forage NDF ranged from 17 – 29% DM and calculated total sugar from 2.3 - 11% DM. Mixed model analysis was conducted using JMP statistical software (SAS Inst. Inc., Cary, NC) with nutrient parameters (CNCPS 6.1 with NDS platform, RUM&N Sas, Italy) as main effects. Model fit used treatment (Control vs. 1.5–3% added sugar vs. 3–5% added sugar vs. 5–7% added sugar), DIM (<150 or >150 DIM) within treatment, and Milk Yield (<33 or >33 kg/d) within treatment as independent factors with experiment as the random effect. Responses were analyzed with the following nutrients (%DM) in the model: starch, soluble fiber, forage NDF, ammonia, RDP, and Protein B2. Protein B2 is true protein that can contribute to dietary RUP. Number of cows per treatment was included as a weighting factor. Nutrients with a positive effect on 3.5% FCM yield were sugar (+1.45 kg) (P < 0.04), starch (P < 0.01) and soluble fiber (P < 0.05). Higher producing cows (>33 kg milk/d) had a greater response (2.14 kg FCM/d) to sugar than cows producing <33 kg of milk (P < 0.0001). Nutrients with a positive effect on milk protein yield were sugar (+0.07 kg; P < 0.05) and starch (P < 0.0001). Cows producing > 33kg milk had a greater milk protein response to sugar (0.09 vs. 0.05 kg/d than cows producing <33 kg milk/d, (P < 0.001). Sugar did not affect milk fat yield (P = 0.16), although starch and soluble fiber had a positive effect (P < = 0.05). Sugar alone did not affect feed efficiency but starch (P = 0.04), soluble fiber (P = 0.01), and Protein B2 (P = 0.03), all had a positive effect with a mean increase of 0.06 units with 3–5% supplemental sugar. Nonlinear statistical analysis using JMP Neural Net function determined optimal total calculated sugar to be 6.75% of diet DM. Optimal range for starch when feeding supplemental sugar was 20 – 25% of diet DM. Sugar did not affect milk fat or protein percent. In conclusion, 3 to 5% supplemental sugar (6 to 8% total sugar (%DM)), and starch (%DM) increased FCM (kg/d), and milk protein yield. To optimize response to supplemental sugar, the diet should contain >17% forage NDF, 10 −11% RDP and less than 30% starch.