Our objective was to determine the effects of chromium propionate (CrPr) supplementation throughout the peripartum period on productive performance and metabolism of dairy cows and to determine the effects of ruminal starch fermentability on production responses to chromium propionate supplementation in the postpartum period. Forty–eight multiparous dairy cows were used in a randomized block design with a 2x2 factorial arrangement of treatments of control or 8 mg chromium (Cr) as CrPr and dry ground corn (DC) or high-moisture corn (HMC). Chromium treatment began 28±3 d before expected parturition and continued until 28±3 d postpartum (PP), and DC and HMC were fed in rations from parturition to 28±3 d PP. A common diet was fed from 28&plusnm;3 d PP to 84±3 d PP. There were no effects of treatment on dry matter intake (DMI) from parturition to 28±3 d PP, but an interaction among Cr, corn, and d PP was detected (P = 0.06) when cows were fed the common diet. A Cr, corn, and time interaction was also detected for 3.5% fat-corrected milk (FCM, P = 0.07) from parturition until 28&plusnm;3 d PP which continued after treatment ceased (P = 0.07).Although CrPr improved productive performance, no evidence of increased insulin sensitivity was observed. Postpartum plasma NEFA increased numerically and maximum NEFA was higher during the glucose challenge with CrPr supplementation. Supplementation of CrPr throughout the periparturient period interacted with starch source in PP diets and d PP to affect production responses after treatment application ceased.
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