Chromium propionate supplementation during the peripartum period interacts with starch source fed postpartum: Production responses during the immediate postpartum and carryover periods

Forty-eight multiparous cows were used in a randomized complete block design experiment with a 2×2 factorial arrangement of treatments to determine the interaction between chromium propionate (CrPr) supplementation and sources of corn varying in ruminal starch fermentability on production responses during the postpartum (PP) and carryover periods. During the peripartum period (28d before expected parturition until 28d PP), diets were top-dressed (20g/d) with either CrPr (KemTRACE Chromium Propionate, Kemin Industries, Des Moines, IA; 8mg of Cr/cow per day) or control (Con; ground corn). At parturition, cows were randomly assigned to corn treatment within CrPr and Con treatments: dry corn (DC) or high-moisture corn (HMC). Treatment combinations (CrPr/DC, CrPr/HMC, Con/DC, and Con/HMC) were fed from parturition until 28d PP (treatment period). Cows were fed a common diet to evaluate potential carryover effects of the treatment diets from 29 to 84d PP (carryover period). The CrPr and corn treatments interacted over time to affect yield of 3.5% fat-corrected milk (FCM) during both the treatment and carryover periods. The CrPr/HMC treatment combination tended to increase FCM compared with Con/DC and Con/HMC by 28d PP (57.4 vs. 48.6 and 48.5kg/d, respectively) and increased FCM compared with Con/DC by 42d PP (59.2 vs. 44.8kg/d). The CrPr tended to increase milk yield (55.4 vs. 51.9kg/d) regardless of corn source during the carryover period after treatment ceased. Daily and cumulative DMI were not affected by treatment during the PP period, but CrPr and corn treatments interacted over time to affect daily DMI during the carryover period; DMI was generally higher for CrPr/HMC, lower for Con/DC, and intermediate for CrPr/DC and Con/HMC from 29 to 84d PP. Supplementation of CrPr throughout the peripartum period interacted with starch source in PP diets over time to affect production responses that were sustained after treatment application ceased.