53 Young Scholar Presentation: Diet starch concentration and starch fermentability affect energy intake and production of dairy cows during the postpartum period
Abstract Our objective was to evaluate the effects of starch concentration and starch fermentability of diets fed during the early postpartum (PP) period on DM and energy intake and production. Fifty-two multiparous Holstein cows were used in a completely randomized block design with a 2 X 2 factorial arrangement of treatments. Treatment diets were formulated to 22% (LS) or 28% (HS) starch with dry-ground corn (DGC) or high-moisture corn (HMC) as starch source. Treatments were fed from 1 to 23 d PP, and cows were switched to a common diet until 72 d PP to measure carryover (CO) effects. Throughout the experiment, DMI and MY were measured daily, and milk components and BW were measured weekly. During the TP, feeds, refusals, and fecal samples were collected and digestibility was determined weekly. During the TP, HMC decreased intakes of DM and net energy of lactation (NEL) more when included in the HS (3.9 kg/d and 3.2 Mcal/d) than in the LS (0.9 kg/d and 0.6 Mcal/d) diets and HMC decreased yields of milk, fat, protein, 3.5% FCM and milk NEL by 4.3, 0.19, 0.18, 4.8 kg/d and 2.8 Mcal/d, respectively. Energy balance was improved by HS compared with LS (-14.7 vs. -16.8 Mcal/d). During the CO period, treatment effects on DMI diminished over time with no main effects of treatment for the entire period. Treatments interacted to affect yields of milk, milk fat and FCM during the CO period, which were greater for HS-DGC and LS-HMC (54.8 and 52.8, 1.76 and 1.81, and 51.3 and 52.2 kg/d, respectively) than for LS-DGC and HS-HMC (51.2 and 51.0, 1.68 and 1.64, and 48.4 and 48.6 kg/d, respectively). Feeding a highly fermentable starch source during the early PP period decreased DM and energy intake and production, with treatment effects diminishing during the CO period.