154 Supplementation of Late Gestation Metabolizable Energy in Beef Cows Reduces Mobilization of Body Reserves Prepartum

Abstract This study evaluated how late gestation metabolizable energy (ME) intake affects performance and metabolism in beef cattle. Primiparous (PP; n = 45) multiparous (MP; 107) Angus-Simmental cows were blocked by calving date randomly assigned to treatments providing 80 (LME; 52), 100 (CME; 51), or 120% (HME; 49) of ME requirements for 53 d prior calving. Postpartum, fed the same diet. Rib rump fat depths measured ultrasonography on -54, -40, -26, -13, 13, 27, 55 relative Plasma serum collected -53, -39, -25, -10, -3, 7, Serum glucose, beta-hydroxybutyrate, non-esterified fatty acids (NEFA), urea, plasma insulin measured. Data analyzed using PROC GLIMMIX with fixed effects treatment, parity, treatment×parity, random block cow (block), accounting repeated measures. Absolute loss rib prepartum was lesser (P ≤ 0.03) HME. heifers lost more < 0.01) prepartum. Prepartum urea NEFA elevated LME, whereas glucose HME compared LME. Multiparous had greater 0.02) prepartum, PP glucose. Treatment did not affect ≥ 0.56) absolute nor postpartum. LME than beta-hydroxybutyrate postpartum postpartum, insulin. Supplementing excess during reduced mobilization body reserves before but continue