Grazing behavior of drylot-developed beef heifers and the influence of postinsemination supplementation on artificial-insemination pregnancy success

Research has indicated that moving drylot-developed heifers to spring forage immediately after AI adversely affects ADG and AI conception rates. Our objective was to determine the effect of adaption to grazing on ADG and activity, and whether post-AI supplementation would improve AI pregnancy success. In Exp. 1, heifers were developed in a single pen. At the start of treatment (d − 44) heifers were blocked by BW and either remained in the drylot (DLT; n = 34) or were moved to forage (GRS; n = 35). Pedometers were placed on 5 heifers per treatment on d − 19. On d 0, DLT heifers were moved to forage. Heifers on GRS had decreased (P < 0.01) ADG from d − 44 to − 35 compared with DLT heifers. Following being moved (d 0) DLT heifers had decreased (P < 0.01) ADG compared with GRS heifers. Initially, GRS heifers took more (P < 0.05) steps, but after being moved, DLT heifers took more (P < 0.05) steps from d 0 to 3. In Exp. 2, drylot-developed heifers (n = 301) at 2 locations were synchronized with the 7-d CIDR protocol. At AI, heifers were randomly assigned within location to be either moved to pasture or moved to pasture plus being supplemented. Pregnancy success was affected by treatment (P = 0.02), with supplemented heifers having improved pregnancy success. In summary, moving drylot-developed heifers to forage affected performance and activity, but supplementation when moved to pasture at AI improved pregnancy success.