Agricultural Research Division of IANR
Date of this Version
2009
Citation
Proceedings, Western Section, American Society of Animal Science Vol. 60, 2009
Abstract
Three experiments evaluated replacement heifer development systems and subsequent effects on gain and efficiency of pregnant heifers. In Exp. 1 and 2, were developed grazing corn residue (CR; 422 ± 5 kg) or fed in a dry lot (DL; 446 ± 5 kg) prior to breeding. In Exp. 1, a subset of pregnant heifers (n = 40) were individually fed a diet composed of 90% grass hay (11.7 % CP; DM basis) and 10% of a wet distillers grains plus solubles/straw mixture (21.8 % CP; DM basis) during late gestation. In Exp. 2, 55 pregnant heifers that grazed CR (437 ± 8 kg) or were fed in a DL (445 ± 8 kg) prior to breeding, or a mixture of the two (435 ± 8 kg), grazed CR with a supplement (0.45 kg/d; 28% CP) during late gestation. In Exp. 3, 49 pregnant heifers that grazed CR (396 ± 7 kg) or dormant winter range (WR; 401 ± 7 kg) prior to breeding, or a mixture of the two (396 ± 8 kg), grazed CR with a supplement (0.45 kg/d; 28% CP) during late gestation. In Exp. 1, pregnant heifers developed in the DL had a greater (P = 0.04) DMI than heifers developed grazing CR, however ADG was not different (P = 0.29). Thus, pregnant heifers developed in the DL had a lower (P = 0.08) G:F than heifers developed grazing CR. In Exp. 2, pregnant heifers grazing CR during late gestation that grazed CR during development gained more (P = 0.04), and maintained a greater (P = 0.08) BCS prior to calving, than heifers developed in the DL. The mixture of CR and DL developed pregnant heifers had an intermediate ADG. In Exp. 3, pregnant heifers grazing CR during late gestation that grazed CR during development gained more (P = 0.02) than heifers that grazed WR or the combination of WR or CR developed heifers. Heifer BCS prior to calving was similar (P = 0.81) in Exp. 3. Heifers grazing CR post weaning gain more and are more efficient while grazing CR as pregnant heifers. The benefit of grazing CR post weaning is most pronounced compared to heifers developed in the DL. These data provide evidence of an adaptive response to grazing low quality forages and may be beneficial in the critical period leading up to the first calving season.