A comparison of voluntary intake and in vivo digestion in guanacos (Lama guanicoe) and sheep given fresh grass

An experiment teas conducted to compare the voluntary intake and in vivo di gestion for guanacos and sheep when offered perennial ryegrass at three dif ferent growth stages: vegetative growth (VG), emerging inflorescence (EI) a nd mature inflorescence (MI). Dry-matter (DM) intake ranged from 1.19 to 2. 12 kg/day for the guanacos and 0.79 to 1.52 kg/day for the sheep. When expr essed on a metabolic live-weight (M-0.75) basis, the intake of the guanacos (55.8, 43.1 and 44.1 g DM per kg M-0.75 daily On the VG, EI and MI grasses respectively) and the sheep (54.4, 45.7 and 47.4 g DM per kg M-0.75 daily respectively) were similar (s.e.d. = 3.70). Apparent digestibilities of all food constituents were also similar. In terms of food choice, the response of the two species to grass stem differed; the guanacos selected (EI) or t olerated (MI) this fraction, while the sheep tolerated (EI) or avoided (MI) it.