EFFECTS OF AMOUNT OFFERED AND CHOPPING ON INTAKE AND SELECTION OF SORGHUM STOVER BY ETHIOPIAN SHEEP AND CATTLE

Experiment 1, with yams (17.0 kg initial weight (M)), and experiment 2 , with steers (203 kg Mi, involved 2 x 2 arrangements of treatments to compare the effect of doubling the amount of stover offered (25 or 50 g/kg M daily) and chopping (unchopped or chopped), upon intake, selec tion and live-weight change. The stover used was a non-bird-resistant, local variety (Dinkamash). The particle length distribution of the ch opped stover (produced by a tractor-driven chaff cutter) was: < 4.5 mm , 0.148; 4.5 to 8 mm, 0.157; 8 to 12 mm, 0.181; 12 to 20 mm, 0.269; 20 to 33 mm, 0.168; 33 to 54 mm, 0.040; 54 to 90 mm, 0.003; > 90 mm, 0.0 34. The stover was supplemented with minerals and cottonseed cake (she ep, 0.1 kg dry matter (DM) per day; cattle, 0.76 kg DM per day). Exper iment 1, over 56 days, involved 48 Menz Highland, 18-month-old, rams, with four replicate pens containing three rams. Experiment 2, over 49 days, used 32, individually penned, Friesian x zebu yearling steers. W ith rams, doubling the amount offered and chopping increased intake, a nd the effects were additive (unchopped: 0.98 v. 1.24; chopped: 1.08 v . 1.60 (s.e. 0.071) kg DM per pen per day). With steers, there was an amount x chopping interaction (P < 0.05) (unchopped: 3.7 v. 4.7 choppe d: 3.6 v. 3.9 (s.e. 0.16) kg DM per day), with chopping reducing intak e of stover offered at 50 g/kg M per day. Increased intakes were assoc iated with increased growth rate. In both experiments refused stover c ontained less leaf-plus-sheath than offered stover but the difference was more pronounced in rams compared with steers indicating the superi or selective ability of the rams. In rams offered unchopped stover, th e increase in stover intake with increasing amount offered was account ed for by a proportional 1.03 unit increase in consumption of leaf-plu s-sheath and a 0.06 unit reduction in intake of stem. Doubling the amo unt of unchopped stover offered increased intake of both rams and stee rs by 0.27 unit. Chopping stover was clearly beneficial for rams but n ot for steers. Doubling the amount of stover offered is it simple exce ss-feeding strategy to apply. Excess feeding also increases the propor tion of stover refused from about 0.2 to 0.5, thus generating an uneat en residue available for other purposes, e.g. mulch or compost.