Wahed and Owen (1986) showed that intake of untreated barley straw increased by up to 40% when the amount offered was increased to allow goats to refuse 50% of the amount offered instead of the 15-20% used in conventional ad libitum intake trials. The increase was attributed to greater opportunity to select the more digestible parts of the straw. The present experiment was made to see whether similar responses occur if digestibility of the straw is increased by alkali treatment.
Thirty-six individually-fed Saanen-type castrates weighing 31-65 kg were used in a 3x2 (3 straw types, 2 rates of offer) factorial design experiment. Goats were blocked according to weight (M) and allocated randomly within block to one of 6 treatments. They were offered untreated barley (var. Triumph) straw (S), ammoniated barley straw (NH3-S) or NaOH-dip-treated barley straw (NaOH-S) at either 20 g DM per g M daily (L) or 50 g DM/kg M.d (H). Straw was ammoniated on 25th August 1987 by the Stack Method (Sundstol and Coxworth, 1984) using aqueous ammonia (35 g NH3/kg straw DM). The stack was opened 30 days later. NaOH-dip-treatment (Sundstol, 1981) involved dipping in a solution containing 15 g/kg NaOH and 7 g/kg urea. Straw was dipped daily and allowed to mature 3-4 d before feeding. Goats were supplemented with concentrates (g/kg DM: milled barley, 600; soya bean meal, 180; fish meal, 180; mineral mix, 40) at 18 g DM/kgM 0.75.d. They were fed twice daily (0800 and 1600 h), offered water ad libitum and individually penned with sawdust bedding.