In Expt 1, lactating dairy cows grazing kikuyu grass (Pennisetum clandestinum) were given no supplement (C), supplements of rolled barley grain at 4 (4R) and 6 (6R) kg/day and supplements of NaOH-treated whole barley grain at 4 (4A) and 6 (6A) kg/day. Daily production of milk (kg/day), fat and protein (g/day) and live-weight changes (g/day) respectively were C 7·82, 303, 276, 450; 4R 9·26, 338, 315, 865; 4A 10·23, 366, 349, 529; 6R 10·09, 352, 343, 672; 6A 10·61, 363, 348, 361.
Milk production was significantly higher (P < 0·05) and live-weight gain significantly lower (P < 0·05) on NaOH-treated grain than on rolled grain.
In Expt 2, yearling steers in pens were fed pasture hay ad libitum with no supplement (C) and 3 kg/day of barley grain which was either rolled (3R) or NaOH-treated whole grain (3A). Mean intakes of hay (g/day) and DOMD in vivo (%) respectively were C 7684, 60; 3R 5224, 65; 3A 6209, 60.
Hay intake was significantly higher (P < 0·05) on NaOH-treated grain than on rolled grain.
Fractional disappearance rates of rolled and NaOH-treated grain from nylon bags suspended in the rumen were, respectively, 0·15 and 0–07/h for the period 0–4 h, and 0·07 and 0·02/h for the period 4–12 h incubation. In Expt 2, rumen pH was higher and the digestion rate of hay in nylon bags in vivo was higher on C than on 3R and 3A. Volatile fatty acid (VFA) concentrations in the rumen did not differ significantly between diets.
It was concluded that greater milk production and hay intakes when cattle were fed NaOH-treated whole barley than when they were fed rolled barley were attributable to the slower rate of digestion of the former. The NaOH treatment (30 g NaOH/kg grain) was probably too low and further study is necessary to determine optimum levels of treatment, which are likely to vary with the ratio of grain: forage in the diet.