EFFECTS OF SODIUM-HYDROXIDE AND OF ENERGY AND PROTEIN SUPPLEMENTS ON THE VOLUNTARY INTAKE AND DIGESTIBILITY OF BARLEY, OAT AND WHEAT STRAW BY CATTLE

Three change-over experiments with yearling cattle examined the effects on voluntary intake and digestibility of treating barley, oat and wheat straws with NaOH. Increases in intake due to the NaOH treatment were: with barley straw 31 %, oat straw 9 % and with wheat straw 1 %, and the corresponding improvements in digestibility were 36, 13 and 24 %. A further three experiments with yearling heifers and steers measured the effects of supplements on the response in feeding value to NaOH treatment of wheat straw. Increasing the daily supplement of rolled barley from 1.0 to 3.4 kg led to a decrease in voluntary intake of treated straw from 4.6 to 3.6 kg organic matter (OM), while including urea, to increase the concentration of nitrogen in a beet pulp supplement from 19 to 24 gN/kg dry matter (DM), gave an increase in intake of straw from 3.4 to 4.8 kg OM. Providing more than c. 15 g N/kg dietary DM did not lead to a significant increase in voluntary intake or digestibility. In a further experiment, isonitrogenous supplements of rolled barley and soyabean meal, or rolled barley and fishmeal, led to similar intakes and digestibilities of treated straw. The variation in response to NaOH treatment is discussed.