Energy and protein supplements to straw-based diets for yearling cattle: effects on straw intake and digestibility

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Abstract
A series of change-over experiments examined the intake and digestibility of straw-based diets in yearling dairy heifers. Voluntary intakes of straws given as the sole food to yearling dairy heifers were 1·28, 1·20 and 0·90 kg dry matter (DM) per 100 kg live weight for barley, wheat and oat straws respectively, and the corresponding digestibility of organic matter was 0·47, 0·53 and 0·48. When supplemented with 2 kg rolled barley the intakes of straw did not alter, nor were they affected by replacing part of the rolled barley with an equal amount of soya-bean meal and thus increasing the dietary concentration of protein from about 50 to 110 g/kg DM. The use of molassed sugar-beet pulp in place of rolled barley reduced the intake of straw. Flaked maize promoted slightly higher intakes of straw than an equal amount of coarsely milled maize. Replacing rolled barley by lucerne hay reduced straw intake. It is estimated that, to provide sufficient energy and protein for a daily gain of 0·5 kg, heifer straw-based diets would require a supplement of 1·2 kg rolled barley and 0·8 kg soya-bean meal.