Abstract
Samples of barley straw, maize stover (1980), wheat straw and maize stover (1981), untreated and treated with 35 g anhydrous ammonia (NH 3)/kg were studied during two successive years (1980–1981) (Trial 1). The ammonia treatment increased their crude protein (CP) content by 52, 144, 47 and 76%, respectively. The organic matter digestibility by wether sheep increased by 10, 19, 19 and 15% and straw voluntary intake increased by 23, 33, 19 and 23%, respectively. In Trial 2, 6 t of barley straw was treated with anhydrous NH 3, 3 t in summer (STS) (38°C ambient temperature) and 3 t in autumn (ATS) (7°C). CP content was 83% higher in the STS than in the ATS. The organic matter digestibility and the quantity of straw consumed by wether sheep were higher ( P < 0.05) in the STS than in the ATS. No differences were found in the amount of retained nitrogen. In Trial 3, the effect of the NH 3 treatment in a commercial oven (24 h at 90°C) on barley straw was studied. As the original straw was of good quality, the effect of the treatment was only a moderate increase (14%) in the ingested digestible organic matter ( P < 0.10), and an increase of 64% in CP content. The amount of nitrogen lost in faeces was higher ( P < 0.01) with treated roughage diets than with untreated diets, but the loss of nitrogen in urine was lower ( P < 0.01). Finally, in Trial 4, the effect of stack size (3.1, 4.2 and 5.0 t of straw) on treatment homogeneity was studied. No differences in CP content or dry matter digestibility in vitro were found between stacks or within stacks of different sizes.
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