Study of a subhumid method of straw processing with urea.

We tested a subhumid processing method which reduces water content by 50% w ithout the contribution of exogenous urease sources. The principle consiste d in applying a 7% urea solution to one out of two layers of straw at a 40% humidity level, the last upper layer being systematically watered. The sta ck was then sealed as for classic ammoniation. At the same time, a classic treatment (also with 7% urea) was performed. At the end of the treatment wh ich lasted for 75 days during the summer, four straw-based diets were evalu ated: untreated straw (NT), classically treated straw (UC), non-damped stra w (ULNH) and damped straw (ULH). Intake and organic matter digestibility we re measured in rams (6 per diet) fed on straw supplemented daily with 200 g concentrate. After processing, the nitrogenous matter content increased fr om 5.8% (NT) to 11.0, 12.6, and 16.1% for ULNH, UC, and ULH, respectively, whereas the dry matter intake of pure straw was 47.5, 52.7, 54.1 against 59 .7 g.kg(-1). PV-0.75 for NT, UC, ULH, and ULNH, respectively. Organic matte r digestibility was higher for ULNH (59.4%) than for ULH (56.3%), UC (51.1% ) and NT (46.0%). The amount of digestible organic matter intake was 23% hi gher for straw derived from the subhumid treatment than that resulting from the classical treatment.