Abstract
A study was made of the influence of 2 levels of nitrogen fertilization and stage of maturity on chemical composition and feeding value of soiling rape (Brassica napus L.). Soiling rape was harvested at the vegetative in winter, vegetative in spring, heading, blooming and seed forming stages as shown in Table 2. Each of these stages was treated with low (6kg/10a) and high (18kg/10a) nitrogen levels applied as ammonium sulphate. Digestion trials of soiling rape were carried out with male rabbits of about 2, 500 grams of body weight and its forage was fed in fresh form cut in small spieces to them. The effects obtained due to the high level of nitrogen fertilization were summarized as follows : 1. The contents of crude protein and nitrate increased throughout all the growing stages. 2. The digestibility of crude fiber increased significantly at each stage (except P<.05 at vegetative in winter, P<.01 at other stages of growth). 3. The content of DCP increased significantly (P<.01) and the content of TDN also increased significantly (P<.01) at each stage of growth except vegetative stage in winter. Both nutrients did not show a tendency of conspicuous decrease with the progress of growth. 4. In this study a significant correlation between the crude protein content and DCP content and between the crude lignin content and TDN content was found, their correlation coefficients having been 0.992 (P<.001) and 0.801 (P<.01) respectively. From above results, the crude protein (CP) was the prominent constituent for the prediction of DCP content and the crude lignin (CL) for TDN content, and their relationships are expressed by the following equations : DCP=0.910 CP-1.4 and TDN=82.5-3.471 CL where DCP, TDN, crude protein and crude lignin are shown in percentage of dry matter.
