Abstract
Relationships between heat temperature and degradation of ruminal nitrogenous compounds in various roughages were discussed on the basis of proportion of nitrogen disappearance from a nylon bag placed in a rumen. First cutting Italian ryegrass (Lolium multiflorum, Lam.) dried at four levels of temperature (freeze, 40℃, 80℃ and 120℃) and ensiled at two levels of temperature (20℃ and 60℃) were prepared, and described as dried materials and ensiled materials, respectively. The materials were put into the rumen by an in situ nylon bag technique and taken out after 2, 4, 6 and 8 hr. rumen exposures. The residual nitrogen content in the bag was measured to determine the proportion of nitrogen disappearance. In order to classify degradation pattern of nitrogenous compounds by a simple and mathematical way, the obtained results were simulated to a logistic equation :Y = M/ (1 + Ke^<-ax>) or Y = M/ (1 + Ke^<-a√<X>>), where Y = proportion of nitrogen disappearance; X = ruminal exposure hours ; K, M and a = coefficients. 1. The proportion of nitrogen disappearance in the rumen of freeze-and 40℃-dried materials and 20℃-ensiled materials showed more than 70% after 2 hr. rumen exposure. While those of 80℃- and 120℃-dried materials showed only 45% and 30%, respectively, after 2 hr. rumen exposure, those values increased up to 85% and 80%, respectively, after 8 hr. rumen exposure. Those of the materials ensiled at 60℃ for 6 and 12 days showed 60% and 45%, respectively, after 2 hr. rumen exposure. The values of 60℃-ensiled materials showed lower throughout 8 hr. rumen exposure than those of 20℃-ensiled materials. 2. Degradation pattern of nitrogenous compounds in the rumen differed between the materials treated under 40℃ and the one over 60℃. It seemed to be reasonable that the pattern could be shown as Y = 100/ (1 + Ke^<-aX>) for freeze-dried, 40℃-dried and 20℃-ensiled materials, and Y = 100/ (1 + Ke^<-a√<X>>) for 80℃-dried, 120℃-dried and 60℃-ensiled materials. 3. On the basis of the speed of nitrogen disappearance in the rumen, total nitrogenous compounds in the materials were grouped into three fractions containing soluble, insoluble-degraded and undegraded nitrogen. In the materials heat-treated over 60℃, the amount of soluble nitrogen fraction was smaller and that of undegraded nitrogen fraction was larger as compared to those heat-treated under 40℃. However, the disappearance speed of insoluble-degraded fraction in the rumen was low and almost constant throughout the rumen exposure.
