Comparison of protein and cell wall degradation of selected tropical and temperate roughages

摘要

Tropical roughages (cassava leaves, corn stover and rice straw) were evaluated as ruminant feeds in comparison to temperate roughages (alfalfa hay, brome grass and wheat straw). Comparisons were made using contrast procedures for comparable roughages, namely alfalfa hay vs. cassava leaves, brome grass vs, corn stover, and wheat straw vs. rice straw. Temperate roughages, as a group, were compared to tropical roughages. Nylon bag technique was used to determine protein and cell wall disappearance and their degradation characteristics. Samples were incubated in a cow rumen at 0, 6, 12, 18, 24, 48, or 72 hours. The nutritive quality of cassava leaves were comparable to alfalfa hay, however, CP and lignin contents of cassava leaves were greater than alfalfa hay. Comparison of brome grass was similar to corn stover, with the exception of CP content of brome grass was much higher than corn stover. Comparison of wheat straw was similar to rice straw, however, both ash and protein content of wheat straw (7.0% and 3.6%) were lower than rice straw (21.8% and 7.1%), respectively. Protein disappearance and degradation characteristics were greater for alfalfa hay than cassava leaves, with exception of the potentially degradable fraction. Protein effective degradability of alfalfa hay (76.0%) was higher than cassava leaves (61.4%). Protein disappearance and degradation characteristics of brome grass were higher than corn stover. There was no significant different in protein disappearance according to incubation time between wheat and rice straw. However, soluble protein in wheat straw was higher than in rice straw, while potentially degradable protein was higher in rice straw than in wheat straw. Overall, the protein nylon bag measurements in temperate roughages were higher than in tropical roughages, with exception for potential degradation fraction. Roughages with higher arabinose : xylose ratio had neutral detergent fiber (NDF) and tended to have higher NDF degradation characteristic and effective degradability.