The in vitro protein degradability of legume and sudan grass forage types and ensiled mixtures

Abstract

This study examined the in vitro crude protein (CP) degradability of wilted, dried for hay and ensiled Medicago sativa, Trifolium pratense and Sorghum sudanense, as well as of ensiled legume-sudan grass mixtures. The rumen degradable protein (RDP) was estimated using the latest Cornell net carbohydrate and protein system (CNCPS v6.5) and with the Streptomyces griseus protease assay (48 h of incubation). Sudan grass forages were the lowest in moderately degradable CP and the highest in CP fraction C, while red clover showed the least values for the soluble true protein like alfalfa forages for slowly degradable protein bound in neutral detergent fibre (NDF). Ensiling of legume-sudan grass mixtures decreases N-NH3 content by 12.2 and 5.1% in comparison with alfalfa and red clover silages, respectively. The RDP values for sudan grass (fresh, wilted, hay) were lower by 7.2 to 7.9% or 10.4 to 15.7% (CNCPS or S. griseus procedure) and up to 0.8 or 5.3 to 9.7% in comparison with alfalfa and red clover, respectively. The reduction of protein degradability in ensiled legume-sudan grass mixtures was 5.5 or 6.1% and 1.5 or 3% compared to alfalfa and red clover silages, respectively. Due to higher rumen undegradable protein content, the sudan grass and legume-sudan grass mixtures may be efficiently used to improve the protein utilization in ruminant nutrition.