CHARACTERIZATION OF IN-SITU DEGRADATION OF LUCERNE PROTEINS ACCORDING TO FORAGE TYPE (GREEN FORAGE, HAY AND SILAGE) USING GEL-ELECTROPHORESIS

We compared the degradation of lucerne proteins in the rumen according to forage type (green forage, hay, silage) and to plant organ (stems and leaves). Four ruminally fistulated sheep were used. They were fed the same forage as that placed in the nylon bags. Forages were incubated in nylon bags at eight different times (0-48 h) in the rumen. Proteins were extracted, and separated by sodium dodecylsulphate-polyacrylamide gel electrophoresis. The theoretical nitrogen degradabilities (Deg) were similar between forages (83.5 for hay to 89.3 for silage treated with formic acid). The main forage protein, ribulose 1-5-diphosphate carboxylase (rubisco), was degraded rapidly in the rumen for fresh forage and hay. Little rubisco was found in stems and degradation apparently was already complete in the silo for silages. Proteins of chloroplast membranes resisted breakdown during early fermentation and completely disappeared at 48 h for all the forages.