PRESERVATION OF PROTEIN IN WILTED LUCERNE USING FORMIC, SULFURIC OR TRICHLOROACETIC-ACID

A laboratory-scale experiment was conducted with lucerne (Medicago sat iva) to determine the effects of acid treatment on proteolysis during ensiling and during subsequent in vitro ruminal protein incubations. L ucerne [300 g dry matter (DM) kg(-1) forage] was either untreated (con trol) or treated with sulphuric, formic or trichloroacetic acid (a pro tein precipitant that stops enzyme activity) at levels sufficient to a djust immediately forage pH to 4.0, then conserved as either silage or hay. Timecourse data indicated that non-protein nitrogen (N) formatio n was 70-90% complete after 1 d of fermentation in the silo. Non-prote in N concentrations (g kg(-1) total N) were 177 at ensiling and increa sed to 567 (control), 426 (sulphuric), 398 (formic) and 263 (trichloro acetic) after 60 d of ensiling. Because non-protein N in silage treate d with formic and sulphuric acids was nearly three times greater than that in silage treated with trichloroacetic acid, it is clear that the typical acid treatments only slow proteolysis and do not destroy prot ease activity during ensiling. The ruminal protein degradation rate of conserved forages was slower than that of fresh-cut forage that was p reserved with dry ice immediately after cutting. The degradation rate of all acid-treated forages was similar, indicating a consistent effec t on ruminal degradation regardless of method of preservation. There w as a clear effect of acid treatment on reducing the rate and extent of ruminal degradation of protein in lucerne hay.