EFFECT OF PLANT MATURITY AND PRESERVATION METHOD ON IN-VITRO PROTEIN-DEGRADATION OF FORAGES

The influence of maturity and method of conservation on protein degrad ation was determined for four different forage species. Alfalfa, smoot h bromegrass, and reed canarygrass were harvested at three maturities, and whole plant corn was harvested at two maturities. Samples of each forage were freeze-dried or wilted and then ensiled in mini silos at two DM contents. Additional samples of all forages except corn were fi eld-dried to hay. Ground sample was incubated for 0, 2, and 24 h with crude enzyme extract from ruminal contents. Degraded protein as a perc entage of total CP was determined as the amount of protein that was so luble in TCA (80 g/L) after degradation. Increased maturity resulted i n lower protein degradation for alfalfa, bromegrass, and canarygrass. For example, the most mature alfalfa or bromegrass, respectively, had 77 or 63% as much N that was soluble in TCA after 2 h of incubation wi th ruminal enzyme than the least mature forage of the same species. Al though protein degradation was higher for ensiled than for dried forag e, silage DM content had no consistent effect. Freeze-dried material g enerally had less degraded protein than hay, but protein degradation o f bromegrass at 24 h was lower for hay than for freeze-dried samples. Protein degradation of forages was highly variable and depended on pla nt maturity and conservation method.