Designing agricultural grasses to help mitigate proteolysis during ensiling to optimize protein feed provisions for livestock

The efficient preservation of protein in silage for livestock feed is dependent on the rate and extent of proteolysis. Previous research on fresh forage indicated enhanced protein stability in certain Festulolium (ryegrass × fescue hybrids) cultivars compared to ryegrass. This is the first report of an experiment to test the hypothesis that a Lolium perenne × Festuca arundinacea var glaucescens cultivar had reduced proteolysis compared to perennial ryegrass (L. perenne) during the ensiling process. Forages were harvested in May (Cut 2) and August (Cut 4), wilted for 24 h and ensiled in laboratory-scale silos. Silage was destructively sampled at 0 h, 9 h, 24 h, 48 h, 72 h, 14 days and 90 days post-ensiling, and dry matter (DM), pH and chemical composition were determined. At Cut 2, there was no difference in crude protein between treatments but ryegrass had higher soluble nitrogen (SN) (P < 0.001) and grass × time interactions (p = 0.03) indicated higher rates of proteolysis. By Cut 4, Festulolium had (5.5% units) higher CP than ryegrass (p < 0.001) but SN did not differ. Ammonia-N did not differ between silages in either cut. DM differences (11.8% units) between treatments in Cut 4 (v.2.2% in Cut 2) may have masked effects on proteolysis, highlighting the importance of management on silage quality. This was despite higher WSC in ryegrass in both cuts (p < 0.001), with grass × time interactions (Cut 2; p = 0.03) showing slower WSC decline in ryegrass in Cut 4 (p < 0.001). Silage pH values did not differ between grasses in either cut, but grass × time interactions (p < 0.001) showed a slower decline in both ryegrass cuts, resulting in higher (p < 0.05) pH at 24 h and 72 h for Cuts 2 and 4, respectively. Overall, the hypothesis for an enhanced protein stability in Festulolium when ensiled as ruminant feed was evidenced by lower SN but not ammonia-N in an early-cut silage with a comparable DM to ryegrass.