In situ degradation of timothy conserved as restrictively or extensively fermented silage or as hay

Abstract

The objective of this study was to determine the effects of three modes of preserving timothy (Phleum pratense L.) on in situ degradation of dry matter (DM), organic matter, crude protein (CP), neutral detergent fiber and acid detergent fiber. First-cut timothy was conserved as hay, as restrictively fermented silage (formic acid 85% applied at 6 L t-1 of fresh crop), or as extensively fermented silage (inoculation with a mixture of Lactobacillus plantarum and Pediococcus cerevisiae yielding 1.25 × 1011 total CFU t-1). Six mid-lactating Holstein cows, previously adapted to the tested forage, were used to study the in situ degradation of each forage type (two cows per forage type). Triplicate bags were filled with 3.5 g DM equivalent of chopped wet forage and incubated in the rumen during 2, 4, 8, 12, 24, 48, or 72 h. Zero-hour bags were not inserted in the rumen. The conservation method affected in situ degradation of CP. Haying decreased (P ≤ 0.03) soluble protein (fraction a), degradation rate (c), lag time and effective degradability of CP in the rumen, and increased (P < 0.01) potentially degradable protein (fraction b) when compared with ensiling. Restricting fermentation in silage decreased (P < 0.01) fraction a and increased (P = 0.01) CP fraction b when compared with extensively fermented silage. Results indicate that conserving timothy as hay significantly decreases solubility, rate and extent of protein degradation in the rumen when compared with ensiling. Results also show that solubilization of protein in silage can be reduced by restricting fermentation with formic acid as compared with promoting fermentation with a bacterial inoculant, without a concurrent decrease in the extent of protein degradation in the rumen.