PSIII-24 - Effect of curing extent on red clover hay and silage in situ degradability kinetics in dairy cattle

Abstract: This objective was to evaluate the effects of insufficient (WET) or ample (CUR) curing on red clover silage (29.4 and 45.3% DM, respectively) and hay (65.1 and 89.1% DM, respectively) ruminal degradation. The red clover field was divided into 5 blocks and each block was divided into 2 plots and then assigned randomly to silage and hay. Hay was packed into mini-bales (~500 fresh g; ~232 kg DM/m³) and silage into mini-silos (19.5 L; ~214 kg DM/m³). Measurements were taken once storage processes had stabilized for hay and silage (50 and 78 d, respectively). Samples were ground to pass 4-mm screen and weighed (5 g DM) into 10 x 20 cm ANKOM R1020 in situ bags. Bags were hooked to a rope, placed in the ventral sac of the rumen of 2 dairy cows for 0, 3, 6, 12, 24, 48, 72, and 96 h. All bags were removed simultaneously, washed, dried, and weighed. This procedure was conducted separately for each block. Data were analyzed as a randomized complete block design (5 blocks) with a 2 (curing extents) x 2 (storage methods) factorial. Differences were declared at P ≤ 0.05. Discrete lag times were higher for WET than CUR (0.23 vs. 0 ± 0.08 h, respectively). The potentially degradable fraction was higher in hay than in silage (50.2 vs. 45.1 ± 1.32% of DM, respectively). Moreover, WET had a higher potentially degradable fraction than CUR (49.6 vs. 45.7 ± 1.32% of DM, respectively). The degradation rate was lower in hay compared to silage (5 vs. 8 ± 0.4%/h, respectively). The WET treatment had a lower degradation rate than CUR (5 vs. 7, respectively). The undegradable fraction was not different between WET and CUR hay (x̅= 23.3 ± 1.13% of DM). In contrast, WET silage had a lower undegradable fraction than CUR silage (17.1 vs. 20, respectively). In conclusion, haymaking increased the potentilly degradable fraction relative to ensiling but reduced the rate of digestion. For both storage methods, curing reduced the potentially degradable fraction but increased the rate of digestion.