Impact of feeding management and tannins on rumen inoculum pH and activity

CLAUDIO A. POZO; GILBERTO V. KOZLOSKI; CECILIA CAJARVILLE; MAIRA CUFFIA

Gramado

Congreso; 53 Annual Meeting of the Brazilian Society of Animal Science; 2016

The aim of this study was to evaluate the effect of the Acacia mearnsii tannin extract (TE) inclusion (15 g kg-1) in a partial mixed ration (PMR) and the feeding management on in vitro fermentative activity of the rumen inoculum collected from grazing dairy cows. The trial was conducted with three Holstein cows averaging 196±16 days in milk, in a 3 × 3 Latin square design, through three 22-days experimental periods. The treatments were either morning pasture allocation and afternoon PMR supply (AM) without TE; morning pasture allocation and afternoon PMR supply with TE (AMt) and morning PMR supply without TE and afternoon pasture allocation (PM). On day 20 of each experimental period, rumen inoculum was collected 6 h after the morning meal, the pH was measured and then used in an in vitro dry matter digestibility assay. Substrate samples were ryegrass, foxtail millet hay, corn silage and two whole-crop oat silages. Substrates were dried and ground (1 mm screen) and weighed (0.5 g) in triplicates into filter bags (F57, Ankom, 25 M porosity) and incubated at 39oC for 48 h in an Ankom Daisy fermenter. Each jar of the fermenter contained 1.6 L of buffer solution and 0.4 L of rumen inoculum. After incubation, the bags were rinsed and then washed for 1 h at 100°C with a neutral detergent solution in an Ankom220 fiber analyzer and dried at 105°C. Statistical analysis was carried out using the MIXED procedure of SAS. The TE inclusion in the PMR neither affected the rumen inoculum pH nor the in vitro dry matter digestibility (IVDMD) of forages. However, both rumen inoculum pH and IVDMD were on average higher when the inoculum was collected from cows grazing in the morning compared to those feeding PMR in the morning (6.41 vs 5.90 and 70.46 vs. 68.35%, respectively; P