The effect of Aspergillus oryzae fermentation product on production parameters, rumen environment, and fiber degradability of Jersey cows grazing ryegrass-dominant pasture.

Aspergillus oryzae fermentation product (AOFP; Amaferm-Biozyme Inc., St. Joseph, MO, USA) is a feed additive produced from a dried fermentation extract of the fungus Aspergillus oryzae NRRL458. Previous research on AOFP supplementation were done on total mixed rations and in vitro systems, with research on pasture-based systems lacking. The aim of the study was to evaluate the impact of AOFP on milk production, milk composition, rumen environment, fiber degradation, and dry matter intake (DMI) in Jersey cows grazing ryegrass pasture. Treatments in this study were as follows: Control-cows received 6 kg per cow per day (as-fed) of a pelleted dairy concentrate (159.6 g.kg-1 DM crude protein and 12.3 MJ metabolizable energy.kg-1 DM), and AOFP treatment-cows received 6 kg per cow per day (as-fed) of the same dairy concentrate with AOFP mixed in at 0.5 g.kg-1 (3 g.cow-1.d-1; as-fed). In the production study, 34 (n = 17) early-to-mid lactation cows were selected, blocked, and randomly allocated to treatments. From this group, 20 cows (n = 10) were randomly selected for the DMI study. For the rumen Study, 6 rumen-cannulated cows were used in a crossover design with 2 treatments and 2 periods. Data collected for the production study included daily milk production and milk composition. DMI was determined using the TiO2 method. During the study of the rumen, rumen pH was recorded for 3 continuous days. Rumen fluid was sampled and analyzed for volatile fatty acid (VFA) and ammonia nitrogen concentrations (NH3-N), and an in sacco dacron bag study was performed to determine dry matter (DMd) and neutral detergent fiber (NDF) disappearance (NDFd). Milk production and composition did not differ between treatment groups (P ≥ 0.05). Milk fat content tended (P ≤ 0.10) to be 2.3 g.kg-1 greater in the AOFP treatment group. DMI was similar (P ≥ 0.05) between treatment groups. Average rumen pH was lower (P < 0.05) for cows on the AOFP treatment but remained within an optimal range for rumen microbial function. Rumen VFA and NH3-N concentrations did not differ (P ≥ 0.05). The in sacco dry matter and NDF disappearance were not affected (P ≥ 0.05) by AOFP supplementation. To conclude, supplementation of AOFP to cows grazing ryegrass did not affect milk production but tended to increase milk fat content. Rumen parameters and degradability of ryegrass were not affected by AOFP supplementation.