Abstract #M167

# M167
Effect of cobalt source on nutrient digestibility, microbial protein production and efficiency and B12 synthesis in dual-flow continuous culture fermentors—Summary of 4 studies.
K. E. Ritz*1, C. L. Engel1, M. T. Socha1, C. S. Kending1, P. Stark1, 1Zinpro Corporation, Eden Prairie, MN.

Four dual-flow continuous culture fermenter studies were summarized to determine effects of Co source, (1 ppm Co) on nutrient digestibility, microbial protein production and efficiency and vitamin B12 synthesis. Three Co sources, CoSO4, cobalt glucoheptonate (COPRO, Zinpro Corp., Eden Prairie, MN) and Co pectin (CoPectin, Zinpro Corp.), were evaluated in 3 to 4 studies. Rumen inoculum was obtained and pooled from 2 ruminally cannulated Holstein cows consuming a lactation diet absent of Co. In each completely randomized study, treatments were run in triplicate over a 17 d fermentation period, sampled d 15–17. A standard lactation diet (100 g DM/d) was fed in 4 meals/d. Artificial saliva was continuously infused into the fermenters (1162 mL volume), for a 13%/h liquid dilution rate and 22 h solid retention time. Select data were analyzed using linear mixed effect regression model of R. Random effects were included in the model to account for different repeated measures intercepts. The 3 Co sources had similar (P ≥ 0.15) total VFA production (376 mmol/d), and DM, OM, ADF, NDF, and NSC digestibilities (65, 57, 42, 41 and 81% respectively). Vitamin B12 production was similar (P ≥ 0.15) among the Co sources but numerically greatest for CoPectin (10870, 10557, 10281 pmol/d; CoPectin, COPRO and CoSO4 respectively). CoPectin tended to have greater CP digestibility and microbial N production than CoSO4, with COPRO intermediate (P ≤ 0.15; 78.6, 72.4 and 76.5% and 2.11, 1.91 and 2.04 g/d, respectively). Greater (P ≤ 0.05) amounts of feed N were converted to microbial N with CoPectin than CoSO4, with COPRO intermediate (93.8, 92.4 and 93.5 respectively). CoPectin and COPRO produced greater amounts of microbial N/kg OM digested than CoSO4 (P ≤ 0.05; 38.9, 37.8 and 35.1 respectively). Replacing 1 ppm Co from CoSO4 with 1 ppm Co from CoPectin or COPRO increased microbial protein production and efficiency and numerically increased vitamin B12 production in continuous culture. CoPectin improved microbial protein production and efficiency over COPRO.

Key Words: cobalt, B12, microbial efficiency