Abstract #T491

# T491
A rapid mold and yeast enumeration technique is comparable to a conventional technique for animal feedstuffs.
Lauren Meyer*1, John Goeser1,2, 1Rock River Laboratory, Watertown, WI, 2University of Wisconsin-Madison, Madison, WI.

Feedstuff and TMR yeast and mold enumerations (cfu/g) have grown in popularity to diagnose opportunities on farm. Turnaround time with conventional enumeration (CON) limits utility, requiring 5 d incubation, extending total time from sampling to reporting to 7d or more. More recent human food grade, rapid yeast and mold enumeration techniques (RAP) offer faster turnaround and may have utility for production agriculture. The objective here was to determine if RAP, tested under 2 incubation lengths, was equivalent to CON. Corn silage (n = 17), TMR (n = 3), alfalfa silage (n = 15), high moisture corn or snaplage (n = 6), small grain silages (n = 6), and concentrate (n = 6) samples submitted for CON in late February 2015 were further assayed using RAP, with both 48-h and 5-d incubation. When samples arrived, roughly 5g feed was blended and stored at 1C for later plating. At plating, 1g wet feed was subsampled and diluted to 100mL in sterile buffer, shaken and then serially diluted 1:1000, 1:10,000 and 1:100,000 for most probable number enumeration. For CON, subsamples of each dilution were taken with sterile glass pipette and plated on potato-dextrose agar using spread-plate method. For RAP, subsamples of each dilution taken with an electronic pipette were plated on Petrifilm, using a Petrifilm flat spreader (3M, St. Paul, MN). For RAP plates were aerobically incubated at 28C for both 48h and 5d and CON for 5d. Post incubation, enumeration was done by direct microscopy. Yeast and mold count mean/median across feeds and techniques were 1.69 × 106/1 × 103 and 2.53 × 105/1 × 104, respectively. Raw and log-transformed data were determined not normally distributed, hence data were fit using one-way analysis option of SAS JMPv11.0. Technique (CON, RAP-48h, and RAP-5d) and feed main effects were compared using non-parametric Wilcoxon/Kruskal-Wallis test. Significance was declared if resulting Chi-squared statistic p-value was < 0.05. For both mold and yeast enumeration, techniques did not differ (P > 0.05) while feed types differed (P < 0.01). Our results suggest both yeast and mold enumeration results are comparable across the techniques tested here.

Key Words: feed, mold, yeast