Effect of sample volume and time on rumen juice analysis in cattle.

Abstract

BACKGROUND: Rumen juice analysis (RJA) involves analysis of a 10mL sample within minutes after sampling. However, it can be challenging to collect 10&#x2009;mL of rumen juice (RJ) from some ruminants, and clinical circumstances can delay RJA. OBJECTIVES: Quantify the effect of sample volume (2, 5, 10, 50, and 100&#x2009;mL), and time-to-analysis (0, 30, and 60&#x2009;minutes) on RJA. ANIMALS: Cannulated cow. METHODS: Observational experimental study. Two liters of RJ were collected at 26 separate times. The samples were subdivided into 2 duplicates of each sample volume at each sampling time; and analyzed at 0, 30, and 60&#x2009;minutes after collection. Rumen juice analysis included pH measurement, methylene blue reduction time (MBRT), and protozoal motility. RESULTS: The pH of 2 and 5&#x2009;mL samples was significantly (P&#x2009;=&#x2009;.01) higher than the pH of 50 and 100&#x2009;mL samples at all time points. The MBRT was significantly lower (faster bacterial reduction) for 100&#x2009;mL samples compared to all other samples at 0&#x2009;minute and to 2, 5, and 50&#x2009;mL samples at 30 min. The pH and MBRT at 60&#x2009;minutes were significantly higher than at 0&#x2009;minute for all volumes (P&#x2009;<&#x2009;.05 and P&#x2009;<&#x2009;.01, respectively). For large protozoa, small sample volumes (2 and 5&#x2009;mL) had significantly lower protozoal motility (scores of 5 and 4.5, respectively) compared to 100&#x2009;mL samples at 60&#x2009;minutes (score of 4; P&#x2009;<&#x2009;.05). CONCLUSIONS AND CLINICAL IMPORTANCE: Interpretation of RJA could be affected by small sample volumes and delays to analysis. Sample volumes of &#x2265;10&#x2009;mL analyzed within 30&#x2009;minutes after collection are recommended.