Evaluation of a microwave method for dry matter determination in faecal samples from weaned pigs with or without clinical diarrhoea
2011
Pedersen, Ken Steen | Stege, Helle | Nielsen, Jens Peter
Microwave drying as a procedure for determination of faecal dry matter in weaned pigs was evaluated and clinical relevant cut-off values between faecal consistency scores were determined. Repeatability and reproducibility were evaluated. Overall coefficient of variation was 0.03. The 95% confidence limits for any future faecal subsample examined by any operator in any replica were ±0.85% faecal dry matter. Robustness in relation to weight of wet faeces was evaluated. The weight categories were 0.5, 1.0, 1.5, 2.0 and 3.0g. Samples of 0.5g gave significantly different mean faecal dry matter content compared to weighing of 1.0–3.0g. Agreement with freeze-drying was evaluated. Lin's concordance correlation coefficient was 0.94. On average the faecal dry matter values was 1.7% (SD=1.99%) higher in freeze dried compared to micro waved samples. Non-parametric ROC analyses were used to determine optimal faecal dry matter cut-off values for clinical faecal consistency scores. The 4 consistency scores were score 1=firm and shaped, score 2=soft and shaped, score 3=loose and score 4=watery. The cut-off values were score 1: faecal dry matter content >19.5%, score 2: faecal dry matter content ≤19.5% and >18.0%, score 3: faecal dry matter content ≤18.0% and >11.3%, score 4: faecal dry matter content ≤11.3%. In conclusion, the microwave procedure has an acceptable repeatability/reproducibility and good agreement with freeze drying can be expected. A minimum of 1.0g of wet faeces must be used for analyses. Faecal dry matter cut-off values between 4 different clinical consistency scores were determined.
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