Assessment of Sampling Technique of Swine Diets on Analytical Variation

This study was designed to evaluate different sampling procedures and number of samples to collect from feeders within a swine facility to achieve an accurate assessment of nutrient fortification in swine diets. Treatments were arranged in a split-plot design with whole-plots receiving 1 of 6 concentrations of dietary Cu (27 to 147 mg/kg total Cu included in the diet) and subplots sampled with 1 of 2 techniques (probe vs. hand grab). A total of 6 feeders per dietary treatment were sampled using a 1.6 m brass open handle probe (Seedburo Equipment Company, Des Plaines, IL), which contained 10 openings spaced approximately 5 cm apart. The probe was inserted into the feeder on average 4 times to obtain ~ 900 g of sample. Alternatively, samples were simply collected by inserting a bare hand into the feeder approximately 8 times to obtain the ~900 g sample. Within a feeder and sampling technique, subsamples (~200 g) were created by using a sample splitter. In addition to the 6 individual feeder samples, a subsample (~33 g) from each individual feeder was pooled within dietary treatment and sampling technique to form a single composite sample. This process was repeated until 4 individual composite samples were created for each diet and sampling technique. All samples were ground through a centrifugal mill and submitted for mineral analysis in duplicate. Results indicated that the variability when sampling feeders with an open handle probe was reduced (P=0.013) for Cu and marginally reduced (P=0.058) for Ca when compared with hand-sampling. There was no evidence for differences detected among sampling techniques when samples were pooled from 6 feeders to form a single composite sample. From these results, sampling frequency calculations were determined to assess sampling accuracy within a 95% confidence interval. Results indicated that the number of feeders or composite samples required to analyze was less when using a probe compared to hand collection. In summary, these results suggest that sampling with a probe is associated with less variability when analyzing individual feeder samples; however, this difference was not evident when pooling individual samples to form a composite sample. In addition, using a probe to obtain complete feed from swine feeders and pooling of individually collected samples reduces variability in analyzed nutrient results leading to a need for fewer replicate samples analyzed, which will help reduce analytical costs.