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ARS Home » Midwest Area » Ames, Iowa » National Laboratory for Agriculture and The Environment » Agroecosystems Management Research » Research » Publications at this Location » Publication #262791

Title: Drying methods effects on nitrogen and energy concentrations in pig feces and urine, and poultry excreta

item JACOBS, B - Iowa State University
item PATIENCE, J - Iowa State University
item DOZIER III, W - Auburn University
item STALDER, K - Iowa State University
item Kerr, Brian

Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/22/2011
Publication Date: 7/1/2011
Citation: Jacobs, B.M., Patience, J.F., Dozier III, W.A., Stalder, K.J., Kerr, B.J. 2011. Drying methods effects on nitrogen and energy concentrations in pig feces and urine, and poultry excreta. Journal of Animal Science. 89:2624-2630.

Interpretive Summary: In animal nutrient metabolism and feed ingredient evaluation research, accurate nutrient estimation in urine, feces and excreta are critical for nutrient digestibility studies. There is however, no universally accepted method of drying feces, urine, or excreta for energy or nitrogen (N) concentration. The current data, along with previously published literature, demonstrates that regardless of drying method, some loss of gross energy and N appears to be inevitable. However, there appears to be no distinct advantage between freeze drying and oven drying on the degree of these losses. This information is important for scientists involved in animal nutrient metabolism studies to understand potential losses of gross energy and N due to processing (drying) of feces, urine, and excreta prior to laboratory analysis.

Technical Abstract: Accurate estimation of digestibility coefficients are critical in nutrient balance and feed evaluation studies as errors that occur are often additive. However, there is no standard universal method for drying feces, urine, or excreta prior to laboratory analysis. The objective of this study was to evaluate the impact of four different drying methods on nutrient concentrations in feces, urine, and excreta. Twelve individually penned growing pigs were fed one of three diets and 16 pens of 10 growing broilers were fed one of four diets that differed in NDF and CP. Feces, urine, and excreta that varied widely in nutrient composition were collected after diet adaptation. Samples were dried using one of four methods: UD-undried, FD-freeze dried, OD55-oven dried at 55°C for 48 h, or OD100-oven dried at 100°C for 48 h, after which DM, GE, N, C, and S were determined. In swine feces, drying resulted in a loss of GE (P < 0.10) and S (P < 0.05) by 5% and 58%, respectively. There was no difference among drying method on DM, GE, N, C, or S concentrations. There were no differences in urinary GE due to drying or between drying methods, however urinary DM was greatest by FD compared to OD (P < 0.05) and higher for OD55 compared to OD100 (P < 0.01). In poultry excreta, GE (P < 0.05), N (P < 0.10), and S (P < 0.01) were reduced by drying by an average of 6%, 10%, and 66%, respectively. There were no differences among drying methods except FD excreta had a greater S concentration than OD (P < 0.10). Regardless of drying method, some GE and N loss appears to be inevitable, but there is no apparent advantage between freeze drying and oven drying. The apparent greater S losses warrants further investigation.