Submitted to: Meeting Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 9/6/2010
Publication Date: 9/6/2010
Citation: Agudelo, J.H., Escobar, C.S., Lindemann, M.D., Kerr, B.J., Cromwell, G.L. 2010. Further Comparison of Direct and Indirect Estimates of Apparent Nutrient Digestibility with Effort to Reduce Variation by Pooling of Multi-day Fecal Samples. In: Crovetto, G.M. (ed.) Proceedings of the 3rd International EAAP Symposium on Energy & Protein Metabolism & Nutrition, September 6-10, 2010 in Parma, Italy. p. 151-152. Interpretive Summary:
Technical Abstract: Total tract apparent digestibility of nutrients (DIG) is traditionally assessed by either total collection (TC) or by the indicator method (IM). The IM saves labor by measuring the concentration of an indigestible indicator (e.g. Cr2O3 [CO]) in feed and feces, purportedly resulting in similar DIG values as TC. Our previous efforts have demonstrated that the IM methodology may not be as discriminating for the detection of treatment differences as TC, depending on how the IM is conducted. We have reported that a multiday IM sample is better than a single grab sample, and that several days of marker observance in feces are required before the marker content stabilizes in the feces (Agudelo et al., 2010). The objective of this experiment was to further define a more efficacious manner of pooling fecal samples that will provide a DIG value that most closely approximates that obtained by TC and that minimizes variation and thereby equals the precision of TC. A total of 24 pigs (mean BW = 46.3 kg) were fed one of 4 diets (a 2 x 2 factorial arrangement of virginiamycin and phytase added to a low P basal diet). The diets were designed to have differences in phosphorus digestibility that would be detectible by TC. Pigs were individually housed in metabolism crates for a 5-day (d) TC in which beginning and ending diets were marked with indigo carmine. The IM phase immediately followed the TC by including CO at 0.25% in the feed for 10 days. Collection of fecal samples for IM started the day after CO was first fed and continued for 9 consecutive days. Feces from collection days 1 to 9 were kept separated and labeled ‘D 1’, ‘D 2’, etc. to ‘D 9’. Similar portions of feces from days 5 to 9 were then composited into 4 samples labeled: ‘D 10’ (composited from days 5 and 6), ‘D 11’ (composited from days 5, 6, and 7), ‘D 12’ (composited from days 5, 6, 7, and 8), and ‘D 13’ (composited from days 5, 6, 7, 8, and 9). The number of samples analyzed was 13/pig for a total of 312 samples for IM DIG in addition to the 24 samples from TC. All diets and samples were then analyzed for dry matter (DM), gross energy (GE), N, P, acid detergent fiber (ADF), and neutral detergent fiber (NDF). The statistical analysis of the data obtained is in process.