Submitted to: American Society of Animal Science Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 6/21/2002
Publication Date: 9/1/2002
Citation: BODINE, T.N., APPEDDU, L.A., PURVIS, H.I., LAMANA, A.F., BASURTO, R.G., WEYERS, J.S. COMPARISON OF ACID DETERGENT INSOLUBLE ASH (ADIA) AS AN INTERNAL MARKER WITH TOTAL FECAL COLLECTION TO ESTIMATE DIGESTIBILITY COEFFICIENTS OF FORAGE-BASED DIETS FED TO BEEF STEERS. AMERICAN SOCIETY OF ANIMAL SCIENCE PROCEEDINGS. 2002. v. 53. p. 581-584.
Interpretive Summary: Acid detergent insoluble ash (ADIA) is a natural forage component with the potential to be used for calculating forage digestibility coefficients. The ADIA content of forage and fecal samples is simply determined from a standard laboratory procedure, as the inorganic component remaining after conducting an acid detergent fiber (ADF) analysis. Fiber digestibility can be calculated by multiplying the ratio of ADIA content in the feed to feces by the ratio of ADF content in the feces to feed. Because ADIA consists of inorganic material, ADIA susceptibility to soil contamination was determined. Soil textures consisting of fine (clay), coarse (sand), or intermediate (clay loam and sandy loam) particle sizes were mixed into the wet feces of forage-fed steers at rates of 0, 2.0, 5.0, 9.7, 18.5, 26.5, 33.8, 46.7, and 57.6 g soil/100 g dry feces. The importance of correcting for organic matter was demonstrated by the artificially high fiber contents detected in unadjusted fecal samples as compared to those adjusted for organic matter content. Unadjusted ADF values were most inflated in samples with higher levels of sand and sandy loam. This point was further illustrated by similar ADF contents being found for samples with or without soil and adjusted for organic matter content, until ADF was increased by higher levels (greater than 33.8%) of soil addition. Fecal ADIA content increased over the baseline values of samples without added soil when more than 18.5% clay, 18.5% clay loam, 9.7% sand, and 26.5% sandy loam were added. As soil level increased, the cumulative effect of soil addition on ADIA content was ranked as sand > sandy loam > clay loam > clay. Fecal ADIA content of field samples should be compared to ADIA values determined by feeding similar forages to confined animals and conducting total fecal collections. Researchers should also consider the effects of pasture soil type and pasture conditions (short pasture, highly digestible forage, excessively wet or windy weather) which may increase soil consumption or soil proportion in feces. Adding pasture soil to fecal samples may serve as a simple test to evaluate whether fecal fiber or ADIA contents are being artificially increased under specific experimental conditions.
Technical Abstract: Acid detergent insoluble ash (ADIA) is the inorganic fraction found after conducting an ADF. It has the potential to be used as an internal marker to estimate digestibility in forage-fed animals, but may be affected by non-plant inorganic components. The objective of this research was to determine how level and type of soil addition can affect fecal ash, ADF, and ADIA content. Four soils commonly found in the Southern Great Plains [Clay (C), Clay Loam (CL), Sand (S), and Sandy Loam (SL)] were sieved (2.38 mm) and added to 200 g wet feces at an estimated 0, 2.5, 5, 10, 15, 20, 30, and 40% of the dry weight. Feces were taken from four, hay-fed steers. Mixed samples were oven-dried and ground (2 mm) before laboratory analysis. Feces without added soil had 18 ± 1.4% ash, 38 ± 1.2% ADF (OM basis), and 12 ± 1.5% ADIA. Average soil ash was 97%. Fecal ash increased 1.2% for each 1% addition of soil (R square = 0.96). An interaction between added soil level and type was detected (P < .001) for ADF and ADIA measures. While fecal ADF content (OM basis) was not affected by C, it increased when 40% CL was added (P < 0.01) or by adding more than 30% SL and S (P < 0.02). Not correcting for ash increased (P < 0.01) fecal ADF as compared to ADF expressed on an ash-free basis. Percent ADIA increased (P < 0.03) when more than 10% C, 10% CL, 5% S, or 15% SL was added to feces. Sand inflated ADIA content the most (P < 0.01). Because ADIA content may be increased by soil ingestion and contamination, monitoring pasture soil type and validating ADIA levels may prevent artificially high digestibility estimates when using ADIA as an internal marker.