In situ estimation of indigestible compounds contents in cattle feed and feces using bags made from different textiles

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Abstract
The objective of this experiment was to evaluate estimates of concentration of indigestible dry matter (iDM), indigestible neutral detergent fiber (iNDF) and indigestible acid detergent fiber (iADF) in samples of cattle feed and feces processed at different particle sizes (1-, 2-, and 3-mm) using bags made from nylon (50 μm), F57 (Ankom®), and non-woven textile (NWT - 100 g/m²) in a in situ evaluation procedure. Eight samples of concentrates, seven samples of forages and two samples of cattle feces were used. The samples were put in the bags according to a ratio of 20 mg of dry matter/cm² of surface by using three bags of each textile for each size of particle, totaling 405 bags, which were submitted to ruminal incubation for 264 hours. The contents of indigestible compounds in the samples were evaluated sequentially. Blank bags were used for microscopic evaluation of textile physical integrity and for evaluation of the physical resistance. The presence of contaminants caused high variability of results of iDM, indicating that its using as internal marker should not be recommended. By using the textiles F57 and NWT, similar estimates for contents of iNDF and iADF were obtained whereas by using nylon (50 μm), the concentration of iNDF was underestimated, possibly because of loss of particles due to its porosity. Nylon presented loss of resistance in all analytical stages, expanding its probality of rupture, especially after extraction with acid detergent. For in situ evaluation of indigestible compounds, it is suggested grinding samples in 2-mm screen sieves.

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