Relationship between intake and faecal excretion of indigestible fractions in trials with sheep: impact of the method of analysis, diet and trial

• Published in: The Journal of agricultural science Vol. 160; no. 3-4; pp. 270 - 277
• Main Authors: Pozo, C. A., Mezzomo, M. P., Frasson, J., Leonardi, L. E., Christmann, C. M., Rösler, D. C., Kozloski, G. V.
• Format: Journal Article
• Language: English
• Published: Cambridge, UK Cambridge University Press 01.06.2022
• Subjects: Animal Research Paper; Cassava; Diet; Dietary fiber; Digestibility; Drinking water; Dry matter; Feces; Feeds; Markers; Methods; Porosity; Sheep; Soybeans; Variables; Brazil; ruminants; indigestible dry matter; internal markers; indigestible neutral detergent fibre; Digestibility
• ISSN: 0021-8596; 1469-5146
• DOI: 10.1017/S0021859622000181

A data set of individual observations was compiled from 17 digestibility trials with sheep with the aim of evaluating the impact of the method of analysis and, within each method, the effect of dietary fibre content and trial on the faecal recovery rate (RR) of indigestible dry matter (iDM) and indigestible neutral detergent fibre (iNDF). Markers concentration in samples of diet and faeces were determined either in polyester filter bags of 40 μm of porosity incubated in situ for 144 h (method A; n = 257) or in bags of 16 μm of porosity incubated in situ for 288 h (method B; n = 321). Regardless of the incubation method, the intake of either iDM or iNDF was linearly (P < 0.05) related to the amount excreted in faeces and, for all linear relationships, the slopes were lower than 1 (i.e. between 0.53 and 0.71). Within both methods, the RR of both markers linearly decreased at increased NDF content in diet (P < 0.05). The root mean square error of the linear relationships varied from 0.147 to 0.189 which represented from 19% to 24% of the respective average RR of markers. In conclusion, regardless of the incubation method, the RR of both markers showed high individual variability and, thus, the use of average RR values obtained in controlled digestibility trials as an index to correct the individual digestibility values obtained with either marker in field trials has the potential to improve the accuracy but not the precision of the digestibility estimates.