Development of NIRS calibrations to estimate fecal composition and nutrient digestibility in beef cattle.

Use of near infrared spectroscopy for the evaluation of forage for ruminants

“…In the application of this technique, instead of a forage spectra, feces is collected, and from this, the calibration and validation equations are built. Brogna et al (2018), using the NIRS technology to predict fecal indigestible neutral detergent fiber for dairy cows, observed R 2 of 0.77 and SEC of 0.90, DM and R 2 of 0.93 and SEC of 0.74 for CP and R 2 of 0.66 and SEC of 0.43 for starch, that can be considered good calibration models, as the results founded by Jancewicz et al (2016) that developed NIRS equations to predict fecal composition (OM, starch, N, NDF, ADF, ADL, and EE) and digestibility [DM, OM, starch, CP, NDF, ADF and gross energy (GE)] and found good results (R 2 ≥ 0.70 and SEP ≤ 6.85) for OM, starch, N, NDF, and ADL, and less promising results for ADF and EE, which can be observed by the lower result of R 2 (0.25) and high SEP (≤ 11.0).…”

Digestibility and growth performance of feedlot cattle fed pelleted grain screenings

“…Principle component analysis demonstrated that none of the fecal samples from the current study were outliers to the population of spectra for chemical composition (95% confidence level; Figure 2A). This was expected as a subset of these samples was used in calibration development (Jancewicz et al 2016a). …”

“…The time points were selected so as to represent the full finishing period. Fresh fecal samples were collected from pats in a manner that ensured that they were not contaminated with soil, bedding, or urine as described previously (Jancewicz et al 2016a;2016b). Samples were pooled by pen on an equal wet weight basis (400 g total), generating 45 samples over the feeding period.…”

“…For fecal samples, previously developed NIRS calibrations (Jancewicz et al 2016a) were used to predict fecal OM, starch, N, NDF, ADF, ADL, EE, and apparent total tract digestibility (aTTD) of DM, OM, starch, NDF, ADF, and gross energy (GE). Fecal samples were packed into a small quartz ring cup and scanned between 1250 and 2350 nm, in 1-nm increments.…”

“…However, NDF and ADF digestibility were 15% higher, a result that may reflect the inclusion of beet pulp in the HSP. Additionally, the NIRS calibrations for NDF and ADF digestibility that we used have substantially lower R 2 cal and SEC values compared to other nutrient digestibility calibrations, hence the risk for error is greater (Jancewicz et al 2016a). Since there were no pelleted ingredients in diets used for the development of the digestibility calibrations, it is likely that the feces of GSP fed cattle are not adequately represented by the calibration set, a possibility that was particularly evident for the LSP diet.…”