What is NIRS?
The NIRS process involves exposing a dried, ground fecal sample
to light energy. The intensity of reflectance is measured across several hundred
wavelengths in the near infrared band. Reflectance is influenced by number and
type of chemical bonds in the feces. Primary wavelengths in prediction equations
appear to be associated with the fiber, alkane and microbial fractions of the
feces.
Predicting Diet Quality
Known diet samples were matched with feces of intact cows
grazing a wide variety of forages. These diet:fecal pairs were used to develop a
reference data set to build prediction or calibration equations. Fecal equation
diet quality predictions were then validated against herds with known diet
qualities. Equations developed to date appear to be highly reliable across a
broad spectrum of forage types. Currently, the lab can predict dietary crude
protein (CP%) and digestible organic matter (DOM%) as well as fecal nitrogen
(FN%) and fecal phosphorus (FP%). Dietary content of dicots can be estimated for
regions of contrasting C3 dicot species (forbs and browse) and C4 warm-season
grasses.
Linking NIRS with Computers
Diet quality information can be linked with the decision support
system Nutritional Balance Analyzer (NUTBAL). This software planning tool lets
the user enter the kind, class, and breed of animal to be monitored,
characterize body condition and environmental conditions, establish weight
performance targets, and then enter the NIRS diet quality results. The program
produces a nutritional balance report for protein and net energy. If a
deficiency exists, the user can use NUTBAL or other analytical tools to
determine the amount of least-cost feedstuff needed to correct the problem.
Prediction of Dietary Protein Fractions Using NIRS Technology
A major limitation to application of a more advanced nutritional management model is the inability to predict the level of degradation of crude protein
in the rumen and lower gut of free-ranging animals. NIRS technology has been successfully used to predict dietary crude protein (CP) and digestible
organic matter (DOM) of free-ranging animals (Lyons and Stuth 1993) and Spanish goats
(Leite and Stuth 1995), via fecal profiling. When combined
with the Nutritional Balance Analyzer (NUTBAL) decision support system, NIRS fecal profiling provides the necessary monitoring tool to allow
assessment of CP and net energy of maintenance/gain (Nem/NEg) (Stuth and Lyons 1995). In order for this nutritional management tool to account
for site of protein degradation, appropriate monitoring technology must be developed to support the decision process. This research explored the
potential of NIRS technology to predict degraded intake protein (DIP), digestible undegraded protein (DUP) and indigestible intake protein
(IIP).
This research project was conducted in collaboration with experiment stations at various sites in the mid-South Texas, Central Texas, Central
Oklahoma, and Central Missouri. Extrusa was subjected to laboratory techniques at the Grazingland Animal Nutrition (GAN) Laboratory on the
campus of Texas A&M University. Laboratory values were regressed against matched fecal spectra using a Perstorp Scientific 6500 machine
equipped with ISI software. In order to derive equation feasibility, hierarchical guidelines were followed, based on recent literature, that addressed
both statistical parameters as well as biological reality.
This research program served as an indication to the feasibility of utilizing NIRS technology to predict differential sites of protein degradation in the
gastro-intestinal (GI) tract of free-ranging cattle. Equations that estimate protein availability in the entire GI tract are available to aid in nutritional
decision making processes. This technology, when coupled with NUTBAL, will yield information that gives insight on requirements being met by
forage at specific sites in the GI tract of free-ranging cattle. Alternatively, supplementation could be evolved around this technology to yield a more
efficient nutritional program based on meeting requirements at specific protein degradation sites.
Citations:
Lyons, R.K. and J.W. Stuth. 1992. Fecal NIRS equations for predicting diet quality of free-ranging cattle. J. Range Manage. 45:238-244.
Leite, E.R., and J.W. Stuth. 1995. Fecal NIRS equations to assess diet quality of free-ranging goats. Small Ruminant Research. 15:223-230.
Stuth J.W., and R.K. Lyons. 1995. NIRS-NUTBAL Nutritional management system for cattle. In: Ellen R. Jordan (ed.) Proceedings of Mid-South
Ruminant Nutrition Conference.
Go to Evan Whitley's Poster Sample titled, "Fecal NIRS Equations for Predicting Protein Absorption Sites of Free Ranging Cattle" for the La
Copita Research Center Progress Report in the Center for Natural Resource Information Technology site.
