The Use Of Near Infrared Reflectance Spectroscopy (NIRS) To Predict The Diet Quality Of Sheep

Fecal NIRS is a non-invasive method to determine diet quality in herbivores, but has not been reported for sheep (Ovis aries) in the US. A diet chemistry: fecal spectra calibration (n = 78) was developed to determine if fecal NIRS can predict diet quality of forage-fed sheep. In 2002 (n = 15) and 2003 (n = 20) mature ewes (55 ?2.4 kg) were fed individual diets for 7 days. Diets ranged from 4.3 to 23.5 % crude protein (CP) and 52.4 to 75.8 % digestible organic matter (DOM) and were composed of various grass, forb and browse components. Daily intake was recorded. Fecal samples were collected on days 6 and 7. CP was determined by micro-Kjeldahl and DOM by an in vivo corrected in sacco technique. Predictive equations for dietary CP (RSQ = 0.95, SE calibration (SEC) = 1.08) and DOM (RSQ = 0.80, SEC = 1.51) were developed. Results from a CP validation set (12 ewes fed northern great plains forages) were: (RSQ = 0.81, SE prediction (SEP) = 1.51, slope = 0.89). Diet quality of forage-fed sheep can be accomplished by fecal NIRS. To determine the effect of individual animal variation on fecal NIRS predictions, 5 ewes were fed the same forage ad libitum for 7 days in 2 trials. Predicted CP (10.9 ?0.28 %, 21.4 ?0.55 %) and DOM (62.0 ?0.23, 64.4 ?0.36) from trials 1 and 2 respectively indicate minimal effect on NIR predicted diet quality due to individual animal variation.The first wavelengths for CP equation, 1556 is indicative of NH group and NH protein. It may indicate the presences of undigested protein, characteristic of lignin-protein and or tannin-protein complex. These protein bonds may also indicate indigested or whole microbial cells. The first wavelength 1556 shows high absorbance for low quality sample, greater absorbance by fecal samples derived from ruminant feed quality diets, is a reflection of bonds in undigested microbial cells due to the proliferation of microbial populations. The first major wavelength for DOM equation is 1940nm is indicative of nitrites, indicating microbial activity, accumulation of nitrites can be associated with slow utilization by microbes due to a lack of readily available carbohydrates.