The use of near infrared reflectance spectroscopy to monitor nutritional status of free-ranging goats

Abstract

Research was conducted to evaluate the viability of predicting the nutritional status of free-ranging goats through analysis of fecal material by near infrared reflectance spectroscopy (NIRS). Diet samples and corresponding fecal samples were collected. Percent crude protein (CP) and in vivo corrected digestible organic matter (DOM) were determined for diet samples. The resulting diet reference data and the fecal spectra were used to develop predictive equations. Standard errors of calibration (SEC) for CP and DOM were 1.12 and 2.02, being within acceptable limits for NIRS. Coefficients of determination (R2), were 0.94 and 0.93 for CP and DOM, respectively, being above and beyond previous results with free-ranging livestock. Primary wavelengths from selected equations presented biological relationships with nutrients studied. Effects of environmental exposure on quality of goat fecal pellets were studied. The results indicated that samples collected on the soil for up to seven days after excretion, in different seasons, are stable enough to predict dietary CP and DOM levels similar to levels that occurred at the time of defecation. Results from a study conducted on three brush levels in South Texas showed that quality of goat diets was affected by browse density and season of the year. In spite of the goats preference for woody species, the availability of fresh herbaceous vegetation improved diet quality in low browse paddocks for a few periods of the year. Due to the accelerated breeding program and the relatively low forage quality in the summer, nannies were in a negative plane of nutrition during most of the lactation period. Results from these studies indicate that prediction of nutritional status of goats by fecal analysis with NIRS is feasible. When fluctuation in diet quality is monitored, improved programs of animal production and reproduction can be established and associated with appropriated schedules of supplementation.