Muscle chemical analysis and muscle identification both were attempted by using visible and near infrared reflectance spectroscopy (NIRS). Seventy-eight beef muscles (m. longissimus dorsi) from Hereford cattle were used. The samples were scanned in a NIRS monochromator instrument (NIRSystems 6500, Silver Spring, MD, USA) in reflectance mode (log 1/R). Both intact and minced muscle presentation to the instrument were explored. Predictive equations were made using ISI software (Infrasoft International, Port Matilda, PA, USA) and muscle identification was performed by Principal Component Analysis (PCA) and Soft Independent Modelling of Class Analogy (SIMCA). The coefficient of determination in calibration (R2CAL) and standard error in cross validation (SECV) for the intact sample presentation were 009 (SECV: 15·6), 0·89 (SECV: 46·9), 0·48 (SECV: 23·9) for moisture (M), fat and crude protein (CP) on g/kg fresh weight basis respectively. R2CAL and SECV for minced sample presentation were 0·41 (SECV: 161), 0·92 (SECV: 43·4), 0·71 (SECV: 20·5) for M, fat and CP on g/kg fresh weight basis respectively. Qualitative analysis of optical information through PCA and SIMCA analysis showed differences in muscles resulting from two different feeding systems.

The aim of the current study was to investigate the effects of level of feeding and level offish-meal supplementation on the carcass composition of young steers and in doing so, to assess the potential for employing near infrared reflectance spectroscopy (NIRS) in such studies. In addition to wet chemical techniques, NIRS was used to examine carcass samples from animals offered silage-based diets at one of four levels of feeding ranging from near maintenance to ad libitum and with one of four levels offish meal (0, 50,100 or 150 g/kg silage dry matter).

Wet chemical data indicated an increase in fat concentration (P < 0·001) and decrease in crude protein concentration (P < 0·05) in the fresh carcass in response to increasing level of feeding but no statistically significant effect of level of fish meal. Ash concentration was not affected significantly by either level of feeding or level of fish-meal supplementation. Ground, freeze-dried samples were scanned in the wavelength range 1100 to 2498 nm. Calibration equations for ash, fat and crude protein concentration (g/kg carcass) were derived using a modified partial least-squares regression technique. Equations were found to be superior for fat compared with those for crude protein and ash. Standard errors of calibration (g/kg carcass) and multiple correlation coefficients of 6·96 and 0·42, 6·61 and 0·95 and 4·36 and 0·61 were obtained for ash, fat and crude protein respectively with corresponding standard errors of cross validation of 7·71, 7·82 and 4·96 g/kg carcass respectively. Qualitative analysis of spectral information using multivariate techniques and difference spectra clearly showed differences in carcass composition resulting from the different levels of feeding and less so the different levels offish-meal supplementation.

It is shown, that NIRS can be used both quantitatively and qualitatively to study the effects of nutrition on carcass composition.