Near-infrared spectroscopy (NIRS) with a fibre-optic probe for the prediction of the amino acid composition in animal feeds

The amino acids alanine, aspartic acid, glutamic acid, glycine, phenylalanine, valine, lysine, proline, and tyrosine present in feeds with different textures (blocks, tablets, granules and flour (meal) and used in different stages of animal feeding regimes (lactation, growth, maintenance, etc.) were analysed using near-infrared reflectance spectroscopy (NIRS) technology together with a remote reflectance fibre-optic probe. The method allows immediate control of the animal feeds without prior sample treatment or destruction through direct application of the fibre-optic probe on the sample.The regression method used was Modified Partial Least Squares (MPLS). The equations developed to determine the amino acid contents of the feeds afforded high values for the RSQ coefficient (0.814–0.963) in all the amino acids with the exception of lysine (0.687). The statistical prediction descriptors SEP, SEP(C) (with values between 0.134 for valine and 0.015 for aspartic acid) and bias indicated that the amino acid values in feeds predicted with NIRS with a fibre optic probe are comparable to those obtained with the chemical ion-exchange HPLC method.