Infrared technology in animal production

Abstract

Infrared (IR) spectroscopy is based on the principle that the chemical bonds in organic molecules absorb or emit infrared light when their vibrational state changes. In the near IR part of the spectrum, large changes in vibrational state are observed (overtones), while in the mid IR region, primary vibrations are produced. The latter yields sharper, more clearly defined peaks that are better suited for quantitative purposes. Raman spectroscopy, in which the decay of the vibration is observed after strong excitation of the sample, is a variant on mid IR spectroscopy. A major challenge in applying IR spectroscopy to animal production is sample presentation. Transmission is the most powerful method well suited to liquids and gases but is inappropriate for undiluted solids. Although reflection offers an alternative for solids, it is less than ideal for quantitative purposes as the path length is not known. For pastes and opaque liquids, attenuated total reflectance offers good possibilities for the future as it acts like a transmission device but sample application is simple. A novel method is photo-acoustics in which the heating of a sample (as it absorbs the IR light) is measured using a microphone. IR spectroscopy is typically fast and easy to use. In feedmills it allows the quality (e.g. proximate and nutritionally relevant parameters such as metabolisable energy) of feed ingredients and complete feeds to be monitored. In meat processing IR spectroscopy offers the opportunity to assess meat and fat quality, and perhaps even palatability (texture and flavour). New developments in IR spectroscopy will expand its applications further. These include hand-held instruments that may find use in determining digestive disorders among birds in the field, fibreoptics that will allow instantaneous measurements to be made in almost any part of a plant, tunable lasers (with their much stronger signals) that will make IR spectroscopy much more powerful, and imaging IR spectroscopy which may be used to determine the homogeneity of meat (e.g. colour). IR spectroscopy, with its speed, ease of use and versatility, could be about to become one of the most powerful analytical techniques available to the animal production industries. It promises to allow for improved quality control in virtually every aspect of production, from feed manufacture to final product evaluation.