Infrared technology in animal production

Infrared (IR) spectroscopy is based on the principle that the chemical bond s in organic molecules absorb or emit infrared light when their vibrational state changes. In the near IR part of the spectrum, large changes in vibra tional state are observed (overtones), while in the mid IR region, primary vibrations are produced. The latter yields sharper, more clearly defined pe aks that are better suited for quantitative purposes. Raman spectroscopy, i n which the decay of the vibration is observed after strong excitation of t he sample, is a variant on mid IR spectroscopy. A major challenge in applyi ng IR spectroscopy to animal production is sample presentation. Transmissio n is the most powerful method well suited to liquids and gases but is inapp ropriate for undiluted solids. Although reflection offers an alternative fo r solids, it is less than ideal for quantitative purposes as the path lengt h is not known. For pastes and opaque liquids, attenuated total reflectance offers good possibilities for the future as it acts like a transmission de vice 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 usi ng a microphone. TR spectroscopy is typically fast and easy to use. In feed mills it allows the quality (e.g. proximate and nutritionally relevant para meters 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 determin ing digestive disorders among birds in the field, fibreoptics that will all ow instantaneous measurements to be made in almost any part of a plant, tun able lasers (with their much stronger signals) that will make IR spectrosco py much more powerful, and imaging IR spectroscopy which may be used to det ermine the homogeneity of meat (e.g. colour). IR spectroscopy, with its spe ed, ease of use and versatility, could be about to become one of the most p owerful analytical techniques available to the animal production industries . it promises to allow for improved quality control in virtually every aspe ct of production, from feed manufacture to final product evaluation.