An experiment was conducted to analyze the evolution of carotenoids and -tocopherol
during the fattening period of beef cattle that were fed with different diets to check the
feasibility of using these compounds to trace grass-feeding in the visible and near-infrared
spectra. A group of Parda de Montana˜ and a group of Pirenaica steers were finished on
mountain meadows, and another group of Pirenaica steers was finished with a dry total
mixed ration (50 alfalfa hay:10 straw:40 maize grain, as-such basis). Plasma samples
were obtained throughout the fattening period to determine the -carotene, lutein and -
tocopherol concentrations via high performance liquid chromatography (HPLC) and plasma
visible-near infrared (VIS-NIR) spectra; the samples were collected using the dry-extract
system for infrared (DESIR) method. Additionally, after slaughter, the carcass subcutaneous
fat color was measured, and a spectrophotometric estimation ofthe carotenoid content was
calculated. Feeding systems had a great effect on the plasma concentrations of -carotene,
lutein and -tocopherol, which increased sharply when the animals were grazing. In the
same way, when the animals were switched over to the dry total mixed ration, their concentrations
sharply decreased to quite low concentrations. Both the VIS-NIR spectra of the
plasma and the subcutaneous fat color are useful in discriminating steers fed with finishing
diets, but neither method is not suitable for discriminating between the Pirenaica and
Parda de Montana˜ breeds. The calibrations that were developed to estimate the lutein and
-tocopherol concentrations could be classified as poor. The calibration used to estimate
the -carotene plasma concentration was useful for analytic purposes, but it should still be
improved. The DESIR method can be interesting to monitor the plasma concentrations of
carotenoids and tocopherol in live animals, whereas the measurement of the subcutaneous
fat color of the carcass is a simple and fast method for discriminating, post-mortem, animals
that were fed diets with different carotenoid contents.
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