Tannins are a complex group of polyphenolic compounds found in a wide range of plant species commonly consumed by ruminants. They are conventionally classified into two major groups: the hydrolysable and the condensed tannins. Although for a long time tannins were thought to be detrimental to ruminants, their effect may be either beneficial or harmful depending on the type of tannin consumed, its chemical structure and molecular weight, the amount ingested, and the animal species involved. High concentrations of tannins reduce voluntary feed intake and nutrient digestibility, whereas low to moderate concentrations may improve the digestive utilisation of feed mainly due to a reduction in protein degradation in the rumen and a subsequent increase in amino acid flow to the small intestine. These effects on nutrition are reflected in animal performance.

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The condensed tannin (CT) content of eight shrub species (Cytisus purgans, Cytisus scoparius, Genista florida, Genista occidentalis, Calluna vulgaris, Erica arborea, Erica australis and Juniperus communis) from a grazing mountain area of northern Spain was analysed and related to various indicators of nutritive value. Chemical composition, in vitro gas production, OM degradation and true DM digestibility were evaluated in samples collected in January and June. With the exception of two samples comprised of considerable amounts of flowers, the shrub legumes examined had low contents of CT (less than 6.51 g quebracho tannin equivalents/kg DM) which would generally be considered unlikely to affect digestion of nutrients in the gastrointestinal tract of animals.However, Ericaceae species and J. communis, which are evergreen species, showed a high CT content (higher than 176 g quebracho tannin equivalents/kg DM) throughout the year. CT were negatively correlated (P<0.05) with OM degradation and cumulative gas production, and positively correlated with lag time, which is consistent with the extensively reported suppressive effect of condensed tannins on rumen degradation and on the interference of these compounds with microbial attachment to feeds. The positive correlation between these plant secondary compounds and the partitioning factor (OM degradation/total gas production) indicates that the effect of CT is more strongly reflected in the reduction of gas production than in the reduction of OM degradation. KeywordsBrowse species, condensed tannins, in vitro degradation, gas production effects on protein metabolism in ruminants, decreasing the rumen degradation of dietary protein and increasing absorption of amino acids in the small intestine of the animal, high dietary CT concentrations (6 to 12% of DM) can depress voluntary feed intake, digestive efficiency and animal productivity.The aim of the present experiment was to analyse the CT content of several shrubs from a grazing mountain area of northern Spain and examine its relationship with traditional indicators of the nutritive value of those shrubs (i.e., chemical composition and in vitro rumen degradation and true digestibility). 4 Materials and Methods Shrub species and preparationNew shoots of less than 6.0 mm in diameter were harvested from eight shrub species in 1998. They were collected first in January and then again in June to cover a wide range of phenological states of the plants at the moment of harvest. The eight species, according to families, were as follows: LEGUMINOSEAE: Cytisus purgans Cytisus scoparius Genista florida Genista occidentalis ERICACEAE Calluna vulgaris Erica arborea Erica australis CUPRESACEAE Juniperus communis From the January harvest, winter-dormant shoots did not contain leaves in samples from C. purgans and C. scoparius. Shoots sampled from Genista spp. included some green leaves. C. vulgaris, E. arborea, E. australis and J. communis are evergreen forms. In the June harvest, all samples comprised the current season's shoots. S...

The potential of NIRS-based models to predict several physical parameters of oxen and young cattle beef protected by a quality mark was evaluated. Fifty-three and 67 samples of Longissimus thoracis muscle corresponding to oxen and young cattle reared in extensive conditions were analyzed for pH, colour (L(∗), a(∗), b(∗)), water holding capacity (WHC) and Warner-Braztler shear force (WBSF), according to the conventional methods. Several factors which might have jeopardized the prediction of pH, a(∗), WHC and WBSF by NIRS are considered in the discussion section. However, the best NIR calibrations, tested by full cross-validation, were for L(∗) (R(2)=0.869; SE(CV)=1.56) and b(∗) (R(2)=0.901; SE(CV)=1.08) colour parameters in meat samples from young cattle. It can be concluded that NIRS could be a useful tool for estimating the colour of young cattle meat samples, primary consideration for consumers when making purchasing decisions.