QUEBRACHO TANNINS WITH OR WITHOUT BROWSE-PLUS (A COMMERCIAL PREPARATION OF POLYETHYLENE-GLYCOL) IN SHEEP DIETS - EFFECT ON DIGESTIBILITY OFNUTRIENTS IN-VIVO AND DEGRADATION OF GRASS HAY IN-SACCO AND IN-VITRO

Quebracho tannins (QT, 50 g/kg diet), with or without two levels (0.1 or 1.0 g/kg diet) of a commercial additive containing polyethylene gly col (Browse Plus), were fed to four cannulated sheep receiving a basal diet of grass hay, grass cubes and whole barley at maintenance level in a 4 x 4 Latin square over periods of 4 weeks. The control treatment consisted of the basal diet alone. Ruminal in-sacco degradation and i n-vitro gas production were measured. Apparent digestibilities of all nutrients were significantly (P < 0.05) depressed by the QTs. Browse P lus was able to remove some, but not all, of the depressions in digest ibilities, with the higher level of Browse Plus (1 g/kg diet) tending to produce a significant (P < 0.05) improvement in the digestibilities of all nutrients. The lower level of Browse Plus used (0.1 g/kg) slig htly (P > 0.05) improved the digestibilities of all nutrients. There w ere no differences (P > 0.05) in the degradation and rate of degradati on of the hay incubated in sacco in the four rumen environments create d by the different tannin content of the experimental diets. However, the rate of degradation of the insoluble but potentially degradable fr action was lowered by the QT diet, indicating the possibility of reduc ed microbial cellulolysis. Microbial activities measured from gas prod uction were also reduced in vitro. However, unlike the in-vivo and in- sacco experiments, Browse Plus in vitro removed all the depressions in activities of the microbes that could be associated with the tannins. Although Browse Plus was unable to alleviate all of the depression in digestibilities in vivo, it may still be a useful digestive modifier which partly offsets the inhibitory effects of condensed tannins in ru minant diets, especially in arid environments with poor quality feeds. (C) 1997 Elsevier Science B.V.