Effect of a Daily Supplementation of Poly(ethylene glycol) on Intake and Digestion of Tannin-Containing Leaves (Ceratonia siliqua) by Sheep

The nutritional value of carob leaves (CL) and the effectiveness of increasing amounts (12.5,25,32, and 50 g/day) of polyethylene glycol 4000 (PEG) supplemented once daily in overcoming the negative effect of tannins in carob leaves, were examined in four Merino ewes. Ewes fed solely CL were not able to sustain their body weights, and excreted in feces more protein than was consumed; the digestibility of cell walls was very low (220 gkg). Supplementation with 25 g/day PEG increased digestible organic matter intake by 2-fold. This increase was associated with a marked improvement in protein and cell wall digestibility and recovery of weight loss. The present results provide evidence for the first time that condensed tannins may induce a marked depressive effect on the intestinal activity of trypsin and amylase in ruminating animals (as indicated by their activity in fecal samples).