Effect of PEG administration to growing lambs feeding sulla.

Increased frequency or amount of metabolic processes, during growth, is associated to enhanced production of reactive oxygen species (ROS). The imbalance between ROS production and antioxidant defence mechanisms can lead to "oxidative stress". Retinol and ?-tocopherol scavenge ROS, and prevent lipid oxidation in growing tissues. Condensed tannins, as reducing protein degradation in rumen and increasing the flow of essential amino-acids toward the intestine, improve protein utilization. Polyethylene glycol (PEG) prevents the formation of tannin-protein complexes. We analysed the effect of a diet, containing condensed tannins, on redox and energy status in growing lambs. Twelve lambs were fed, for two months, by grazing on sulla (Hedysarum coronarium L.) (5 hours/day), and on Italian ryegrass sward. Twelve lambs received the same diet, supplemented by PEG. Plasma samples, collected weekly, were analysed for retinol and ?-tocopherol levels. Plasma nitro-tyrosine concentration was measured, and used as marker of protein oxidation. The levels of retinol, tocopherol, and nitrotyrosine were not different between the two groups. Similarly, plasma levels of cholesterol, triglycerides, and glucose, titrated to evaluate the energetic status, did not differ between the groups. Our data demonstrate that plasma levels of the analysed parameters were not affected by PEG administration, and suggest that condensed tannins, as not influencing energy and redox status, might regulate other physiological functions of growing lambs.