Self-regulation of intake of polyethylene glycol by sheep fed diets varying in tannin concentrations

Tannins occur in many plant species, and they often suppress intake by redu cing nutrient availability or by causing malaise. Polyethylene glycol (PEG) binds to tannins and may thereby increase the availability of macronutrien ts and decrease malaise. Supplemental PEG increases intake of tannin-contai ning plants by sheep, goats, and cattle. Given the strong response to suppl emental PEG, we speculated that animals might self-regulate their intake of PEG when offered foods high in tannins. The objective of the first experim ent was to determine if the amount of supplemental PEG (0, 25, 50, 75, or 1 00 g; molecular weight, 3,350) affected intake by lambs of a food (milotann in mix) containing 20% quebracho tannin. There was a linear relationship (Y = 272 + 1.2X; R-2 = .86; P =.023) between the amount of supplemental PEG i ngested and the subsequent intake of milo-tannin food by lambs. The objecti ve of the second experiment was to determine whether lambs self-regulated i ntake of PEG when fed a ration that contained 0, 5, 10, 15, or 20% quebrach o tannin and whether they adjusted their intake of PEG when tannin was remo ved from the diet. There was a positive relationship between the amount of PEG ingested and intake of food and tannin (P = .0001). Lambs fed high-tann in diets ate more PEG than controls (P = .03). Lambs fed the 20% tannin die t ate the most PEG, and controls ate the least PEG. Tannin limited intake o f the diets, but PEG attenuated the response to a great degree (P = .065). Immediately after tannin was removed from the ration, lambs that formerly h ad been fed the 20% tannin ration ate more PEG than lambs fed the ether rat ions (P = .0075). Ten of the lambs (5 from the 20% tannin group, 1 from the 15% tannin, and 2 each from the 10 and 5% groups) continued to eat PEG for 7 d after tannin was removed from their ration. When they were tested agai n 6 wk after the trial and offered tannin-free diets, their intake of PEG h ad decreased.