Twelve lactating ewes were surgically prepared with permanent arterio-venous catheters across the gastrointestinal tract at 1 week post partum. From week 3 to 6 of lactation, all sheep were fed fresh sulla (1500 g dry matter/day; condensed tannins (CT) 4.4 g per 100 g dry matter). Half the ewes were orally drenched (4 times/day) with polyethylene glycol (PEG) (160 g/day in water) to remove the effects of the CT whilst the remaining ewes received a water drench. At week 6, para-aminohippurate was infused for 7 h into the cranial mesenteric vein for measuring mesenteric and portal plasma flow and 4-methylphenol concentrations. The mesenteric and portal plasma flows were not affected (P > 0.05) by the treatments. The concentration of 4-methylphenol in the mesenteric artery (Control: 2.8 vs PEG: 9.0 ± 1.2 μg/ml) was lower (P < 0.01) in the control ewes. The net portal appearance of 4-methylphenol was higher (P < 0.01) in the PEG ewes (Control: -663 vs PEG: -1430 ± 159 μg/minute). These results establish that sulla CT reduced the portal flux and peripheral concentration of 4-methylphenol and it is likely that this was a consequence of reduced formation of that metabolite in the rumen due to lowered ruminal protein degradation in the CT-treated ewes. KEYWORDS: plasma net fluxes; gastrointestinal tract; 4-methylphenol; lactation; sheep.
Proceedings of the New Zealand Society of Animal Production, Volume 65, Christchurch, 178-181, 2005
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