Abstract
Cannulas were surgically implanted in the portal and mesenteric veins and femoral artery of eight crossbred steers averaging 270 kg. They were given primed, continuous 3-hour infusions of U-[14C]-L-lactate and 2-[3H]- or 6-[3H]-glucose into the jugular vein and para-aminohippuric acid (portal blood flow indicator) into the mesenteric vein before and after being changed from a pelleted alfalfa hay to a pelleted 85% concentrate diet. Blood samples were collected at 20-minute intervals during infusions. Reliable blood flow data were obtained on four of the eight steers during the first infusion; the other four were not infused the second time. Dry matter intake, portal blood flow, net portal d-lactate absorption (P < 0.10), net portal glucose absorption and L-lactate turnover rate (P < 0.10) increased as a result of increased concentrate (energy) intake. Glucose turnover rate (P < 0.10), L-lactate absorbed as a percentage of turnover rate, L-lactate converted to glucose and glucose derived from L-lactate concomitantly decreased. Net portal L-lactate absorption was not affected. The direction of the response for portal blood flow, net portal d-lactate absorption, net portal glucose absorption, L-lactate turnover and L-lactate absorbed as a percentage of turnover was the same as that previously observed in lambs under similar experimental protocol. Differences in responses between lambs and steers for glucose turnover and L-lactate converted to glucose may be attributable to differences in dry matter or energy intake or both.steers glucose metabolism lactate metabolism
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