Effects of β-hydroxy β-methyl butyrate supplementation to sows in late gestation on absorption and hepatic metabolism of glucose and amino acids during transition

A multicatheter sow model was established to study the effects of dietary beta-hydroxy beta-methyl butyrate (HMB) supplementation on net portal flux (NPF) and net hepatic flux (NHF) of HMB, glucose, and the AA Ala, Gly, Ile, Leu, Phe, Tyr, and Val. Eight second parity sows were fitted with permanent indwelling catheters in an artery and in the portal, hepatic, and mesenteric veins. Eight hourly sets of blood samples were taken starting 30 min before the morning meal on day -3 and day 3 relative to parturition. Four control (CON) sows were fed a standard lactation diet from day -15 and throughout the experiment, and 4 HMB sows were fed the control diet supplemented with 15 mg Ca(HMB)(2)/kg BW mixed in one third of the morning meal from day -10 until parturition. Net portal flux of HMB was affected by treatment (Trt; P < 0.01) and peaked in the HMB sows at 6.9 mmol/h 30 min after the morning meal and then decreased towards preprandial level (0.0 mmol/h) 3.5 h after the meal, revealing that dietary HMB was rapidly absorbed from the intestine. The NHF of HMB tended to be affected by Trt (P = 0.06) showing a small hepatic uptake of HMB (1.1 mmol/h) in HMB sows. Net portal flux of glucose and all measured AA, except for Gly and Tyr, were affected the Trt x time interaction (P < 0.01). The NPF was positive for all nutrients, indicating absorption from the intestine to the portal blood. Absorption rates appeared to be more stable for HMB than for CON sows. Net hepatic flux of glucose was not affected by Trt. It was negative from 1.5 to 2.5 h after the meal, indicating hepatic uptake, but positive before and after, indicating net hepatic release of glucose. Net hepatic fluxes of AA were negative and were not affected by Trt (P > 0.10), except for Phe (P < 0.05). In conclusion, HMB reduced the variation in net portal flux of glucose and AA during 8 h of blood sampling and suggest that the improved sow productivity observed by others may be due to a more uniform nutrient absorption pattern into portal blood.