A multicatheter sow model was established to study the effects of dietary β-hydroxy β-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 × 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.

This study examined the potential of plant cell wall fractions as predictors of indigestible neutral detergent fibre (INDF) in forages with respect to species within plant type, cut number and stage of maturity (harvest time) within primary growth, and for concentrates with respect to species within plant type, where INDF is defined as the portion of plant cell walls not digested after 288 h rumen incubation in Dacron bags with 12 mu m pore size. INDF is one of the more important parameters determining the net energy (NE) value of a diet in some recently developed ruminant feed evaluation systems. Effects of maturity and cut number on INDF in three legumes and 18 grasses were determined based on an experiment in which each forage was cut at three times of primary growth and once in each of the following three regrowths. These data were supplemented with data from earlier experiments to develop regression equations for INDF intended for use in practice based on a total of 321 samples. Plant type and species within plant type affected (P<0.001) all cell wall fractions. The INDF/lignin(sa) ratio varied substantially from the 2.4 factor used in the Cornell Net Carbohydrate and Protein System (CNCPS) to predict INDF, averaging 2.6 for legumes, grains and grain byproducts, 2.7 for grasses and 1.0 for oilseeds including byproducts. The INDF/IOM ratio varied less among plant species within plant type than among plant types. Multiple linear regression analysis revealed higher INDF prediction accuracy compared to simple regression equations. Estimation of INDF in DM was more accurate than estimation of INDF in ash-free neutral detergent fibre (aNDFom). Results indicate that universal regression equations among plant types are not possible, and, within plant types, prediction equations are not promising for grasses and legumes if only lignin(sa) is included. Comparing plant types, INDF prediction was best for grains and byproducts in simple linear regression and best for grass/clover in multiple linear regression equations. Variations within and among plant type were related to stage of maturity and cut number. (c) 2012 Elsevier B.V. All rights reserved.