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Splanchnic metabolism of energy-yielding nutrients and their uptake by the hind limb were studied in finishing lambs receiving ryegrass harvested at grazing stage (ear at 10 cm) with or without barley supplementation. Six ruminally cannulated and multi-catherized lambs (40.2 [+ or -] 1.5 kg) were fed with frozen ryegrass (RG) at 690 kJ of metabolizable energy intake (MEI) * [d.sup.-1] * B[W.sup.-0.75] successively with and without barley supplementation (RG + B), according to a triplicated Latin square design. Barley supplementation represented 21% of DM intake and increased the MEI by 32% (P < 0.002). In ruminal fluid, barley supplementation increased the acetate and butyrate concentrations by 21.2 and 49.6%, respectively (P < 0.04), without modifying those of propionate. Thus, molar proportions of acetate and butyrate were not modified, and those of propionate tended (P < 0.06) to decrease from 26 to 23%. As a result, the net portal appearance of propionate was not modified. Net portal appearance of butyrate and [beta]-hydroxybutyrate increased (P < 0.03), and that of acetate was not modified. Consequently, hepatic up take of butyrate increased and probably spared acetate from hepatic metabolism. The hepatic fractional extraction of propionate decreased (P < 0.03), whereas the net flux of lactate switched from a net release to a net uptake, suggesting an alteration in the contribution of gluconeogenic substrates to glucose synthesis without modification in net hepatic glucose release. As a consequence, barley supplementation increased net splanchnic release of acetate (P < 0.02), propionate (P < 0.001), and [beta]-hydroxybutyrate (P < 0.01) by 60, 157, and 78%, respectively. In addition, the net splanchnic release of insulin increased (P < 0.03) because of a decrease (P < 0.02) in its hepatic extraction. Despite those changes, the net uptake of nutrients by the hind limb was not modified and even decreased in the case of glucose (P < 0.02), suggesting a stimulation of lipogenesis in adipose tissues. Results from the present study suggested that supplementation of a ryegrass-based diet would likely have little effect on the orientation of muscle energy metabolism and on meat quality because the net uptake of nutrients by the hind limb was unchanged. Key Words: Barley, Energy Intake, Liver, Lolium, Nutrients, Portal Vein

An experiment was conducted with four preruminant calves to measure the energy cost and the diurnal pattern of physical activity in tethered, fed calves and to determine whether differences in activity could interfere with the interpretation of circadian changes in heat production. Measurements were carried out in large respiration chambers (3,650 L of inner volume), and a computation method was presented that allowed the calculation of the energy cost of standing for each standing period. This cost averaged 449 cal[center dot]kg [BW.sup.-1][center dot][h.sup.-1] (SE = 41.6, n = 4). It represented a 23 to 27% increase in heat production above that measured in the lying state. This estimate and its standard error were lower than values obtained by regression (2,131 cal[center dot]kg [BW.sup.-1][center dot][h.sup.-1], SE = 862.2, n = 8). The energy cost of standing was highest after meal times and lowest at night. These variations could reflect the nonuniform activity patterns of calves while standing. The time spent standing per hour showed the same variations during the day as the energy cost of standing. Noteworthy, the elevated energy expenditure measured in the 1st h after the morning meal was due to activity cost rather than to meal thermogenesis. Standardization of diurnal heat production profiles to a given activity pattern thus seemed to be necessary.

The objective of this study was to determine the maintenance requirements in metabolizable energy (M|E.sub.m~) of adult, nonlactating, nonpregnant Charolais cows. A feeding trial was conducted using 12 cows fed at one of two feeding levels (75 |L~ and 113 |H~ kcal of ME|center dot~kg B|W.sup.-.75~|center dot~|d.sup.-1~) for 116 d. Body composition was estimated from subcutaneous adipocyte diameter. Body weight changes averaged -468 and +46 g/d, respectively. Diet DM digestibility averaged .496. The L cows spent less time eating and ruminating but had other behavioral characteristics similar to those of H cows. Estimates of M|E.sub.m~ were calculated from BW or body composition changes and amounted to 109 and 124 kcal of ME|center dot~kg B|W.sup.-.75~|center dot~|d.sup.-1~, respectively. Heat production (HP) was then measured over 67 d in a second trial on two L and two H cows from the feeding trial and planes of feeding were switched after 14 d. Estimates of M|E.sub.m~ varied from 112 to 105 kcal|center dot~kg B|W.sup.-.75~|center dot~|d.sup.-1~. Within animal, day-to-day variations in heat production were high (4.6% on average) and prevented the detection of any precise changes of HP with time on treatment. None of the trials showed any significant effect of level of feeding on M|E.sub.m~.