Optimizing ammonia processing conditions to enhance susceptibility of legumes to fiber hydrolysis: alfalfa.

An ammonia process was applied at several ammonia loadings, moisture contents, temperatures, and dwell times. A cellulase loading of 5 FPU/g dry matter and a 24 h incubation time were used to produce the sugars, which were measured as reducing sugars and by HPLC. Optimal processing conditions caused a 76% of theoretical yield (2.9-fold above untreated). Cellulose and hemicellulose conversions were 68 and 85% (vs 38 and 34% in untreated, respectively). The short hydrolysis time and relatively low enzyme loading suggests great potential to produce sugars from alfalfa.

Optimizing ammonia processing conditions to enhance susceptibility of legumes to fiber hydrolysis: Florigraze rhizoma peanut.

A warm-season legume, Florigraze rhizoma peanut (FRP), was used as the source of fiber to produce sugars. FRP was subjected to several ammonia-processing conditions using temperature, biomass moisture content, and ammonia loading as process variables during a 5-min treatment. A cellulase loading of 2 FPU/g DM and 24 h incubation were used to produce the sugars. Total sugar yield was 3.34-fold higher in the optimal treatment (1.5 g ammonia/g DM-60%-90 degrees C) compared to untreated and was 65.3% of theoretical. Cellulose and hemicellulose conversions increased from 30 and 15.5% in untreated FRP to 78 and 34% in treated FRP.

Physical and mechanical characteristics of tibias from transgenic mice expressing mutant bovine growth hormone genes.

Physical and mechanical characteristics of tibia from mice expressing either the M4, M11, or G119K mutant bovine growth hormone (bGH) gene and displaying large, near-normal, or small-size phenotypes, respectively, were compared to those of non-transgenic, control mice (NTC). Three animals of each strain were euthanized at 28, 38, 48, 58, and 68 days of age. Variables were regressed against age to establish the pattern of change throughout the experiment, and the regression results are presented. Tibias from G119K were shorter (13.1 mm) and lighter (37.3 mg) than those from other strains, and M4 tibias were heavier (87.9 mg) and longer (16.6 mm) at 70 days of age. The ratio of tibia length to body weight suggests longitudinal bone growth was not reduced as much as overall growth in G119K mice. The external and internal dimensions of the G119K tibias were smaller than the other strains whereas the M4 tibias were somewhat larger. Differences in physical dimensions between the NTC and M11 mice did not greatly affect bone mechanical characteristics. Tibias from M4 mice resisted more load at both flexure and breaking compared to the other strains. At 50 days of age, stress at flexure was greater at all ages for G119K mice (12.4 kg/mm2) and was decreased in M4 mice (8.5 kg/mm2). The bGH mutations produce different effects on bone growth and its mechanical characteristics. There also may be differential tissue responsiveness to the mutant bGH analogs, as longitudinal growth was not as affected as empty body growth in the G119K mice. These transgenic mouse strains provide valuable models to study bone growth, formation, and reformation in response to GH regulation, and more importantly, the M4 and G119K mice may serve as a model in which the priorities for GH action on bone vs muscle may be determined.

Effects of acute fresh water exposure on water flux rates and osmotic responses in Kemp's ridley sea turtles (Lepidochelys kempi).

Water flux rates and osmotic responses of Kemp's Ridley sea turtles (Lepidochelys kempi) acutely exposed to fresh water were quantified. Salt-water adapted turtles were exposed to fresh water for 4 d before being returned to salt water. During the initial salt water phase, absolute and relative water flux rates were 1.2+/-0.1 l d(-1) and 123.0+/-6.8 ml kg(-1) d(-1), respectively. When turtles were exposed to fresh water, rates increased by approximately 30%. Upon return to salt water, rates decreased to original levels. Plasma osmolality, Na(+), K(+), and Cl(-) decreased during exposure to fresh water, and subsequently increased during the return to salt water. The Na(+):K(+) ratio was elevated during the fresh water phase and subsequently decreased upon return to salt water. Aldosterone and corticosterone were not altered during exposure to fresh water. Elevated water flux rates during fresh water exposure reflected an increase in water consumption, resulting in a decrease in ionic and osmotic concentrations. The lack of a change in adrenocorticoids to acute fresh water exposure suggests that adrenal responsiveness to an hypo-osmotic environment may be delayed in marine turtles when compared to marine mammals.

Optimizing ammonia pressurization/depressurization processing conditions to enhance enzymatic susceptibility of dwarf elephant grass.

An ammonia pressurization/depressurization process was investigated to evaluate the potential of producing reducing sugars from dwarf elephant grass, a warm-season forage. Moisture, temperature, and ammonia loading affected sugar yield (p < 0.0001). At optimal conditions, ammonia processing solubilized 50.9% of the hemicellulose and raised the sugar yield (percentage of theoretical) from 18 to 83%. Glucose and xylose production were increased 3.2- and 8.2-fold, respectively. The mild processing conditions of the ammonia treatment (90-100 degrees C, 5 min), the low enzyme loading (2 international filter paper units/g), and the short hydrolysis time (24 h), greatly enhance the potential of using forages to produce sugars valuable for several applications.

Direct measurements of methane emissions from grazing and feedlot cattle.

Methane (CH4) emissions from animals represent a significant contribution to anthropogenically produced radiatively active trace gases. Global and national CH4 budgets currently use predictive models based on emission data from laboratory experiments to estimate the magnitude of the animal source. This paper presents a method for measuring CH4 from animals under undisturbed field conditions and examines the performance of common models used to simulate field conditions. A micrometeorological mass difference technique was developed to measure CH4 production by cattle in pasture and feedlot conditions. Measurements were made continuously under field conditions, semiautomatically for several days, and the technique was virtually nonintrusive. The method permits a relatively large number of cattle to be sampled. Limitations include light winds (less than approximately 2 m/s), rapid wind direction changes, and high-precision CH4 gas concentration measurement. Methane production showed a marked periodicity, with greater emissions during periods of rumination as opposed to grazing. When the cattle were grazed on pasture, they produced .23 kg CH4 x animal(-1) x d(-1), which corresponded to the conversion of 7.7 to 8.4% of gross energy into CH4. When the same cattle were fed a highly digestible, high-grain diet, they produced .07 kg CH4 x animal(-1) x d(-1), corresponding to a conversion of only 1.9 to 2.2% of the feed energy to CH4. These measurements clearly document higher CH4 production (about four times) for cattle receiving low-quality, high-fiber diets than for cattle fed high-grain diets. The mass difference method provides a useful tool for "undisturbed" measurements on the influence of feedstuffs and nutritional management practices on CH4 production from animals and for developing improved management practice for enhanced environmental quality.

Estimation of water turnover rates of captive West Indian manatees (Trichechus manatus) held in fresh and salt water.

The ability of West Indian manatees (Trichechus manatus) to move between fresh and salt water raises the question of whether manatees drink salt water. Water turnover rates were estimated in captive West Indian manatees using the deuterium oxide dilution technique. Rates were quantified in animals using four experimental treatments: (1) held in fresh water and fed lettuce (N=4), (2) held in salt water and fed lettuce (N=2), (3) acutely exposed to salt water and fed lettuce (N=4), and (4) chronically exposed to salt water with limited access to fresh water and fed sea grass (N=5). Animals held in fresh water had the highest turnover rates (145+/-12 ml kg-1 day-1) (mean +/- s.e.m.). Animals acutely exposed to salt water decreased their turnover rate significantly when moved into salt water (from 124+/-15 to 65+/-15 ml kg-1 day-1) and subsequently increased their turnover rate upon re-entry to fresh water (146+/-19 ml kg-1 day-1). Manatees chronically exposed to salt water had significantly lower turnover rates (21+/-3 ml kg-1 day-1) compared with animals held in salt water and fed lettuce (45+/-3 ml kg-1 day-1). Manatees chronically exposed to salt water and fed sea grass had very low turnover rates compared with manatees held in salt water and fed lettuce, which is consistent with a lack of mariposia. Manatees in fresh water drank large volumes of water, which may make them susceptible to hyponatremia if access to a source of Na+ is not provided.

Expression of mutant bovine growth hormone genes in mice perturbs age-related nutrient utilization patterns.

Three lines of transgenic mice expressing mutant bovine growth hormone (bGH) genes and displaying small (G119K), near normal (M11) or large (M4) phenotypes and nontransgenic control (NTC) mice were used to determine GH-associated, age-specific changes in empty body composition. The single amino acid substitution in G119K mice reduced the quantities (P < 0.001) and early rates (P < 0.05) of deposition for water, protein and ash but resulted in similar quantities of fat as the NTC mice. The change in relative quantities of empty body components indicated the G119K analogue altered nutrient partitioning, basal metabolism and (or) nutrient availability to effect the differential observed in body composition. The two amino acid substitutions in the bGH gene expressed by the M11 mice caused only a small change in phenotype, but age-related changes in the accretion of protein, fat and ash indicated these mice were not mature by 68 d of age. The bGH analogue produced by the M4 mice resulted in a doubling (P < 0.001) of body weight in comparison with the NTC mice, a result of the increasing (P < 0.001) rate of weight gain. Empty body component gain of the M4 mice also indicated they had not yet matured by 68 d of age. The G119K and M4 mutant forms of bGH altered rates and composition of growth, possibly through redirection of tissue nutrient utilization, modification of nutrient metabolism, and(or) nutrient availability.

Effects of bovine somatotropin treatment and intermittent growth pattern on mammary gland development in heifers.

Angus x Holstein heifers (initial age and BW: 6.0 +/- .4 mo; 159 +/- 12 kg) were assigned to one of four treatments (n = 10) in a 2 x 2 factorial arrangement to examine the effects of bovine somatotropin (bST) or vehicle treatment and continuous (CG) or intermittent growth (IG) pattern treatment on mammogenesis. Subcutaneous injections of bST (500 mg) or vehicle were administered at 14-d intervals. The CG heifers were limit-fed a diet to gain .8 kg/d throughout the experiment, whereas IG heifers underwent two successive growth restriction-compensation phases with each phase consisting of a 3-mo growth restriction period (.25 kg/d) followed by a growth compensation period. All heifers were individually fed during the experiment and slaughtered when average treatment BW reached 390 kg. Mammary gland development was measured by dissection, chemical analysis, and computed tomography scanning. Overall ADG were increased (P < .001) 20% by bST treatment of CG heifers, although ADG of IG-vehicle and IG-bST heifers were similar to ADG of CG-vehicle heifers. Dissectable extraparenchymal tissue (EPT) mass was reduced 23% (P < .05) and 36% (P < .001) by IG pattern and bST treatments, respectively, although the bST effect on dissectable EPT tended (P = .08) to be greater in CG than in IG heifers. Fat-free parenchymal tissue (PT) mass (P = .11) and PT volume (P = .08) tended to be greater in IG than in CG heifers. Fat-free PT was 60% greater (P = .01) and PT volume onefold higher (P = .01) in bST than in vehicle heifers. The bST and IG pattern treatments increased the proportional weight of fat-free PT mass, although the effect of bST was greater than IG pattern treatment. There was no evidence to suggest that the two treatments were additive in affecting mammogenesis.

Influence of incremental zeranol implant doses on the chemical and physical characteristics of third metacarpal bone and chemical composition of liver and soft tissue from feedlot steers.

Chemical and physical characteristics of third metacarpal bones and liver and rib soft tissue composition from feedlot steers were determined. Steers were selected (32 from each experimental location) to represent the range in slaughter weight and composition for each treatment group in three (total n = 1,088) feedlot experiments. Steers were implanted with 0, 24, 36, 48, 60, 72, 84, or 96 mg of zeranol at approximately 140 d before slaughter. Cattle at each location were fed for the same number of days and slaughtered as a group. Zeranol dose had no effect on the chemical composition of bone, liver, or rib soft tissue with the following exceptions: zeranol decreased (P < .01) bone Ca concentration and increased (P < .07) liver P concentration. Zeranol implantation decreased medullary cavity anterioposterior (AP) diameters and AP cortical width (P < .08). Loads withstood by the bones up to flexure (P < .08) and the strain at flexure (P < .09) were inversely related to the quadratic of zeranol dose. However, modulus of elasticity at flexure and breaking increased numerically with zeranol dose. Stress withstood by bones at flexure was greater (P < .09) for implanted steers. Strain data indicate that metacarpals from steers receiving zeranol would exhibit less deformation upon loading to flexure (P < .09) than controls. These data indicate that administration of intermediate doses of zeranol altered bone deposition of Ca, which resulted in modified third metacarpal physical and mechanical characteristics.

Growth patterns and body composition of transgenic mice expressing mutated bovine somatotropin genes.

The objectives of this study were to determine growth rates, feed intakes, feed efficiencies, and chemical composition of mice from three transgenic lines in 10-d periods from weaning to near maturity. Lines M4, M11, and G119K express bovine somatotropin (bST) mutations E117L, L121P-E126G, and G119K and display phenotypes of large, near normal, and small body size, respectively. M4 mice were 28% larger at 28 d and 84% larger at 68 d than non-transgenic control (NTC) mice. M11 mice were the same size at 28 d as NTC but were 25% larger at 68 d. G119K mice were 34% and 25% smaller than NTC at 28 and 68 d, respectively. Growth rates of G119K mice and NTC were similar, whereas growth rates of M11 and M4 mice were increased (P < .05). Feed intakes of M4 and M11 mice were greater than those of NTC mice (P < .05), whereas feed intakes of G119K mice were lower than those of NTC mice (P < .05). Feed efficiency (gain/feed) was improved in M4 and M11 mice (P < .05) and not altered in G119K mice compared to that of NTC mice (P > .05). Chemical composition was also altered by expression of bST analogs in transgenic mice. G119K and M4 mice had increased body fat percentages and decreased body protein percentages in comparison to M11 and NTC mice (P < .05).(ABSTRACT TRUNCATED AT 250 WORDS)

Periodic changes in body composition and in priorities for tissue storage and retrieval in mature beef cows.

Sixty mature (4 to 6 yr), nonpregnant, nonlactating beef cows of two breed types, Angus (n = 30) and Simmental (n = 30), were used in a four-period, split-plot study (371 d) to determine the seasonal differences in body composition. Periods were chosen to represent each of the four seasons in one year that ran consecutively from June 14, 1986 to June 20, 1987. Initially, all cows were assigned randomly within breed type to one of four feeding levels based on the cows' estimated maintenance requirement (75, 87.5, 112.5, and 125% of weight maintenance) and were rotated such that all animals were fed at all four feeding levels during the course of the study. Body composition was estimated via isotope dilution initially and at the end of Periods 1 through 3 and via derived regression relationships after Period 4. Body composition differed by breed; Simmental cows had greater (P less than .05) amounts of empty body protein (79.4 vs 55.8 kg, respectively) and less (P less than .05) empty body fat (85.3 vs 93.9 kg, respectively) than the Angus cows. These differences also were apparent when expressed as a percentage of live weight. Season altered components of the empty body. On the average, both breeds mobilized (P less than .05) empty body protein (-3.6 and -5.4 kg for Angus and Simmental cows, respectively) in the summer while simultaneously gaining (P less than .05) empty body fat (15.3 and 30.1 kg for Angus and Simmental cows, respectively). Both breeds subsequently tended to gain empty body protein in the winter and spring.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of zeranol and two dietary levels of calcium and phosphorus on performance, carcass and bone characteristics, and calcium status in growing lambs.

Seventy-two crossbred wether lambs (average initial weight, 25.1 kg) were used to determine the interaction between zeranol treatment and two dietary levels of Ca and P (.8 and .6% vs .4 and .3% Ca and P, respectively) in a 2 x 2 factorial arrangement on performance, carcass and bone characteristics, and serum concentrations of parathyroid hormone (PTH) and Ca. Lambs were implanted on d 0 and 56 with 12 mg of zeranol. Lambs had ad libitum access to feed for 105 d. On d 99, blood samples were collected. Implanted lambs had 12% greater (P less than .01) daily feed intake, 26% greater (P less than .10) ADG, and a 12% improvement in (P less than .10) feed efficiency compared with nonimplanted lambs. Zeranol-treated lambs had increased (P less than .05) bone cortical area, breaking load, and width of the metacarpal compared with nonimplanted lambs. Lambs fed the .8% Ca and .6% P diet had a higher (P less than .05) percentage of bone ash than lambs fed the .4% Ca and .3% P diet. However, there were no differences (P greater than .05) in the percentage of Ca, P, Mg, or Zn in metacarpal bones due either to higher dietary Ca and P or to implant treatments. Serum concentration of PTH was greater (P less than .10) in lambs fed .8% Ca and .6% P than in those receiving .4% Ca and .3% P. Serum concentrations of PTH and Ca pooled across treatments were greater (P less than .05) before feeding than at 1 h after feeding.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of season on the maintenance requirements of mature beef cows.

Sixty mature, nonpregnant, nonlactating beef cows of two breed types, Angus and Simmental, were used in a four-period, split-plot study to determine the effects of season on maintenance requirements. Periods were chosen to represent each of the four seasons and ran consecutively from June 14, 1986 through June 20, 1987. All cows were fed at one of four feeding levels (75, 87.5, 112.5, and 125% of estimated ME required for maintenance) a cottonseed hull-based diet in each of the four seasons and were rotated such that all cows received all feeding levels during the study. Retained energy for all cows within periods was determined through changes in body composition determined initially and at the end of each period. Mean DM digestibility (DMD) was similar for both breeds (54.4%), and in both breeds DMD was similar in the summer, fall, and spring and lower (P less than .05) in the winter. Mean DE was 61.4% and also was similar between breeds. Season affected DE, which was greatest (P less than .05) for both breeds in the fall (62.5%). Simmental cows had a 16.1% greater (P less than .05) overall daily ME requirement for weight maintenance than Angus cows (123.5 vs 103.6 kcal/kg.75), and both breeds had greater (P less than .05) requirements during the summer and lower (P less than .05) requirements during the winter (122.6 vs 91.4 and 145.9 vs 109.3 kcal/kg.75 for Angus and Simmental cows, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

Site and extent of apparent magnesium absorption by lambs fed different sources of magnesium.

Ten abomasally cannulated crossbred wether lambs (avg wt, 33 kg) were used in a replicated 5 x 5 latin square design to determine the site and extent of apparent absorption of Mg when fed different sources of Mg. Lambs were fed twice daily 220 g of chopped mixed grass hay and 180 g of a corn-based supplement (control; .13% mg, DM basis), or the control diet supplemented with Mg (.26% Mg, DM basis) from MgO, magnesium citrate (MgC), smectite-vermiculite (Mg-Mica) or MgOH. Lambs were maintained in metabolism stalls during each of the five experimental periods. Each period consisted of a 7-d dietary adjustment followed by a 3-d collection of abomasal samples, feces and urine. Abomasal contents were sampled four times daily during the 3-d collection period. The diet contained .5% chromium oxide as a digestion marker. Apparent absorption of Mg was .17, .55, .85, .78 and .82 g/d for lambs fed the control, MgO, MgC, Mg-Mica and MgOH diets, respectively. Apparent absorption of Mg (g/d) was similar (P greater than .05) in the lambs fed the supplemented diets and greater (P less than .05) than in those fed the control diet. Preintestinal absorption of Mg was .21, .57, 1.08, .14 and .92 g/d when the control, MgO, MgC, Mg-Mica and MgOH diets were fed. Lambs fed the control and Mg-Mica diets absorbed similar (P greater than .05) quantities of Mg in the preintestinal region and less (P less than .05) than lambs fed the MgO, MgC and MgOH diets.(ABSTRACT TRUNCATED AT 250 WORDS)

Relationship of anabolic status and phase and rate of growth to priorities for protein and fat deposition in steers.

The effects of anabolic implants, growth phase (growing vs finishing) and rate of growth on the priorities for protein and fat deposition were determined in yearling cattle. Santa Gertrudis crossbred yearling steers weighing 290 kg were individually fed diets varying in forage and grain content and either not implanted (n = 16) or implanted (90-d intervals) with Ralgro (n = 13) or Synovex-S (n = 12) implants. The cattle were fed toward a similar expected final empty BW (455 kg). Initial and interim empty body composition was measured via deuterium oxide dilution; final composition was determined by carcass specific gravity. During a 100-d growing phase, rates of protein gain were increased (P less than .12) to 118 and 131 g/d from 98 g/d for Ralgro and Synovex vs nonimplanted cattle, respectively. Concurrently, the fraction of protein in empty body growth was increased (P less than .09) from 17.5% for controls to 23.8 and 19.7% for Ralgro- and Synovex-implanted steers, respectively. This change in protein growth occurred concomitant with mobilization of fat and a reduction (P less than .04) in fat gain with Ralgro and Synovex implants. During the 136-d finishing phase, protein accretion was 115 and 132 vs 93 g/d for Ralgro- and Synovex-implanted cattle vs nonimplanted cattle; this represented a 24 and 42% increase (P less than .03) with Ralgro and Synovex, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of nutritional level and biological type on gonadotropin-releasing hormone-induced luteinizing hormone release and plasma progesterone, estrone and estradiol concentrations in pre- and post-partum beef heifers.

Forty-six beef heifers (16 to 23 mo) of two biological types (small = Red Poll-sired, large = Charolais-sired) were individually fed from d 90 of gestation through parturition to evaluate the effects of nutritional restriction on plasma LH and steroid hormone concentrations. Heifers were allotted to one of two nutritional treatments to achieve a BW reduction (loss, fed at 1% of BW/d) or to maintain initial BW (maintenance, fed 1.5% of BW/d) to parturition. Gonadotropin-releasing hormone (100 micrograms) was injected i.m. three times during gestation (d 130; d 200; d 270) and twice after parturition (d 1 to 14; d 23 to 36). Blood samples were collected at 20-min intervals after GnRH for 4 h. Maternal BW change from d 90 to parturition differed (P less than .01) between loss and maintenance heifers. Mean plasma progesterone concentrations were greater (P less than .05) at d 130 and 270 of gestation in small than in large heifers and were greater (P less than .01) at d 23 to 36 postpartum in maintenance than in loss heifers. Mean concentrations of estrone and estradiol were greater (P less than .05) in large than in small heifers at d 200 of gestation. Mean plasma LH concentrations following GnRH injection were greater (P less than .01) in loss than in maintenance heifers at 200 and 270 d of gestation. Metabolizable and retained energy were related inversely to LH release during mid and late gestation.(ABSTRACT TRUNCATED AT 250 WORDS)

Anabolic implant and frame size effects on growth regulation, nutrient repartitioning and energetic efficiency of feedlot steers.

Rates of growth and partitioning of nutrients among tissues were measured in large (Simmental x [Hereford x Brahman]; n = 34) and very large (Chianina x Angus and Maine Anjou x Angus; n = 37) steers implanted with different anabolic growth regulators. All cattle were fed individually a whole shelled corn (13% crude protein) diet. Implant strategies were: none (n = 13), Ralgro 36 mg (n = 15), Ralgro 72 mg (n = 14), Synovex-S (n = 15) and Ralgro 36-Synovex-S (n = 14) administered at d 0 and 90. Empty body composition of all cattle was measured initially and at 90 d by D2O dilution procedures and at slaughter (average, 182 +/- 4.1 d) by carcass specific gravity. Empty body weight for large and very large cattle averaged 274 and 324 kg (P less than .05) initially and 497 and 603 kg (P less than .05) at slaughter. Empty body protein differed (P less than .05) for large and very large steers and averaged 51 and 61, 67 and 79, and 87 and 103 kg initially, at midpoint and at slaughter, respectively. Percentage empty body fat was lower for very large steers (13.5 vs 15.6%) initially (P less than .05) but was similar for very large and large steers at the midpoint (18.7 vs 18.1%) and at slaughter (23.2 vs 21.9%). Daily rates of empty body gain (DEBG) were greater (P less than .05) for very large vs large steers for both growing and finishing periods and averaged 1.53 vs 1.26 kg/d overall. Daily rates of protein gain (DPG) were similar for very large and large steers for the growing phase (204 vs 202 g/d) but greater (P less than .05) in very large steers for the finishing phase and overall (253 vs 204, and 229 vs 202 g/d). All implant strategies, except R36, increased DEBG and DPG and tended to decrease the percentage of fat in daily gain. In both large and very large cattle, implant growth regulators increased growth rate and partitioned nutrient use away from fat toward protein accretion, with the magnitude of partitioning toward protein increasing with greater rates of growth. These data indicate that anabolic growth regulators are viable strategies to enhance lean beef production in steers, regardless of animal size.

Ionophores alter hepatic concentrations of intermediary carbohydrate metabolites in steers.

The effects of ionophores on liver weight and function were determined in finishing steers (n = 24; avg weight 440 kg). Steers were group-fed one of three treatments (control, lasalocid or monensin at 33 mg/kg feed) for 46 d prior to slaughter. Three days prior to slaughter, blood was collected for the determination of serum Ca and Mg. At slaughter, the liver was removed, weighed, sampled, frozen in liquid nitrogen and subsequently analyzed for concentrations of carbohydrate metabolites and minerals. Liver weight (5.9 kg) was unaffected by treatment. Serum and hepatic Ca and Mg were not affected by ionophore treatment. Hepatic glycogen levels in steers fed ionophores were unaffected by treatment. Fructose 1,6-bisphosphate was 21% lower (P less than .10) in hepatic tissue of steers fed ionophores, whereas dihydroxyacetone phosphate was 15 to 37% greater in hepatic tissue of steers fed monensin (P less than .20) or lasalocid (P less than .10). Glyceraldehyde 3-phosphate was elevated more extensively by lasalocid than by monensin with increases of 72 (P less than .05) and 132% (P less than .001), respectively, over controls. Glycerol 3-phosphate levels were 37% (P less than .05) and 12% (NS) greater with these ionophores. Hepatic levels of pyruvate were elevated 12 (NS) to 36% (P less than .17) for monensin and lasalocid. Fructose 2,6-bisphosphate levels were 25% lower (P less than .25) in hepatic tissue of steers fed ionophores than in hepatic tissue from control steers. Other metabolites of carbohydrate metabolism in hepatic tissue were not altered appreciably. Changes in levels of intermediary metabolites of carbohydrate metabolism suggest alterations in hepatic carbohydrate metabolism favoring gluconeogenesis in steers fed ionophores.