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Congenital hereditary endothelial dystrophy (CHED) is a corneal disorder that presents with diffuse bilateral corneal clouding. Vision may be severely impaired, and many patients require corneal transplantation. Both autosomal dominant (AD) and autosomal recessive (AR) forms of the disorder have been described. The gene responsible for AD CHED (HGMW-approved symbol CHED1) has been mapped to the pericentromeric region of chromosome 20. Investigating a large, consanguineous Irish pedigree with autosomal recessive CHED, we have previously excluded linkage to this AD CHED locus. We now describe a genome-wide search using homozygosity mapping and DNA pooling. Evidence of linkage to chromosome 20p was demonstrated with a maximum lod score of 9.30 at a recombination fraction of 0.0 using microsatellite marker D20S482. A region of homozygosity in all affected individuals was identified, narrowing the disease gene locus to an 8-cM region flanked by markers D20S113 and D20S882. This AR CHED (HGMW-approved symbol CHED2) disease gene locus is physically and genetically distinct from the AD CHED locus., (Copyright 1999 Academic Press.)

Eight multicatheterized wethers (35.9 +/- .8 kg BW) were used in a replicated 4 x 4 Latin square design to measure N retention and net uptake and release of plasma metabolites across the portal-drained viscera (PDV), hepatic (HEP), and total splanchnic (TS) tissues in response to changes in supplemental N source. Treatments selected to provide different amounts of undegradable intake protein (UIP) were urea, soybean meal (SBM), poultry by-product meal (PBM), and bloodmeal:corn gluten meal (BMCGM; 50:50 CP basis). Diets (urea, SBM, PBM, and BMCGM) contained 12.9, 13.8, 13.6, and 13.2% CP, respectively. Periods were 10 d, with total feces and urine collected on d 7 to 10 and blood sampled on d 10. Wethers were fed at 2% of BW in 12 daily portions. Nitrogen retention was 2.2, 3.3, 4.1, and 4.4 g/d for urea, SBM, PBM, and BMCGM, respectively. Urea had less (P < .01) N retention than SBM, PBM, and BMCGM; SBM had less N retention (P < .01) than PBM and BMCGM. Arterial, portal, and hepatic plasma flows were greater (P < .09) for SBM than for PBM and BMCGM (21 vs 16, 17; 84 vs 72, 72; 105 vs 87, 88 L/h). Portal plasma flow was greater (P < .10) for urea than for SBM, PBM, and BMCGM (85 vs 84, 72, 72 L/h). Portal-drained viscera and TS alpha-amino N (AAN) fluxes were less (P < .05) for PBM than for BMCGM (20.5 vs 26.6 and 7.2 vs 15.1 mmol/h), but TS AAN flux was less (P < .05) for urea than for SBM, PBM, and BMCGM (6.9 vs 16.9, 7.2, 15.1 mmol/h). Portal-drained viscera flux and HEP removal of NH3 N were greater (P < .001) for SBM than for PBM and BMCGM (27.7 vs 19.4, 20.6; -28.1 vs -20.0, -21.4 mmol/h). Gut use was less (P = .07) and HEP and TS fluxes of urea N were greater (P < .01) for SBM than for PBM and BMCGM (-4.92 vs -8.32, -7.93; 25.87 vs 16.54, 20.00; 20.95 vs 8.22, 12.07 mmol/h). These data suggest that PBM and BMCGM improved efficiency of N use compared with urea and SBM by reducing urinary N loss.

Four Angus steers (318 +/- 16 kg) fitted with ruminal, duodenal, and ileal cannulas were used in a 4 x 4 Latin square design to determine carbohydrate disappearance from the small intestine (SI). Steers were fed fescue hay at 1.8% of BW and abomasally infused with starch hydrolysate (SH) at 10, 20, or 40 g/h or glucose (G) at 30 g/h. Starch hydrolysate was raw cornstarch digested by a heat-stable alpha-amylase. Experimental periods were 10 d with 6 d of adaptation, 3 d of digesta and feces collection, and 1 d of rest. Glucose (% of infused) had greater (P < .001) apparent small intestinal and postruminal disappearance (% of infused) compared with 20 and 40 g/h SH. Starch hydrolysate infusion linearly increased (P < .001) apparent SI, large intestinal (LI), and total intestinal starch disappearance (g/d) and quadratically increased (P < .003) apparent SI and total intestinal starch disappearance (% of infused). Ileal starch flow from infusion increased quadratically (P < .03) as SH infusion increased. True SI and total intestinal starch disappearance increased linearly (P < .001; g/d) with SH infusion. However, SH infusion quadratically decreased (P < .02) efficiency of true SI starch disappearance (% of infused). True LI starch disappearance (g/d and % of infused) quadratically increased (P < .03) as SH infusion increased. These data demonstrate that, even in animals fed all-forage diets, there is a significant flow of alpha-glucosides, and these need to be considered when evaluating intestinal carbohydrate digestion.

Six Angus steers (260+/-4 kg initial BW) fitted with ruminal, duodenal, and ileal cannulas were used in a 6 x 6 Latin square design to evaluate the effect of feeding poultry by-product meal (PBM) on small intestinal flow and disappearance of amino acids. The diets were provided at 2% of BW on a DM basis, formulated to contain 11.5% CP, and consisted of 49% corn silage, 36% cottonseed hulls, and 15% supplement on a DM basis. Supplements were formulated to contain 37% CP with sources of supplemental N being soybean meal (100% SBM) and 0, 25, 50, 75, and 100% PBM, with urea used to balance for N. Duodenal flow of all amino acids increased linearly (P < .07) as PBM increased in the diet and, except for His, increased (P < .09) for 100% PBM compared with 100% SBM. Similar results were observed for duodenal flow of nonbacterial amino acids, which linearly increased (P < .05) with PBM and were greater (P < .05) for 100% PBM than for 100% SBM. Soybean meal increased (P < .09) the duodenal flow of nonbacterial Lys compared with 0% PBM, and 0% PBM increased (P < .04) flow of Val, Ala, and Pro compared with 100% SBM. Duodenal bacterial essential, nonessential, and total amino acid flows were not affected (P > .80) by PBM; however, they were greater (P < .02) for 100% SBM than for 100% PBM. In addition, nonessential and total bacterial amino acid flows were increased (P < .06) for 100% SBM compared with 0% PBM. Small intestinal disappearance of Lys and Pro increased linearly (P < .09) as PBM increased, and 100% PBM increased (P < .07) disappearance of Arg and Ala compared with 100% SBM. Supplemental N source had no effect (P > .31) on apparent small intestinal disappearance of essential, nonessential, and total amino acids. These data suggest that when PBM, SBM, and urea were used as sources of supplemental N, the daily disappearance of amino acids from the small intestine of steer calves consuming a corn silage- and cottonseed hull-based diet was similar.

Ergot and pyrrolizidine alkaloids, either extracted from endophyte-infected tall fescue, synthesized, or purchased commercially, were evaluated in cultured cells to estimate their binding to the D2 dopamine receptor and subsequent effects on cyclic AMP production in GH4ZR7 cells, transfected with a rat D2 dopamine receptor. Ergopeptide alkaloid (alpha-ergocryptine, bromocryptine, ergotamine tartrate, and ergovaline) inhibition of the binding of the D2-specific radioligand, [3H]YM-09151-2, exhibited inhibition constants (K(I)) in the nanomolar range, whereas dopamine was less potent (micromolar). The lysergic acid amides (ergine and ergonovine) were 1/100th as potent as the ergopeptide alkaloids. Ergovaline and ergotamine tartrate were equally effective in inhibiting vasoactive intestinal peptide (VIP)-stimulated cyclic AMP production, with consistent nanomolar effective concentration (EC50) values. The remaining ergopeptide alkaloids (alpha-ergocryptine and bromocryptine), lysergic acid amides (ergonovine and ergine), and dopamine were 1/100th as potent. Two representative pyrrolizidines, N-formylloline and N-acetylloline, exhibited no binding activity at the D2 dopamine receptor or effects on the cyclic AMP system within the concentration ranges of nanomolar to millimolar. Our results indicate that the commercially available ergot alkaloids ergotamine tartrate and ergonovine may be used interchangeably in the D2 dopamine receptor system to simulate the effects of extracted ergovaline and ergine and to examine responses in receptor binding and the inhibition of cyclic AMP.

Mild hyperhomocysteinemia is a risk factor for atherosclerotic vascular disease. Homozygosity for the C677T mutation in the gene for 5,10-methylenetetrahydrofolate reductase (MTHFR) is frequently associated with hyperhomocysteinemia, particularly in individuals with low levels of serum folate, and has been directly associated with cardiovascular disease in certain populations. The purpose of this study was to establish whether the C677T mutation, which causes thermolabile MTHFR, is a risk factor for ischemic stroke in the Irish population. The homozygous C677T genotype has previously been associated with coronary heart disease in Ireland. We collected blood from 174 individuals (minimum age 60 years) who had suffered an ischemic stroke that was confirmed by computed tomography brain scan. Control subjects (n=183) aged >/=60 years, who had never suffered a stroke or transient ischemic attack, were recruited from hospitals and active retirement groups in the same geographical area. MTHFR genotypes were determined and other known risk factors for stroke were documented. In the control group, the frequency of subjects with the homozygous C677T genotype was 10.4%. In patients who had suffered ischemic stroke, the frequency was 15.5%. This difference was not statistically significant. The odds ratio of stroke for C677T homozygotes, with other genotypes as a reference group, was 1.59, 95% CI=0.85, 2.97. The data indicate that the homozygous C677T MTHFR genotype is at most a moderate risk factor for ischemic stroke.

We conducted three studies with steers to evaluate poultry by-product meal (PBM) as a supplemental N source for ruminants. An in situ study compared the solubility, degradation rate, and ruminal escape of PBM N with blood meal (BM), corn gluten meal (CGM), and soybean meal (SBM) N. Additionally, an 84-d growth study (n = 95, 228+/-5 kg BW) and a digestion trial (6 x 6 Latin square) were conducted. The basal diet for the growth and digestion studies consisted of 49% corn silage, 36% cottonseed hulls, and 15% supplement (DM basis). Sources of supplemental N (% of total supplemental N) were 100% SBM and 0, 25, 50, 75, and 100% PBM, with urea used to balance for N. In situ ruminal escape N (25.2, 55.3, 86.7, and 98.9% for SBM, PBM, CGM, and BM, respectively) was greater (P < .05) for PBM than for SBM; however, a greater (P < .05) proportion of BM and CGM N escaped ruminal degradation compared with PBM. Dry matter intake, ADG and gain/ feed increased linearly (P < .003) as PBM increased; however, no differences (P > .48) were observed in these variables for 100% PBM compared with 100% SBM. Duodenal N flow and small intestinal N disappearance increased linearly (P < .05) as PBM increased in the diet. Bacterial N flow to the small intestine was not affected (P > .19) by treatment; however, 100% SBM decreased (P < .04) bacterial CP synthesis (g bacterial N/kg OM disappearance from the stomach) compared with 0 and 100% PBM. In vivo ruminal escape N of PBM and SBM was 40.6 and 13.7%, respectively. Ruminal NH3 N decreased linearly (P < .001) as PBM increased. These data suggest that PBM can replace SBM as a source of supplemental N for steer calves that consume a diet based on corn silage and cottonseed hulls.

We used eight Polypay wethers (36 +/- .6 kg BW) fitted with hepatic portal, hepatic venous, mesenteric arterial and venous, and duodenal catheters in a crossover design experiment to determine the influence of somatostatin (SRIF) on splanchnic metabolism. Each crossover period consisted of 14 d, with net flux of nutrients and hormones (venoarterial differences x blood flow) measured on d 14. Before flux measurements, wethers received an i.v. dose (0 h) of either 0 (vehicle) or 50 mg x kg BW(-1) x 10 min(-1) cysteamine (CSH, SRIF-depleting agent) followed by a continuous duodenal infusion (h 10 to 22) of a starch hydrolysate-casein solution. Six sets of arterial, portal, and hepatic blood samples were obtained (h 12 to 16), after which a primed (10 microg), continuous jugular infusion of SRIF-14 (5.0 microg x kg BW(-1) x h(-1)) was initiated and sampling protocol repeated (h 18 to 22). Cysteamine administration increased (P < .01, vs control) portal and hepatic blood flow in the absence of exogenous SRIF (CSH x SRIF, P < .01). Net portal-drained viscera (PDV) release of glucose, alpha-amino N, ammonia N, beta-hydroxybutyrate, and oxygen consumption were decreased (P < or = .10) and lactate release increased (P = .005) during SRIF infusion. The CSH increased (P < .05) PDV release of beta-hydroxybutyrate and insulin and increased (P = .09, CSH alone vs control) net release of glucose in the absence of exogenous SRIF. Exogenous SRIF increased (P = .10) and CSH decreased (P = .09) net hepatic glucose output, whereas liver oxygen consumption was decreased (P = .04) with exogenous SRIF and increased (P = .01) with CSH. Net total splanchnic alpha-amino N release and oxygen consumption were decreased (P < .10) with exogenous SRIF, but CSH increased (P < .05) insulin release and oxygen consumption. These data provide initial evidence for a regulatory involvement of SRIF in visceral metabolism in ruminants.

The complexity of ruminant digestion necessitates a greater variety and complexity of experimental methods than with any other species. The fact that dietary ingredients are first subjected to microbial fermentation requires elaborate measures to ascertain nutrients presented for absorption. Numerous approaches have been attempted to obtain representative samples of digesta at sites throughout the gastrointestinal tract. The choices of a researcher before an experiment include animal(s), site(s) for cannula placement, style of cannula, cannula material, and numerous other more subtle factors that may contribute to the success of an experiment. This review compares the advantages and disadvantages of various approaches, cannula types, and cannula materials that should be considered before experiments are conducted.

Every 3 mo for a 2-yr period, two weaned Holstein steer calves (94.5 kg) were randomly assigned to each of four slaughter age groups (3, 6, 9, and 12 mo). Urea dilution was performed before slaughter, and urea space (US) was calculated as total volume and as a percentage of body weight (BW) and empty body weight (EBW). The relationships between US (kg, % EBW and % BW), BW, and EBW and carcass soft tissue composition (protein, fat, moisture, and ash) were studied. One- and two-pool models were fitted using the urea dilution data and the coefficients of those equations (zero time, A + B), and the intercepts of compartments A and B were used to estimate body volume. Body weight and EBW effectively predicted the amount of water, fat, and protein in the carcass soft tissue. Equations expressed in kilograms were more accurate than those expressed as percentages. Urea space overestimated body water, probably because of the fast rate of urea disappearance in plasma. Correlation coefficients between US and carcass soft tissue water (kg) based on the pooled data ranged from .74 at 6 min to .48 at 42 min after infusion. The biexponential models coefficients explained more of the variation of carcass soft tissue composition than US; correlation coefficients using volume B and the soft tissue composition (in kg) with pooled data were .78 (water), .68 (fat), .69 (ash), and .76 (protein). The relationships between A and soft tissue composition were weaker (water .59, fat .51, ash .58 and protein .59). The highest correlation coefficients were obtained when A + B was used for water, fat, ash, and protein (.83, .70, .74 and .81, respectively). Equations combining BW, EBW, and two-model coefficients (A, B, A + B) explained much of the variation of soft tissue composition. No significant benefit was found in using the urea space at various times after infusion over BW or EBW alone to estimate carcass soft tissue composition in Holstein steers.

Mild hyperhomocysteinaemia is a major risk factor for vascular disease and neural tube defects (NTDs), conferring an approximately three-fold relative risk for each condition. It has several possible causes: heterozygosity for rare loss of function mutations in the genes for 5,10-methylene tetrahydrofolate reductase (MTHFR) or cystathionine-beta-synthase (CBS); dietary insufficiency of vitamin co-factors B6, B12 or folates; or homozygosity for a common 'thermolabile' mutation in the MTHFR gene which has also been associated with vascular disease and NTDs. We quantified the contribution of the thermolabile mutation to the hyperhomocysteinaemic phenotype in a working male population (625 individuals). Serum folate and vitamin B12 concentrations were also measured and their relationship with homocysteine status and MTHFR genotype assessed. The homozygous thermolabile genotype occurred in 48.4, 35.5, and 23.4% of the top 5, 10, and 20% of individuals (respectively) ranked by plasma homocysteine levels, compared with a frequency of 11.5% in the study population as a whole, establishing that the mutation is a major determinant of homocysteine levels at the upper end of the range. Serum folate concentrations also varied with genotype, being lowest in thermolabile homozygotes. The MTHFR thermolabile genotype should be considered when population studies are designed to determine the effective homocysteine-lowering dose of dietary folate supplements, and when prophylactic doses of folate are recommended for individuals.

Six crossbred steers (261 +/- 18 kg BW) fitted with hepatic portal, mesenteric venous and arterial catheters, and duodenal, midjejunal, and ileal cannulas were used in a replicated 3 x 3 Latin square design to determine the effect of varying levels and site of glucose plus 2-deoxyglucose (2DG) infusion on net portal-drained visceral flux. Steers were fed chopped alfalfa in six equal portions daily at 1.5% of BW. Glucose (0, 9, or 18 g/h) and 2DG (0, 1, or 2 g/h) were infused continuously through the duodenal or midjejunal cannula (two infusion sites) at total glucose plus 2DG infusion rates of 0, 10, or 20 g/h. Arterial and portal blood samples were taken simultaneously at 20-min intervals from 5 to 9 h of infusion. Portal blood flow was determined by continuous infusion of p-aminohippurate and net flux was calculated as venous-arterial concentration (PA) difference times blood flow. Arterial concentration of glucose was not affected (P > .10) by glucose plus 2DG infusion, whereas arterial concentration of 2DG was greater (P < .05) when glucose plus 2DG was infused into the duodenum and increased (linear, P < .10) as amount of glucose plus 2DG infused into both the duodenum and midjejunum increased. Net portal flux and PA difference of glucose and 2DG were greater (P < .05) when glucose plus 2DG was infused into the duodenum. Although 2DG was infused at 10% of the total glucose plus 2DG infusion, it accounted for only 1.7 and .7% of the glucose plus 2DG appearing in portal blood when glucose plus 2DG was infused at 10 and 20 g/h, respectively. We conclude that glucose is more readily absorbed across the proximal-half than the distal-half of the small intestine, and that passive diffusion is a minor route of glucose absorption.

A procedure is described for the determination of alpha-amylase activity in bovine pancreatic juice. Bovine pancreatic juice was incubated with potato amylopectin for 6 min, and then alkaline potassium ferricyanide was added to stop the enzymatic reaction. Tubes were placed in a boiling water bath for 10 min and then cooled, and 40 mL of distilled water was added. Optical density was read at 420 nm, and the amount of end product (reducing sugars) was determined by comparison with maltose standards. Ten dilutions of bovine pancreatic secretion were assayed to determine the intraassay precision of this method, resulting in a CV of 1.05%. A pooled sample was assayed five times over five separate days to determine the interassay precision, resulting in a CV of 7.3%. This alpha-amylase assay provides a repeatable, rapid, and economical determination of alpha-amylase activity from bovine pancreatic juice.

The rates of amino acid replacement in cytokines and their receptors are high and vary considerably. To determine whether this reflects the action of positive selection, rates of nonsynonymous DNA substitution were examined and found to exceed the synonymous substitution rate in certain exons of rodent IL-3, granulocyte-macrophage stimulating factor, and IL-4. To determine the extent to which positive selection could account for correlations between the amino acid replacement rates of hemopoietins and their receptors, rates were examined in various domains: the correlation with ligand rate was not confined to the ligand-binding domain of the receptor, but extended into the transmembrane and cytoplasmic domains and even to leader peptide domains of both ligand and receptor. As the majority of these replacements are unlikely to be strongly advantageous, different levels of both positive and purifying selection contribute to the extensive variation in hemopoietin/receptor evolutionary rates. Changes in a few residues critical for ligand-receptor interaction may be followed by changes of lesser selective importance in both molecules: replacements of growth hormone residues that form hydrogen or salt bridges with the receptor occur in lineages in which there are many concurrent replacements. A ligand/receptor rate correlation is not found between the seven-transmembrane receptors and their ligands, whose mature forms are often short and completely conserved. This study predicts that a minority of concurrent evolutionary changes in hemopoietins and their receptors reflect directly compensatory changes.

Seven Holstein steers (234 +/- 6.4 kg) surgically fitted with pancreatic cannulas, ruminal and abomasal infusion cannulas, and hepatic-portal vein catheters were used in a 4 x 7 incomplete Latin square design experiment to examine the influence of ruminal and abomasal carbohydrate infusion on enzyme secretion and composition of pancreatic juice. Four treatments were arranged in a 2 x 2 factorial: 1) ruminal starch hydrolysate (SH; 34.2 g/[h.site]) or abomasal water and 2) abomasal SH or ruminal water. Starch hydrolysate is raw cornstarch that has been partially digested by a heat-stable alpha-amylase. Experimental periods were 14 d with 9 to 10 d of adaptation, 4 d of pancreatic collection, and blood collection on d 14. Abomasal SH infusion tended (P < .10) to increase pancreatic fluid secretion. The pH of pancreatic juice was higher (P < .01) for ruminal SH infusion, and abomasal SH infusion tended (P < .10) to result in lower pH of pancreatic juice. alpha-Amylase concentrations (units/milliliter and units/milligram of protein) and secretion (units/hour) were less (P < .002) for abomasal SH infusion. Chymotrypsin concentration (units/liter; P < .01) and secretion (units/hour; P < .10) were less for abomasal SH infusion; however, a rumen x abomasal interaction was found (P < .05). Chloride concentration (milligrams/deciliter) and secretion (milligrams/hour) were increased (P < .01) for abomasal SH infusion. Abomasal SH infusion resulted in increased (P < .01) portal blood glucose concentrations; however, portal plasma insulin concentration was not affected (P > .10). Abomasal SH infusion altered alpha-amylase secretion in steers, but ruminal SH infusion had minimal effect on alpha-amylase secretion. These changes suggest abosamal infusion of SH may negatively impact secretion of pancreatic alpha-amylase.

The effects of cysteamine (CSH; 0, 50, or 100 mg/kg BW), a somatostatin depleting agent, on growth hormone (GH) and insulin (INS) secretion were studied in sheep (Ovis aries). Cysteamine was administered as a single intragastric bolus on day 0 (0900). Jugular blood samples were collected at 15-min (GH) and 2-hr (INS) intervals over an 8-hr period (1100-1900) on day 0, 3, and 7. Intragastric administration of CSH at 50 mg/kg BW augmented (quadratic, P = .04) mean plasma GH concentration, with the greatest response occurring on day 3. Baseline GH concentrations were elevated in wethers dosed with 50 mg/kg BW CSH on day 3, whereas wethers dosed with 100 mg/kg BW CSH had lower baseline GH concentrations on day 0 (CSH x day interaction, P = .02). Cysteamine administration increased GH pulse amplitude (quadratic, P = .15), with the greatest magnigtude of change occurring with 50 mg/kg BW CSH on day 0 and 3. Frequency of GH pulses was increased (quadratic, P = .10) following CSH treatment. Administration of 100 mg/kg BW CSH augmented plasma INS on day 0 (CSH x day interaction, P = .09). These findings indicate that CSH alters GH and INS secretion in a dose-dependent and temporal manner. The observed changes in mean and baseline plasma GH concentrations associated with 50 mg/kg BW CSH are consistent with somatostatin depletion; however, higher doses of CSH appear to disrupt GH secretion by an alternative mechanism.

Twenty crossbred wethers (41.9 +/- 4.0 kg BW), each fitted with a ruminal cannula and a jugular catheter, were used in a completely randomized design to examine the effects of ruminal acidosis on plasma activities of pancreatic enzymes and fractional rates of VFA absorption. Lambs had ad libitum access to a 50% concentrate diet. Acidosis was induced by an intraruminal dose of glucose at 0, 6, 12, or 18 g/kg BW via the ruminal cannula. Ruminal fluid and plasma were collected 0, 4, 8, 12, 18, 24, 36, 48, and 72 h after dosing. Ruminal fluid pH was reduced (linear, P < .001) with increasing ruminal glucose. Total ruminal VFA concentration decreased (linear, P < .01) and D(-)-lactate (linear, P < .01) and L(+)- lactate (linear, P = .07) concentrations increased with increasing ruminal glucose. Activities of amylase and lipase in plasma were not affected by ruminal glucose (P > .10). Ten days after the acidosis insult, rumens were evacuated and contents were replaced with an isotonic Cr:VFA solution to measure ruminal VFA absorption. Ruminal fluid was collected hourly from 0 to 6 h. Fractional rate of acetate absorption was 13% lower for lambs receiving 18 g/kg BW glucose than for control lambs. In addition, fractional liquid passage rate was lower (P < .05) in lambs receiving 18 g/kg BW glucose 6 mo after the insult of acidosis. These data suggest that a short-term, severe insult of acute acidosis does not result in pancreatic tissue damage but may result in reduced ruminal VFA absorption for an extended period of time.

The evolutionary expansion of the haematopoietic cytokines and their receptors is characterized by the duplication of both cytokines and receptors. A systematic analysis of primary sequence homology indicates that receptors for gp130-associated cytokines group into signal transducing and non-signal transducing receptors. This observation is consistent with the evolution of the interleukins 6, 11 and 12, granulocyte colony stimulating factor (G-CSF), leukemia inhibitory factor (LIF), oncostatin M, and the ciliary neurotrophic factor complexes from a common ancestral complex which included a homodimer of gp130-like signalling receptors and an interleukin 6 receptor-like non-signalling receptor. Alterations in the components of the complex are proposed to have arisen by receptor duplication and divergence to allow signal transduction via a LIF receptor/gp130 heterodimer, and loss of the non-signalling receptor component in the G-CSF and the LIF lineage. The short-chain haematopoietins and their receptors do not group clearly, although interleukins 4 and 13 grouped together, as did 2 and 10. Internal duplication of the ligand-binding domain appears to have occurred independently in three separate lineages. These observations have implications for the classification of cytokines and receptors, and for the modelling by homology of their structures and interactions.

Extraction methods and HPLC procedures were developed for analysis of potential ruminal metabolites of dietary phenolics (reduced phenolics). Hepatic portal venous blood from wethers fed bromegrass, bermudagrass, ryegrass-wheat, and alfalfa hays also was analyzed for hippuric (HA), 3-(4-hydroxyphenyl)propionic (4OHPPA), benzoic (BA), 3-phenylpropionic (PPA), and t-cinnamic (CA) acids. Additionally, mesenteric arterial and hepatic venous blood was analyzed and, in conjunction with blood flow measurements, fluxes for portal-drained viscera (PDV) and liver were calculated. Ruminal fluid from four steers fed two levels of forage and two forage particle sizes in a Latin square design was analyzed for PPA and CA. 3-Phenylpropionic and benzoic acids were the most concentrated reduced phenolics identified in hepatic portal venous blood. Concentrations of PPA in ruminal fluid varied with ruminal disappearance of p-coumaric and ferulic acids. Additionally, hepatic portal venous concentrations of PPA were correlated (P < .05) with p-coumaric acid (r = .57) and ferulic acid (r = .67) intakes. Net release of PPA from PDV was observed, suggesting absorption of PPA from the gut. The liver removed PPA and BA with less efficiency. Given the relatively high concentrations of PPA in blood of ruminants, specific effects of this reduced phenolic on liver metabolism of ruminants should be assessed.

Four crossbred steers (380 +/- 6 kg) and seven Polypay wethers (40.3 +/- 6 kg) fitted with hepatic venous, hepatic portal, mesenteric venous and arterial, ruminal, and abomasal (steers) or duodenal (wethers) catheters were used in two crossover design experiments to evaluate adaptation to small intestinal starch and glucose transport. Steers were fed 8.6 kg/d and sheep were fed .9 kg/d of alfalfa hay in 12 equal portions and infused with an alpha-amylase partial starch hydrolysate (SH) either postruminally (adapted) or ruminally (unadapted) for 4 (steers; 40 g/h) or 5 (sheep; 6 g/h) days before measuring splanchnic flux of metabolites. On the day of flux measurements, ruminal SH infusion was switched to the postruminal site in unadapted animals. Flux measurements were made 3 to 6 h after switching infusion site for steers and 2 to 5 h for sheep. Phlorizin, a competitive inhibitor of Na/glucose cotransport, was then postruminally infused (550 and 500 mumol/h for steers and sheep, respectively) and flux measurements repeated from h 9 to 12 (steers) and h 7 to 10 (sheep). In the steers, adaptation increased (P < or = .09) portal-drained visceral (PDV) glucose release 26 mmol/h and decreased hepatic uptake of lactate 20 mmol/h. Abomasal infusion of phlorizin decreased (P = .01) net PDV glucose flux 40 mmol/h and concomitantly increased (P = .05) hepatic release of glucose by 47 mmol/h. In sheep, duodenal infusion of phlorizin increased (P < or = .005) portal and hepatic blood flow and decreased (P < or = .02) PDV release of glucose and lactate by 9 and .4 mmol/h, respectively. The liver released 4.2 mmol/h more (P = .09) glucose and removed 3.2 mmol/h more lactate (P = .09) glucose and removed 3.2 mmol/h more lactate (P = .001); arterial glucose decreased (P = .003) .75 mM in response to phlorizin. Phlorizin also caused loss of glucose in the urine of sheep (.09 mmol/h). Adaptation did not alter net splanchnic flux of glucose, lactate, oxygen, or alpha-amino N. These studies indicate that ruminants maintain the Na/glucose cotransporter when consuming little preformed alpha-glucosidic polymers and that the liver increases glucose release to compensate for reduced PDV delivery of glucose to maintain glucose homeostasis. In addition, the steers maintain at least 960 mmol/d and the sheep maintain at least 216 mmol/d of glucose transport capability regardless of adaptation.(ABSTRACT TRUNCATED AT 400 WORDS)

Three castrated male Holstein cattle (423 (SD 19)kg live weight) fitted with elevated carotid artery, portal, and mesenteric venous catheters, and abomasal and ileal cannulas were used to study small-intestinal starch digestion. The cattle were infused abomasally with water (275 ml/h), glucose (66 g/h), maize dextrin (66 g/h) or maize starch (66 g/h) in an incomplete Latin square design, with eight infusion periods. Infusion with carbohydrate resulted in higher arterial glucose concentrations and greater net portal glucose flux than when cattle were infused with water. Arterial glucose concentration and net portal glucose flux were highest when glucose was infused. In the small intestine, 85% of abomasally-infused glucose, 78% of infused dextrin, and 66% of infused starch disappeared. Of the carbohydrate that disappeared in the small intestine, that which could be accounted for as net portal glucose flux was 73% for glucose, 60% for dextrin, and 57% for starch. Ileal digesta contained unpolymerized glucose, and short-chain soluble alpha-glucoside. Of the infused dextrin flowing past the ileum (14 g/h), 0.3 g/h was glucose, 6.2 g/h was soluble alpha-glucoside, and 7.5 g/h was insoluble alpha-glucoside. Of the infused starch flowing at the ileum (22.2 g/h), 0.9 g/h was glucose, 5.3 g/h was soluble alpha-glucoside, and 15.9 g/h was insoluble alpha-glucoside. The average chain lengths of the soluble alpha-glucosides in ileal digesta were 2.07 and 2.36 for dextrin and starch infusions respectively, indicating mostly di- and to a lesser extent trisaccharides. We conclude that (1) when 66 g raw starch is presented to the small intestine per h, about half of the intestinal disappearance appears as glucose in the portal vasculature, and (2) alpha-1,4 glucosidase (EC 3.2.1.20) activity at the brush border is the rate-limiting step to small-intestinal starch digestion in cattle.

Eight crossbred wethers (51 +/- 2 kg BW), surgically fitted with abomasal cannulas, were used to determine the extent and time course of cysteamine (CSH)-induced depletion of somatostatin (SRIF) in abomasal tissue and associated changes in plasma metabolites, insulin, and growth hormone (GH). Cysteamine was administered as a single i.v. bolus (50 mg.kg BW-1 x 10 min-1) on d 0. Abomasal biopsies were obtained on d -7, -3, 0, 1, 3, and 10. On d 0, additional biopsies were taken at 2, 4, and 8 h after CSH administration. Jugular blood samples were collected over 8 h at 15-min intervals on d -2, 0, and 1. Cysteamine administration decreased (P < .05) tissue SRIF on d 0 (2, 4, and 8 h), 1, and 3; maximal depletion (42 to 55% of Pre-treatment; Pre-trt) occurred during the initial 24 h, returning to Pre-trt by d 10. Gel chromatography of pooled -7 d abomasal tissue extracts showed five peaks of SRIF immunoreactivity; the predominate peak eluted in the same position as synthetic SRIF-14. Plasma glucose, lactate, and NEFA concentrations increased (P = .001) after CSH administration and reached peak at 2 h after treatment and declined to Pre-trt concentrations by 24 h. Insulin increased (P = .001) to a maximum at h 4 and returned to Pre-trt by 24 h. Mean and baseline GH were higher (P < .07) on day of CSH administration, and pulse amplitude was lower (P < .10) on d 0 and 1. These data show that CSH rapidly reduces SRIF in abomasal tissue in a reversible manner; suggesting that CSH-treated sheep may provide a SRIF-deficient model for studying the physiological role of SRIF in ruminants.

Nine mature mongrel dogs were used to evaluate a surgical technique for the cannulation of the terminal ileum and used in two experiments to determine the effect of carbohydrate source on starch and dry matter digestion. Dogs (16.2 +/- 2.0 kg body weight; means +/- SD) were fitted with an ileal T-cannula constructed of polyvinyl chloride pipe. The cannula was inserted into the terminal ileum approximately 10 cm proximal to the ileocecal junction and the cannula was exteriorized through a small incision on the right flank. Dogs recovered quickly from surgery (5d). A preliminary study using Cr:EDTA in the food indicated that sampling for 12 h postprandially allowed near complete representation of digesta flow for a meal; peak flow occurred 4-to 8-h postfeeding. Two experiments were performed evaluating the effect of carbohydrate source on ileal starch and dry matter digestibility. Dogs were fed two meals daily with Cr2O3 used as a digesta marker. Diets contained 67% extruded grain (corn, rice, oats or barley) and 33% canned meat supplement on a dry matter basis. Starch digestion was complete (> 98%) within the small intestine and was unaffected by carbohydrate source. In experiment 1, prececal and total tract dry matter digestibilities were higher for rice than corn, and in experiment 2, barley was higher than oats. The ileal T-cannula allows for measurement of small intestinal nutrient disappearance without the confounding effects of colonic microflora. This method may be useful when applied to the study of other nutrients in dogs.

Effects of diet forage:concentrate ratio and mesenteric vein L-alanine infusion on net VFA metabolism by portal-drained viscera (PDV) and liver were determined in four multicatheterized Hereford x Angus heifers (443 kg BW) fed in equal meals every 2 h pelleted, isonitrogenous diets containing 75% alfalfa or 75% corn:soybean meal (SBM) in a balanced single reversal of diets with 6 wk for adaptation. In addition, effects of L-alanine infusion on net metabolism of individual amino acids (AA) by PDV and liver was determined when heifers were fed 75% corn:SBM. Four measurements of blood flow (p-aminohippurate dilution) and net flux of VFA and AA (venous-arterial difference times blood flow) were obtained at 30-min intervals immediately before beginning and ending a 24-h mesenteric vein infusion of L-alanine at 75 mmol/h. Net PDV absorption of acetate (P < .02), propionate (P < .02), and total VFA (P < .02) was lower when 75% corn:SBM was fed, reflecting increased carbohydrate digestion postruminally and only partially balanced by increases in net PDV glucose absorption reported previously. In addition, net PDV absorption of n-butyrate was lower when 75% alfalfa was fed. Excluding acetate, net liver removal of VFA was 83 to 108% of their net PDV release. L-Alanine infusion did not affect net PDV or liver flux of VFA but decreased net total splanchnic (PDV plus liver) release of propionate (P < .07) and n-butyrate (P < .03) and decreased (P < .10) net PDV release and liver removal of glycine. In spite of the increase in liver L-alanine removal, the ratio of glucose release to precursor removal remained remarkably constant across the liver when L-alanine was infused, emphasizing the tight control of liver glucose release and the dynamic interplay of precursor supply and removal in the maintenance of liver carbon balance.

The predictability of diet effects on milk composition is limited by the lack of understanding of the metabolic transformations that absorbed nutrients undergo within the portal-drained viscera and liver of high yielding dairy cows. The mass of splanchnic tissues increases dramatically in early lactation, but little is known about the regulation of gut growth and adaptation in early lactation, and further research may provide strategies for optimizing gut adaptation. Glucose is critical for milk synthesis, but portal-drained visceral tissues normally use rather than absorb glucose on a net basis. Dietary starch of low ruminal digestibility increases postruminal starch digestion and decreases net use of glucose by portal-drained viscera slightly, but increases in glucose absorption by portal-drained viscera never account fully for increases in starch disappearance from the small intestine and occur at the expense of VFA absorption. For cows in positive energy balance, greater glucose availability increases tissue energy balance and glucose oxidation, but has little effect on milk or milk protein yield. Similarly, chronic increases in propionate absorption have little effect on milk or milk protein yield. In contrast, casein infusion into the small intestine consistently increases milk and milk protein yield, but the mechanisms responsible remain unclear. There are few data describing the absorption and metabolism of AA by splanchnic tissues of lactating dairy cows, but, as for glucose and VFA, utilization of many AA by portal-drained viscera is substantial. In addition, the contribution of peptides to AA absorption and transport is uncertain and must be clarified. Therefore, measurements of nutrient disappearance from the lumen of the gut cannot be equated with nutrient appearance in the portal vein. Data describing metabolism of nutrients by portal-drained viscera and liver of high yielding dairy cows are needed to improve feeding standards.

Three Holstein steers (345 +/- 22 kg) surgically fitted with a pancreatic cannula were used in two 3 x 3 Latin square design experiments to examine the effects of slaframine (SF), a muscarinic agonist, or 4-diphenylacetoxy-N-methylpiperidine methiodide (4DAMP), an M3 muscarinic glandular receptor antagonist, on pancreatic exocrine secretion. Pancreatic exocrine secretion was collected for 8 h postdosing at 30-min intervals beginning 1 h postfeeding. In experiment 1, steers were dosed with 0, 25, or 50 micrograms.kg-1 body weight (BW) of SF. Secretion of pancreatic juice and the pH of the secreted juice increased linearly (p < 0.05) with SF; however, secretion rate showed a time by treatment interaction (p < 0.05), as treatments converged 7 h postdosing. Trypsin secretion tended (p < 0.10) to show a quadratic response to SF administration, with the 25 micrograms SF.kg-1 BW dose having the lowest value. In experiment 2, steers received 50 micrograms.kg-1 BW of SF (positive control), 113 micrograms.kg-1 BW of 4DAMP (isosmolar with SF), or both. SF caused a greater pancreatic fluid secretion (p < 0.10) than 4DAMP, with SF plus 4DAMP intermediate. A time by treatment interaction (p < 0.04) was found, since treatments converged 8 h postdosing. Trypsin secretion was higher (p < 0.05) for SF than the other treatments. Chymotrypsin, alpha-amylase, and protein secretion were not affected. SF and 4DAMP alter pancreatic fluid secretion in the steer but have minimal effects on enzyme secretions.

One feedlot trial (116 d; 192 steers) with a factorial arrangement of treatments was conducted to determine effects of supplemental fat and ionophores in corn-based finishing diets. Factors were level of fat (0 or 4% tallow) and ionophore type (none [N], lasalocid [L], monensin plus tylosin [MT], or daily rotation of L and MT [LMT]); L, M, and T were fed at 31, 25, and 10 ppm (DM basis), respectively. Fat and ionophore interacted for DMI (P < .10), ADG (P < .01), and gain:feed G/F, P < .05). Compared with 0%-fat diets, 4% fat decreased (P < .005) DMI by steers fed MT by 8.9%. In 0%-fat diets, MT increased (P < .05) ADG and G/F compared with N or L; however, this increase was negated or reversed in 4%-fat diets. Fat and ionophore interacted (P < .16) on dietary NE concentration. In the 0%-tallow diet, MT increased NEm and NE(g) by 5.1 and 7.0%, respectively, but MT had not effect on NE concentration of the 4%-tallow diet. Alternate feeding of L and MT did not increase animal performance above that of separate, continuous feeding. Six ruminally fistulated steers were used in a metabolism study to evaluate potential mechanisms underlying the interactions observed in the feedlot trial. Treatments were the same as the feedlot trial, except that LMT was not included. Ruminal digesta kinetics were not altered (P > .30) by the addition of fat or ionophores to the diet. Fat and ionophore interacted (P < .05) for molar proportions of ruminal acetate and propionate.(ABSTRACT TRUNCATED AT 250 WORDS)

Nutritional regulation of digestive enzymes has received limited study in ruminants. Comparable studies with nonruminants report adaptations occurring in pancreatic and mucosal enzyme concentrations and synthesis in response to increased consumption of carbohydrate, lipid, or protein. Adaptations in carbohydrases apparently are mediated through changes in blood glucose and insulin, and changes in lipase are mediated through changes in circulating beta-hydroxybutyrate. Increased synthesis and secretion of pancreatic proteases apparently are mediated directly through luminal effects of protein, possibly through a messenger peptide. Available information for ruminants suggests that pancreatic alpha-amylase concentration increases with increased energy intake, but not with increased carbohydrate intake, independent of energy. This result may indicate an adaptation mechanism similar to that of nonruminants, one that is mediated through increased glucose turnover, not intestinal carbohydrate supply alone. Increased intake of energy or increased intestinal supply of carbohydrates results in little or no increase in mucosal carbohydrases in the ruminant. Comparable data for effects of changing intestinal supply of protein are limited to the developing ruminant. Experiments involving lipid feeding are not available, but duodenal lipid infusion decreases pancreatic lipase secretion. Ruminant data are inadequate to predict accurately an adaptive response to feeding any diet.

Four multiparous, ruminally fistulated Angus x Hereford cows (average BW = 568 kg) were bred to the same bull and used to monitor periparturient changes in DMI, ruminal capacity, and digestion and fermentation characteristics. Cows were individually fed alfalfa hay (16.0% CP, 51.3% NDF) at 130% of the average DMI of the previous 5-d period. Ruminal capacity and DM fill were measured once every 2 wk by removing the ruminal contents from each cow and filling the empty rumen with water. Dry matter intake was measured daily. Ruminal VFA, pH, NH3, and total tract DM digestibility (DMD) were measured during three 7-d periods (average of 58 d before calving, 16 d before calving, and 25 d after calving). Ruminal capacity and DM fill varied in a quadratic manner (P < .01); both were least 6 d before calving. Forage DMI (quadratic effect; P = .02) increased moderately during the prepartum period but increased dramatically after parturition. Although postpartum (d 22) ruminal capacity was only 5% greater than at 61 d before calving, postpartum DMI was 69% greater than DMI measured 61 d before calving. Indigestible ADF (IADF) passage rate changed quadratically with period (P = .01); the greatest IADF passage rate was observed 6 d before calving. Ruminal VFA (mM) also tended to change quadratically (P = .08); the highest concentrations occurred 25 d after calving. The acetate:propionate ratio declined linearly with period (P = .01). Ruminal fluid dilution rate, pH, NH3, and DMD did not change significantly over time.(ABSTRACT TRUNCATED AT 250 WORDS)

Forty Angus x Hereford 2-yr-old primiparous cows (358 kg) were used to determine the effects of source and amount of CP on performance, reproductive function, and metabolic status of suckled primiparous cows. A 2 x 2 factorial treatment arrangement was used; cows received either 100 or 150% of NRC recommendations for CP in diets that contained either soybean meal (low escape = L) or corn gluten meal/blood meal (high escape = H) as the principal supplemental protein source. Resulting treatments were 100-L, 100-H, 150-L, and 150-H. Cows were individually fed diets for 100 d or until they were observed to be in standing estrus. Diets were isoenergetic and limit-fed to meet NRC recommendations for NE, Ca, and P for 364-kg, 2-yr-old primiparous cows producing 4.5 kg of milk daily and gaining .23 kg/d. Increased CP tended (P = .09) to increase ADG in cows, but body condition score was unaffected. Increased CP and use of a CP source with higher potential for ruminal escape increased ADG in calves from d 0 to 97 (P = .002 and .04, respectively), which corresponded with numerical changes in milk production. Feeding high escape CP sources decreased plasma glucose and urea N (P = .04 and .0001, respectively). Increased CP tended (P = .12) to increase plasma glucose and increased (P = .0001) plasma urea N. Treatment had no effect on profiles of LH or progesterone. Although numerical differences in conception rate seemed large for 100-L compared with the remaining treatments, statistical significance was not detected.(ABSTRACT TRUNCATED AT 250 WORDS)

We have identified two new point mutations in the beta-hexosaminidase alpha subunit (HEX A) gene in a non-Jewish Tay-Sachs disease patient with an unusual late infantile onset disease phenotype. The patient was a compound heterozygote with each allele of the HEX A gene containing a different mutation in exon 1. One of these is a T to C transition in the initiation codon, expected to produce no alpha subunit and therefore a classical infantile phenotype. The unusual clinical aspects and later onset in the patient must therefore be a result of residual hexosaminidase A activity associated with a mutant alpha subunit containing the second mutation, substitution of serine for proline at amino acid 25 owing to a C to T change at nucleotide 73. Western blotting and DE-52 ion exchange chromatography have been used to examine the behaviour of this mutant alpha subunit.

Six Holstein steers (381 +/- 11 kg BW; mean +/- SE) surgically fitted with hepatic portal (n = 6), hepatic venous (n = 4), mesenteric venous, and arterial catheters were used in a replicated crossover design experiment to evaluate the influence of monensin addition to an alfalfa hay diet on net portal and hepatic nutrient flux. Steers were fed 6.5 kg of DM/d in 12 portions using automatic feeders. Diets included chopped alfalfa hay (20.4% CP) plus 418 g of DM/d of finely ground corn (8.5% CP) with monensin added (240 mg/d) for treated steers. Experimental periods lasted 21 d, with blood samples taken on the final 2 d of each period. Five sets of arterial, portal, and hepatic blood samples were collected hourly from 0900 to 1300 each day. Ruminal fluid samples were collected by stomach tube at the end of each sampling day for VFA analysis. Blood flow was determined by a primed-continuous infusion of p-aminohippurate into the mesenteric venous catheter. Addition of monensin increased (P = .04) the molar percentage of ruminal propionate and decreased ruminal isobutyrate (P = .02) and isovalerate (P = .03). Percentages of the other ruminal VFA, total ruminal VFA concentration, and pH were not affected by feeding monensin. The arterial concentrations of L-lactate (P = .02) and beta-hydroxybutyrate (P = .01) were greater with monensin; however, none of the arterial concentrations of the other metabolites was changed. Feeding of monensin also did not affect (P > .10) portal, hepatic, or hepatic arterial blood flow.(ABSTRACT TRUNCATED AT 250 WORDS)

Collection of exocrine pancreatic secretions from cattle by use of a single-unit cannula was performed. The major advantage of the cannula was simple technical management. A small pouch of the duodenum into which the major pancreatic duct drains was formed. Continuity of the duodenum was reestablished by end-to-end anastomosis. A side arm of the cannula was inserted into the pouch to collect exocrine secretions, and the main portion of the cannula was placed cranial to the anastomosis to return pancreatic secretions to the small intestine between collection periods. The accessory pancreatic duct was ligated in 2 of 4 cattle to evaluate possible secretory contribution from this source. All cattle remained healthy after cannulation, and cattle gained approximately 100 kg of body weight in the 5 months after surgery. The mean secretory rate for exocrine pancreatic secretion in cattle was 106 +/- 6.8 ml/h. There was no effect of feeding on the pattern of secretion nor were there significant differences between cattle. A fistula formed between the pouch and duodenum approximately 120 days after surgery in the first 2 cattle used. Development of fistulas was prevented for 300 days in subsequently prepared cattle by use of surgical mesh around the cannulas, leading to functional cannulation sites. Preparation of a duodenal pouch appeared useful for long-term studies of pancreatic exocrine secretion in cattle.

Three experiments were conducted to determine whether emulsifiers improve utilization of fat from diets for early-weaned pigs. In Exp. 1, 96 weanling pigs (17 d old) were used in metabolism cages, with main effects of fat source (soybean oil, tallow, lard, and coconut oil) and emulsifier treatment (no emulsifier, lecithin, and lysolecithin as 10% of the added fat). Soybean oil and coconut oil were more digestible than tallow and lard (P < .001). Tallow was more digestible when lecithin and lysolecithin were added (P < .007), and pigs fed lecithin had lower serum triglycerides and cholesterol than pigs fed lysolecithin (P < .03). In Exp. 2, 270 weanling pigs (21 d old) were used in a growth assay. Treatments were 1) control diet; 2) Diet 1 with soybean oil; 3) Diet 1 with tallow; 4, 5, and 6) Diet 3 with lecithin replacing 5, 10, and 30% of the tallow, respectively; and 7, 8, and 9) Diet 3 with lysolecithin replacing 5, 10, and 30% of the tallow, respectively. At d 14 of the experiment, digestibility of tallow was improved more by lecithin than lysolecithin (P < .008). For the total experiment (d 0 to 35), the control pigs had poorer gain:feed ratio than did the pigs fed the fat sources (P < .002). In Exp. 3, 420 weanling pigs (21 d old) were used. Treatments were 1) control diet with soybean oil; 2) Diet 1 with tallow; and 3, 4, and 5) Diet 2 with 10% of the added fat as soybean oil, lecithin, or monoglyceride, respectively. Adding soybean oil, lecithin, and monoglyceride to tallow increased digestibility of total fat (P < .07). From d 0 to 14, pigs fed soybean oil gained weight faster than pigs fed the other treatments (P < .06), and pigs fed tallow without emulsifiers had the lowest ADG. Considering all experiments, addition of emulsifiers increased digestibility of nutrients but had minimal effect on growth performance.

Because of the unique features of the ruminant digestive system, variations in diet composition and intake produce dramatic changes in ruminal fermentation. Optimizing nutritional management requires an understanding of how these variations and changes influence digestion and metabolism. Although the pancreas plays a central role in digestion and subsequent nutrient metabolism, relatively little is known about pancreatic adaptation to nutritional changes in the ruminant. Increasing starch intake has been suggested to increase pancreatic alpha-amylase; however, recent work suggests that dietary energy per se may drive these changes, and interactions with other nutrients, such as protein, may exist. Studies describing the influence of altered protein and lipid intakes on pancreatic adaptation in ruminants are lacking. Pancreatic secretion of both insulin and glucagon respond to the intravenous infusion of VFA in a dramatic fashion; however, feeding studies suggest that the influence of VFA on insulin and glucagon may be more subtle. Interactions exist between stimulatory signals and physiological state, such as lactation. Assessment of pancreatic endocrine secretion is further complicated by a variable removal of insulin and glucagon by hepatic tissues. These studies point out that pancreatic hormone secretion is controlled by integrated and complex mechanisms. Studies of these controlling mechanisms should consider the entire array to more fully understand hormone secretion.

Six Holstein steers (mean +/- SE BW = 344 +/- 10 kg) fitted with hepatic, portal, and mesenteric vein and mesenteric artery catheters and a ruminal cannula were used in a 6 x 6 Latin square design to evaluate the effects of increasing ruminal butyrate on net portal-drained visceral and hepatic nutrient flux. Steers were fed a 40% brome hay, 60% concentrate diet in 12 portions daily at 1.25 x NEm. Water (control) or butyrate at 50, 100, 150, 200, or 250 mmol/h was supplied continuously via the ruminal cannula. Simultaneous arterial, portal, and hepatic blood samples were taken at hourly intervals from 15 to 20 h of ruminal infusion. Portal and hepatic blood flow was determined by continuous infusion of P-aminohippurate, and net nutrient flux was calculated as the difference between venous and arterial concentrations times blood flow. Ruminal and arterial concentrations and total splanchnic flux of butyrate increased (P less than .01) with increased butyrate infusion. Arterial concentrations of acetate (P less than .10), alpha-amino-N (P less than .05), and glucose (P less than .01) decreased with increased butyrate, whereas arterial beta-hydroxybutyrate (P less than .01) and acetoacetate (P less than .05) increased. Increased butyrate produced an increased portal-drained visceral flux of acetoacetate and an increased net hepatic flux of beta-hydroxybutyrate. Urea N and glucose net portal and hepatic fluxes were not affected by ruminal butyrate. Alpha-amino-N uptake by the liver decreased with increased butyrate (P less than .10). Simple linear regression (r2 = .985) indicated that 25.8% of ruminally infused butyrate appeared in portal blood as butyrate. Only 14% could be accounted for as net portal-drained visceral flux of acetoacetate plus beta-hydroxybutyrate.

Data describing the influence of diet composition and intake on amylolytic and disaccharidase activities in the ruminant small intestine are reviewed. Changing dietary components from forage to grain increased pancreatic alpha-amylase activities in most studies; however, when metabolizable energy intake was equalized, concentrations of alpha-amylase in the pancreas and the total quantities in the small intestinal lumen were greater in forage-fed than in grain-fed animals. Concentration of pancreatic alpha-amylase increased with dietary energy intake. Changing diet composition or metabolizable energy intake exerted a small effect on intestinal disaccharidase activities, with hydrolytic capacity altered principally through changes in intestinal length. Other studies suggest a small contribution of intestinal disappearance of carbohydrates to net portal appearance of glucose. The fate of large portions of intestinal carbohydrate disappearance have not been adequately defined. For the importance of intestinal carbohydrate supply to be understood, the quantity of carbohydrate undergoing both enzymatic hydrolysis and absorption must be determined.

Six ruminally fistulated steers (550 kg) and 24 heifers (315 kg) were used to determine the effect of source and amount of ruminal-escape lipid in a supplement on forage intake and digestion. Steers were used in a 6 x 6 Latin square digestion study to evaluate six supplementation treatments: 1) negative control (NC), no supplement; 2) positive control (PC), soybean meal:grain sorghum supplement; 3) low-Megalac (calcium salts of fatty acids; LM) supplement; 4) high-Megalac (HM) supplement; 5) low-Alifet (crystallized natural animal fat, LA) supplement; and 6) high-Alifet (HA) supplement. Supplements were fed at .30% of BW on a DM basis and were isoenergetic within fat levels (high vs low). Steers were fed mature brome hay (7.2% CP) at 1.5% of BW on a DM basis. In the forage intake trial, heifers were assigned randomly to the same supplement treatments. Prairie hay (4.4% CP) was offered at 130% of ad libitum intake. Dry matter and NDF digestibility, ruminal DM fill, indigestible ADF passage rate, and fluid dilution and flow rates were not different (P greater than .10) among treatments. Total VFA concentrations were greater (P less than .01) and acetate-to-propionate ratio (Ac:Pr) was less (P less than .01) in supplemented groups; however, neither source nor level of escape lipid influenced either total VFA or Ac:Pr. Forage intake was greater (P less than .01) for supplemented groups than for the NC. At the high level of fat inclusion, heifers supplemented with Alifet ate slightly more (P less than .05) forage than those supplemented with Megalac.(ABSTRACT TRUNCATED AT 250 WORDS)

Six ruminally fistulated crossbred steers (BW = 369 kg) were used in a randomized complete block experiment to test the efficacy of continuous-infusion pumps and controlled-release boluses for administering external markers to predict fecal output. Steers, limit-fed chopped alfalfa hay at 2% of BW daily, were fitted with continuous-infusion pumps that administered Co-EDTA and YbCl3 solutions intraruminally. In addition, a controlled-release bolus containing Cr2O3 was inserted into the rumen of each steer. Fecal grab samples were taken every 6 h for 7 d during initial marker equilibration; after this period, fecal grab samples were taken every 3 h for 48 h to evaluate diurnal variation patterns. Steers were subsequently fitted with fecal bags for 7 d to allow total fecal collection. Grab samples also were taken during the total fecal collection period at 0600 (AM) and 1400 (PM). The marker X time effect was nonsignificant. Similarly, time of grab sampling (AM or PM) did not affect estimates of fecal output (P greater than .10), but the Cr2O3 bolus overestimated fecal output (P less than .05). Fecal marker concentrations during the 48-h profile showed little diurnal variation regardless of marker used. All markers equilibrated in the feces at approximately 100 to 120 h after initiating infusions. The continuous-infusion pumps evaluated were efficacious for administering markers for estimating total fecal output in limit-fed steers; however, the Cr2O3 boluses evaluated overestimated fecal output when the manufacturer's suggested release rate was used for fecal output calculations.

Twelve multiparous Simmental cows (584 kg) were used to determine the influence of calcium soaps of fatty acids (CSFA) incorporated in a range supplement on postpartum reproductive characteristics. Cows were assigned randomly to receive a control [C; containing grain sorghum (GS) and soybean meal (SBM)] or CSFA-based (containing Megalac [a source of CSFA], GS, and SBM) supplement. Supplements plus prairie hay were individually fed. Diets were isonitrogenous and met the NEm requirement for heavy-milking beef cows in early lactation. Supplement feeding and daily blood collection began at parturition. Calves were removed permanently from cows at 25 +/- 2 d postpartum. Duration of first postpartum estrous cycles was determined by both visual observations and changes in concentrations of progesterone in serum. Concentrations of LH in serum (15-min intervals for 6 h) were determined 12 h before and 48 and 96 h after calf removal. Concentrations of progesterone and estradiol-17 beta in serum were determined daily. Cows receiving CSFA had higher (P = .06) mean concentrations of LH than those receiving C (1.47 vs 1.12 +/- .13 ng/ml). Concentrations of estradiol-17 beta were lower (P less than .02) and serum progesterone were higher (P less than .02) between d 6 and 8 of the induced cycle in CSFA-fed cows. Plasma cholesterol was greater (P less than .01) in cows fed CSFA although plasma triglyceride concentrations were similar between treatments.(ABSTRACT TRUNCATED AT 250 WORDS)

Twenty calves (7 mo old) were blocked by breed, sex, and weight into five groups of four calves and randomly assigned to either a 90% forage (alfalfa) or a 90% grain (50% sorghum and 50% wheat) diet fed at one (1M) or two (2M) times NEm for 140 d. Samples of ruminal epithelial tissue were collected from the anterior ventral sac, and papillae were cut free by hand and used for in vitro incubations and acyl-CoA synthetase assays. Substrates were acetate (90 mM), propionate (60 mM), butyrate (30 mM), and glucose (20 mM). Net productions of beta-hydroxybutyrate and acetoacetate from acetate were greater (P less than .01) with the 2M feeding; however, 14CO2 production from acetate was greater (P less than .05) with the grain diet. Net production of lactate (P = .09) and pyruvate (P less than .01) from propionate increased with the 2M feeding, whereas net lactate production from glucose decreased (P less than .01). Uptakes of VFA were similar with 1M and 2M feeding and were about 10-fold greater than uptakes of glucose. Production of 14CO2 from propionate was two- to fivefold greater than from acetate, butyrate, or glucose. Oxygen consumption was greater (P less than .01) with 2M feeding and unaffected by substrate. Activities of butyryl-CoA synthetase (nmol.mg of tissue-1.h-1) were greater (P less than .05) for animals consuming the forage diets. Addition of butyrate inhibited acetyl- and propionyl-CoA synthetase activity by 63 and 92%, respectively for all dietary treatments. Overall, metabolism of ruminal epithelial tissue tended to increase with the 2M feeding. Influence of dietary forage content on metabolism and activity of acyl-CoA synthetases was minimal, but the high-forage diet caused slight increases.

Wheat and high-moisture corn (HMC) were fed singly and in three combinations using dry-rolled wheat (DRW) (ratios of 75:25, 50:50, and 25:75, respectively, Trial 1), or singly and in two combinations using steam-rolled wheat (SRW) (ratios of 67:33 and 33:67, respectively, Trial 2) to finishing beef cattle fed a high-concentrate diet. In situ rate of starch digestion (Trial 3) was measured on grains used in Trial 1 (excluding the 25 HMC: 75 DRW mixture) and ground dry corn. In Trial 1 (132 d), gain/feed did not differ (P greater than .10); however, final weight, hot carcass weight, and ADG decreased linearly (P less than .05) and DMI exhibited a cubic response (P less than .05) as the percentage of wheat in the diet increased. Carcass characteristics were not different. In Trial 2 (113 d), there were no differences attributable to treatment for ADG, DMI, gain/feed, or carcass characteristics. Positive associative responses for gain efficiency (gain/feed) were greatest for the first increment of wheat addition (25% DRW and 33% SRW in Trials 1 and 2, respectively) and for the early portion of the feeding period (57 and 28 d for Trials 1 and 2, respectively), indicating a more rapid diet adaptation and(or) less propensity for subacute acidosis. In Trial 3, the treatment grains or mixtures did not differ in rate of starch digestion. Although the differences were not statistically significant, starch in the 100% wheat diet was digested twice as fast as the 100 or 75% HMC mixtures.(ABSTRACT TRUNCATED AT 250 WORDS)

Four multicannulated Holstein steers (initial BW 424 +/- 16 kg) were used in a 4 x 4 Latin square to determine the influence of protein supplementation on forage intake, site and extent of digestion, and nutrient flow in steers consuming dormant bluestem-range forage (2.3% CP). Treatments were 1) control, no supplement; 2) 1.8 kg of low-protein supplement, 12.8% CP (Low-CP); 3) 1.8 kg of moderate-protein supplement, 27.1% CP (Mod-CP); and 4) 2.7 kg of dehydrated alfalfa pellets, 17.5% CP (Dehy). The Dehy supplement was fed to provide the same amount of CP/d as Mod-CP, and all supplements provided similar amounts of ME/d. Forage DMI was increased (P less than .05) by feeding Mod-CP and Dehy. Ruminal OM digestibility was 39% greater (P less than .05) for the Mod-CP and Dehy supplementations than for the Low-CP supplementation and control. Ruminal CP digestibility was negative for all treatments, and control (-326%) was less (P less than .05) than supplemented treatments (average -27%). Total tract OM digestibility was greatest (P less than .10) for steers fed Mod-CP and least for control steers; Low-CP and Dehy steers were intermediate. Total tract NDF digestibility tended (P = .15) to be less with Low-CP than with Mod-CP and Dehy. Duodenal N flow was greater (P less than .05) with Mod-CP and Dehy than with Low-CP and control. In summary, supplementation with Mod-CP increased forage intake, digestion, and duodenal N flow compared with Low-CP or control; however, the response was similar when Mod-CP and Dehy supplements were fed to provide equivalent amounts of CP and ME daily.

A 111-d finishing study evaluated animal growth and carcass characteristics using 138 steers (366 kg) in a randomized complete block design with a 2 x 3 factorial arrangement of treatments. The dietary treatments consisted of no supplemental fat or 3.5% tallow or soybean oil soapstock (SS) fed with .6% and .9% dietary Ca. Fat increased DMI (P less than .05) but interacted with Ca level (P less than .05) for gain/feed and ADG. All diets containing fat or .9% Ca were converted more efficiently to gain than the .6% Ca, no supplemental fat diet (P less than .05). The .9% Ca interacted with fat source to decrease gain (P less than .05) and tended to decrease efficiency in the tallow diet but improved efficiency (P less than .05) and tended to improve gain in the no-fat diet. In the SS diet, .9% Ca had no effect on ADG, DMI, or efficiency of gain. Fat addition increased backfat (P less than .10) and interacted with Ca on hot carcass weight, final weight, and dressing percentage (P less than .05). Feeding fat increased the proportion of 18:0 (P less than .02) and decreased the proportion of 16:1 fatty acids (P less than .06) in intermuscular fat. A replicated 3 x 3 Latin square design, using six Holstein steers (349 kg) fed three diets, with no supplemental fat or 3.5% SS or tallow with 1.0% Ca, was used to explore the effects of fat sources when fed with high Ca on digestion and metabolism. Ruminal fluid pH was higher (P less than .10) when steers were fed fat. Adding fat did not affect (P greater than .10) duodenal or ileal pH, VFA proportions or total concentration, or ruminal liquid volume or flow rate. Liquid retention time was shorter and liquid rate of passage was higher (P less than .05) with dietary fat addition. Adding fat did not affect site or extent of starch or DM digestion. There was net synthesis of 16:0, 18:0, and 18:1 fatty acids in the rumen. When steers were fed tallow, synthesis of 16:0 and 18:0 fatty acids in the rumen was lower (P less than .10) than when steers were fed SS. Feeding fat tended to decrease (P = .11) bacterial N flowing at the duodenum but did not affect nonbacterial N or total N. Fat addition seems to affect ruminal kinetics, and the effects may vary with fat source, particularly relative to fatty acid synthesis and digestion.

Six Holstein steers (313 +/- 10 kg BW) surgically fitted with hepatic portal, mesenteric venous, mesenteric arterial, and hepatic venous catheters were used in a replicated crossover design experiment to evaluate the feeding of Acremonium coenophialum-infected fescue hay on portal-drained visceral and hepatic nutrient metabolism. Only four steers had functional hepatic catheters. Infected (INF) and endophyte-free (EF) fescue hays were harvested on the same day in May, at the soft dough stage of maturity, from a similar location in southeast Kansas. The hay was chopped through a 2.5-cm screen and fed in 12 portions daily. Intake was limited to 5.2 kg of DM/d to equalize consumption. Each experimental period lasted 21 d. Dietary CP concentration was greater for INF than for EF (9.9 vs 8.6%); however, apparent digestibilities of DM (52.6%) and N (37%) were not different. Ruminal total VFA concentrations and molar proportions were not different with the exception of butyrate, which was increased (P less than .10) for steers when they were fed INF. Feeding of INF increased (P less than .05) arterial beta-hydroxybutyrate concentration and decreased (P less than .10) arterial butyrate concentration. Steers fed EF showed a greater (P less than .05) portal-arterial concentration difference for acetate and an increased (P less than .05) net portal flux of acetate (500 vs 620 mmol/h). No differences in net flux were noted for any of the other VFA, glucose, lactate, urea N, insulin, glucagon, or prolactin.(ABSTRACT TRUNCATED AT 250 WORDS)

Eight Holstein steers (four at 300 kg, four at 406 kg) fitted with an elevated carotid artery, hepatic portal and mesenteric venous catheters, and abomasal and ileal cannulas were used in several 4 x 4 Latin square experiments to evaluate small intestinal starch digestion. They were fed alfalfa hay at 1.5% of BW and abomasally infused with water or glucose, corn starch or corn dextrin (one carbohydrate per Latin square) at 20, 40 or 60 g/h, with subsequent determination of small intestinal disappearance and net portal glucose absorption. Increasing the amount of all three carbohydrates infused abomasally increased the amount of carbohydrate disappearing in the small intestine. Increased infusion of glucose caused a continual increase (linear, P less than .01) in net glucose absorption, whereas net glucose absorption for starch and dextrin was maximal at the 20 g/h infusion (quadratic, P less than .05). With the 60 g/h infusion, 94% of the glucose but only 38% of starch and 29% of small intestinal dextrin disappearance could be accounted for as net glucose absorption, leaving a large portion of starch and dextrin disappearance unaccounted for. Of the infused starch and dextrin passing the ileum, 5.8 and 7.3%, respectively, was unpolymerized glucose, indicating that, at least in the distal small intestine, complete starch hydrolysis exceeded the capacity for glucose disappearance. It is concluded that only about 35% of the raw corn starch disappearing in the steer's small intestine resulted in net portal glucose absorption.