Influence of substrate and/or neurohormonal mimic on in vitro pancreatic enzyme release from calves postruminally infused with partially hydrolyzed starch and/or casein

Our objectives were to determine the effects of neuroendocrine challenge and substrates on in vitro alpha-amylase and trypsin release in pancreatic tissue collected from Holstein calves (n = 24; 88 +/- 3 kg) abomasally infused for 10 d with tap water (control), partially hydrolyzed starch (SH; 4 g/[kg of BW x d]) and/ or casein (0.6 g/[kg of BW x d]). The caudal portion of the pancreas was removed, rinsed with ice-cold saline, cut into approximately 2 x 2-mm segments, and incubated in oxygenated Krebs Ringer bicarbonate buffer containing no substrate (control), glucose, amino acids, or VFA at 39 degrees C. After 60 min of incubation, neurohormonal mimics (none; control), carbachol (acetylcholine analog; 10 microM final), or caerulein (cholecystokinin mimic; 100 nM final) were added to the flasks and tissue was incubated for 60 min. Pancreatic tissue concentrations and in vitro release of alpha-amylase and trypsin decreased (P < 0.001) in calves abomasally infused with SH. Carbachol increased (P < 0.10) alpha-amylase and trypsin release in tissue collected from all calves. An effect of caerulein to increase alpha-amylase release (P < 0.10) was only observed with prior exposure to abomasal casein infusion in vivo or with simultaneous incubation with amino acids in vitro. Caerulein increased (P < 0.10) trypsin release in tissue collected from all calves except for those receiving SH + casein. Glucose decreased (P < 0.10) alpha-amylase release from pancreatic tissue collected from calves receiving abomasal control and casein treatments. Amino acids decreased (P < 0.10) alpha-amylase and trypsin release from pancreatic tissue collected from calves receiving the abomasal control treatment. Glucose, amino acids, and VFA decreased (P < 0.10) trypsin release from tissue collected from calves receiving abomasal SH. These data indicate that carbachol can stimulate pancreatic enzyme release in vitro. Caerulein, however, is only effective in stimulating in vitro pancreatic enzyme release in tissue from calves with an increased postruminal protein supply or in tissue incubated with amino acids. The results indicate that postruminal and local nutrients might be important in altering the responsiveness to a neuroendocrine challenge and could be an important regulatory event involved with dietary adaptation in ruminants.     

Performance of finishing pigs in hoop structures and confinement during winter and summer

Performance of finishing pigs in hoop structures or confinement during winter and summer was evaluated in Iowa. Hoops are large, tent-like shelters with cornstalks or straw for bedding. During summer and winter seasons for 3 yr (1998 to 2001), six trials were conducted using three hoop barns (designed for 150 pigs per pen, one pen per hoop) or a mechanically ventilated confinement barn with slatted floors (designed for 22 pigs per pen, six pens in the barn). A total of 3,518 pigs started the trials. Summer trials were June through October, and winter trials were December through April. Target stocking density was 1.11 m2/pig in hoops and 0.74 m2/pig in confinement. Identical corn-based diets were fed ad libitum from 16 to 118 kg for 127 d. Pigs were scanned before harvest for backfat and loin muscle area. When seasons were merged (season x housing interaction, P > or = 0.05), hoop-fed pigs had more backfat (21.8 +/- 0.3 vs 20.8 +/- 0.2 mm; P < 0.001), smaller loin muscle area (41.3 +/- 0.3 vs 43.0 +/- 0.2 cm2; P < 0.001), less lean percentage (51.1 +/- 0.2 vs 52.1 +/- 0.1%; P < 0.001), and less yield (74.9 vs 75.8 +/- 0.1%; P < 0.001) than confinement-fed pigs. When season x housing type interactions were observed (P < 0.004), summer hoop-fed pigs had greater ADG (834 +/- 5 vs 802 +/- 3 g/d; P < 0.001), required fewer days to 113 kg (174.9 +/- 0.9 vs 178.5 +/- 0.6 d; P < 0.01), had similar ADFI (2.40 +/- 0.03 vs 2.35 +/- 0.02 kg/d, as-fed basis) and gain:feed (G:F; 348 +/- 4 vs 342 +/- 3 g/kg) compared with confinement-fed pigs. Lean gain/day and efficiency of lean gain did not differ between housing systems. During winter, hoop-fed pigs had similar ADG (794 +/- 5 vs 801 +/- 3 g/ d), required more days to 113 kg (176.7 +/- 0.9 vs 172.9 +/- 0.6 d; P < 0.01), had greater ADFI (2.54 +/- 0.03 vs 2.35 +/- 0.02; P < 0.001), less G:F (313 +/- 4 vs 341 +/- 3; P < 0.001), less lean gain/day (312 +/- 2 vs 322 +/- 1 g/d; P < 0.01), and less efficiency of lean gain (130 +/- 2 vs 144 +/- 1 g lean gain/kg feed; P < 0.01) than confinement-fed pigs. Percentage of mortalities and culls did not differ between housing systems. During summer, there was a trend for fewer light pigs at marketing (< 100 kg) from hoops (0.8 vs 1.7%; P = 0.10). During winter, there were more light pigs at marketing from hoops (3.9 vs 1.3%; P = 0.01) than from confinement. Bedding use in hoops was 92 and 122 kg/pig for summer and winter, respectively. Performance of finishing pigs in bedded hoop structures depends in part on thermal environment.     

Modeling multiscale effects of light limitations and edge-induced mortality on carbon stores in forest landscapes

Analyses of carbon (C) dynamics at broad scales usually do not consider spatial interactions. The assumption is that C dynamics can be modeled within homogenous (i.e., even-aged) patches and then summed to predict broad-scale dynamics (an additive approach). The goal of this paper is to elucidate the scales over which this additive approach is sufficient to explain observed C dynamics at broad scales. We define emergent behaviors (vs. emergent properties) as those behaviors that cannot be predicted solely from the additive properties of units at a finer scale. We used a forest process model to check for possible emergent behaviors due to pattern-process interactions at multiple levels, from the patch to the landscape. Specifically, using artificial forest landscapes with various spatial structures, we estimated the relative effects of edge-induced, tree mortality (mainly due to wind) and light limitations on C dynamics. Emergent behaviors were observed at all levels examined, indicating that emergent behaviors did not cease as one proceeded from the patch to the landscape level, as we had expected. However, the magnitude of the emergent behaviors depended on the level of spatial interaction considered as well as the type and intensity of the processes included. In all simulations, interactions of light and wind processes resulted in significant emergent behaviors only when parameters controlling wind mortality were set to the highest levels observed in the literature. In one simulation, the magnitude of emergent behaviors differed among the landscapes, indicating that interactions among patches may not be accounted for by an additive correction for edge effects unless spatial interactions are addressed. The implication is that some C dynamics in fragmented landscapes may not be captured at broad-scales using an additive approach, whereas in other cases spatial interactions are small enough to be ignored.This revised version was published online in May 2005 with corrections to the Cover Date.     

Effect of a leukocyte-depleting filter in an extracorporeal circuit used for low-flow ischemia and reperfusion of equine jejunum

OBJECTIVE: To determine effect of leukocyte depletion on hematologic, morphologic, and metabolic variables of equine jejunum after induction of arterial low-flow ischemia and reperfusion by use of an extracorporeal circuit. ANIMALS: 14 healthy adult horses. PROCEDURE: A segment of jejunum was surgically removed and maintained in an isolated circuit for 3 hours (control group), arterial flow was reduced to 20% of baseline for 40 minutes followed by 1 hour of reperfusion (low-flow group), or leukocyte depletion was filter-induced, and low-flow ischemia and reperfusion were conducted as in the low-flow control group (filter-treated group). Various metabolic, hemodynamic, and histomorphologic variables were evaluated, including effects of electrical field stimulation and L-N-nitro-arginine-methyl-ester (L-NAME) on contractile activity. RESULTS: The extracorporeal circuit appeared to maintain the jejunum within physiologic limits for an extended period. Low-flow ischemia with reperfusion induced significant differences in various measurements, compared with control specimens. Significant differences were not detected between the low-flow and filter-treated groups. Myeloperoxidase activity was greater in the low-flow group than the control group, whereas a difference was not detected between control and filter-treated groups. CONCLUSIONS AND CLINICAL RELEVANCE: The extracorporeal circuit maintained intestine for 3 hours in a physiologic state and may be used for simulation of tissue injury. Leukocyte depletion generally did not attenuate the effects of low-flow ischemia and reperfusion on equine small intestine.     

Influence of alpha-linked glucose on sodium-glucose cotransport activity along the small intestine in cattle

Thirteen steers (378+/-23 kg) were used in a split-plot experimental design to evaluate the effect of small intestinal carbohydrate on sodium-glucose cotransport in brush border membrane vesicles prepared from five equidistant sites along the small intestine. The steers consumed 7.2+/-0.4 kg/d ground fescue hay and soybean meal-based supplement and were infused ruminally or postruminally with a partial alpha-amylase starch hydrolysate (914.5+/-8.3 g/d) for 7 d. On d 7, five equidistant 1-m small intestinal sections were harvested and frozen in liquid N for later preparation of brush-border membrane vesicles. Maltase activity of the homogenate and vesicle preparations changed (P < 0.001; lowest in the duodenum, highest in the jejunum) and alkaline phosphatase decreased (P < 0.001) along the small intestine. With respect to the original homogenates, the vesicle preparations were enriched 9.80+/-0.83- and 7.64+/-0.67-fold for alkaline phosphatase and maltase, respectively; enrichments were not different between treatments (P = 0.76 and 0.39, respectively). However, alkaline phosphatase and maltase enrichment changed (P < 0.001) along the small intestine. Recoveries of alkaline phosphatase and maltase activities (25.0+/-0.2% and 19.5+/-0.2%, respectively) in the vesicle preparation were not affected (P = 0.29 and 0.21, respectively) by treatment but changed (P < 0.001) along the intestine. Recovery of protein in the vesicle preparation was 2.60+/-0.01% and was not affected by treatment or intestinal site. Sodium-glucose cotransport activity (220+/-44 pmol x mg(-1) x s(-1)) was not affected (P = 0.34) by treatment but did change (P < 0.001; lowest in the ileum, highest in the proximal and mid-jejunum) along the small intestine. Apparent Km of the sodium-glucose cotransporter for glucose was 62.8+/-5.8 microM. The specific activity of maltase was highest in the jejunum, and sodium-glucose cotransport was highest in the first two jejunal sites. However, duodenal maltase activity was lowest and ileal sodium-glucose cotransport activity was lowest. Sodium-glucose cotransport activity may limit small intestinal starch assimilation in the distal small intestine. It does not seem that glucose arising from carbohydrate hydrolysis regulates activity of sodium-dependent glucose transport in cattle.     

Effects of dietary monensin and sodium propionate on net nutrient flux in steers fed a high-concentrate diet

Four Holstein steers (mean body weight, 211 +/- 20 kg) were utilized in a Latin-square design with a 2 X 2 factorial arrangement of treatments to investigate the effects of monensin (0 or 220 mg/d) and sodium propionate (0 or 450 g/d) on net nutrient flux. Steers were surgically prepared with hepatic portal and mesenteric venous catheters and an elevated carotid artery, after which they were adjusted to their basal diet (85% concentrate) and initial treatment over 19 d. Samples of arterial and portal venous blood were taken hourly over 3 h for the final 3 d of each 2-wk period. Portal blood flow was determined by primed continuous infusion of para-aminohippurate. No changes were seen in dry matter intake, portal blood flow, or net portal flux of any of the volatile fatty acids with the exception of butyrate flux, which decreased with monensin addition. Addition of monensin decreased net portal flux of ammonia, decreased recycling of urea, and tended to increase the net portal flux of glucose. Addition of sodium propionate increased the net portal flux of glucose and decreased the net portal flux of alpha-amino-N. These results are interpreted to suggest that changes in the products of ruminal fermentation may not be exactly translated into the products appearing in the portal circulation, and more information is needed to describe these relationships.     

Influence of abomasal infusion of glucose or partially hydrolyzed starch on pancreatic exocrine secretion in beef steers

Five crossbred steers (348 +/- 12 kg) fitted with a pancreatic pouch draining the main pancreatic duct and duodenal re-entrant and abomasal infusion cannulas were used in a 5 x 5 Latin square design to determine the influence of postruminal carbohydrate source and level on pancreatic exocrine secretion in beef steers. Abomasal infusion treatments (250 mL infused/h) were water (control), 20 g/h glucose, 40 g/h glucose, 20 g/h starch hydrolysate (SH), and 40 g/h SH. Infusion periods were 8 d with 3 to 4 d of rest between periods. Pancreatic juice was collected for 6 h on d 8 of each collection period. Every 30 min a 10% subsample was composited and frozen and the remainder was infused into the duodenum via the reentrant cannula. Abomasal infusion of glucose or SH increased (P < 0.10) total secretion of pancreatic juice and decreased (P < 0.10) secretion of alpha-amylase activity. Abomasal carbohydrate infusion did not influence total secretion of protein, trypsin activity, or chymotrypsin activity. This experiment indicates that increasing postruminal glucose or SH decreases pancreatic alpha-amylase secretion.     

Effects of Developmental Stage, Embryonic Interferon-τ Secretion and Recipient Synchrony on Pregnancy Rate after Transfer of in vitro Produced Bovine Blastocysts

Three separate trials of bovine embryo transfers were performed consisting of 32, 41 and 33 transfers, respectively, to examine the effects of (a) the developmental stage of in vitro‐derived blastocysts, (b) the amount of interferon‐τ (IFN‐τ) they secreted during culture and (c) the cyclic stage of the recipient at the time of transfer on the probability of establishment of pregnancy. One blastocyst was transferred into the ipsilateral uterine horn to the CL. At the time of transfer, blastocysts were classified into one of three developmental stages (early blastocyst, blastocyst and expanded blastocyst) and the cyclic stage of each cow was assessed (?12 h, on time, +12 h, +24 h, >24 h). Prior to the second and third trials, blastocysts were individually cultured for 24 h in 50 μl medium droplets and the IFN‐τ concentration in the droplet was determined. Logistic regression analyses revealed that expanded blastocysts had a significantly higher likelihood of establishing pregnancy (p = 0.009), and that there was a significant interaction with the cyclic stage of the recipient in this group with lower rates of pregnancy resulting from decreasing synchrony with the recipient (p = 0.033). IFN‐τ secretion during culture was significantly higher in expanded blastocysts than in the other two groups (p < 0.05). A significant effect of the pre‐transfer level of IFN‐τ secretion was found only in the ‘Blastocyst’ group where transfer of embryos with lower IFN‐τ production prior to transfer resulted in higher pregnancy rates (p = 0.047). These results demonstrate that IFN‐τ secretion may be a useful tool to predict pregnancy outcome, but only within certain developmental stages.