The Effects of Dietary Manganese and Selenium on Growth and the Fecal Microbiota of Nursery Piglets

The objective of this study was to determine the impact of varying dietary manganese and selenium concentrations, antioxidant cofactors, on the growth performance and fecal microbial populations of nursery pigs. The piglets (N = 120) were blocked by weight (5.22 ± 0.7 kg) and sex. The pens (n = 5/treatment) within a block were randomly assigned to diets in a 2 × 3 factorial design to examine the effects of Se (0.1 and 0.3 mg/kg added Se) and Mn (0, 12, and 24 mg/kg added Mn) and were fed in three phases (P1 = d 1-7, P2 = d 8-21, P3 = d 22-35). The pigs and orts were weighed weekly. Fecal samples were collected d 0 and 35 for 16S rRNA bacterial gene sequencing and VFA analysis. The data were analyzed as factorial via GLM in SAS. There was a linear response (p < 0.05) in overall ADG across dietary Mn. Supplementing 24 mg/kg Mn tended to decrease (p < 0.10) the relative abundance of many bacteria possessing pathogenic traits relative to Mn controls. Meanwhile, increasing Mn concentration tended to foster the growth of bacteria correlated with gut health and improved growth (p < 0.10). The data from this study provide preliminary evidence on the positive effects of manganese on growth and gut health of nursery pigs.

PSVII-9 The Impact of Increasing Dietary Manganese on the Reproductive Performance of Sows

The objective of this study was to determine the effect of dietary manganese (ProPath Mn, Zinpro Corporation) on the reproductive performance of sows. Sows (N = 39; 231 ± 8 kg) were randomly assigned to 1 of three dietary levels of Mn (CON: 0 ppm Mn; PRO20: 20 ppm Mn; PRO40: 40 ppm Mn). Experimental treatments were initiated at breeding and continued through 2 parities. Sows were blocked by parity within each farrowing group and dietary treatments were represented within each block. Data were analyzed as a randomized complete block design using the MIXED procedure of SAS with diet as a fixed effect and block as a random effect. Dietary treatment did not affect sow body weights (P &gt; 0.10). Lactation feed intake was increased in PRO20 sows compared with CON and PRO40 sows (P &lt; 0.05). PRO20 and PRO40 sows farrowed heavier piglets (CON 1.23 kg; PRO20 1.57 kg; PRO40 1.40 kg; P = 0.001) with improved average daily gain to weaning (CON 213 g/day; PRO20 237 g/day; 220 g/day; P &lt; 0.05), compared with CON sows. Milk fat content (average from d 7 and 14 of lactation) was reduced in PRO20 (5.5%) and PRO40 sows (6.1%; P &lt; 0.05) compared with CON sows (7.8%), possibly due to increased milk demand from the piglets. There were no significant differences in milk mineral concentrations during lactation or piglet tissue Mn-superoxide dismutase (MnSOD) activity at weaning (P &gt; 0.10). On day 3 of lactation, prolactin concentrations were similar across treatments (P &gt; 0.10), whereas progesterone concentrations tended to differ in response to Mn level (CON 23.70 ng/mL; PRO20 26.15 ng/mL; PRO40 22.10 ng/ml; P = 0.09). Supplementary dietary Mn throughout 2 gestation and lactation cycles led to increased birth weights and pre-weaning growth of piglets.

Interaction of dietary carbohydrate and fat on glucose metabolism in growing pigs

Increased consumption of fructose has been suggested to be a contributing cause of the increased rates of obesity in humans. Rodent studies have shown an increase in de novo lipogenesis and decreased insulin sensitivity in response to feeding high levels of fructose, but it is unclear if these effects occur in the same progression in humans. We aimed to develop a swine model for studying changes in glucose metabolism and insulin resistance resulting from dietary carbohydrate alone or in combination with high dietary fat. Two experiments were conducted to determine if the source of dietary carbohydrate, with or without added fat, had an effect on body weight gain, glucose metabolism, or insulin response in growing pigs. In the first experiment, pigs (24 barrows, initial body weight 28 kg) were fed one of 4 diets in which the source of carbohydrate was varied: 1) 20% starch; 2) 10% glucose + 10% starch; 3) 10% fructose + 10% starch; and 4) 20% fructose for 9 weeks. There were no differences in growth rate or glucose clearance observed. Experiment 2 was conducted as a 3 × 2 factorial with the main effects of carbohydrate source (20% starch, glucose, or fructose) and added fat level (0 vs 10%). Pigs (24 barrows, initial body weight 71 kg) were fed one of 6 experimental diets for 9 weeks. Compared to the other dietary treatments, pigs fed fructose with high fat had an elevated glucose area under the curve during the GTT (Carbohydrate x Fat interaction, P < 0.01). This same group had a lower insulin response (Carbohydrate x Fat, P < 0.05). This work demonstrates that pigs can be a viable model to assess the long-term effects of dietary carbohydrates on metabolism and body composition. Studies of longer duration are needed to determine if these changes are indicative of insulin resistance.

PSIV-9 A Multistate Evaluation of an Additional Iron Injection Administered to Piglets Before Weaning

A cooperative study utilizing 514 weanling pigs from 7 experiment stations was conducted to determine the effects of an additional iron injection administered to piglets before weaning on growth performance and hematological measures. All pigs received an initial iron injection at the time of processing postfarrowing. At each station, pigs were assigned to either the control or an added-injection treatment by pairing two same-sex pigs with a BW difference ≤ 0.453 kg within a litter. One pig within each pair received the additional iron injection (same dose received at processing) 3 to 5 days preweaning. Once weaned, both the control and added-injection group received common station-specific nursery diets. Body weight was recorded weekly by all stations. Blood samples were also collected at second injection, weaning, 14 and 28 days postweaning by 3 of the 7 stations. All data were subjected to ANOVA with the model containing the terms treatment, station, and treatment by station interaction. Average daily gain (Table 1) was greater for the added-injection group during d 0 to 14 (212.5 vs. 202.6 g, P = 0.03) which resulted in an increase in d 14 BW (P = 0.05). Although there was no treatment effect for overall ADG (d -4 to d 28), the tendency for a treatment by station interaction (P = 0.09) illustrated both responsive and nonresponsive stations, indicating that iron status was not the most limiting factor for growth at all stations. Hemoglobin concentration was greater (P &lt; 0.0001) for the added-injection group at weaning and d 14 postweaning. In conclusion, an additional iron injection administered before weaning may lead to early success in the nursery resulting in a heavier BW in subsequent periods; however, the beneficial effects of an additional iron injection are likely dependent on herd status and characteristics.

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58 The Effect of Altering Dietary Manganese and Selenium Levels on the Growth Performance and Blood Manganese-superoxide Dismutase Activity in Nursery Pigs

The objective of this study was to determine the effect of altering dietary levels of manganese and selenium on growth performance and MnSOD specific activity. Weaned piglets were blocked by weight (n = 216; 5.21 ± 1.17 kg; 21 ± 3 d) and sex (2 barrows and 2 gilts/pen). Pens within a block were randomly assigned to dietary treatments in a factorial design with main effects of Se (0.1 and 0.3 ppm) and Mn (0, 12, and 24 ppm). Diets (n = 9 pens/treatment) were fed in three phases (P1 = d 1–7, P2 = d 7–21, P3 = d 21–35). Pigs and orts were weighed weekly and pigs were bled on d 0, 7, 21, and 35 for analysis of specific activity of red blood cell MnSOD. Data were analyzed as 2x3 factorial design via SAS PROC GLM. There were no Se effects or Mn x Se interactions observed. There was a linear increase (P &lt; 0.05) in overall ADG (397, 424, and 438 g day-1pig-1 for 0, 12, 24 ppm Mn, respectively). There was a linear trend (P &lt; 0.1) in overall ADFI (557, 560, 592 g day-1pig-1 for 0, 12, 24 ppm Mn, respectively). Feed efficiency (d 0–35) across increasing Mn levels were 0.71, 0.76, 0.74 (P &gt; 0.1). MnSOD activity in RBC increased from d 0–7, peaked on d 7 and decreased to d 35. On d 7, diets with 12 and 0 ppm Mn had significantly increased (P &lt; 0.05) MnSOD activity (0.91 and 0.87 IU mg-1 protein, respectively) compared to diets with 24 ppm Mn (0.67 IU mg-1 protein). The dietary treatment that best maintained MnSOD activity was 0.3 ppm Se and 12 ppm Mn supplemented, while ADG was maximized in the diet with 0.3 ppm Se and 24 ppm Mn supplementation.

Early barriers to neonatal porcine islet engraftment in a dual transplant model

Porcine islet xenografts have the potential to provide an inexhaustible source of islets for β cell replacement. Proof-of-concept has been established in nonhuman primates. However, significant barriers to xenoislet transplantation remain, including the poorly understood instant blood-mediated inflammatory reaction and a thorough understanding of early xeno-specific immune responses. A paucity of data exist comparing xeno-specific immune responses with alloislet (AI) responses in primates. We recently developed a dual islet transplant model, which enables direct histologic comparison of early engraftment immunobiology. In this study, we investigate early immune responses to neonatal porcine islet (NPI) xenografts compared with rhesus islet allografts at 1 hour, 24 hours, and 7 days. Within the first 24 hours after intraportal infusion, we identified greater apoptosis (caspase 3 activity and TUNEL [terminal deoxynucleotidyl transferase dUTP nick end labeling])-positive cells) of NPIs compared with AIs. Macrophage infiltration was significantly greater at 24 hours compared with 1 hour in both NPI (wild-type) and AIs. At 7 days, IgM and macrophages were highly specific for NPIs (α1,3-galactosyltransferase knockout) compared with AIs. These findings demonstrate an augmented macrophage and antibody response toward xenografts compared with allografts. These data may inform future immune or genetic manipulations required to improve xenoislet engraftment.

Blood collection from the orbital sinus of swine

Swine (Sus scrofa domesticus) are increasingly used as animal models in biomedical research. Often blood samples from these animals are needed for research protocols, but phlebotomy can be difficult, especially with young swine. This column describes a relatively simple technique for blood collection that can be used specifically with young swine.

Dual islet transplantation modeling of the instant blood-mediated inflammatory reaction

Islet xenotransplantation is a potential treatment for diabetes without the limitations of tissue availability. Although successful experimentally, early islet loss remains substantial and attributed to an instant blood-mediated inflammatory reaction (IBMIR). This syndrome of islet destruction has been incompletely defined and characterization in pig-to-primate models has been hampered by logistical and statistical limitations of large animal studies. To further investigate IBMIR, we developed a novel in vivo dual islet transplant model to precisely characterize IBMIR as proof-of-concept that this model can serve to properly control experiments comparing modified xenoislet preparations. WT and α1,3-galactosyltransferase knockout (GTKO) neonatal porcine islets were studied in nonimmunosuppressed rhesus macaques. Inert polyethylene microspheres served as a control for the effects of portal embolization. Digital analysis of immunohistochemistry targeting IBMIR mediators was performed at 1 and 24 h after intraportal islet infusion. Early findings observed in transplanted islets include complement and antibody deposition, and infiltration by neutrophils, macrophages and platelets. Insulin, complement, antibody, neutrophils, macrophages and platelets were similar between GTKO and WT islets, with increasing macrophage infiltration at 24 h in both phenotypes. This model provides an objective and internally controlled study of distinct islet preparations and documents the temporal histology of IBMIR.

Supplementation of organic and inorganic selenium to diets using grains grown in various regions of the United States with differing natural Se concentrations and fed to grower-finisher swine

Grains grown in various regions of the United States vary in their innate or natural Se contents. A regional study evaluated the effects of adding inorganic Se (sodium selenite) or organic Se (Se yeast) to diets with differing innate Se contents. A 2 × 2 + 1 factorial experiment evaluating 2 Se sources (organic or inorganic) at 2 Se levels (0.15 or 0.30 mg/kg) in 18 total replicates (n = 360 total pigs). A basal diet was fed without supplemental Se and served as the negative (basal) control. The study was conducted as a randomized complete block design in 9 states (Georgia, Illinois, Kentucky, Nebraska, North Carolina, Ohio, South Dakota, Texas, and Wisconsin) with each station conducting 2 replicates. Pigs were fed from 25 to approximately 115 kg BW. Similar dietary formulations were used at each station, incorporating a common source of trace mineral and Se premixes. Three pigs per treatment in 16 replicates (n = 240) were bled at 55, 85, and 115 kg BW and serum Se and glutathione peroxidase (GSH-Px) activities were determined. Three pigs (n = 260) from each treatment pen were killed at 115 kg BW and issues (liver, loin, and hair) were analyzed for Se. The corn Se content from the various states ranged from 0.026 to 0.283 mg Se/kg while the soybean meal Se content ranged from 0.086 to 0.798 mg Se/kg. Tissue and serum Se concentrations were greater (P < 0.01) when supplemental organic Se was fed, whereas serum GSH-Px was greater (P < 0.01) as Se level increased. There were linear increases (P < 0.01) in loin and quadratic increases (P < 0.01) in liver and hair Se concentrations as dietary Se level increased within each state. There was a source × level interaction (P < 0.01) for each tissue resulting in a greater increase when organic Se was fed. Serum Se and GSH-Px activity increased (P < 0.01) when both Se sources were fed and plateaued at each state at 0.15 mg Se/kg. There was a high and significant correlation between each tissue Se, serum Se, and GSH-Px activity to dietary Se level indicating that those states having greater grain natural Se contents also had greater tissue Se concentrations. These results indicate that a large difference in corn and soybean meal Se concentrations exists between states, that the addition of organic or inorganic Se to these grains increased tissue and serum Se in each state, and that organic Se was incorporated at greater concentrations in the loin, liver, and hair tissues of grower-finisher pigs than inorganic Se.

Development and characterization of a Yucatan miniature biomedical pig permanent middle cerebral artery occlusion stroke model

BACKGROUND

Efforts to develop stroke treatments have met with limited success despite an intense need to produce novel treatments. The failed translation of many of these therapies in clinical trials has lead to a close examination of the therapeutic development process. One of the major factors believed to be limiting effective screening of these treatments is the absence of an animal model more predictive of human responses to treatments. The pig may potentially fill this gap with a gyrencephalic brain that is larger in size with a more similar gray-white matter composition to humans than traditional stroke animal models. In this study we develop and characterize a novel pig middle cerebral artery occlusion (MCAO) ischemic stroke model.

METHODS

Eleven male pigs underwent MCAO surgery with the first 4 landrace pigs utilized to optimize stroke procedure and 7 additional Yucatan stroked pigs studied over a 90 day period. MRI analysis was done at 24 hrs and 90 days and included T2w, T2w FLAIR, T1w FLAIR and DWI sequences and associated ADC maps. Pigs were sacrificed at 90 days and underwent gross and microscopic histological evaluation. Significance in quantitative changes was determined by two-way analysis of variance and post-hoc Tukey's Pair-Wise comparisons.

RESULTS

MRI analysis of animals that underwent MCAO surgery at 24 hrs had hyperintense regions in T2w and DWI images with corresponding ADC maps having hypointense regions indicating cytotoxic edema consistent with an ischemic stroke. At 90 days, region of interest analysis of T1 FLAIR and ADC maps had an average lesion size of 59.17 cc, a loss of 8% brain matter. Histological examination of pig brains showed atrophy and loss of tissue, consistent with MRI, as well as glial scar formation and macrophage infiltration.

CONCLUSIONS

The MCAO procedure led to significant and consistent strokes with high survivability. These results suggest that the pig model is potentially a robust system for the study of stroke pathophysiology and potential diagnostics and therapeutics.

Gait analysis in a pre- and post-ischemic stroke biomedical pig model

Severity of neural injury including stroke in human patients, as well as recovery from injury, can be assessed through changes in gait patterns of affected individuals. Similar quantification of motor function deficits has been measured in rodent animal models of such injuries. However, due to differences in fundamental structure of human and rodent brains, there is a need to develop a large animal model to facilitate treatment development for neurological conditions. Porcine brain structure is similar to that of humans, and therefore the pig may make a more clinically relevant animal model. The current study was undertaken to determine key gait characteristics in normal biomedical miniature pigs and dynamic changes that occur post-neural injury in a porcine middle cerebral artery (MCA) occlusion ischemic stroke model. Yucatan miniature pigs were trained to walk through a semi-circular track and were recorded with high speed cameras to detect changes in key gait parameters. Analysis of normal pigs showed overall symmetry in hindlimb swing and stance times, forelimb stance time, along with step length, step velocity, and maximum hoof height on both fore and hindlimbs. A subset of pigs were again recorded at 7, 5 and 3 days prior to MCA occlusion and then at 1, 3, 5, 7, 14 and 30 days following surgery. MRI analysis showed that MCA occlusion resulted in significant infarction. Gait analysis indicated that stroke resulted in notable asymmetries in both temporal and spatial variables. Pigs exhibited lower maximum front hoof height on the paretic side, as well as shorter swing time and longer stance time on the paretic hindlimb. These results support that gait analysis of stroke injury is a highly sensitive detection method for changes in gait parameters in pig.

A regional evaluation of the effect of fiber type in gestation diets on sow reproductive performance

A cooperative regional research study using 194 sows, from which data were collected from 381 litters, was conducted at 3 research stations to determine the effects of added psyllium (a concentrated fiber source) or soybean hulls to gestation diets on reproductive performance of sows and preweaning performance of their pigs. Primiparous and multiparous sows were allotted to the 3 treatments of control (corn and soybean meal-based), 0.30% psyllium, or 20% soybean hulls. Sows fed the control and 0.30% psyllium diets were provided 1.82 kg/d, and sows fed the 20% soybean hulls diet were provided 2.0 kg/d to equalize ME, Lys, Ca, P, and vitamin and trace mineral intake. Treatments 1 to 3 had 130, 130, and 121 litters per treatment from 64, 64, and 63 sows, respectively. Gestating sows fed psyllium had a greater (P < 0.01 to 0.10) d 110 gestation, farrowing, weaning, and 17 d postpartum BW and gestation ADG compared with sows fed soybean hulls. Sows fed psyllium also had a greater (P < 0.10 and 0.08) d 110 gestation BW and gestation ADG than the control sows. Sows fed soybean hulls had a reduced (P < 0.06) farrowing BW compared with the control sows. Sows fed psyllium weaned lighter (P < 0.09) pigs than sows fed the control diet. Litter size was not affected (P > 0.10) by diet. Sows fed psyllium had a reduced (P < 0.03) feed intake compared with sows fed soybean hulls for d 5 to 7 postpartum, and sows fed the control diet were intermediate. Fecal scores (1 to 5 with 1 = dry and 5 = watery) were greater (P < 0.001) and DM content was less (P < 0.001 to 0.01) in the feces of sows fed soybean hulls compared with sows fed psyllium or the control diet on d 112 of gestation and d 4 postpartum. Fecal scores were greater (P < 0.10) and fecal DM content was less (P < 0.02) in sows fed psyllium compared with sows fed the control diet only on d 4 postpartum. In summary, sows fed soybean hulls during gestation had reduced BW compared with sows fed the control diets. In contrast, sows fed psyllium had an increased BW.

A regional evaluation of injections of high levels of vitamin A on reproductive performance of sows

A regional study involving 443 litters from 182 sows was conducted at 5 cooperating experiment stations to determine the effects of an i.m. injection of vitamin A at weaning and breeding on subsequent litter size of sows. Sows were assigned to 1 of 3 treatments given at weaning and again at breeding: 1) a placebo i.m. injection (2 mL of corn oil), 2) i.m. injection with 250,000 IU of vitamin A (1 mL of vitamin A palmitate in oil), and 3) i.m. injection with 500,000 IU of vitamin A (2 mL of vitamin A palmitate in oil). Corn-soybean meal diets in gestation were formulated to contain 13% CP and 0.60% total Lys. Lactation diets were formulated to contain 17% CP and 0.90% Lys. A common vitamin-mineral premix that supplied 11,000 IU of vitamin A/kg of diet (as-fed) was used by all stations. As expected, station effects were noted for many response measures. Analysis of the data also revealed both treatment x station and treatment x parity interactions for litter size responses. The treatment x parity interactions were stronger than the treatment x station effects, and when the litter size response was separated into early parity sows (parity 1 and 2) and late-parity sows (parity 3 to 6), the treatment x station interactions were no longer present in either subgroup. For sows of parity 1 and 2, litter sizes were increased linearly (P Collapse

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MESH Headings

• Age Factors
• Animal Feed
• Animals
• Body Weight
• Breeding/methods
• Dietary Proteins/administration & dosage
• Dose-Response Relationship, Drug
• Female
• Injections, Intramuscular/veterinary
• Lactation/metabolism
• Lactation/physiology
• Litter Size
• Lysine/administration & dosage
• Parity
• Pregnancy
• Random Allocation
• Reproduction/drug effects
• Glycine max
• Swine/growth & development
• Swine/physiology
• Vitamin A/pharmacology
• Vitamins/pharmacology
• Weaning
• Zea mays

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Affiliation(s)

M D Lindemann S-145 Regional Research Committee on Nutrition and Management of Swine for Increased Reproduction Efficiency, Department of Animal and Food Sciences, University of Kentucky, Lexington, Kentucky 40546, USA.
J H Brendemuhl
L I Chiba
C S Darroch
C R Dove
M J Estienne
A F Harper

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A regional evaluation of chromium tripicolinate supplementation of diets fed to reproducing sows1,2

A cooperative research study involving 353 litters was conducted at three stations to determine the effects of graded levels of supplemental Cr from chromium tripicolinate (CrPic) on reproductive performance of sows and preweaning performance of their pigs. Primiparous and multiparous sows were fed fortified corn-soybean meal diets with supplemental levels of 0, 200, 600, or 1,000 ppb Cr (as-fed basis). Each station used at least three of the supplemental Cr levels, with two of those levels being 0 and 200 ppb. Station effects were observed for sow gestation weight gain, lactation weight change, lactation feed intake, litter size at birth and weaning, and pig weight at birth and weaning (P = 0.001 to 0.087). Supplemental Cr increased the number of pigs born live per litter (9.49, 9.82, 10.94, and 10.07; quadratic, P = 0.05) and sow lactation weight change (-0.2, 0.8, -4.1, and -3.9 kg; linear, P = 0.01) but decreased individual birth weight of total pigs born (1.61, 1.57, 1.47, and 1.56 kg; quadratic, P = 0.10). Tissues were obtained from a subset of sows from one station after they had completed three parities on the study. The content of Cr in the adrenal gland (16.4, 20.0, 34.0, and 48.4 ppb), kidney (35.8, 56.4, 132.6, and 176.0 ppb), and liver (22.8, 37.4, 87.6, and 92.2 ppb) was increased linearly (P = 0.001 to 0.005) by increasing CrPic supplementation. The results suggest that the supplementation level that maximizes the biological response is above that currently allowed. Additionally, supplementation of Cr at 1,000 ppb (five times currently permitted supplementation levels) was not detrimental to sow performance, even when fed continuously for three parities. There may be merit to continued research to evaluate higher supplementation rates.

Variability in mixing efficiency and laboratory analyses of a common diet mixed at 25 experiment stations

An experiment involving 25 experiment stations in the North Central and Southern regions (NCR-42 and S-288, respectively) was conducted to assess the degree of uniformity of diet mixing among stations and to assess the variability among station laboratories in chemical analysis of mixed diets. A fortified corn-soybean meal diet was mixed at each station using a common diet formula (except for vitamin and trace-mineral additions). The diet was calculated to contain 14% crude protein (CP), 0.65% Ca, 0.50% P, and 125 ppm Zn (based on 100 ppm added Zn). After mixing, samples were collected from the initial 5% of feed discharged from the mixer, after 25, 50, and 75% was discharged, and from the final 5% of discharged feed. The five samples were sent to the University of Kentucky, finely ground, and divided into subsamples. Each set of five subsamples from each station was distributed to three randomly selected stations for analysis of CP, Ca, P, and Zn (i.e., each station analyzed five diet sub-samples from three other stations). In addition, two commercial and two station laboratories analyzed composites of the five subsamples from each of the 25 mixed diets. Based on the laboratories that analyzed all diets, means were 13.5, 0.65, and 0.52%, and 115 ppm for CP, Ca, P, and Zn, respectively. Ranges of 11.8 to 14.6% CP, 0.52 to 0.85% Ca, 0.47 to 0.58% P, and 71 to 182 ppm of Zn were found among the 25 diet mixes. The coefficients of variation among the 25 diet samples for CP, Ca, P, and Zn were 4.3, 9.3, 4.1, and 17.4%, and among the 25 laboratories were 3.6, 12.5, 10.7, and 11.1%, respectively. Overall analyses of the five sub samples were, respectively, CP: 13.4, 13.6, 13.4, 13.5, and 13.4% (P < 0.06); Ca: 0.66, 0.67, 0.67, 0.66, and 0.67%; P: 0.50,0.51,0.51,0.50, and 0.50%; and Zn: 115, 116, 112, 113, and 120 ppm (P < 0.001). Diets were not uniformly mixed at all stations (station x sample No. was P < 0.08 for Ca and P < 0.01 for CP, P, and Zn). Among stations, the range of the five samples, expressed as a percentage of the mean and averaged for CP, Ca, P, and Zn, varied from +/- 1.1% (i.e., 98.9 to 101.0%) to +/- 12.9% (84.6 to 110.4%), with an overall average of +/- 5.2%. Neither type nor volume of mixers was related to mixing uniformity. The results suggest that uniformity of diet mixes varies among experiment stations, that some stations miss their targeted levels of nutrients (especially Zn), and that the variability among experiment station laboratories in analysis of dietary Ca, P, and Zn in mixed diets is quite large.

Growth promotion effects and plasma changes from feeding high dietary concentrations of zinc and copper to weanling pigs (regional study)

An experiment was conducted to determine the effect of high dietary intakes of Zn and Cu and their combination on growth performance of weanling pigs with diverse health status and management strategies. Twelve experiment stations cooperated and used a total of 1,356 pigs that averaged 6.55 kg BW and 22.2 d age at weaning. The four dietary treatments, all of which met or exceeded NRC requirements, were 1) control, 2) 3,000 ppm Zn (from Zn oxide), 3) 250 Cu ppm (from Cu sulfate), or 4) 3,000 ppm Zn and 250 ppm Cu. The diets were fed as a complex Phase I diet (1.4% lysine) for 7 d followed by a Phase II diet (1.2% lysine) for 21 d. Chlortetracycline (220 ppm) was added to all diets. Fecal color (1 = yellow to 5 = black) and consistency (1 = very firm to 5 = very watery) were scored daily for 3 wk. At the end of the 28-d study, 412 pigs were bled at five stations, and plasma Cu, Zn, and Fe concentrations were determined at one station with atomic absorption spectrophotometry. Average daily gain (375, 422, 409, 415 g/d), feed intake (637, 690, 671, 681 g/d), and gain/feed (586, 611, 611, 612 g/kg) were improved (P < .01) by the addition of Zn and(or) Cu. Significant Cu x Zn interactions imply that the responses to Zn and Cu were independent and not additive. There were significant (P < .01) Zn and Cu effects and a Zn x Cu interaction on fecal color (3.17, 3.24, 4.32, 3.57) and consistency (2.39, 2.14, 2.14, 2.13). Dietary additions of Cu and Zn resulted in elevated plasma concentrations of Cu and Zn, respectively. These data indicate that pharmacological additions of 3,000 ppm Zn (oxide) or 250 ppm Cu (sulfate) stimulate growth beyond that derived from intakes of Zn and Cu that meet nutrient requirements. However, the combination of Zn and Cu did not result in an additive growth response.

Metabolic changes during the transition from the fed to the acute feed-deprived state in prepuberal and mature gilts

The present study compared the metabolic response to acute feed deprivation in ovariectomized prepuberal (P; n = 6), 62 +/- 2 kg BW, and mature (M; n = 6) gilts, 124 +/- 4 kg BW. Blood was collected at 1, 2, 3, 4, 6, 8, 12, 16, 20, 24, 28, 32, 40, and 48 h after initiation of feeding. Samples were quantified for glucose, insulin, free fatty acids (FFA), beta-hydroxybutyrate (HBA), IGF-I, IGF binding proteins (BP)-1 to -4, cortisol, and amino acids (AA). At 24 h, blood samples were collected every 15 min for 8 h and an additional 1 h after i.v. injection of GnRH (.2 microgram/kg BW) and growth hormone-releasing factor (GRF; 1 microgram/kg BW). Samples were assayed for growth hormone (GH) and LH. Serum insulin concentrations were lower (P < .05) in P gilts. Plasma glucose concentrations were similar. Serum FFA concentrations were greater (P < .05) in P gilts. Serum concentrations of HBA were greater (P < .001) in P gilts at 48 h. Serum IGF-I concentrations were lower (P < .05) in P gilts by 16 h. Serum IGFBP-1-4 levels were similar. Serum cortisol concentrations were similar. Serum concentrations of the essential AA, isoleucine, lysine, threonine, valine, and phenylalanine were greater (P < .05) in P gilts at 40 h. Serum LH concentrations and response to GnRH were similar. Basal serum GH concentrations and peak response to GRF were greater (P < .05) in P than in M gilts. The transition from fed to unfed state occurs more rapidly in P than in M gilts.

Protection of pigs by vaccination of pregnant sows against eastern equine encephalomyelitis virus

Serum-virus neutralizing antibodies were detected in serum and colostrum of sows vaccinated during pregnancy with commercially available vaccines against eastern equine encephalomyelitis virus (EEEV), and antibodies were detected in serum from nearly all pigs from vaccinated sows following colostrum uptake. Serum-virus neutralizing antibody (SVN) test titers were measured in colostrum and pigs at the next farrowing, and additional vaccination of sows prior to the third farrowing led to elevated SVN titers in serum, colostrum and all pigs. Six pigs from vaccinated sows challenged at 8 to 9 days of age with 1 x 10(6) TCID50 EEEV did not develop the high temperatures or signs of central nervous system disease that 6 pigs from non-vaccinated sows developed. Virus was isolate from blood and oropharyngeal swabs from all pigs from non-vaccinated sows with blood virus titers as high as 9.3 x 10(4) TCID50, while only low levels of virus were detected in blood and oropharyngeal swabs from pigs from vaccinated sows. Virus was also isolated from tonsils collected at necropsy from 3 pigs from non-vaccinated and 1 pig from vaccinated sows. Vaccination of pregnant sows leads to development of maternal antibodies that are transmitted via colostrum to pigs and are protective against clinical EEEV related disease after experimental challenge with EEEV. In addition, vaccination prevents amplification of virus in infected pigs and could result in protection of animals and farm labor in the environment of infected pigs.

Effect of dietary copper and fat on nutrient utilization, digestive enzyme activities, and tissue mineral levels in weanling pigs

Two 15-d nutrient balance trials were conducted using a total of 32 weanling barrows (averaging 6.8 kg, 26 d). The effect of the addition of 15 or 250 ppm Cu (as CuSO4.5H2O) to diets containing 0 or 5% added animal fat on nutrient utilization, digestive enzyme activities, and tissue mineral levels in weanling pigs was investigated. In each trial, four groups of four littermate barrows were randomly assigned to one of four treatments in a 2 x 2 factorial arrangement. The addition of 250 ppm Cu improved apparent fat digestibility and apparent nitrogen retention (P < .02). The addition of 5% fat increased apparent fat digestibility (P < .01). There were no Cu x fat interactions (P > .10) for any of the digestibility indices measured. The addition of 250 ppm of Cu stimulated small intestinal lipase (P < .01) and phospholipase A (P < .05) activities but had no effect (P > .10) on pancreatic lipase or phospholipase activities and no effect on trypsin, chymotrypsin, or amylase activities in the small intestine or the pancreas. The addition of 250 ppm Cu to the diet increased Cu (P < .001) in plasma, liver, and kidney and decreased Fe in plasma (P < .05) and liver (P < .02). The addition of 5% fat increased Fe in kidney (P < .05) and heart (P < .08). Copper x fat interactions were observed for spleen Ca (P < .01), Mg (P < .08), Na (P < .05), and K (P < .08) and spleen weight (P < .05). In additional in vitro assays, increased Cu concentrations tended to consistently stimulate purified porcine pancreatic lipase activity (linear, P < .01) but not purified porcine pancreatic phospholipase A activity (P > .10). The results from this study indicate that 250 ppm Cu stimulated intestinal lipase and phospholipase A activities, leading to an improvement of dietary fat digestibility in weanling pigs.

Supplemental lysine for sows nursing large litters

A cooperative experiment involving 501 litters was conducted at four stations to assess the effects of supplemental lysine on lactational performance of sows nursing large litters. Basal diets were formulated to contain .60% lysine from corn or sorghum and soybean meal. Lysine.HCl (78.8% lysine) was substituted for grain to achieve dietary lysine levels of .75 and .90%. First-parity sows nursed a minimum of nine pigs per litter and older sows a minimum of 10 pigs per litter by d 3 of lactation. Overall mean litter size at 21 d of age was 9.7 pigs. Sows remained on treatment for three successive parities unless culled for structural unsoundness or reproductive failure. Dietary lysine did not affect body weight or backfat loss during lactation, sow ADFI, interval from weaning to estrus, or litter size at birth or at 21 d of age. Mean pig weights at birth and at 21 d of age increased quadratically to increasing lysine, with improvements found at all stations from increasing lysine from .60 to .75%. Twenty-one-day pig weights did not increase at the highest lysine level at stations feeding corn, but did improve at the station feeding sorghum, which resulted in a treatment x station interaction (P < .05). The different responses to lysine on different grain sources indicates intake of one or more other amino acid may have limited lactation performance at the highest level of lysine. These data indicate that a 13% CP corn-soybean meal containing .60% lysine is inadequate for sows nursing large litters and that supplemental synthetic lysine beyond .15% additional lysine will not be beneficial due to a deficiency of one or more other amino acids.

The effect of copper level on nutrient utilization of weanling pigs

The effect of addition of 15 or 250 ppm of Cu (as CuSO4.5H2O) and 0 or 5% added animal fat on the utilization of nutrients by weanling pigs was evaluated. Two trials were conducted with four groups of four littermate barrows (6.8 kg, 26 d) in each trial. Dietary treatments were arranged in a 2 x 2 factorial. Data were collected at the beginning of the trial and at the end of each 3-d period. There were no treatment x period interactions (P > .15). There was a Cu level x fat level interaction for ADG (P < .01), feed efficiency (P < .01), N intake (P < .09), fat intake (P < .01), and ash intake (P < .09). Pigs fed 250 ppm of Cu and 5% fat had increased ADG and gain:feed, whereas pigs fed 5% fat and 15 ppm of Cu had decreased ADG and gain:feed compared to pigs fed the other treatments. Apparent digestibility of DM and ash and N retention were increased (P < .05) by the addition of 250 ppm of Cu, whereas the addition of 5% fat decreased (P < .05) DM and ash digestibility. Fat digestibility increased from 28.3% to 75.6% when 5% fat was added to the diet containing 15 ppm of Cu and from 60.8% to 85.1% when 5% fat was added to the diet containing 250 ppm of Cu (Cu level x fat level, P < .01). Pigs fed diets containing 5% fat and 15 ppm of Cu had decreased (P < .06) Na, Cu, Fe, and Zn retention compared to pigs fed the other diets.(ABSTRACT TRUNCATED AT 250 WORDS)

The effect of various diet nutrient densities and electrolyte balances on sow and litter performance during two seasons of the year

An experiment involving 289 farrowings during a 2-yr period was conducted to determine the effect of increasing dietary nutrient concentration, electrolyte balance, and season of the year on the lactational performance of sows. Experimental diets were corn-soybean meal-based. The basal diet was formulated to meet or exceed the NRC requirements and the high-nutrient diet was formulated to contain approximately 20% higher levels of the nutrients than the basal diet, with or without adjustment of the electrolyte balance (Na+K-Cl) to 250 mEq/kg. Experimental diets were fed in both the warm (May through October) and cool (November through April) seasons of the year, resulting in a 2 x 2 x 2 factorial arrangement of treatments. There were no season x treatment interactions for any of the indices measured. During the first 21 d of lactation, sows farrowing in the cool season consumed more feed (P < .001) and produced heavier (P < .001) pig weights and litter weight gains than sows farrowing in the warm season. Increasing nutrient density from 100 to 120% of the NRC requirements resulted in decreased (P < .05) daily feed consumption, but it increased (P < .001) daily CP and GE intake, 21-d pig weights, and litter weight gains. Adjusting the dietary electrolyte balance from normal (130 mEq/kg) to 250 mEq/kg tended to increase (P < .07) 21-d pig weights, but it had no effect on other indices measured. These data indicate that under the environmental and management conditions of this experiment, the nutrient requirements of the lactating sow are higher than the current NRC standards.

The effect of adding copper and various fat sources to the diets of weanling swine on growth performance and serum fatty acid profiles

An experiment involving 540 weanling pigs was conducted to determine the effect of the addition of Cu (5, 125, or 250 ppm) on the growth performance and serum fatty acid profiles of pigs fed diets that contained no added fat (NO FAT), 5% added soybean oil (SBO), 5% added animal fat (ANI), or 5% added medium-chain triglycerides (MCT). Pigs had ad libitum access to corn-soybean meal-based diets that contained 10% whey and 5% fish meal during the 28-d trial. Pigs were weighed and pen feed intakes were recorded weekly. Blood samples were collected for serum fatty acid analysis on d 1, 14, and 28 of the trial. The addition of all sources of fat to the diet increased (P < .001) ADG and gain:feed ratios during the 28-d trial. Increasing levels of dietary Cu linearly increased (P < .001) ADG and quadratically increased (P < .05) ADFI during the 28-d experiment. A Cu x fat source interaction was observed d 14 to 28 for ADG. The ADG of pigs fed NO FAT or SBO linearly increased with increasing levels of Cu, and pigs fed MCT or ANI had quadratic increases in ADG as Cu levels increased. Compared with the NO FAT diet, d-28 serum saturated fatty acid concentrations were decreased (P < .01) by the addition of SBO or ANI, monounsaturated fatty acid concentrations were decreased (P < .001) by the addition of SBO, and polyunsaturated fatty acid concentrations were increased by the addition of SBO (P < .001).(ABSTRACT TRUNCATED AT 250 WORDS)

The effect of copper and fat addition to the diets of weanling swine on growth performance and serum fatty acids

A 2 x 3 factorial experiment, encompassing three 28-d trials involving a total of 420 weanling pigs, was conducted to determine the effect of dietary Cu (5 or 250 ppm) and animal fat (0, 2.5, or 5%) on the performance and serum fatty acid profiles of weanling pigs. Pigs had ad libitum access to corn-soybean meal-based diets containing 10% whey and 5% fish meal and similar lysine:calorie ratios. Pigs were weighed and pen feed intakes were recorded weekly. Weekly blood samples were collected during the first two trials (n = 270) for serum fatty acid analysis. There was a Cu x fat interaction for ADG from d 1 to 14 (P less than .07) and over the 28-d experiment (P less than .05). The ADG of pigs fed 250 ppm of Cu increased, whereas the ADG of pigs fed 5 ppm of Cu was not affected as dietary fat increased. The addition of 250 ppm of CU increased (P less than .01) ADFI throughout the 28-d experiment. The addition of fat quadratically increased ADG (P less than .05) during d 14 to 28 and gain:feed ratios (P less than .01) during d 14 to 28 and over the 28-d experiment. The addition of fat decreased (P less than .05) the weight percentage of serum saturated fatty acids and increased (P less than .01) the weight percentage of serum monounsaturated fatty acids on d 28. The addition of 250 ppm of Cu decreased (P less than .01) the weight percentage of monounsaturated fatty acids on d 14 and 28.(ABSTRACT TRUNCATED AT 250 WORDS)

Lipid profiles, serum immunoglobulins, dietary intake, and drug use of older rural Iowa women

Serum lipid profiles, serum immunoglobulins, and serum proteins were investigated in 65 noninstitutionalized older women living in a rural community. All women were mentally and physically able to participate in the study. They did not have any overt disease nor were they taking any prescription or nonprescription drugs that would interfere with the study. Personal interview elicited medical history, drug usage, dietary information, height, and weight from 25 reference women (50 through 64 years old), 28 young-old women (65 through 84 years old), and 12 old-old women (85 through 92 years old). Blood samples were obtained from fasting participants and analyzed for total serum cholesterol, high-density-lipoprotein cholesterol, serum triglyceride, serum immunoglobulins (IgG, IgA, and IgM), serum albumin, and total serum protein. Serum lipids were not significantly affected by age, drug use, or age-by-drug use interaction. Effects of age were observed for IgA and serum albumin. Mean concentrations of serum immunoglobulins, serum albumin, and total serum proteins were within normal limits for all participants. Based on this small sample of rural older women, our results indicate that the normal levels of high-density-lipoprotein cholesterol and the healthy life-styles of these women may help offset any possible negative effects of elevated serum cholesterol concentrations.

Effect of vitamin E and copper on the vitamin E status and performance of growing pigs

A 13-wk trial was conducted with 32 pigs to determine the effects of dietary Cu (250 ppm) and alpha-tocopheryl acetate (ATA, 22 IU/kg) on the performance, serum enzymes, serum and tissue tocopherols, and antibody production in growing pigs. Pigs were fed corn-soybean meal diets containing 21% CP the first 4 wk and 18% CP during the rest of the trial. All feed was stored a minimum of 14 d before it was fed. The addition of Cu decreased (P less than .01) the concentration of alpha-tocopherol in the feed. alpha-Tocopherol concentrations were less than .01 mg/kg in the starter diet and less than 2 mg/kg in the grower diet after 14 d of storage. Supplemental Cu or ATA had no effect on ADG, feed intake, or gain:feed during the first 4 wk. During wk 5 to 13, the addition of Cu to diets containing no ATA increased daily feed intake and decreased gain:feed, but with ATA addition, feed intake decreased and gain:feed increased, resulting in a Cu x ATA interaction (P less than .05). The addition of Cu or ATA had no effect (P greater than .1) on serum glutathione peroxidase or lactic dehydrogenase activity. Serum tocopherols were reduced (P less than .05) by the addition of Cu during wk 1 to 4, 6 (P less than .01), and 7 (P less than .05) and increased (P less than .01) by ATA addition during the entire experiment. The addition of ATA increased the tocopherol concentrations in bile, ham, heart, pancreas, kidney, spleen, liver, psoas and longissimus muscle (P less than .01), kidney fat, backfat, and adrenal gland (P less than .05).(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of trace minerals on the stability of vitamin E in swine grower diets

The stability of alpha-tocopheryl acetate and inherent tocopherols in swine grower diets containing high levels of trace minerals was studied in a 12-wk experiment. Corn-soybean meal diets with either 0 or 1% crude soybean oil and without trace minerals added (NOTM) were supplemented with a standard trace mineral mix (TM), TM + 250 ppm of Cu, TM + 1,000 ppm of Fe, TM + 1,000 ppm of Zn, or TM + 100 ppm of Mn. Alpha-tocopheryl acetate decreased linearly (P less than .0001) during 12 wk of storage in diets containing NOTM, TM, Zn, or Mn at a rate of .015 mg/d. Addition of Fe (P less than .005) or Cu (P less than .05) increased the rate of alpha-tocopheryl acetate loss. The addition of soybean oil had no effect (P greater than .1) on the rate of alpha-tocopheryl acetate loss. The alpha-tocopherol levels of the NOTM diet decreased (P less than .01) by approximately 50% during the 12-wk storage period. Addition of TM alone in diets that did not contain soybean oil had no effect P greater than .1) on the rate of alpha-tocopherol loss. The addition of Cu, Fe, Zn, or Mn (P less than .05) to diets that did not contain soybean oil increased the rate of alpha-tocopherol loss in comparison with NOTM and TM diets. Addition of Cu decreased alpha-tocopherol below 10% of initial levels in approximately 10 d. The addition of soybean oil to the diets containing TM, Fe, Zn (P less than .005), or Mn (P less than .05) further increased the rate of alpha-tocopherol loss.(ABSTRACT TRUNCATED AT 250 WORDS)

The effect of copper addition to diets with various iron levels on the performance and hematology of weanling swine

A 2 x 6 factorial experiment with Cu added at 5 or 250 ppm and Fe added at 50, 100, 150, 200, 250, or 300 ppm was conducted using 480 crossbred weanling pigs with an average initial weight of 7.0 kg. The basal corn-soybean meal-whey diet contained 4 ppm Cu, 169 ppm Fe, and 199 ppm Zn. Pigs were allotted by weight, sex, and litter outcome group and had ad libitum access to feed and water during the 28-d trials. Animals were weighed and pen feed intake was recorded weekly. Blood samples were collected on d 1, 14, and 28 of the experiment. The addition of 250 ppm Cu increased ADG (P less than .001) and average daily feed intake (ADFI, P less than .01) during the 28-d trials. The addition of Fe had no effect on ADG and ADFI (P greater than .10). A Cu x Fe interaction (P less than .01) was observed for feed/gain. Increasing Fe levels linearly improved hematocrit status (P less than .05) on d 28 of the trial. A Cu x Fe interaction (P less than .08) was observed for hemoglobin at the end of the trial; hemoglobin levels were increased by the addition of Fe to the diet containing 250 ppm of Cu. Plasma Cu was increased (P less than .001) by the addition of 250 ppm of Cu. Plasma Fe was low when either 50 or 100 ppm of Fe was added in the presence of 250 ppm of Cu, but it was not affected at other levels, resulting in a Cu x Fe interaction (P less than .05). These data indicate that levels of added Fe up to 300 ppm may help to improve the hematological status of weanling pigs fed growth-promoting levels of Cu but that it has little effect on performance.

Effect of roasted or raw peanut kernels on lactation performance and milk composition of swine

A lactation trial involving 105 sows was conducted to determine the effect of 12% roasted or raw, ground, whole, shelled peanuts on sow weight change during lactation, feed intake, piglet and litter weight gain, milk composition, and days to return to postweaning estrus. The trial was conducted using three sow groups during two farrowing seasons, summer (July to September) and winter (December to February). Diets were based on corn plus soybean meal. Diets contained either 5% animal fat or equivalent added fat from 12% roasted or raw, ground, shelled peanuts. The replacement of animal fat by roasted or raw peanuts had no effect (P greater than .20) on sow weight change, average daily feed intake during lactation or days to estrus postweaning, or on piglet weight gain or survival. Milk composition (percentage fat and protein) was not altered (P greater than .20) by source of fat in the summer; however, in the winter, sows fed roasted peanuts had higher (P less than .05) milk fat and protein percentage at 3 d postfarrowing than other treatment groups. At d 7, sows fed 12% roasted or raw peanuts had higher (P less than .05) milk protein than sows fed 5% animal fat. Sows farrowing in the summer had greater (P less than .01) weight loss and consumed less (P less than .05) feed during lactation than sows farrowing in the winter. Sows farrowed in the summer had larger (P less than .05) litters at birth and 14 d postfarrowing and greater (P less than .10) piglet and litter weight gain postfarrowing than those farrowed in the winter.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of excess dietary copper, iron or zinc on the tocopherol and selenium status of growing pigs

Two experiments were conducted to evaluate the effect of the addition of high levels of Cu (as CuSO4), Fe (as FeSO4) or Zn (as ZnO) to swine starter and grower diets on performance and vitamin E and Se status. The stability of natural tocopherols in mixed feeds was evaluated during storage. Addition of 1,000 ppm Fe or 1,000 ppm Zn had no effect on rate or efficiency of weight gain in either experiment. In Exp. 1, the addition of 250 ppm Cu improved daily gain and efficiency of feed utilization (P less than .05) during the first 3 wk of the experiment. Copper had no effect on pig performance during the rest of Exp. 1 or in Exp. 2. Serum lactate dehydrogenase or glutathione peroxidase activity was not affected (P greater than .1) by any of the mineral additions. Serum tocopherols were not affected by the mineral treatments in Exp. 1. In Exp. 2, addition of 250 ppm Cu decreased (P less than .01) serum tocopherol levels throughout the 8-wk experiment. The alpha-tocopherol levels of the starter diet decreased (P less than .05) during storage. Addition of 250 ppm Cu (P less than .01) or 1,000 ppm Fe (P less than .05) or 1,000 ppm Zn (P less than .05) increased the destruction of alpha-tocopherol in the starter diet. Alpha- and gamma-tocopherol levels of the starter diet decreased to near zero in 22 d in the presence of 250 ppm Cu. In the grower diet, the addition of 250 ppm Cu (P less than .01) or 1,000 ppm Fe (P less than .05) increased the destruction of tocopherols.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of jejunal loop location on the activity of Escherichia coli heat-stable enterotoxin in 4- to 5-week-old pigs

Heat-stable enterotoxin (STa) from Escherichia coli strain 431 was injected into the jejunum of 4 pigs from each of 3 litters, using a ligated intestinal loop assay (with loops beginning 1 m caudad to the pylorus). The jejunum was divided into 4 contiguous areas, with 4 loops in each area. Doses of 0, 10, 100, or 1,000 ng of purified toxin (10 ng/mouse unit) were injected into the loops within an area, using a 4 X 4 Latin square design. Fluid accumulation in the loops increased (P less than 0.05) with increasing concentrations of STa in pigs in all litters, but the magnitude of the response varied across litters. Fluid responses to the STa varied in the different areas of the jejunum, with pigs in 2 litters having a decrease (P less than 0.05) in the response to STa in the caudal areas. These data quantitate the variability within the different areas of the jejunum of the young pig.

Reversal of the biological activity of Escherichia coli heat-stable enterotoxin by disulfide-reducing agents

Various disulfide-reducing agents, mostly thiols and thiol precursors, were examined for their ability to reduce the disulfide bonds in the Escherichia coli heat-stable enterotoxin STa; reduction of the bonds results in loss of biological activity. The biological activity measured was the stimulation of guanylate cyclase in pig intestinal brush border membranes by STa. Nearly all of the compounds inactivated STa, although at different rates; a smaller number appreciably decreased guanylate cyclase activity when they were introduced into the reaction mixture after STa bound to its receptor. With dithiothreitol, the decrease in reaction rate was both time and concentration dependent and resulted in a reversal to basal activity. The anionic thiols were relatively ineffective in reversing activation, the neutral monothiols were moderately effective, and the aminothiols and neutral dithiols were the most effective. The order of effectiveness of the compounds was S-2-(3-aminopropylamino)ethanethiol greater than 2,3-dimercaptopropanol = 2-aminoethylisothiuronium bromide greater than dithiothreitol greater than 2-mercaptoethylamine greater than alpha-thioglycerol. These compounds were used in weanling pig ligated-intestinal-loop bioassays to determine if STa-induced secretion was reduced when they were injected 20 min after the STa. Instead of S-2-(3-aminopropylamino)ethanethiol we used the phosphorylated derivative S-2-(3-aminopropylamino)ethylphosphorothioic acid; this compound and 2,3-dimercaptopropanol were the only compounds that reduced STa-induced secretion and had no direct secretory or pathological effects.

Simultaneous cecostomy and ileal cannulation with a modified flexible T cannula in gilts

A surgical procedure was developed for the simultaneous cannulation of the ileum and fistulation of the cecum in breeding-age gilts to study the effects of enteric microflora on the nutritional requirements and/or status of the pig. Flexible T-shaped cannulae were made from plastic tubing, placed surgically in the caudal part of the ileum, and exteriorized in the right paralumbar fossa. After the exteriorization of the cecal apex in the right flank area, a cecal fistual was made caudoventral to the ileal cannula. Prececocolonic contents could be collected from the ileal cannulae and/or substances could be infused into the cecum. The flexible cannulae were light weight (35 g), were easily replaced when dislodged with minimal tissue trauma and minimal discomfort to the animal, and had good animal tolerance and patency in long-term experiments. The cecal fistulae allowed the direct introduction of various substances into the cecum. There was little external projection from the abdominal wall, and the fistulae were subject to minimal leakage. The procedure did not adversely affect the subsequent health or performance of the 43 gilts used in the experiment. Postmortem examination of gilts euthanatized 12 to 26 weeks postoperatively revealed normal tissue adhesions around the surgical sites with no detrimental effects on the gastrointestinal tract.