Browsing by Author "Pfeiffer, Carl J."

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    Effects of High-density Stocking in a Recirculating Aquaculture System on Gill Morphology ofHybrid Striped Bass (Morone saxatilis x M. chrysops)
    Smith, B. J.; Smith, Stephen A.; Pfeiffer, Carl J. (Commercial Fish and Shellfish Technologies Program, Virginia Tech, 2000-06-01)
    The types and distribution of gill lesions observed in hybrid striped bass (Morone saxatilis x M. chrysops) reared in a commercial-scale recirculating aquaculture system are described. When placed in the system as fingerlings and reared there for eight months at typical stocking density, the gills of all examined fish presented a variety of extensive, non-specific lesions typically resulting from poor water quality. Lesions included epithelial cell hyperplasia, infiltration of the interfilamental region by mixed inflammatory cells, hyperplasia of mucous and lamellar epithelium, lamellar fusion and occasional filamental fusion. Up to 76% of the gill sample surface of individual fish was affected, with lesions being most severe in the distal filamental regions. Fish transferred to and maintained at low stocking densities in water of superior quality demonstrated that all lesions were fully reversible by five weeks post-transfer. This study demonstrates that culture of hybrid striped bass under intensive aquaculture management induced pathological changes in the gills, and suggests that maintenance of fish under improved water quality conditions will reduce gill lesions, which could potentially increase the fishes' performance.
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    The Effects Of Mercuric Chloride On Cultured Atlantic Spotted Dolphin (Stenella Plagiodon) Renal Cells And The Role Of Selenium In Protection
    Wang, Amy (Hui-Shan) (Virginia Tech, 1998-04-24)
    Marine mammals are known for their low susceptibility to mercury toxicity, and it was hypothesized that selenium may play a role in protection against mercury toxicity. To gain insight into the mechanisms of the low susceptibility of cetaceans, we investigated the in vitro effects (1) of mercuric chloride (HgCl₂) on the ultrastructure and cell death of Atlantic spotted dolphin renal cells (Sp1K cells), (2) of HgCl₂ on the cell proliferation and cell cycle status of Sp1K and Rhesus monkey renal cells (MK2), and (3) of sodium selenite (Na₂SeO₃) on cell proliferation and cell death of control and HgCl₂-treated Sp1K cells. HgCl₂ affected multiple organelles and nuclei in Sp1K cells, and induced apoptosis in a time-and dose-dependent manner. Both ultrastructural changes and induction of apoptosis were milder than seen in other cell types in previous publications. In addition, Sp1K cells were able to proliferate at 25 µM HgCl₂ while MK2 cells were killed at 15 µM HgCl₂. An increase in percentage of cells in the G0/G1 phase in the cell cycle and a decrease in S, and G2/M phase cells were seen in Sp1K cells exposed to more than 10 uM HgCl₂ more than 72 hours. MK2 cells showed cell cycle changes only at 24 hours exposure, and may be due to a sensitive subgroup. These data suggested that Sp1K cells were less susceptible than other cell types in a cell-specific way, which was independent of selenium protection. Concurrent exposure to Na₂SeO₃ provided protection against the HgCl₂-induced decrease in cell proliferation of Sp1K. The protective effects were greater if Na₂SeO₃ and HgCl₂ were premixed, but disappeared if exposures did not overlap. Although pretreatments with Na₂SeO₃ alone did not provide protection, they increased the protection of selenium administered later. Furthermore, Na₂SeO₃ decreased HgCl₂-induced apoptosis. These data demonstrated the Na₂SeO₃ protection against HgCl₂ toxicity in Sp1K cells in terms of cell proliferation and apoptosis. This study is the first report that reveals the existence of mercury-selenium antagonism in cultured cetacean cells. The data supported the hypothesis that selenium protection against mercury toxicity is, at least partially, through competition of binding sites and formation of mercury-selenium complex.
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    Endovascular trophoblast cell behavior in normal and abnormal pregnancy
    Endo, Yasuhiro (Virginia Tech, 1995-04-05)
    Preeclampsia is an important disease during pregnancy and causes significant maternal and fetal mortality and morbidity. Despite intense research efforts, the etiology and pathogenesis of the disease remain largely unknown. Since placentas from preeclamptic patients are smaller than normal, and cytokine growth factors are suggested to be important in placental growth, the effects of macrophage-colony stimulating factor (M-CSF) on human trophoblast cells were examined. While term trophoblast cells did not respond to M-CSF, those from early trimester and choriocarcinoma cells showed enhanced growth after treatment. In addition, the serum level of M-CSF in hypertensive pregnant women at the second trimester were significantly lower than those of normal pregnant women. These data suggest possible roles of M-CSF in preeclampsia. When M-CSF was administered to pregnant rats on days 8-11, rats had smaller placentas at day 12 and increased fetal resorption rate at day 20. The effects of interleukin-12 (IL-12) was also examined on days 8-11. While placental development was normal at both days 12 and 20, fetuses were significantly smaller at day 20. To remedy the difficulties and dangers associated with obtaining human placentas, I characterized endovascular trophoblast cell behavior in pregnant rats. In normal pregnancy, rat trophoblast cells simulated all features of human endovascular trophoblast behavior including selective invasion into the spiral arteries, retrograde migration, embedding, and secretion of PAS-positive materials as well as IIphysiological changes," In pregnancy terminated with a certain type of spontaneous fetal resorption, defective endovascular trophoblast cell behavior was observed, which was similar to that reported in preeclamptic pregnancy. Finally, the roles of cytoskeleton on trophoblast cell locomotion were investigated in vivo with a cytoskeleton-disrupting agent, cytochalasin B. This treatment impaired trophoblast cell invasion at day 12 and induced smaller fetuses at day 20, suggesting the importance of cytoskeleton in trophoblast movement. In conclusion, the results suggest the importance of the use of appropriate specimens and endpoints in the study of pregnancy, and rats may serve as a suitable animal model for the study of endovascular trophoblast cell behavior with clinical relevance to preeclampsia.
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    Epidermal growth factor receptor in equine gastric stratified squamous mucosa: effect of progressive ulceration on receptor density
    Jeffrey, Stuart C. (Virginia Tech, 1996-02-05)
    The objective of the study reported here was to document the distribution of epidermal growth factor receptor (EGFr) and quantitate receptor density in normal as well as ulcerated equine gastric squamous mucosa. Fifteen horses with endoscopically normal stomachs were divided into three equal groups. Group 1 was a normal control. A protocol that alternated 24 hour periods of free-choice hay with 24 hours of feed deprivation was utilized to induce squamous mucosal gastric ulceration in Group 2 (48 hours total off-feed) and Group 3 (96 hours total off-feed). Gastric tissue was collected from 3 stomach locations at post-mortem examination and an avidin-biotin immunoperoxidase technique was developed to stain the formalin-fixed tissue for EGFr. A computerized image analysis system was used to measure EGFr area and mean intensity values at four sites within the epithelium from the basal cell layers to the lumen in the ulcer/erosion margin, erosion bed, and 10-14 mm distant from the lesion.
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    Evaluation of the microcirculation of the equine small intestine following intramural distention and reperfusion
    Dabareiner, Robin Marie (Virginia Tech, 1992-04-05)
    The effects of intraluminal distention (25 cm H₂O, 120 minutes) and subsequent decompression (60 minutes) on the intramural vascular patterns of the equine small intestine was evaluated in 7 anesthetized horses. The vascular system of experimental and control segments were injected with a blue-colored radiopaque medium for microangiography and histology or a diluted methyl methacrylate (MERCOX CL-2B) for scanning electron microscopy. The distended segments had shortened villi that were separated by expanded crypts and mesothelial cell loss, neutrophil infiltration and edema in the seromuscular layer. The number of filled vessels was decreased in the seromuscular layer and to a lesser extent in the mucosal layer in the distended segments compared to controls. Following reperfusion, the morphologic lesions progressed and the number of observed vessels increased in all layers; however the vascular density did not return to the pre distention state. This study identifies altered intramural vascular patterns in the equine jejunum during luminal distention and reperfusion.
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    The Gastroduodenal Effects of Buffered Aspirin, Carprofen, And Etodolac in the Healthy Dog and Comparison of the CLOtest® to Histopathologic Evaluation in Identifying the Presence of Helicobacter Spp. in Healthy Dogs
    Reimer, Michele E. (Virginia Tech, 1999-02-24)
    Twenty-four healthy, mixed breed dogs were divided into four groups. Group I received a placebo PO BID, group II received an average 16.5 (range, 15.1-17.8) mg/kg buffered aspirin PO BID, group III received an average 2.2 (range, 2.0-2.4) mg/kg carprofen PO BID, and group IV received an average 12.8 (range, 11.7-13.8) mg/kg etodolac PO QD (with a placebo in the P.M.). All treatments continued for 28 consecutive days. Gastroduodenal endoscopy was performed on days – 9, 0, 5, 14 and 28. Multiple gastric biopsies were obtained endoscopically on day – 9 to determine each dog's Helicobacter spp. status. Five areas, consisting of four regions in the stomach and one in the proximal duodenum, were evaluated endoscopically, and each was assigned a score from 1 to 11 based on qualitative assessment of submucosal hemorrhage, erosion, or ulceration. These scores for each region were then summed to give a total score for each endoscopic evaluation. Erosions and submucosal hemorrhages were seen in all dogs receiving aspirin. Only minor gastric lesions were observed in the carprofen, etodolac, and control groups. No adverse clinical signs were noted in any dog given any treatment during the course of the study. There was no predilection site for lesion development in any group. Median total score on days 0, 5, 14, and 28 were as follows: group I, 5.0, 5.0, 5.0, 5.0; group II, 5.0, 27.0, 26.0, 27.5; group III, 5.0, 5.0, 6.0, 5.0; group IV, 5.0, 7.0, 5.0, 5.0, respectively. There was no significant difference between dogs receiving carprofen, etodolac, or placebo. The administration of carprofen, etodolac, or placebo to healthy dogs resulted in significantly less gastroduodenal lesion development than in dogs receiving buffered aspirin. Thirty healthy, random source, dogs were evaluated to determine the prevalence of Helicobacter spp., and to compare the ‘Campylobacter-like organism’ test (CLOtest®) to histopathologic identification of Helicobacter spp. organisms. Gastric mucosal biopsies from each of four gastric regions (cardia, pyloric antrum, greater curvature, and angularis incisura) were obtained endoscopically for use in the CLOtest® and for histopathologic evaluation. Twenty-seven of 30 dogs (90%) were positive for spiral bacteria suspected to be Helicobacter spp. by histopathologic evaluation in at least one of the four gastric regions. Three dogs (10%) were negative for Helicobacter spp. in all gastric regions by histopathologic evaluation. The CLOtest® was found to have a sensitivity, specificity, and positive predictive value of 84%, 81%, and 92%, respectively, when compared to histopathologic evaluation. When only the angularis incisura was evaluated, the sensitivity, specificity, and positive predictive value increased to 92%, 94%, and 96%, respectively. The angularis incisura had the highest, whereas the pyloric antrum had the lowest, prevalence of positive test results when compared to dogs determined to be overall Helicobacter spp. positive (histopathologic positive in at least one gastric region). The results of this study suggest the prevalence of Helicobacter spp. in apparently healthy dogs is high. For accurate and economical detection of Helicobacter spp. in a dog undergoing upper gastrointestinal endoscopy, a tissue sample should be taken from the angularis incisura for CLOtest® sampling.
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    Gross and Microscopic Observations on the Lingual Structure of the West Indian Manatee (Trichechus manatus latirostris)
    Levin, Milton Jay (Virginia Tech, 2004-03-19)
    The West Indian manatee tongue was examined macroscopically, light microscopically, and electron microscopically (scanning and transmission). The tongue was slender, muscular, and firmly fixed in the oral cavity. Only the cranial tip was free and mobile. Numerous filiform papillae were distributed over the dorsal surface of the rostral lingual region. Caudal to the filiform papillae, multiple raised, round papillae were distributed over the majority of the dorsum. Fungiform papillae were restricted to the lateral margins of the tongue. Caudally, the dorsal and lateral regions showed numerous open fossae and pits. Microscopic examination showed the majority of the lingual dorsum to be covered with a thick stratified squamous epithelium. The caudal dorsal and lateral open pits led to well-developed mucous salivary glands. Foliate papillae, located on the caudal region of the tongue, contained taste buds embedded in the epidermis. Glands within the foliate papillae were mostly mucous, though some seromucous glands were evident. Throughout the tongue, striated muscle was abundant below the epidermis. Blood vessels, lymph channels, and nerve fibers were freely distributed throughout the intermuscular stroma. Nerve fibers reacted positively with neuron specific enolase antibody throughout the lingual structure, including nerve bundles, muscle bundles, glands, and taste buds. Electron microscopy revealed cytoplasmic vacuoles juxtaposed to the nucleus in the stratum spinosum of the foliate papillary region.
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    Mechanism of TNF-α cytotoxicity in a leukemia virus transformation model
    Mishra, Shrikant (Virginia Tech, 1991)
    Abelson murine leukemia virus (A-MuLV)-induced transformation was investigated to determine whether cells not sensitive to TNF-α could be made sensitive to the cytolytic action of TNF-α when infected with this retrovirus. Mouse embryonic fibroblast cell line CL.7 was found to be relatively insensitive to TNF-α. Upon transformation with A-MuLV, these cells gave rise to a clone (3R.1) which was found to be insensitive to TNF-α and another clone (6R.1) which had an increased sensitivity to TNF-α. The differential cytotoxicity was observed when cells were treated with TNF-α, for 18 hr, at 0 to 100 units/ml, at 37°C. The mechanism of this differential cytotoxicity was further investigated. Thus, TNF-R levels on the cell surface were found to be not correlated with the differential TNF-α response. The A-MuLV transformation suppressed the epidermal growth factor-receptor (EGF-R) in 3R.1 clone and induced its levels significantly in the 6R.1 clone (p<0.05). Cell surface EGF-receptor (EGF-R) levels in CL.7 and 3R.1 clones were lower than the 6R.1 clone (p<0.05). Although the EGF-R levels in all the clones were induced with TNF-α, the expression of EGF-R correlated with the susceptibility to TNF-α. The role of antioxidants, such as α-tocopherol and β-carotene, (known anti-cancer agents) in modulating TNF-α-induced EGF-R expression was investigated. In both the untransformed and the transformed clones, f-carotene suppressed the constitutive and the TNF-α induced EGF-R levels whereas α-tocopherol was found to have an enhancing effects. Studies with metabolic inhibitors on TNF-R and EGF-R expression indicate that inhibitors of the arachidonic acid cascade and modulators of protein kinase-C (PK-C), could influence the binding and internalization of TNF-α and thereby controlling the physiologic future of the cells. The A-MuLV specific V-abl protein, p120, tyrosine phosphorylation was determined by a radio-labelled anti-phosphotyrosine antibody in an antigen capture assay. TNF-α had little effect on p120 phosphotyrosine levels of TNF-α insensitive CL.7 and 3R.1 clones. The, TNF-α sensitive, 6R.1 clone, however, was found to induce its p120 specific phosphotyrosine upon exposure to TNF-α for 8 hr. Thus, TNF-α modulated the tyrosine phosphorylation of p120 only in the TNF-α-sensitive cell line. The mitochondrial toxicity of TNF-α was determined by monitoring the rate of quenching of a cationic spin probe CAT 16. Mitochondrial preparation from CL.7 and 3R.1 clones had higher ability to quench CAT 16 signal with TNF-α incubation time than mitochondria from the 6R.1 cells. This indicates that the differential TNF-α cytotoxicity manifested in A-MuLV transformed clones may, in part, be due to the differential mitochondrial toxicity of this cytokine. The hypothesis that TNF-α cytotoxicity was mediated via an oxidative process was tested on the TNF-α sensitive L929 cells. Using a flow cytometric detection system it was determined that TNF-α produced intracellular hydrogen peroxide in these cells which was sensitive to concentration and incubation time of TNF-α. Superoxide radicals were also generated during TNF-α action on L929 cells, as determined by the use of the spin trap PBN in conjunction with EPR spectroscopic techniques. The PBN-OOH spin adduct spectrum peaked at 9 hr of TNF-α incubation and was inhibitable upto 30 % with 10 µM of desferral-Mn complex (a known SOD mimic). These data indicate that superoxide and hydrogen peroxide are common events in TNF-α dependent cell killing process. The differential TNF-α cytotoxicity was found to depend on differences in the antioxidant status of the target clones. Thus, it was found that Cu/Zn-SOD, Mn-SOD, GSH-Peroxidase and GSH-Reductase enzymes were all induced significantly in the CL.7 clone (p<0.05) upon incubation with 100 units/ml of TNF-α for 18 hrs. TNF-α had little effect on the antioxidant enzymes of both 3R.1 and 6R.1 cells. However, the constitutive levels of most antioxidant enzymes were found to be higher in 3R.1 cells than in the 6R.1 cells. Therefore, the susceptibility of 6R.1 to TNF-α may, in part, be due to a low level of antioxidant enzymes present in this clone. In conclusion we found that the differential cytotoxicity of TNF-a may, in part, due to: (1) differential EGF-R expression, (2) differential mitochondrial cytotoxicity, and (3) differential ability to modulate the tyrosine phosphorylation in untransformed and A-MuLV transformed cells and (4) differential antioxidant status of these cells to handle oxidative stress imposed by TNF-α.
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    Mechanisms by which hypoxia augments Leydig cell viability and differentiated cell function in vitro
    Kukucka, Mark A. (Virginia Tech, 1993-04-18)
    The 1980's heralded the discovery and identification of extra-pituitary sources of the neurohypophysial hormone oxytocin in non-neural tissues of several animal species. The presence, location and biosynthesis of significant amounts of oxytocin in the ovarian corpus luteum was followed by the immunocytochemical demonstration of an oxytocin-like peptide in the testicular interstitial cells. Leydig cells, which comprise up to 80% of the testicular intertubular cell population, are known to synthesize testosterone in situ. Indirect evidence indicated that an oxytocin-like peptide was also present in Leydig cells. The question arose whether this peptide was synthesized de novo by Leydig cells or was taken up and stored by the cells following biosynthesis at some other intra- and/or extra-gonadal source(s). Since luteinizing hormone (LH) and ascorbate are known to augment the production of oxytocin in ovarian granulosa cells, varying concentrations of these two stimulants were used to monitor the biosynthesis of oxytocin from isolated Leydig cells in culture.
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    Microanatomic structure of cetacean skin in the urogenital region
    Jones, Flynn Margaret (Virginia Tech, 1993-08-05)
    It was hypothesized that there may be microanatomic specializations in the urogenital slit and mammary region of cetaceans. There may be an integumentary-linked mechanism in these animals similar to that which causes the milk let-down response in terrestrial mammals. This hypothesis was tested on tissue samples from fourteen animals collected in a standardized array of fourteen samples from the urogenital area, and one each from the ventral aspect of the flipper and the mid-dorsal body wall for comparison. Using standard histological and ultrastructural procedures, including both transmission and scanning electron microscopy, tissues from nine species were investigated. These included the bottlenose dolphin (Tursiops truncatus), striped dolphin (Stenella coeruleoalba), harbor porpoise (Phocoena phocoena), pygmy sperm whale (Kogia breviceps), short and long finned pilot whales (Globicephala macrorhynchus and malaena respectively), beluga whale (Delphinapterus leucas), humpback whale (Megaptera novaeangliae), and fin whale (Balaenoptera physalus). Measurements were taken of the height of the epidermis, the thickness of the epidermal stratum externum, and the height and number of dermal papillae. Co1lagen bundles of the reticular dermis were measured and ranked by diameter. Nervous structures were quantitatively evaluated by type and location. No differences were found in the epithelial, connective, or nervous tissue of the skin in this region that would imply an increased sensitivity in this area. However, an observed unique organization of the connective tissue may imply a functional difference in the skin of the urogenital region unrelated to the milk let-down phenomenon. Possible alternative mechanisms for the initiation of milk let-down in cetaceans are discussed, including myoepithelial cell contraction caused by urogenital bumping by calves, vocalization by calvest and tacto/acoustic stimulation of the urogenital area by the calf. Epidermal thickness and papillary height varied among animals of different cetacean species, although there seemed to be a structural 'formula' applicable to the skin of all cetaceans that would permit efficient turnover of the epidermis. The significance of integumentary lipids is discussed. Deviations in cellular and subcellular structures of cetacean skin from those described in previous reports are mentioned, and a previously undescribed location for nerves in dermal papillae was revealed.
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    Ontogenic Morphology and Enzyme Activities of the Intestinal Tract of the Nile Tilapia, Oreochromis Niloticus
    Tengjaroenkul, Bundit (Virginia Tech, 2000-04-26)
    The gross intestinal configuration of the Nile tilapia intestine changed dramatically from a short, straight intestinal tube at hatch (day 0) to a very complex, coiling pattern first attained at 9 weeks post-hatch. During the developmental period, gut length increased from 90% to 410% of body length. The rate of increase in both intestinal and body lengths took place at an accelerating rate as the fish aged. The great intestinal length provides an advantage to the fish in digestion and absorption of nutrients present in the less energy-efficient herbivorous diet. Formulation of commercial diets to match the development of the fish's intestine may offer commercial advantage. Appearance, localization and distribution of intestinal enzymes were observed in the fish at hatch and at mature stages using enzyme histochemistry. At hatch (day 0), most gut enzymes were already present in the intestinal brush border. As the fish matured, activities of the enzymes were widely distributed along the intestinal tract. The early appearance and broad distribution of activities of all studied intestinal enzymes may be one factor contributing to the rapid growth rate characteristic of tilapia, which differs markedly from other fish species. To investigate the possibility of using alfalfa as a potential protein food replacement in tilapia, the effects of different levels of alfalfa in feeds on growth and intestinal enzyme activities were observed in the fish aged 3-15 weeks. Results demonstrated that replacing 20% and 40% of a commercial diet with alfalfa had an overall negative effect on body and intestinal growth, as well as the intestinal enzyme activities from age 3-9 weeks. Thus, using alfalfa as a food replacement is not optimal for fish of these young ages, but may yet be suitable for older fish.
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    Physiological effects of diet and exercise in the equine
    Worth, Melyni J. (Virginia Polytechnic Institute and State University, 1988)
    Two experiments were conducted to investigate the effect of conditioning on the ability of the equine to digest and utilize nutrients and to determine the effect of dietary fat as an energy source on the physiological parameters associated with fitness using a standard exercise test. Conditioning horses increased apparent digestibilities of crude protein (CP) (P<.05), dry matter(DM), and acid detergent fiber (ADF) (P<.1). Conditioning also tended to increase the apparent digestibility of neutral detergent fiber (NDF), cellulose, cell contents, and energy. Heart rates and blood lactate levels indicated that the conditioned horses were fitter than their unconditioned controls. In the second experiment, horses were fed isocaloric diets, one containing added fat and the other a standard hay/corn diet. Adding fat while maintaining equal available energy concentration depressed apparent digestibility of dry matter (56.7 vs 67.3 % P<.05), cell contents (75.6 vs 82 %, P<.05), energy (61.2 vs 71.8 %, P<.05) and NDF (29.2 vs 51.3 %, P<.05), in unconditioned horses. There was a trend towards decreased apparent digestibility of CP and ADF. Addition of fat increased apparent digestibility of ether extract (89.2 vs 65.6 %, P<.05). Conditioning increased apparent digestibility of CP (64.8 vs 73.7 %, P<.05) and energy (61.2 vs 65.6 %, P<.05) and tended to increase apparent digestibility of DM (56.7 vs 60.8 % ) and ADF (26.8 vs 17.8 %) for horses fed a fat supplemented diet. Conditioning did not cause a change in apparent digestibility of ADF, CP, and DM in horses fed the control diet, or apparent digestibilities of NDF, ether extract, cell contents, or energy for either diet. There were no differences in physiological parameters used for assessing fitness (heart rate, blood lactate, and respiration rate), between horses fed a diet containing 14% added fat and no added fat. There was no difference in body temperature, blood glucose levels, blood urea-N (BUN), or creatine phosphokinase (CPK) between horses fed the two diets.
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    Supplementing weanling pigs with high concentrations of Zn and the Zn availability of Zn sources for weanling pigs
    Schell, Timothy C. (Virginia Tech, 1994)
    Thirteen trials (n=930) were conducted to investigate the supplementation of weanling pigs with high levels of Zn and to compare the availability of Zn from several Zn sources for weanling pigs. In the first four trials, supplementing Zn by injecting Zn acetate either i.m. or i.p. at various times near weaning did not improve postweaning growth performance compared with pigs that were not injected. Additionally, stressing pigs by regrouping and then injecting Zn acetate did not improve growth performance. Serum Zn concentrations were increased in all of the trials by the injection of Zn. In the next five trials, feeding 3,000, 2,000 or 1,000 mg Zn/kg of diet from ZnSO₄, Zn-lysine or Zn-methionine did not improve growth performance immediately after weaning compared with pigs fed diets with 105 mg Zn/kg of diet. Feeding 3,000 mg Zn/kg of diet as ZnO (P < .05) improved growth performance above that of pigs fed 3,000 mg Zn/kg of diet from the other sources, but did not improve growth performance compared to controls. Lower tissue Zn concentrations suggested a lower availability of Zn from ZnO compared with ZnSO₄, Zn-lysine and Zn-methionine. There was little difference in Zn availability among the other sources. In the next three trials, feeding diets with different levels of lysine had little influence on the availability of Zn from Zn-lysine compared to ZnSO₄. Results indicate that Zn from Zn-lysine is not absorbed in conjunction with the lysine component of the complex. Additionally, there were no differences in the availability of Zn from ZnSO₄ compared to Zn-lysine. In the last trial, Zn from ZnO was less available (P < .05) to Zn deficient pigs than ZnSO₄, Zn-lysine or Zn-methionine when rib bone Zn concentration was used as an indicator of Zn availability. In summary, supplementing weanling pigs with high levels of Zn immediately before or after weaning does not appear to improve growth performance. Furthermore, Zn from ZnO is less available to weanling pigs than Zn from ZnSO₄, Zn-lysine or Zn-methionine.