Pharmacokinetics and Acute Lethality of Perfluorooctanesulfonate (PFOS) to Juvenile Mallard and Northern Bobwhite

Ten-day-old mallards (Anas platyrhynchos) and northern bobwhite quail (Colinus virginianus) were fed perfluorooctanesulfonate (PFOS) in their diet for 5 days. The birds were then observed for 3 days while being given uncontaminated feed, and half of the birds were sacrificed on Day 8 of the trial. The remaining birds were maintained for an additional two weeks prior to being euthanized on Day 22 of the trial. Birds were assessed for growth, rate of feed consumption, behavior, physical injury, mortality, and gross abnormalities. Liver weight and concentrations of PFOS in blood serum and liver were also assessed. Based on the average daily intake (ADI) of PFOS calculated over the 5-day exposure period, the LD₅₀ for juvenile mallards was determined to be 150 mg PFOS/kg body weight (bw)/day, equivalent to a total cumulative dose of 750 mg PFOS/kg bw calculated over a 5-day period. For juvenile quail, the LD₅₀ based on the ADI was 61 mg PFOS/kg bw/day, equivalent to a total cumulative dose of 305 mg PFOS/kg bw. Reductions in weight gain and body weight were observed in quail from the 141 mg PFOS/kg treatment, but these measures returned to control levels by Day 22. The no-mortality dietary treatments were 70.3 and 141 mg PFOS/kg feed for quail and mallards, respectively. Both mallards and quail accumulated PFOS in blood serum and liver in a dose-dependent manner. The half-lives of PFOS in mallard blood serum and liver were estimated to be 6.86 and 17.5 days, respectively. In quail, the half-life of PFOS in liver was estimated to be 12.8 days, while the half-life of PFOS in quail blood serum could not be estimated. Concentrations of PFOS in juvenile mallard and quail liver associated with mortality are at least 50-fold greater than the single maximum PFOS concentration that has been measured in livers of avian wildlife.     

Transfer of Perfluorooctanoic Acid (PFOA) and Perfluorooctane Sulfonate (PFOS) From Contaminated Feed Into Milk and Meat of Sheep: Pilot Study

A pilot study was performed with dairy sheep to generate the first data on the transfer of perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) from feed into food of animal origin. Corn silage was cultivated on cropland in Lower Saxony in Germany where, as a result of illegal waste disposal in 2006, farmland was contaminated with perfluorinated alkylacids (PFAAs). Two sheep were exposed by way of PFAA-contaminated corn silage to PFOS (1.16 and 1.45 μg/kg body weight [bw]/d, respectively) and PFOA (0.43 and 0.53 μg/kg bw/d) during a period of 21 days. During the PFAA-feeding period, PFOS levels in plasma increased continuously to maximum concentration of 103 and 240 μg/L for sheep 1 and sheep 2, respectively. The PFOA plasma concentration remained low (sheep 1 = 3.3 ± 2.2 μg/L; sheep 2 = 15.6 ± 8.3 μg/L). Data indicate that urinary excretion is the primary clearance route for PFOA (sheep 1 = 51 %; sheep 2 = 55 %), whereas PFOS excretion by way of urine could not be quantified. The highest PFOS excretion (4 to 5 %) was detected in faeces. PFOS was also excreted at higher levels than PFOA by way of milk. During a period of 21 days, a total PFOS transfer into milk ≤ 2 % was calculated. Overall, total excretion of PFOS was significantly lower compared with that of PFOA (PFOS 6 %; PFOA 53 to 56 %). PFOS levels in sheep 1 and sheep 2 were highest in liver (885 and 1,172 μg/kg weight wet [ww], respectively) and lowest in muscle tissue (24.4 and 35.1 μg/kg ww, respectively). PFOA levels in muscle tissue were low for sheep 2 (0.23 μg/kg ww) and not detectable after the PFAA-free feeding period in sheep 1. A slight background load of PFOS in liver (1.5 μg/kg ww) and kidney (0.3 μg/kg ww) was detected in sheep 3 (control).     

Magnesium proteinate is more protective than magnesium oxide in heat-stressed quail

We evaluated the effects of dietary supplementation with Mg-oxide and Mg-proteinate on performance; nutrient digestibilities; malondialdehyde (MDA) concentrations in serum, liver, and thigh meat; and serum cholesterol and triacylglycerol concentrations in Japanese quail (Coturnix coturnix japonica) exposed to high ambient temperature. The birds (n = 360; 10 d old) were randomly assigned to 12 treatment groups consisting of 6 replicates of 5 birds each in a 2 x 2 x 3 factorial arrangement (temperature, Mg source, Mg level). Birds were maintained in temperature-controlled rooms at 22 degrees C for 24 h/d or 34 degrees C for 8 h/d (0900-1700 h) and fed a basal diet or that diet supplemented with 1 or 2 g Mg-oxide or Mg-proteinate/kg of diet. Heat exposure decreased (P = 0.0001) live weight gain, feed intake, feed efficiency, and carcass weight in quail fed the basal diet. A linear increase in feed intake (P = 0.008) and body weight (P = 0.001), and improvements in feed efficiency (P = 0.001), carcass weight (P < 0.0001), digestibility of dry matter, organic matter, crude protein, and ether extract were found in Mg-supplemented, heat-stressed quail. The effects of Mg-proteinate were greater than those of Mg-oxide (P < or = 0.0001). Serum Mg (P = 0.001) concentration increased, whereas the concentration of MDA in serum (P = 0.0001), liver (P = 0.04), and thigh meat (P = 0.0001) and serum triglyceride and cholesterol concentrations decreased linearly (P = 0.001) with the level of Mg in the diet. Interactions between dietary Mg source, temperature, and level of supplementation (P < or = 0.05) were found for several variables. Results of the present study suggest that supplementation with Mg-proteinate is more protective than Mg-oxide in reducing the negative effects of heat stress in quail.     

Mallard reproductive testing in a pond environment: A preliminary study

A 2-year preliminary study was conducted on mallard ducks (Anas platyrhynchos), to determine the feasibility of using outdoor pond enclosures for reproductive studies and to evaluate the effects of the insecticide chlorpyrifos on mallard reproduction. No significant reproductive effects were observed for mallards receiving 8 ppm (mg/kg of feed) chlorpyrifos in their diet. Birds receiving 80 ppm chlorpyrifos hatched significantly (p < 0.05) fewer ducklings per successful nest (5.8) than controls (10.2). None of the ducklings on treatment ponds survived to 7 days. Control birds produced 8.4 ducklings per successful nest surviving to 7 days or longer. Birds in the 80 ppm treatment group consumed less feed than did controls (p < 0.01). Weight loss from reduced feed consumption did not occur to the extent expected, indicating that birds supplemented their diets with natural foods found in and around the ponds. In spite of relatively low treated feed consumption, brain acetylcholinesterase was significantly (p < 0.05) depressed (57% of controls) for 80 ppm treated birds. Studies on indoor penned mallards fed 80 ppm chlorpyrifos in their diet also resulted in acetylcholinesterase depression to the same extent, but at much higher feed consumption levels. The study demonstrated the potential of using outdoor pond enclosures to evaluate chemical effects on food consumption, brain acetylcholinesterase, and reproduction in mallards. Improvements to the study design and to the pond enclosures are discussed.     

Chromium Geochemistry and Bioaccumulation in Sediments from the Lower Hackensack River, New Jersey

Total and hexavalent chromium [Cr(VI)] were measured in sediment and sediment porewater in the lower Hackensack River (NJ) to assess the relationship between sediment geochemistry and chromium speciation, which in turn controls the mobility, bioavailability, and toxicity of chromium. Between 2003 and 2005, >100 surface (0 to 15 cm) sediment samples were tested for total chromium and Cr(VI), acid-volatile sulfides (AVS), ferrous iron (Fe(II)), divalent manganese (Mn(II)), ammonia, and organic carbon. Sediment porewater samples were collected by centrifugation or using in situ samplers colocated with the collection of sediments. In whole sediments, total chromium and Cr(VI) concentrations ranged from 5 to 9190 mg/kg dry weight (dw) and from <0.47 to 31 mg/kg dw, respectively. Sediment porewater concentrations ranged from <10 to 83 μg/l for total chromium; Cr(VI) was not detected in sediment porewater (n = 78). Concentrations of AVS (ranging between <10.6 to 4178 mg/kg) and other geochemistry measurements indicated anoxic, reducing conditions in the majority of sediment samples. In polychaetes (Nereis virens) and clams (Macoma nasuta) exposed in the laboratory for 28 days to sediments contained between 135 and 1780 mg/kg dw total chromium, concentrations in whole tissues after 24-hour depuration ranged between 1.2 and 14.8 mg/kg wet weight (ww; median 1.6 mg/kg ww) total chromium. In whole tissues of indigenous polychaetes collected from the sediment, tissue concentrations of total chromium ranged between 1.0 and 37.5 mg/kg ww (median = 2.1 mg/kg ww). Chromium concentrations in whole tissues of animals exposed in the field or in the laboratory showed no relationship with total chromium or Cr(VI) concentrations in the sediment. There were no statistical differences among animals exposed to sediments from site and reference locations. The results of this study are consistent with sediment studies conducted elsewhere indicating low chromium bioavailability in sediment under reducing conditions. This study also highlights the importance of sediment geochemistry and in situ porewater measurements to understand the ecological significance of chromium in sediment and the potential for human health and ecological exposures.     

Chromium supplementation can alleviate negative effects of heat stress on egg production,egg quality and some serum metabolites of laying Japanese quail

This study was conducted to determine the effects of Cr (chromium picolinate, CrPic) supplementation at various levels (0, 200, 400, 800 or 1200 microg/kg of diet) on egg production, egg quality and serum concentrations of insulin, corticosterone and glucose in laying Japanese quail (Coturnix coturnix japanica) reared under conditions of heat stress (32.5 degrees C). Laying Japanese quail (n = 150; 45 d old) were divided into five groups of 30 birds. The quail were fed either a control diet containing 965 microg Cr/kg diet or the control diet supplemented with 200, 400, 800 or 1200 microg of Cr/kg diet. Increased supplemental chromium increased body weight (P = 0.05, linear), feed intake (P = 0.05, linear), egg production (P = 0.01, linear) and also improved feed efficiency (P = 0.01, linear). Increased supplemental chromium linearly increased egg weight (P = 0.01), eggshell thickness, egg specific gravity (P = 0.05) and Haugh unit (P = 0.01). Serum insulin concentration increased linearly (P = 0.01), whereas corticosterone and glucose concentration decreased linearly (P = 0.05) as dietary chromium increased. The best results were obtained with 1200 microg Cr/kg diet, and chromium supplementation at such a level can be considered to be protective management practice in a quail diet, reducing the negative effects of heat stress.     

Organ Distribution and Food Safety Aspects of Cadmium and Lead in Great Scallops, Pecten maximus L., and Horse Mussels, Modiolus modiolus L., from Norwegian Waters

The purpose of the study was to determine the levels and organ distribution of the potentially harmful inorganic elements cadmium and lead in great scallops and horse mussels from unpolluted Norwegian waters. The scallops far exceeded the EU-limit for cadmium in bivalves when all soft tissues were analysed. When only muscle and gonad were included, however, the level of cadmium was acceptable, because cadmium accumulated in the digestive gland with a mean of 52 mg/kg ww (wet weight). In horse mussel, lead was the most problematic element and the concentration varied from 1.4 to 6.6 mg/kg ww with a mean of 3.7 mg/kg ww, exceeding the EU limit of 1.5 mg Pb/kg. The highest concentration of lead was found in the kidney with an average of 120 mg/kg ww and with a maximum value of 240 mg/kg ww. The kidney tissue accounted for approximately 94% of the lead burden in the horse mussel. In order to consume these bivalves, only muscle and gonad of great scallops should be used for consumption and the kidney of horse mussel should be removed prior to consumption.     

Effects of methylmercury on reproduction in American kestrels

Sixty breeding pairs of captive American kestrels (Falco sparverius) were exposed to a range of sublethal dietary concentrations of mercury (Hg), in the form of methylmercuric chloride, and their subsequent reproduction was measured. Egg production, incubation performance, and the number and percent of eggs hatched decreased markedly between 3.3 and 4.6 mg/kg dry weight of Hg (1.2 and 1.7 mg/kg wet wt), in the diet. The number of fledglings and the percent of nestlings fledged were reduced markedly at 0.7 mg/kg dry weight (0.3 mg/kg wet wt) and declined further between 2 and 3.3 mg/kg dry weight (0.7 and 1.2 mg/kg wet wt). Dietary concentrations of >or=4.6 mg/kg dry weight (1.7 mg/kg wet wt) were associated with total fledging failure. The estimated decline in fledged young per pair (24%, Bayesian regression) for kestrels consuming 0.7 mg/kg dry weight (0.3 mg/ kg wet wt) raises concerns about population maintenance in areas subject to high inputs of anthropogenic Hg. Mercury concentrations in 20 second-laid eggs collected from all groups were related to dietary concentrations of Hg, and the Hg concentrations in 19 of these eggs were related to eggs laid and young fledged. Concentrations of Hg in eggs from the highest diet group (5.9 mg/kg dry wt; 2.2 mg/kg wet wt) were higher than egg concentrations reported for either wild birds or for captive birds (nonraptors) fed dry commercial food containing 5 mg/kg methylmercury. Accumulation ratios of Hg from diets to eggs were higher than those reported for feeding studies with other species.     

Alkaline Digestion and Solid Phase Extraction Method for Perfluorinated Compounds in Mussels and Oysters from South China and Japan

Perfluorinated compounds (PFCs), such as perfluorooctane sulfonate (PFOS), have been identified in the coastal waters of China and Japan. An alkaline digestion method, coupled with solid-phase extraction (SPE), and high-performance liquid chromatography interfaced with high-resolution electrospray tandem mass spectrometry was developed to determine PFCs in mussel and oyster samples from coastal waters of south China and Japan. These techniques produced adequate recoveries and reporting limits with small quantities of PFCs. Concentrations of individual PFCs in mussels and oysters from south China and Japan ranged from 113.6 to 586.0 pg/g, wet weight (ww) for PFOS, 63.1 to 511.6 pg/g, ww for perfluorohexane sulfonate, 9.3 to 30.1 pg/g, ww for perfluorobutane sulfonate and 37.8 to 2957.0 pg/g, ww for perfluorooctane sulfonamide. The quantification of perfluorinated carboxylates was compromised by interferences from carboxylates in the procedural blanks. Perfluoroundecanoate and perfluorononanoate had relatively great blank interferences, which resulted in relatively poor limits of quantification for these compounds. Some PFCs were only identified in a limited number of samples: perfluorododecanoate in samples from Tokyo Bay, Japan (195.9 pg/g, ww); and perfluorodecanoate in Fuzhou, China (131.7 pg/g, ww) and Tokyo Bay (118.6 pg/g, ww). The greatest concentrations of perfluorooctanoate, perfluoroheptanoate, and perfluorohexanoate were observed in samples from Tokyo Bay and Bei Hai, south China.     

Effects of Vinclozolin on Spermatogenesis and Reproductive Success in the Japanese Quail (<Emphasis Type="Italic">Coturnix coturnix japonica</Emphasis>)

In a one-generation reproduction study, the major agricultural fungicide vinclozolin was administered to adult Japanese quail for a period of 6 weeks at dietary levels of 125 and 500 ppm. Fertility and reproductive performance were not affected up to the highest concentration, although the examination of additional endpoints in the drakes (spermatid count, histology of the testis) provided some evidence of an inhibition of spermatogenesis at both dietary concentrations. Likewise, there were no indications of systemic toxicity in the adult birds. Plasma hormone concentrations (estradiol, testosterone, progesterone, T3, and T4) showed a large interindividual variance but treatment-related differences between the groups could not be established. There were no clear-cut indications of antiandrogenic effects in quail, although a limited transfer of the test substance into the eggs was proven.     

Immunocompetence of juvenile chinook salmon against Listonella anguillarum following dietary exposure to polycyclic aromatic hydrocarbons

Juvenile chinook salmon (Oncorhynchus tschawytscha) were fed a mixture of 14 polycyclic aromatic hydrocarbon (PAH) compounds that reflected the PAH composition of salmon stomach contents in an urban estuary of Puget Sound, Washington (USA). Following a 28-d dietary exposure, a standardized Listonella anguillarum challenge model was used to determine whether PAH exposure (16, 64, and 252 mg/kg wet wt feed) causes reduced disease resistance under the conditions examined in this study. To assess innate immunity, five replicate groups of fish per dose were acclimated for one week, exposed to a lethal concentration 60 of bacteria, and monitored for 14 d. In a parallel experiment, the effects of PAH exposure on the acquired immune response were examined by immersion vaccinating fish against L. anguillarum and allowing specific immunity to develop for three weeks prior to challenge. All mortalities were aseptically sampled to confirm L. anguillarum infections. No significant differences in fish length, weight, or coefficient of condition were observed. These controlled laboratory experiments suggest that dietary exposures to an environmentally relevant mixture of PAH compounds do not alter the immunocompetence or growth of juvenile chinook salmon.     

Risk assessment of the organophosphate pesticides isazofos and pyraclofos using a 21-day dietary toxicity study in Japanese quail

Six-week-old male and female Japanese quails (Coturnix japonica) received two organophosphate pesticides, isazofos and pyraclofos, for a 21-day dietary toxicity test, based on the OECD workshop report. During the treatment period, body weight and food consumption of the quail decreased with exposure to either isazofos or pyraclofos. Using the up-and-down procedure to determine the 50% mortality value, we found that the 21-day LC(50) of isazofos and pyraclofos were 40 and 87 mg/kg body weight, respectively. Ataxia, salivation, diarrhea, ruffled feathers, and convulsions at a dead point were observed with both pesticides. The tips of the villi were necrotic in the high dosage groups of isazofos- and pyraclofos-treated quail. Based on these results, body weight, food consumption, clinical signs, and histopathological findings may be useful parameters for detecting the dietary toxicity associated with isazofos and pyraclofos exposure. In addition, Japanese quail could be an excellent bird model for monitoring the toxicological risks of pesticides in Korea.     

Hematology and serum biochemistry of Japanese quail fed dietary tri-n-butyltin oxide during reproduction

During a subchronic toxicity and reproduction study with tri-n-butyltin oxide (TBTO) concentrations of 0, 24, 60, and 150 mg/kg diet in Japanese quail, preliminary data on hematology and serum biochemistry were obtained. The absence of serious effects in blood parameters in both adult quail and developing chicks are discussed in view of the adverse effects of TBTO on reproduction.     

Swallows as Indicators of Environmental Pollution of the Rio Grande/Rio Bravo Basin: Are Persistent Organic Pollutants a Concern?

Swallows from two locations in the Rio Grande/Rio Bravo Basin and one reference site located 500 km away were analyzed for organochlorine pesticides (OCs), polychlorinated biphenyls (PCBs), and polybrominated diphenyl ethers (PBDEs). Of the OC pesticides, only p,p′-DDE was observed at levels of concern (carcass geometric mean range 642 to 8511 ng/g wet weight [ww]). DDE residues in carcass were significantly greater at El Paso than at other locations. PCBs were relatively low compared with locations in the northeastern United States and the Great Lakes. Geometric mean PBDE concentrations ranged from 18 to 258 ng/g ww (280 to 3395 ng/g lipid weight). PBDE congeners 47 and 99 comprised approximately 60% of total PBDEs. Concentrations of DDE measured in swallows from El Paso in 2000 and 2005 are among the highest observed in the last 20 years along the United States–Mexico border. The results from this study indicated that swallows are still being exposed to high concentrations of DDE, which could have adverse effects on reproduction or on predators that feed on swallows.     

The Effects of Sub-lethal Dietary Mercury on Growth Performance,Bioaccumulation, and Activities of Antioxidant Enzymes in Sea Cucumber, <Emphasis Type="Italic">Apostichopus japonicus</Emphasis>

Triplicate groups of sea cucumbers (4.83?±?0.15 g) were exposed to one of the four nominal concentrations of dietary mercury [0 (control), 67.6, 338, and 676 mg/kg dry weight, and actually total mercury were 17.55, 87.00, 275.50, 468.50 mg/kg, respectively; Table 3] for 21 days. Mercury accumulation in the intestine showed the greatest mercury burden (77.96?±?1.20 mg Hg/kg tissue wet weight basis). However, survival rate (SR) was not affected. Body weight gain after the 676 mg Hg/kg treatment was significantly lower than the control group. The feed conversion rate of the 676 mg Hg/kg treatment group was significantly higher than the control group. Additionally, the superoxide dismutase (SOD) and total antioxidant capacity (T-AOC) of sea cucumbers decreased as the mercury dose increased. SOD, T-AOC and alkaline phosphatase of the 676 mg Hg/kg treatment group were significantly lower than the control group. However, there were no significant differences between the four groups in acid phosphatase and catalase (CAT) activity.     

Dietary oral exposure to l,3,5-trinitro-1,3,5-triazine in the northern bobwhite (Colinus virginianus)

The potential risk to wildlife from exposure to explosives, including 1,3,5-trinitro-1,3,5-triazine (RDX), has been an issue at numerous U.S. military installations where these substances are found in soil and water. Presently, no data describing the effects of RDX exposure in avian species exist. Therefore, an acute lethal dose (ALD) and 14- and 90-d subchronic dietary exposures to RDX were evaluated in a species potentially present at many contaminated sites, i.e., the northern bobwhite (Colinus virginianus). The ALDs for females and males were 187 and 280 mg/kg, respectively. Data from the 14-d dietary trial suggested that RDX exposure inhibited food consumption, weight gain, and egg production. Dietary RDX exposure for 90-d produced a dose-dependant decreasing trend in total feed consumption, total egg production, and hen-housed production parameters. These collective data suggest that quail may respond differently to oral RDX exposure compared with mammals.     

Effects of megadoses of dietary vitamin E on the antioxidant status of rats fed lard or salmon oil

This study was undertaken to investigate whether megadoses of vitamin E in the diet of rats can have pro-oxidative activity. Two experiments with rats were conducted in which both the dietary vitamin E concentration (Experiment 1: 100; 500; 3000; 10,000 mg all-rac-alpha-tocopheryl acetate/kg, and Experiment 2: 100; 1000; 10,000 mg all-rac-alpha-tocopheryl acetate/kg) and the type of dietary fat (lard vs. salmon oil) were varied. Experimental parameters were the concentrations of thiobarbituric acid-reactive substances, 7 beta-hydroxycholesterol, the activities of several antioxidative enzymes, the concentration of glutathione in the liver, and the lag time during copper-induced low-density lipoprotein (LDL) oxidation. Increasing the dietary vitamin E concentration to 10,000 mg all-rac-alpha-tocopheryl acetate/kg led to a significant reduction of thiobarbituric acid-reactive substances in the liver after feeding salmon oil, and also to a significant reduction in 7 beta-hydroxycholesterol after feeding both dietary fats. Megadoses of vitamin E (3000 and 10,000 mg all-rac-alpha-tocopheryl acetate/kg) also led to a reduction in the activity of superoxide dismutase and the concentration of glutathione in the liver of rats fed salmon oil. The lag time during LDL oxidation was independent of the dietary vitamin E concentration. The study shows that megadoses of vitamin E, far from having pro-oxidative activity, actually increase the anti-oxidative capacity of the liver, especially after ingestion of salmon oil.     

Studies on the nutrition of marine flatfish. The thiamin requirement of turbot (Scophthalmus maximus).

1. Seven groups of young turbot (Scophthalmus maximus) were given diets containing graded levels of thiamin (0-19--50 mg/kg) for 16 weeks and their growth rate was measured during this period. 2. Good growth was obtained on all these treatments except in the group given the lowest dietary thiamin level (0-19 mg/kg). These fish grew normally until the 12th week but thereafter their weight did not increase. 3. Measurements of erythrocyte transketolase (sedoheptulose-7-phosphate: D-glyceraldehyde-3-phosphate glycolaldehydetransferase; EC 2.2.1.1) activity at the end of the experiment and of percentage stimulation of erythrocyte transketolase by thiamin pyrophosphate indicated that the apoenzyme was saturated with coenzyme at a dietary thiamin level of 2-6 mg/kg, but not at 1-1 mg/kg. 4. An 8th group of turbot given the thiamin antagonist pyrithiamin (40 mg/kg diet) grew normally for 6 weeks. Thereafter mortalities began to occur and all fish died by the 10th week. No clear-cut signs of thiamin deficiency were observed. 5. The dietary thiamin requirement of turbot is much lower than published requirements of freshwater fish other than carp (Cyprinus carpio) and appears to be between 0-6 and 2-6 mg/kg diet.     

Effects of fentin hydroxide on reproduction of the Japanese quail (Coturnix coturnix japonica)

In a one-generation reproductive study, the fungicidal compound triphenyltin hydroxide (fentin) was administered to adult Japanese quail for 6 weeks at dietary levels of 3 and 30 ppm. Reproduction was significantly impaired in the high-dose group. The principal adverse finding was a marked increase in embryonic mortality, resulting in a lower hatch rate. Furthermore, a reduction in egg production was observed with ongoing duration of treatment. Most of the other reproduction-related parameters were not affected. The in ovo losses are assumed to result from a direct toxic effect of the test substance on chick embryos. At the low dietary level, reproduction was not altered. In contrast to the obvious reproductive toxicity, there was only limited evidence of adverse treatment-related findings in the adult birds. However, because such minor effects as an increase in mean liver weight, which was accompanied by macroscopic liver findings and a decrease in T4 serum concentration, were still seen at 3 ppm, a no-observed-effect level could not be established.     

Dietary supplementation with zinc oxide increases Igf-I and Igf-I receptor gene expression in the small intestine of weanling piglets

This study was conducted to investigate the mechanism for the effect of elevated levels of dietary zinc oxide (ZnO) in enhancing the intestinal growth of weanling piglets. In Experiment 1, 4-wk-old (8.1 +/- 0.6 kg) crossbred barrows (n = 36) were assigned randomly to 1 of the 2 dietary groups, with 6 pens/group (3 pigs/pen). One group was fed the basal diet containing 100 mg Zn/kg diet. The other group was fed the basal diet supplemented with ZnO to provide 3000 mg Zn/kg diet. Pigs consumed their feed ad libitum for 14 d. In Experiment 2, 4-wk-old (7.6 +/- 0.16 kg) crossbred barrows (n = 16) were housed individually and assigned to 1 of the 2 dietary groups (8 pigs/group) as in Experiment 1, except that the 2 groups were pair-fed the same amount of feed. At the end of a 14-d treatment period, all of the pigs in both Experiments 1 and 2 were weighed, feed consumption was measured, and blood samples were collected for assays of insulin-like growth factor-I (IGF-I). In addition, 1 pig from each pen in Experiments 1 and 2 was selected randomly to obtain the small-intestinal mucosa for analyzing IGF-I and IGF-I receptor (IGF-IR) gene expression and to determine the small-intestinal morphology. In Experiment 1, dietary supplementation of ZnO increased (P < 0.05) the daily body weight gain and daily feed intake. In Experiment 2, dietary supplementation of ZnO increased (P < 0.05) the daily body weight gain and feed conversion efficiency. In both experiments, the villous height of the small-intestinal mucosa and both the mRNA and protein levels for IGF-I and IGF-IR in the small intestine were markedly enhanced (P < 0.05) by feeding elevated levels of Zn. Serum IGF-I levels did not differ between the control and Zn-supplemental groups in either experiment. Collectively, these results suggest that dietary Zn supplementation exerts its beneficial effects on the intestinal growth of weanling piglets through increasing IGF-I and IGF-IR expression in the small-intestinal mucosa.