No abstract

We conducted a 30-day acute toxicity test of zinc (Zn) shot using 6- to 8-month-old wild-type game-farm Mallards (Anas platyrhynchos), 40 of which (20 males and 20 females) were dosed with 6 No. 4 candidate shot pellets containing 98% Zn and 2% tin (Sn); the remaining 40 ducks were dosed with 6 No. 4 steel (Fe) shot and served as controls. The Zn shot resulted in high mortality, with a greater proportion of females dying than males. For the 30-day study, survival averaged 18 and 23 days for female and male Zn-dosed ducks, respectively; all Fe-dosed ducks survived to Day 30. Ataxia/paresis and other signs of intoxication were noted in a large portion of Zn-dosed ducks. For all ducks retaining 6 shot pellets, including those that survived < 30 days, shot retention, percent of the original shot weight dissolved, and dissolution rates were similar for Zn- and Fe-dosed ducks. For those ducks that retained 6 pellets and survived to Day 30, percent loss of the original shot weight and the dissolution rate were higher in Zn-dosed ducks. Mean body weight in Zn-dosed ducks decreased between Days and 15, and between Days 15 and 30 in Zn-dosed females. Zn-intoxicated ducks lost a considerable proportion of their body weight between dosing and death. The kidneys of Zn-dosed ducks as a group were heavier, and the pancreases, livers, and gizzards lighter, as compared with Fe-dosed ducks. The liver (males) and kidneys of Zn-dosed ducks that died as a result of Zn intoxication were heavier, whereas thegonads (females) and gizzards were lighter, as compared with those that survived. The liver, pancreas, and kidneys increased, whereas the gonads (males) and gizzards decreased, as a proportion of total body weight in Zn-dosed ducks that died prior to Day 30. Mean packed cell volume (PCV) decreased between Days and 15 and increased between Days 15 and 30 in male and female Zn-dosed ducks. PCV values changed little in Fe-dosed ducks over the course of the study; however, PCV decreased dramatically in Zn-intoxicated ducks. A variety of gross lesions was observed, most often associated with the gastrointestinal tract. Grossly, cecal lesions were the most consistent and dramatic changes observed. No macroscopic lesions were observed in the Fe-dosed ducks, and histologic lesions in this group were considered within normal limits for game-farm ducks. Histologic lesions observed in Zn-dosed Mallards most often included pancreatic apoptosis, splenic lymphoid depletion and/or lympholysis, necrohemorrhagic typhlitis, and necrosis of the epithelial cells of the renal tubules. We detected high concentrations of Zn, and alterations in levels of other elements, in the tissues of Zn-dosed ducks relative to Fe-dosed controls. Mean Zn concentrations were greater in Zn-dosed ducks for all tissues examined, and levels in the kidneys, livers, and pancreases of Zn-intoxicated Mallards were similar to levels associated with toxic effects reported in other studies. Mean tissue tin (Sn) concentrations were below the Method Detection Limit (MDL) in all cases; few individual Sn values were above MDLs. Changes in tissue element concentrations tended to be more dramatic in ducks that died as a result of Zn intoxication than in Zn-dosed ducks that survived the experiment. Gender differences in analyte concentrations were detected for some tissues. These results indicated that dosing of 6- to 8-month-old game-farm Mallards with 6 No. 4 shot comprised of 98% Zn and 2% Sn produced toxic effects under the test conditions.

In a 30-day study involving penned game-farm mallards (Anas platyrhynchos), no harmful health effects were detected from dosing with either six, No. 4, bismuth/tin (Bi/Sn) alloy shot or six, No. 4, steel (Fe) shot, as compared with sham (0 shot) dosing. Survival, hematocrit (Hct) values, body weight, and mean weights of kidneys, livers, gonads, and gizzards were not affected. Mean concentrations of nutritionally essential elements (calcium [Ca], phosphorous [P], magnesium [Mg], zinc [Zn], copper [Cu], Fe, and Sn) were different among doses and between sexes in kidneys, livers, and gonads. However, concentrations of these elements in these organs and tissues in Bi-dosed ducks were not different from both 0- and Fe-dosed ducks. Bi/Sn alloy shot, as tested in this study, elicited no indications of toxicity in game-farm mallard ducks.

Six- to eight-month-old female farm-raised mallards (Anas platyrhynchos) were used to examine the accumulation of and association among cadmium (Cd), zinc (Zn), and copper (Cu) from an impoundment constructed to contain sediments dredged from a lake contaminated by a zinc smelter. Cd was not detectable in the livers t of farm-raised mallards (day 0), although sentinel mallards accumulated hepatic Cd in the first 7 days after release. By day 14, mean concentrations of Cd in kidneys (= 2.82 mg/kg wet weight) had increased 3.4-fold. The mean pancreatic Cd concentration increased 59% between days 7 and 14. Renal Zn increased nominally, whereas pancreatic Zn increased 63% in sentinel ducks after release. Hepatic Zn increased significantly in the first week of release. Renal and pancreatic Cu concentrations did not change significantly, whereas concentrations of Cu in livers of ducks increased 50% in the 7 days after release before decreasing by nearly the same degree. Concentrations of Cd and Zn were correlated in livers of sentinel mallards on days 7 and 14. Cd and Cu were not correlated in the tissues of any cohort. Cu and Zn were correlated in the livers of farm-raised mallards, in the pancreases of sentinel mallards at day 7, and in the kidneys of the ducks in all three treatments. The relationship between Cd and Zn in tissues of ducks in our study was complicated by simultaneous exposure to increased and heterogeneous concentrations of Cd and Zn, both of which can induce metallothionein and compete for this and other ligands.

Effects of five lead (Pb), iron (Fe), or bismuth (Bi)/tin (Sn) alloy shot embedded in the breast muscles of game-farm mallards (Anas platyrhynchos) were studied from 28 March 1994 through 27 March 1995. We detected no differences in the mean survival times, mean hematocrits, or mean body weights among the three shot types. Connective tissue encapsulated Pb and Bi/Sn shot but only slight changes occurred in tissues surrounding the shot. Recovered Pb and Bi/Sn shot were essentially unchanged in appearance and weight. A thin zone of "oxide" surrounded Fe shot with a slight inflammatory response and a small amount of scarring adjacent to the embedded shot. Fe shot decreased slightly in weight while embedded. Bacterial infections were absent in all dosed ducks. Mean weights of kidneys, livers, and gonads did not vary by type of shot. Kidneys and livers of Bi-dosed ducks had higher concentrations of Bi than in Pb- and Fe-dosed ducks. Muscle and blood showed no differences in Bi concentrations among doses. We found no histological dose-related effects in kidneys, liver, and gonads from the embedded shot.