Effect of method of delivering nicarbazin to mallards on plasma 4,4'-dinitrocarbanilide levels and reproduction.

Nicarbazin (NCZ), a coccidiostat used in the poultry industry, has been developed as a contraceptive for resident Canada geese. We tested the efficacy of NCZ as a contraceptive using mallards (Anas platyrhynchos) as a model for Canada geese. Nicarbazin-treated corn was fed ad libitum for 14 d at 0, 750, 1,000, or 1,500 ppm. Plasma and egg levels of 4,4'-dinitrocarbanilide (DNC), the active anticoccidial component of NCZ, differed among treatment groups in a dose-response relationship, but plasma levels did not differ between sexes. Nicarbazin caused a decrease in egg weight, but there was no effect of NCZ on the numbers of eggs laid per female per day. Nicarbazin did not significantly impact bird health. An additional trial tested the effect of the method of NCZ delivery on plasma DNC levels. Mallards were given NCZ daily for 12 d either by gavage with a corn oil suspension, gavage with a water suspension, peroral administration of a capsule, or feeding 500 mg of NCZ/kg of pelleted feed ad libitum. The method of delivery significantly affected plasma DNC levels, with the highest levels in the corn oil suspension group and the lowest levels in the pelleted feed group. This is likely due to decreased availability of NCZ in a pellet compared with gavage with a suspension or capsule. Mallards receiving 34.2 mg of NCZ/kg of BW when fed cracked corn coated with NCZ daily for 14 d had higher plasma DNC levels than those obtained by liquid gavage, capsule, or pelleted NCZ feed. For maximum effect in the field, NCZ should be coated onto corn. A higher concentration of NCZ is needed in pelleted feed to obtain comparable plasma DNC levels to allow for the decreased absorption of DNC.

Evaluation of nicarbazin as a potential waterfowl contraceptive using mallards as a model.

Contraception may provide a useful nonlethal management tool to reduce wild bird populations. We tested the efficacy of nicarbazin (NCZ) as a contraceptive for waterfowl and assessed health effects of NCZ, using domestic mallards (Anas platyrhynchos) as a model for Canada geese (Branta canadensis). Mallards were given gelatin capsules containing 0, 8.5, 17.0, or 33.75 mg of NCZ/kg of BW perorally once daily for 14 d. Fecal 4,4'-dinitrocarbanilide (DNC) and fluorescein were evaluated as potential markers of plasma and egg DNC levels. Plasma, egg, and fecal DNC levels differed among treatment groups in a dose response relationship. There were no significant effects on the numbers of eggs laid per female per day, proportion of fertile eggs, proportion of eggs hatching, or egg yolk mottling. Hatchability was 0.55 +/- 0.1 in the control group compared with 0.26 +/- 0.1 in the 33.75 mg/kg of BW group. Degeneration of the vitelline membrane was evident at all treatment levels; severity was dose-related and greater in the outer vitelline membrane than the inner vitelline membrane. No significant health effects were observed for birds treated with NCZ. The heterophil:lymphocyte ratio was elevated during the treatment and posttreatment periods in all groups, indicating birds were experiencing stress due to handling. Fecal DNC levels did not correlate well with plasma DNC levels, likely due to NCZ being administered as a bolus dose rather than being fed ad libitum. Fluorescein correlated well with plasma DNC levels during the treatment period and can therefore be used successfully as a noninvasive marker to determine the approximate amount of NCZ a bird is consuming. As a contraceptive, NCZ likely would have minimal adverse health effects on the target animal, although field studies with the species of interest need to be conducted. Further research using higher NCZ levels needs to be conducted to determine whether NCZ can inhibit reproduction in waterfowl.

Comparison of nicarbazin absorption in chickens, mallards, and Canada geese.

Nicarbazin (NCZ), a coccidiostat commonly used in the poultry industry, causes reduced hatchability and egg quality in layer hens at a concentration of 125 ppm (8.4 mg/kg) in the feed. Although this effect is undesirable in the poultry industry, NCZ could provide a useful wildlife contraception tool for waterfowl, particularly urban geese. We tested the absorption of NCZ in chickens (Gallus gallus), mallards (Anas platyrhynchos), and Canada geese (Branta canadensis) gavaged with 8.4 mg of NCZ/kg per bird each day for 8 d. Plasma levels of 4,4'-dinitrocarbanilide (DNC) differed significantly among species. Peak plasma DNC levels were 2.87 +/- 0.15 microg/mL, 2.39 +/- 0.15 microg/mL, and 1.53 +/- 0.15 microg/ mL in chickens, mallards, and Canada geese respectively. It took 6 d to obtain peak DNC levels in chickens as opposed to 8 d in mallards and Canada geese. The half life of DNC in plasma was 1.43 d in chickens, 0.72 d in mallards, and 1.26 d in Canada geese. Mallards eliminated 100% of plasma DNC 4 d post-treatment, whereas Canada geese eliminated 100% of plasma DNC 8 d post-treatment. Chickens had only eliminated 99% of plasma DNC 8 d post-treatment. Mallard plasma DNC levels were highly correlated with Canada goose plasma DNC levels. This research showed mallards are an ideal model species for the Canada goose for future reproductive studies on NCZ in a laboratory setting. However, levels higher than 8.4 mg/kg must be fed to waterfowl in order to obtain a plasma level comparable to chickens.

Porcine zona pellucida (PZP) immunocontraception of wild horses (Equus caballus) in Nevada: a 10 year study.

Porcine zona pellucida (PZP) immunocontraception was investigated for possible use in free-roaming wild horses in the western USA. A protocol of two injections (3-4 weeks apart) of vaccine lasting 1 year was first used and a single-injection controlled-release vaccine of 1 year duration was developed and tested in the field. Studies of a presumptive vaccine of 2 year duration were initiated. The parameters of anti-PZP antibody titre response, pregnancy testing and offspring production were used, and PZP vaccine was found to provide up to 94% infertility in free-roaming wild mares. In addition, a single-injection PZP vaccine of 1 year duration and containing a controlled-release component of PZP in a polymer matrix can provide infertility equivalent to the two-injection PZP vaccine. All the PZP vaccine preparations tested were associated with a return to normal fertility within 1 year. During the course of these studies, attention was given to practical aspects of management application of PZP contraception. Preparation of the controlled-release portion of the vaccine in pellets, which fit into the needle of a dart or syringe, has simplified vaccine handling and permitted long-term storage of the controlled-release component. Vaccine delivery is now performed using a jabstick on captured mares restrained in a field stock chute during routine horse gathers. Provision of a vaccine-training programme has maximized personnel safety during vaccine preparation and use.