Nicarbazin complex yields dinitrocarbanilide as ultrafine crystals with improved anticoccidial activity

Nicarbazin Residue in Tissues from Broilers Reared on Reused Litter Conditions

Nicarbazin (NCZ) is a worldwide used anticoccidial in poultry farming to avoid coccidiosis disease when chickens are reared on conventional poultry litter. If proper dosage and withdrawal time are not followed, the component dinitrocarbanilide (DNC) of NCZ may be present in chicken tissues, therefore posing a risk to consumers if the residues are above 200 µg/kg. Litter reuse is a common and important practice in commercial chicken production. Literature is lacking about the influence of litter reuse on DNC deposition in chicken tissues and its impact on food safety. We aimed to evaluate DNC residues in breast and liver by LC-MS/MS from broilers from an experiment with 10 consecutive flocks during 2 years. The experiment included three treatments containing NCZ in the diet (T1 = 125 mg/kg, 1−21 d; T2 = 125 mg/kg, 1−32 d; T3 = 40 mg/kg, 1−32 d). DNC residues in chicken breast at 21 d in T1 ranged from 648.8−926 µg/kg, at 32 d in T2 and T3 varied, respectively, from 232−667 µg/kg and 52−189 µg/kg. Regarding liver, DNC residues at 21 days in T1 ranged from 11,754−15,281 µg/kg, at 32 days in T2 and T3 varied, respectively, from 10,168−15,021 µg/kg and 2899−4573 µg/kg. When NCZ was withdrawn from feed, DNC residues dropped to <LOQ at 42 d in all treatments. Therefore, the reuse of poultry litter does not compromise food safety regarding DNC residues in chicken tissues, as shown herein up to 10 flocks.

Preparation of DNC Solid Dispersion by a Mechanochemical Method with Glycyrrhizic Acid and Polyvinylpyrrolidone to Enhance Bioavailability and Activity

To exploit aqueous-soluble formulation and improve the anticoccidial activity of 4,4'-dinitrocarbanilide (DNC, active component of nicarbazin), this paper prepared DNC/GA/PVP K30 solid dispersion (SD) with glycyrrhizic acid (GA) and polyvinylpyrrolidone (PVP) K30 by a mechanical ball milling method without using any organic solvent. Fourier transform infrared spectroscopy, X-ray diffraction, differential scanning calorimetry, and scanning electron microscopy were used for the solid state characterization. High performance liquid chromatography, critical micelle concentration, particle characterization, and transmission electron microscopy were used to evaluate the behavior in aqueous solution. In addition, the oral bioavailability, tissue distribution, and anticoccidial activity of DNC/GA/PVP K30 SD were investigated as well. Compared with free drug, the novel formulation not only improved the solubility and dissolution rate of DNC, but also inhibited the fecal output of oocysts and enhanced the therapeutic effect of coccidiosis. According to the experiment results, the DNC/GA/PVP K30 SD increased 4.64-fold in oral bioavailability and dramatically enhanced the concentration in liver which provided a basis for further research in schistosomiasis. In summary, our findings suggested that DNC/GA/PVP K30 SD may have promising applications in the treatment of coccidiosis.

Use of Fertility Control (Nicarbazin) in Barcelona: An Effective yet Respectful Method towards Animal Welfare for the Management of Conflictive Feral Pigeon Colonies

Simple Summary

Feral pigeon is one of the most common urban species worldwide. Living free in urban areas, pigeons have found a favorable environment with the conditions to have a high fertility, thus leading to overcrowding, which causes thousands of millions in damages yearly. The management of overpopulated pigeon colonies presents numerous challenges, and several methods have been proposed and used. In recent decades, the concern in the society about animal welfare has grown, and now demands non-lethal methods in the management of wildlife, especially in cities. The management of feral pigeons in Barcelona, Spain, used to be carried out, like in many cities, by capture and elimination. However, as this method has been proven to be ineffective and the public concern about animal welfare has increased, in 2016, the Barcelona City Council decided to change the management towards a fertility control method. This study describes and evaluates, during three years, an efficient fertility control protocol that is able to reduce the number of pigeons in the treated colonies by 55.26% at the end of the study. The results of this study provide animal management administrations and companies with a non-lethal protocol to control pigeon populations while respecting animal welfare.

Abstract

This study describes a three-year evaluation (2017–2019) of a fertility control protocol using nicarbazin (Ovistop^®) to reduce the abundance of the most conflictive colonies of feral pigeon, Columba livia var. domestica, in Barcelona, Spain, as a long-term strategy based on animal welfare. The treatment was supplied to 34 pigeon colonies by automatic hopper feeders installed in public areas. A superiority study and a population monitoring study were carried out to evaluate differences in the abundance of the colonies, as well as the proportion of juveniles, the possible intake of nicarbazin by non-target species and the movement of individuals among colonies. The results showed statistical differences in the population trends between the test (−22.03%) and control (+12.86%) groups, and a significant steady decreasing trend in the pigeon abundance (−55.26%) was registered until the end of 2019. The proportion of juveniles was significatively lower in the test colonies, and a non-target species (Eurasian collared doves, Streptopelia decaocto) was observed consuming in a residual form. The protocol using nicarbazin is able to both control the abundance of pigeons, with no impact over non-target species, and respond to the public interest about animal welfare by providing an ethical method to manage overabundant and/or conflictive populations.

Nicarbazin has no effect on reducing feral pigeon populations in Barcelona

BACKGROUND

Nicarbazin is an anti-coccidial product sometimes used as a contraceptive to reduce the size of feral pigeon populations. However, its effectiveness in reducing pigeon population size in cities has caused some controversy. Here, we evaluate its effectiveness in the city of Barcelona.

RESULTS

In 2017, the Barcelona City Council set 23 feeding stations with nicarbazin and ten with placebo (untreated corn). Censuses were undertaken before and after one year of treatment, within a 200-m radius around each feeder. We also censused 28 circles of 200 m radius distributed randomly 200 m from the feeders and 28 circles > 500 m from the feeders, which acted as controls. Population size across the whole city was also evaluated pre- and post treatment. We found that feral pigeon density did not change after one year of treatment, either in the circles around feeding stations with nicarbazin or in the areas around control stations at 200 and > 500 m from the feeders. Population size in placebo circles rose after a year by 10%. A pigeon census for the whole of Barcelona showed a 10% increase.

CONCLUSION

Overall, our results indicate that the nicarbazin treatment had no effect on feral pigeon population size, and we advise against its use as a pigeon control method, at least in large cities.

Detection of p-Nitroaniline Released from Degradation of 4,4'-Dinitrocarbanilide in Chicken Breast during Thermal Processing

The diphenylurea 4,4'-dinitrocarbanilide (DNC) is the residue of concern left in edible tissues of broilers fed diets containing the anticoccidial nicarbazin. When chicken meat is submitted to thermal processing, p-nitroaniline (p-NA) is expected from DNC degradation. This work aimed at evaluating whether thermal processing of DNC-containing chicken meat induces p-NA appearance. First, a hydrolysis assay was performed in aqueous solutions at 100 °C in different pH, confirming that DNC cleavage yields p-NA. Then a novel LC-MS/MS method was used to detect traces of this aromatic amine in DNC-containing chicken breast fillets subjected to cooking methods. Our evidence showed p-NA occurrence in such chicken meat samples, which corroborated results from hydrolysis assay. The p-NA appearance in fillets was rather discrete during boiling treatment, but its concentration became pronounced over time for grilling, frying, and roasting, achieving respectively 326.3, 640.0, and 456.9 μg/kg. As far as we are concerned, no other research identified degradation products from DNC residue in heat-processed chicken fillets. Therefore, this study leads to additional approaches to assess impacts on food safety.

Degradation of 4,4'-Dinitrocarbanilide in Chicken Breast by Thermal Processing

Nicarbazin is one of the major anticoccidials used in broiler feeds. The compound 4,4'-dinitrocarbanilide (DNC) is the marker residue of concern left from nicarbazin in chicken meat. The effect of thermal processing on DNC content accumulated in chicken breast was assessed, and samples were analyzed by liquid chromatography-tandem mass spectrometry. Five conventional cooking methods were evaluated: boiling, grilling, microwaving, frying, and roasting. To ensure DNC in meat, broilers were fed nicarbazin without withdrawal period. All heating methods surpassed the 70 °C end point core temperature in chicken breast. Maximum DNC degradation was reached at 10 min for boiling, at 30 min for grilling, and at 2 min for microwaving, and no further reduction was observed for longer thermal processing time. Boiling was more efficient in reducing DNC (69%). Grilling, microwaving, and frying achieved on average 55% of degradation. The outcomes reported herein may be considered in decision-making regarding further review of maximum residue limits.

Current research, regulation, risk, analytical methods and monitoring results for nicarbazin in chicken meat: A perspective review

This review presents up-to-date information about current research on nicarbazin, one of the most used anticoccidials in poultry production. The focus is to elucidate regulation concerning nicarbazin, limits for its residues in food, how maximum residue limits in different countries are calculated regarding edible chicken tissues and the possible implications in human health. Analytical methods to extract and quantify this residue, expressed as dinitrocarbanilide (DNC) are presented and discussed, including qualitative screening and quantitative/confirmatory analytical methods. Monitoring results and occurrence of DNC residues in chicken meat are discussed. Additionally, the causes of eventual chicken meat contamination and possible solutions to reduce or eliminate DNC residue in tissues are also presented. The paper concludes with perspectives, the current state of DNC residue analysis and suggestions for future research, especially considering the gap in the study of residue recycling effect due to continuous chicken litter use.

Nicarbazin bait reduces reproduction by pigeons (Columba livia)

Development of effective methods for reducing populations of overabundant nuisance bird species continues to challenge wildlife biologists. Reproductive inhibition, although conceptually pleasing, has been difficult to implement because of the lack of a safe, approved avian contraceptive. Recently, however, nicarbazin received regulatory approval in the United States for use as a bait to decrease hatchability of resident Canada goose (Branta canadensis) and feral pigeon (Columba livia) eggs. In anticipation of the feral pigeon registration, we evaluated efficacy by exposing captive pairs of nesting pigeons to nicarbazin bait for 4 h daily. Egg production was unaffected, but only 9 of 22 eggs hatched, a 59% reduction from pre-treatment when each of the 11 test pairs produced 2 nestlings. In the recovery phase, when treated bait was removed, the 11 pairs produced 18 nestlings. All nestlings produced during the study appeared healthy and normal, and there was no mortality among the adult pairs. Nicarbazin is an effective and safe means of reducing hatchability of feral pigeon eggs that can be used within an integrated management plan to reduce feral pigeon populations.

Molecular effects of nicarbazin on avian reproduction

Nicarbazin (NCZ) is an anticoccidial drug routinely used in the poultry industry that can negatively affect reproduction by reducing egg production, egg weight, and egg hatchability. The molecular mechanisms by which NCZ affects reproduction are unknown. Lipoprotein lipase, vitellogenin, transglutaminase, and calcium are all involved in egg formation and embryogenesis. Therefore, in vitro assays were used to evaluate 4 potential mechanisms of action of NCZ on egg formation and embryogenesis. First, a lipoprotein lipase assay was conducted to determine if NCZ increases lipoprotein lipase activity. Second, vitellogenin phosphorylation was evaluated to determine if NCZ acts as a vitellogenin phosphatase. Third, transglutaminase activity was measured to determine if NCZ inhibits transglutaminase activity. Finally, bull sperm was used as a model to determine if specific channel-mediated calcium uptake can be blocked by NCZ. Nicarbazin increased the activity of lipoprotein lipase in vitro at 3.9 and 7.8 microg of NCZ/mL. Nicarbazin increased intracellular calcium levels in bull sperm, suggesting it also acts as a calcium ionophore. The portion of the NCZ molecule responsible for the increase in intracellular calcium is 2-hydroxy-4,6-dimethylpyrimidine. Nicarbazin affected vitellogenin phosphorylation but only at a concentration many times higher than expected plasma values. Nicarbazin also inhibited transglutaminase activity in vitro. Whereas the 4,4'-dinitrocarbanilide portion of the NCZ molecule inhibited transglutaminase activity, the 2-hydroxy-4,6-dimethylpyrimidine portion increased transglutaminase activity. All of these assays were conducted in vitro; therefore these results should be viewed as preliminary findings to aid in directing further research on the effect of NCZ on reproduction in vivo. Because NCZ increases lipoprotein lipase activity and acts as a calcium ionophore, future experiments should investigate these effects in particular.

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.

4,4'-Dinitrocarbanilide (DNC) concentrations in egg shells as a predictor of nicarbazin consumption and DNC dose in goose eggs

Nicarbazin is being investigated as an infertility agent for the control of non-migratory Canada geese (Branta canadensis L) populations. Nicarbazin is presently registered for use as a coccidiostat for poultry. Geese fed sufficient quantities of nicarbazin will lay non-viable eggs. We established nicarbazin consumption by measuring the concentration of a component of the formulation, 4,4'-dinitrocarbanilide (DNC) in the egg contents (yolk, albumin) in non-viable eggs. To estimate the nicarbazin consumption of birds that laid viable eggs (eggs that hatched or contained an embryo), a high-performance liquid chromatography method was developed to measure the concentration of DNC in egg shells. A statistically significant correlation was established using linear regression between the mean concentrations of DNC in the egg shell and in the egg contents in non-viable eggs. Viable eggs were estimated to contain lower levels of DNC than non-viable eggs. DNC concentrations in both the egg contents and the egg shell increased with increases in nicarbazin dose in feed. Our method allows for the estimation of nicarbazin consumption and DNC dose in eggs under field conditions, which is important in developing an effective infertility agent for over-abundant non-migratory goose populations.

Determination of 4,4'-dinitrocarbanilide (DNC), a component of Nicarbazin, in Canada goose (Branta canadensis) eggshells using high-performance liquid chromatography

A method was developed using high-performance liquid chromatography to assay 4,4'-dinitrocarbanilide (DNC), the active ingredient in Nicarbazin, in eggshells collected from Canada geese fed a formulated feed fortified with Nicarbazin at doses of 0, 125, 250, and 500 microg/g. The method was developed using chicken eggshells fortified with DNC. The method was used to quantify DNC in both the shell-associated membranes and the calcified shell extracellular matrix. These values were compared to those obtained for a composite sample consisting of both the membranes and the calcified shell extracellular matrix. The validated method was used to quantify DNC in eggshells from geese fed fortified feed to ascertain the effect of Nicarbazin feed concentration on shell DNC concentration. DNC levels in the eggshells were highly correlated with feed dose.

Feed Additives: Do They Add to Animal Welfare? An Evaluation

The welfare of farm animals is strongly influenced by the man-made environment. Welfare problems also arise from reduced homeostatic capacities in animals. Feed additives, used to promote growth or to prevent diseases can alter the animals' self-regulating capacities thus affecting their welfare. The EU regulates the use of these additives within specified groups of Directive 70/524/EEC. Although these feed additives can be regarded as prescription-free veterinary drugs, critical remarks on their desired and adverse effects have received little attention.

A survey of the available literature shows that about one-third of licensed feed additives alter adrenal function in vitro. Reports of the adverse effects of anticoccidial additives in vivo suggest they can be classified under three headings: (i) substances with a very narrow safety margin (the difference between the permitted dose and the dose with adverse effects) and often irreversible effects on growth and feed conversion; (ii) substances with a narrow safety margin and largely reversible effects; (iii) substances with an adequate safety margin. The growth promoters (including antibiotic growth promoters) can - on the basis of their adverse effects - be classified into two groups: (i) substances with a very narrow safety margin; and (ii) substances with an adequate safety margin.

On the one hand, animal welfare considerations require use of disease-preventing additives, but on the other hand, they also demand discontinuation of current practices. Judicious use of additives can add to animal welfare. However, their unlimited use to obscure defects in husbandry is detrimental to animal welfare. A major obstacle to the judicious use of feed additives, is the lack of published, unbiased information on their efficacy and safety for farm animals.