Literature about nicarbazin

R-12 is a registered veterinary medicinal product containing nicarbazin as the active ingredient. Nicarbazin has been used around the world as a coccidiostat for broiler chickens since the 1950s. Coccidiostats are added to the feed of broilers to prevent coccidiosis, a common intestinal infection in birds. They are administered until the last days of the chickens’ life, which means that they are safe in regard to human consumption.

The use of nicarbazin as a contraceptive is relatively new. Nicarbazin is not a classic contraceptive. Unlike progesterone, a hormonal contraceptive, nicarbazin metabolises in the body very quickly. Once nicarbazin is absorbed, it immediately breaks down into 2 parts: DCN, the active part, and HDP, which ensures it is absorbed by the bird’s intestines.

Regulatory authorities such as the FDA and EPA in the United States, the EFSA in the EU, and the MAFF in Japan have approved nicarbazin for use as a veterinary medicine in food-producing animals, as well as a contraceptive.

Nicarbazin has been extensively studied over the years, and these studies have looked at the impact it has on the environment. Multiple research has shown that, within realistic amounts, nicarbazin is non-toxic and safe for humans, animals and the environment. There is no risk of secondary poisoning. Some leading sources are highlighted below. The articles referenced are available as an attachment at the bottom of the page, or can be viewed online via the attached links.

1. European Food Safety Authority (EFSA)

The European Food Safety Authority (EFSA) conducts safety studies and provides independent scientific advice on risks in the food chain. The articles below explain the effect and safety of 3 coccidiostats that contain nicarbazin as the active ingredient: Koffogran, Maxiban at Monimax. The articles can be viewed online via the EFSA website.

EFSA Scientific Opinion on the safety and efficacy of Koffogran (nicarbazin) feed additive for fattening

Koffogran is a registered veterinary medicine (coccidiostat) for broiler chickens. Active ingredient: nicarbazin.

  • Koffogran is safe for broilers in the highest recommended dose
  • Koffogran has a waiting time of 1 day before the animal can be consumed
  • Nicarbazin is not genotoxic
  • No major problems were identified in multi-generation rat reproduction studies
  • No safety risk was identified for soil, groundwater or via secondary poisoning

EFSA Scientific Opinion on the safety and efficacy of Maxiban® G160 (narasin and nicarbazin) for chickens for fattening

Maxiban is a registered veterinary medicine (coccidiostat) for broilers. Active ingredients: nicarbazin and narasin.

  • Maxiban is safe for broilers in the highest recommended dose
  • Koffogran has a waiting time of 0 days before the animal can be consumed
  • Nicarbazin does not exhibit anti-microbial properties; therefore, there are no micro-biological concerns associated with it
  • No consequences in terms of the quality of the meat are expected after administration of the highest recommended dose
  • No safety risk was identified for soil, groundwater or via secondary poisoning

EFSA Scientific Opinion on the safety for the environment of Monimax® (monensin sodium and nicarbazin) for chickens for fattening, chickens reared for laying and for turkeys for fattening

Monimax is a registered veterinary medicine (coccidiostat) for broilers, laying hens and fattening turkeys. Active ingredients: monensin sodium and nicarbazin.

  • Nicarbazin does not pose a risk to water, soil, or sediment
  • The bioaccumulation potential of DNC in the environment is low
  • The risk of secondary poisoning via manure from animals in agriculture administered with Monimax is unlikely

2. OvoControl®

OvoControl® is the North American equivalent of R-12. The nicarbazin concentration in OvoControl® (0.50 g/100 g) is 6 times higher than the nicarbazin concentration in R-12 (0.08 g/100 g). OvoControl® is used as a contraceptive for pigeons. The company behind the brand, Innolytics LLC, published an article on the secondary toxicity of nicarbazin, i.e. its effect on others. The University of Nebraska also published a publication on the use of OvoControl® as a contraceptive for wild animals, including city pigeons.

The Secondary Toxicity of OvoControl® (nicarbazin) in Birds (Innolytics LLC)

  • Both of the nicarbazin components (DNC and HDP) are required to achieve the contraceptive effect. Consequently, secondary toxicity or infertility in animals consuming treated pigeons is very unlikely and secondary animals are not affected.
  • Nicarbazin concentrations in an animal treated with OvoControl® are far too low to reach the dose required to interfere with the viability of the eggs in a second animal
  • The bioavailability of nicarbazin is extremely limited once it has been ingested by the animal that consumed OvoControl®
  • After 7 days, all detectable traces of nicarbazin will have disappeared from the tissue
  • The concentration of nicarbazin in the egg is less than 0.0005 g/100 g
  • Nicarbazin takes 5-7 days to reach the yolk
  • An egg is generally formed in 14 days, and the last 5-7 days are crucial for development. Infertility can only occur if a pigeon consumes the required amount during this development phase.
  • For a nicarbazin concentration of 0.5 g/100 g, the nicarbazin concentration in the tissue and egg is well below the toxic level
  • If a bird of prey were to eat a pigeon that has not yet fully digested the OvoControl®, and therefore not broken down the nicarbazin, the dose would not be high enough to cause infertility in the bird of prey. Infertility is only achieved with the correct amount and the correct duration of administration.
  • Example: A 1500 g peregrine falcon would require 5 times the dose of a 300 g treated pigeon. In order to become infertile, the peregrine falcon would have to eat 5 treated pigeons a day every day for at least 5 days a week, which equates to 25 pigeons in 5 days.

Source: OvoControl®

Reviews of issues concerning the use of reproductive inhibitors, with particular emphasis on resolving human-wildlife conflicts in North America (University of Nebraska)

  • Nicarbazin leaves the body within 48 hours
  • The effect of nicarbazin, namely infertility, is completely reversible
  • Nicarbazin has no effect on mammals and is safe for both target and non-target birds, even when administered at a dose higher than the dose required to achieve the contraceptive effect

Source: University of Nebraska

3. Other sources

Molecular Effects of Nicarbazin on Avian Reproduction

This scientific article takes a closer look at the molecular action of nicarbazin and examines how nicarbazin affects egg production and hatchability.

Source: Research Gate

The product nicarbazin

Barcelona (Spain) has been successfully using R-12 to control the city’s pigeon population for years. An explanation of the effect and safety of nicarbazin can be found on the city's website:

  • When DNC and HDP are split, the DNC particles are too large to be absorbed by the intestine, which means the organisms are unable to assimilate DNC
  • The same thing happens when nicarbazin dissolves in water or penetrates the soil surface
  • Nicarbazin is not toxic
  • The effect is reversible: once the administration of R-12 is stopped, the pigeons can reproduce again
  • Nicarbazin only has a contraceptive affect when it is administered continuously and in a certain dose (10 g per pigeon per day)
  • The impact on mammals and other birds, including birds of prey, is minimal both in the short and long term
  • The environmental impact has been investigated on both the medicine itself and the faecal metabolites. The amounts of nicarbazin that find their way into the environment are far below the permitted amount set by the EU (ERA). The presence of nicarbazin in the environment is limited due to the fact that R-12 breaks down into 2 parts and is sensitive to ultraviolet light.

Source: City of Barcelona website

Nicarbazin, the active ingredient in R-12 is safe:

  • When used as a veterinary medicine in poultry farming, it has a short waiting time, which means it can be administered to food-producing animals until (almost) their last day of life. This means it is safe, both for the animal itself and for subsequent consumption of the animal.
  • The amount of nicarbazin in R-12 is very limited.
  • Nicarbazin is only toxic in very high doses. These doses are unrealistic and physically impossible.
  • Pigeons are not fed R-12 all year round, only during the breeding period.
  • The pigeons are not hindered by this. They are fed nutritious food and protected against coccidiosis.
  • They also lay eggs as usual, but they will not hatch. The eggs are lighter, with a thinner shell, while the inside of the egg is “beaten”.
  • There is no danger to other birds, mammals, humans or the environment.

R-12 is registered as veterinary medicine for city pigeons.