Nicarbazin is used as an anti-coccidial drug in broilers. Athough it is a very effective medication for broilers, inclusion of even traces of Nicarbazin in a broiler breeder diet can have very negative effects.
Nicarbzin is very toxic to embryos, and even slight traces in the feed can increase the number of early deads during incubation significantly. These embryos however die so early that it is often assumed to be an infertility problem.

To illustrate how low the levels can be that cause prolems, even using feed trucks for broiler breeder feed after they have been used for broiler feed (with Nicarbazin included) without a proper cleaning can already result in significant problems.

If Nicarbazin is included in higher quanitities, one of the first signs that can be noticed (after an increase of early deads in incubation) is an increase of the number of white-shelled eggs. If higher levels are used, also production and mortality will be influenced.

Research has shown that an inclusion level of 50 ppm for 5 days decreased hatchability with 15%

As traces of Nicarbazin in breeder diets already can cause problems, the use of one feed mill for producing both broiler feed and broiler breeder feed should be prohibited. If it is necessary to use one feed mill, strict practises should be applied to separate the two production systems, including different feed trucks. If the same feed truck has to be used, then first of all the feed to the breeder flocks should be delivered, before the broiler farms are delivered.

Whenever a problem with certain drops in fertility/hatchability is observed, one of the first questions should be if contamination with Nicarbazin or other toxic materials is a possibility. The first question in this respect should be if the breeder feed is produced in a feed mill where also broiler feed, turkey feed or pig feed is produced. If that is the case, than the possibility of cross contamination of toxic materials should be examined first.