Effect of high levels of Larvadex on reproduction in Leghorn breeders.

The insect growth inhibitor, Larvadex, was fed to egg type breeder hens for 8 weeks at levels of 0, 50, 100, 500, 1000, and 2000 ppm and to the same strain of males at 0 and 2000 ppm. All birds were kept in individual cages. Fertility was determined following artificial insemination. Egg production was significantly increased in Experiment 1 but numerically decreased in Experiment 2 by feeding 1000 ppm Larvadex. Feeding 2000 ppm significantly decreased egg production in both experiments. Egg weight was highest at 100 ppm and decreased with higher treatment levels. Specific gravity of eggs was improved with all Larvadex treatments. Fertility was not affected by treatment of females or males. Hatchability was reduced by the 1000 and 2000 ppm levels in the hen's diet. Semen quality was not significantly affected by feeding Larvadex at 2000 ppm.