Study Finds Standard ENU Dosing Temporarily Reduces Fertility—but Does Not Induce Sterility—in Male Japanese Quail

2026-08-31 09:37:42 Environment

Ilorin, Nigeria — A new study examining genetic improvement strategies in Japanese quail has found that a commonly used dose of the chemical mutagen N-ethyl-N-nitrosourea (ENU) temporarily reduced male fertility but was not strong enough to produce the transient sterility normally associated with successful ENU mutagenesis. The findings highlight how differences in reproductive biology between animal species can influence the effectiveness of genetic research protocols.

Published in the Asian Journal of Research and Review in Agriculture, the research was conducted by Abdulhakeem T. Hassan-Okoh and Ayokunle A. Toye of the Department of Animal Production, Faculty of Agriculture, University of Ilorin, Nigeria. The study investigated whether an established ENU treatment protocol could provide an initial pathway towards generating useful genetic variation in Japanese quail.

Why Japanese Quail Genetic Improvement Matters
Japanese quail farming has potential within Nigeria's poultry sector, but its growth has been constrained by several factors, including relatively low meat yield, limited consumer awareness, processing challenges and market acceptance. Because some of these limitations are associated with the birds' small body size, researchers are exploring genomic approaches that could eventually support improvement of economically important traits.

ENU is a chemical that can create random changes, or mutations, in DNA. In animal genetics research, it has been used to generate new genetic variation and identify genes associated with particular biological traits. A period of temporary or "transient" sterility after ENU treatment is commonly used as an indicator that the chemical has effectively affected germline cells—the cells responsible for transmitting genetic information to offspring.

What the Researchers Found
The researchers administered a total ENU dose of 300 mg per kilogram of body weight to male Japanese quail, divided into three weekly doses of 100 mg/kg. Fertility fell significantly during the first three weeks after treatment. At its lowest point, the ENU-treated group averaged 7.0 fertile eggs compared with 8.8 and 9.2 in the two control groups.
However, fertility recovered rapidly. By the fourth week, ENU-treated males had returned to fertility levels comparable with the controls, and transient sterility never occurred. Even at the lowest point, average fertility remained at approximately 70%.

The treatment also produced no statistically significant changes in semen morphology, sperm mortality, motility, sperm concentration or semen volume when compared with control birds.

How the Study Was Conducted
Researchers initially raised 350 Japanese quail chicks to sexual maturity. Ninety males were assigned to three groups: ENU treatment, a sham-solution control and a normal-saline control. Selected males were paired with hens for fertility testing, while semen quality was assessed before and after treatment. Eggs were incubated and examined for evidence of fertility, with post-treatment monitoring continuing for six weeks.

Implications for Genetic Research
The researchers suggest that Japanese quail's unusually rapid reproductive cycle may help explain the limited effect. The complete spermatogenic process in quail has been estimated at about 12.77 days—considerably faster than in several other commonly studied animal models. This rapid renewal could allow reproductive tissues to recover before ENU produces sustained germline suppression.
Rather than demonstrating that ENU cannot be used in Japanese quail, the findings indicate that protocols developed for other species should not automatically be transferred without modification. Future research should test alternative doses, treatment schedules, developmental windows and earlier semen-assessment periods to determine whether ENU mutagenesis can be optimised for quail.

References
Hassan-Okoh, A. T., & Toye, A. A. (2026). Evaluation of fertility response and transient sterility following N-ethyl-N-nitrosourea exposure in male Japanese quails. Asian Journal of Research and Review in Agriculture, 8(1), 116–127. https://doi.org/10.56557/ajrra/2026/v8i1200
Lin, M., Jones, R. C., & Blackshaw, A. W. (1990). The cycle of the seminiferous epithelium in the Japanese quail (Coturnix coturnix japonica) and estimation of its duration. Reproduction, 88(2), 481–490. https://doi.org/10.1530/jrf.0.0880481
Salinger, A. P., & Justice, M. J. (2008). Mouse mutagenesis using N-ethyl-N-nitrosourea (ENU). Cold Spring Harbor Protocols, 2008(4), pdb.prot4985. https://doi.org/10.1101/pdb.prot4985