Can FMD Vaccination Temporarily Influence Bull Fertility? Key Insights for Breeding Programs

Foot-and-Mouth Disease (FMD) vaccination remains one of the most important tools for protecting cattle populations against severe production and economic losses. But in breeding bulls, vaccination timing and reproductive performance are often discussed together because temporary semen quality fluctuations have been observed after vaccination in some animals^1,2. 

These changes are not associated with permanent infertility, but they can become important in semen stations, artificial insemination programs, and organized breeding farms where semen quality directly influences conception rates and frozen semen production. 

Which Semen Parameters May Change? 

Different semen characteristics evaluated after vaccination include: 

• Sperm motility 

• Sperm concentration 

• Semen volume 

• Live sperm percentage 

• Total sperm abnormalities 

Some bulls showed temporary reductions in sperm motility and concentration after vaccination, while increased sperm abnormalities were also reported during the post-vaccination period¹. 

Not all bulls respond in the same way. In some cases, semen changes remained mild, while pooled analysis also identified a temporary increase in semen volume approximately four weeks after vaccination¹. 

Breed differences, environmental conditions, management systems, and individual immune responses may all influence how bulls respond after vaccination. 

Why Can These Changes Occur? 

One major factor linked with temporary semen quality fluctuations is post-vaccination hyperthermia. 

Bull testes normally function at temperatures lower than core body temperature. Even mild transient fever may interfere with: 

• Spermatogonial development 

• Sertoli cell activity 

• Sperm maturation 

• Chromatin integrity 

• Mitochondrial function 

Because spermatogenesis is a prolonged process, temporary heat stress may continue affecting semen quality for several weeks after the febrile phase subsides^1,3. 

Another important mechanism involves oxidative stress. 

Immune stimulation following vaccination may increase reactive oxygen species (ROS), which can damage sperm membranes and impair sperm function. Spermatozoa are especially vulnerable because their membranes contain high concentrations of polyunsaturated fatty acids⁴. 

Temporary oxidative stress may contribute to: 

• Reduced sperm motility 

• Membrane instability 

• Reduced viability 

• Increased sperm defects 

• Acrosomal damage 

Why This Matters in Breeding Programs 

Even temporary reductions in semen quality may influence: 

• Frozen semen production 

• Semen freezability 

• AI scheduling 

• Conception efficiency 

• Genetic dissemination programs 

Because of this, breeding bulls may benefit from reproductive planning around vaccination schedules, particularly during intensive semen collection periods. 

In valuable bulls, semen cryopreservation after the brief post-vaccination febrile phase may also become an important consideration. 

The duration and severity of semen changes may vary between bulls, which makes fertility monitoring especially relevant in organized breeding systems. 

Vaccination Still Remains Essential 

Temporary semen quality fluctuations should not be interpreted as a reason to avoid FMD vaccination. 

Natural FMD infection itself causes far greater production and reproductive losses than the temporary changes reported after vaccination. 

The more practical approach is balancing strong FMD prevention with reproductive planning in breeding bulls, especially in semen production and artificial insemination programs. 

Reference 

1. Sitali MC, Matumba L, Chelenga M. Do foot and mouth disease vaccines affect bovine bull fertility? A systematic review and meta-analysis. Veterinary and Animal Science. 2026 May 6:100677. https://www.sciencedirect.com/science/article/pii/S2451943X26001122 

2. Gupta MD, Rathi G, Sontakke SH, Vinod S, Mushtaque M, Kadam H, Dash S, Khadse JR. Effect of foot and mouth disease vaccination on seminal traits in pure Holstein Friesian bulls. Indian J Anim Res. 2018 Dec 1;52:1770-3. http://arccarticles.s3.amazonaws.com/webArticle/Final-attachment-published-B-3445.pdf 

3. Rao M, Xia W, Yang J, Hu LX, Hu SF, Lei H, Wu YQ, Zhu CH. Transient scrotal hyperthermia affects human sperm DNA integrity, sperm apoptosis, and sperm protein expression. Andrology. 2016 Nov;4(6):1054-63. https://onlinelibrary.wiley.com/doi/pdfdirect/10.1111/andr.12228 

4. Bollwein H, Bittner L. Impacts of oxidative stress on bovine sperm function and subsequent in vitro embryo development. Animal Reproduction. 2018 Aug 3;15(Suppl 1):703. https://pmc.ncbi.nlm.nih.gov/articles/PMC9536048/pdf/1984-3143-ar-15-s1-0703.pdf