We studied whether wildfire smoke and fine particulate matter (which makes up most of smoke by mass) impacts bulls’ reproductive health, specifically if sperm samples collected at a Colorado breeding facility were saved for future use or were discarded due to poor quality. We analyzed 11,217 sperm quality records collected February 2021–October 2023 from 100 bulls. We used models to predict how likely it was for a sample to be discarded based on conditions during the previous 61-d sperm development period, including average monitor readings for relevant air pollutants, how many days satellites showed smoke in the area, and other factors like temperature, humidity, and bull age and breed. Over multiple models, we found that fine particulate exposure (or wildfire smoke specifically) is associated with increasing likelihood for discarded sperm samples, and that Angus and Red Angus bulls in this population are especially sensitive to fine particulate matter. This suggests that smoke (or overall fine particulate) exposure harms bull reproductive health, with some breeds being more vulnerable than others. With further research, these results could aid cattle breeders and other stakeholders in planning for smoke-associated health impacts and help humans better understand smoke-associated reproductive health risks.

Read the full article in the Journal of Animal Science.