**4. Conclusions**

Temperature and relative humidity were monitored in 45 locations on 28 commercial trips hauling market-size broilers to processing plants. Weather-dependent managemen<sup>t</sup> employed by companies, including side boards attached on the open area of modules in winter and fan trailers with mists used during loading in summer, were analyzed for their effect on altering micro-environment of the trailers. During cold weather transport when ambient temperatures were below 0 ◦C, on-board temperatures were lower near the exterior than in the middle, and decreased steadily as transport duration increased. Trailer temperatures on double board trailers in winter averaged 8 ◦C above ambient T. During warm weather transport, on-board temperatures were within ± 2 ◦C of the ambient, and higher near the top module of the trailers. Temperatures throughout the trailer increased by 1 to 3 ◦C as transit time increased in summer. Apparent equivalent temperatures of the monitored summer trips averaged 80.5 ◦C, indicating possible heat stress conditions based on literature reported index values. Improvement in equipment or transport managemen<sup>t</sup> would therefore be necessary during extremely cold or hot weather.

**Author Contributions:** Conceptualization, Y.L., K.C. and S.E.W.; Formal analysis, D.J.A., K.L. and C.G.S.; Investigation, D.J.A. and K.L.; Methodology, D.J.A., K.L. and Y.L.; Supervision, Y.L.; Writing—original draft, D.J.A.; Writing—review & editing, Y.L., S.E.W. and C.G.S.

**Funding:** This research was funded by USA Poultry & Egg Association, gran<sup>t</sup> number BRF001.

**Acknowledgments:** We would like to thank the University of Arkansas Systems Division of Agriculture and United States Department of Agriculture National Institute of Food and Agriculture for the base support of this project. We are also grateful to the poultry companies for sharing their resources for the field data collection.

**Conflicts of Interest:** The authors declare no conflict of interest.
