*Article* **Thermal Micro-Environment during Poultry Transportation in South Central United States**

#### **Douglas J. Aldridge 1, Kaushik Luthra 2, Yi Liang 2,\*, Karen Christensen 3, Susan E. Watkins 1 and Colin G. Scanes 1**


Received: 10 December 2018; Accepted: 17 January 2019; Published: 21 January 2019

**Simple Summary:** This project monitored the internal micro-environments of live poultry transport trailers during loading and transport. For the 28 trips evaluated, trailers were modified using common USA industry mitigation practices designed to optimize bird comfort under a wide range of environmental conditions. In the cold season, double boarding of the exterior area of the transport modules elevated the internal temperature more than 8 ◦C above ambient temperatures as low as −16 ◦C. However, the temperature elevation may not be sufficient when ambient temperature was below 0 ◦C. In the warm season, surface wetting of birds and evaporative cooling applied during on-farm loading maintained trailer thermal conditions at or below ambient temperature for part of the road transport. However, this study suggests that additional improvement in equipment design or managemen<sup>t</sup> is warranted when temperatures are extremely cold or hot.

**Abstract:** This observational study was conducted to characterize the thermal micro- climate that broilers experienced in commercial poultry transporters under various weather conditions and typical managemen<sup>t</sup> practices in the South Central USA. We continuously monitored temperature and relative humidity in 45 interior locations of 28 fully-loaded commercial trailers over 2 year spans from 2015–2016 in South Central USA. In the cold season, double boarding of the exterior area of the transport modules maintained temperatures at least 8 ◦C warmer than ambient temperatures as low as −16 ◦C. Overall, temperature at all locations decreased as transporters traveled from farms to processing plants during winter trips with double boards. In the hot season, assistance by evaporative cooling during on-farm loading resulted in interior temperatures within ± 2 ◦C of ambient conditions (up to 36 ◦C) during road transport. In the summer months, trailers uniformly gained 2 ◦C as vehicles travelled for 45 min from farms to plants. Apparent equivalent temperatures of the monitored summer trips averaged 80.5 ◦C, indicating possible heat stress conditions based on the thermal comfort zones defined by literature index values. For longer trips, cooling assistance on the farms may be insufficient to prevent temperatures from rising further into extremely hot conditions in the transporters, leading to a dangerous thermal environment.

**Keywords:** broiler transport; thermal micro-environment; heat stress; animal welfare
