Commercial transport of spent layer breeder chickens: process and strain-specific physiological and behavioral responses

Abstract

Understanding the underlying issues related to animal transport is essential for promoting animal welfare. However, no research has focused on the transport process and its physiological effects on spent layer breeder chickens. Therefore, this study aimed to investigate a single commercial transport process in spent layer breeder chickens and evaluated its physiological and behavioral effects across three strains of focal hens: Sakura, Lohmann Julia (Julia), and Hy-Line Brown (Brown). A total of 1,611 chickens (1,547 hens and 64 roosters, aged 700 days) including various crossbreeds and lineages were transported over 32.9 km in 55 min. The total mortality rate was 0.25%. Each chicken was sequentially housed in two transport crate types and remained there until shackling. The maximum duration from initial capture to shackling was 7 hr 30 min. Temperatures inside cages and crates were higher than ambient conditions. Transported focal hens showed reduced body weight and elevated heterophil-to-lymphocyte ratios. Brown hens exhibited higher heterophil-to-lymphocyte ratios and lower core body temperatures compared to the overall mean. Additionally, transported focal hens exhibited wet plumage, shivering, and piloerection due to rain exposure, although temperatures near them remained within their thermal comfort zone. These findings reveal the complexity of the transport process and its adverse effects on spent layer breeder chickens, highlighting genetic differences among strains in physiological and behavioral responses. They also underscore the need for careful animal monitoring, preventing wetting, and adopting strain-specific transport management practices to improve animal welfare.