Effect of endoplasmic reticulum stress on bone and cartilage growth via endochondral ossification in broilers.

Broilers in modern farming systems gain significant body weight, resulting in leg disorders in broilers. Long bones in the limbs extend after birth through endochondral ossification (EO), a process where bone replaces cartilage in pre-formed templates, making it essential for bone and cartilage development. The endoplasmic reticulum stress (ERS) pathway has been implicated in bone development and key steps of EO, but the mechanism remains unclear. In this study, broilers were reared on wire flooring to induce persistent footing instability and physiological stress. Salubrinal (SAL), an ERS inhibitor, was administrated to explore its effects on bone disorders. Parameters such as weight, length, bone mineral density, and strength were measured to assess bone and cartilage integrity in broilers. And staining and gene expression detection were performed to explore the effects of ERS on EO. The results indicated that broilers raised on wire flooring had an increased incidence of severe gait defects and bone disorders, especially femoral head necrosis. Meanwhile, broilers on wire flooring had increased chondrocyte hypertrophy and apoptosis, vascularity, and trabecularity, along with impaired cartilage and disrupted bone remodeling, all of which are key activators of EO. SAL treatment could inhibit EO by reducing chondrocyte apoptosis, vascular invasion, and bone resorption in broilers on wire flooring. Overall, this study highlights the negative effects of wire flooring on bone and cartilage, which are closely related to the occurrence of bone disease. Additionally, it suggests that blocking ERS may protect broilers from poor flooring conditions by regulating EO.