Morphological and Transcriptomic Analysis of the Supplemental Boron in the Liver of Ostrich Chicks

African ostrich chicks (Struthio camelus) were divided into six groups, and each received different levels of boric acid (source of boron) in the drinking water (0, 40, 80, 160, 320, and 640 mg/L respectively) to examine the histological, apoptotic, biochemical, and transcriptomic parameters. Morphological analysis in different groups was assessed by hematoxylin and eosin (H&E) staining, periodic acid Schiff (PAS) staining, and terminal deoxynucleotide transferase dUTP Nick-End Labeling (TUNEL) assay. The biochemical profile was evaluated spectrophotometrically. Detailed RNA-Seq of the data was performed using the transcriptomic method. H&E staining showed well-developed liver structure up to the 160 mg/L boric acid (BA) supplement groups, while BA doses (320 mg/L and 640 mg/L) caused changes in hepatocytes and portal triads. PAS staining showed that glycogen levels were optimal in the 80 mg/L BA dose group, but a reduction in glycogen levels was observed after this group, particularly in the 640 mg/L BA supplement group. Cellular apoptosis showed a biphasic pattern, and the BA dose above 160 mg/L enhanced cell death. In addition, serum analysis showed that doses of 80-160 mg BA were beneficial for ostrich liver. Then, the transcriptome analysis of the 80 mg dose also showed mainly positive effects on the liver. These results demonstrated that chronic BA exposure (320-640 mg) can cause significant histological, apoptotic, and biochemical changes in African ostrich liver, while the adequate dose of supplementation (particularly 80 mg BA) promotes liver growth.