Pathophysiological characteristics and gene transcriptional profiling of bone microstructure in a low calcium diet fed caged laying hens

Authors: JIANG, SHA - Southwest University; WU, X - Southwest University; JIN, M - Southwest University; WANG, X - Southwest University; TANG, Q - Southwest University; SUN, Y - Southwest University; Cheng, Heng-Wei

Submitted to: Poultry Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/23/2019
Publication Date: 12/11/2019
Citation: Jiang, S., Wu, X.L., Jin, M.L., Wang, X.Z., Tang, Q., Sun, Y.X., Cheng, H. 2019. Pathophysiological characteristics and gene transcriptional profiling of bone microstructure in a low calcium diet fed caged laying hens. Poultry Science. https://doi.org/10.3382/ps/pez271.
DOI: https://doi.org/10.3382/ps/pez271

Interpretive Summary: Skeletal disorder has been recognized as a critical issue impairing health of farm animals including poultry. The objective of this study was to examine the pathophysiological characteristics and molecular mechanisms of osteoporotic damage in caged laying hens fed a low calcium diet. Results showed that low calcium diet fed hens have high bone turnover and micro-architectural damage compared to regular layer diet fed hens. The results further evidence dietary supplement of calcium is a critical nutrient strategy for improving hen skeletal health. This information can be used by poultry producers to develop a management strategy for improving chicken health and welfare.

Technical Abstract: Calcium depletion is a valuable non-invasive tool for studying skeletal system diseases and disorders. A low calcium diet was used to examine the pathophysiological characteristics and molecular mechanisms of osteoporotic damage in caged laying hens. Sixty 64-week-old laying hens were randomly housed in single-bird cages, and the cages were divided into 2 treatments: fed a regular calcium diet (RCD, 3.7%) or a low calcium diet (LCD, 1.5%) for 60 days. The diet-induced changes of serum bone remodeling indicators, bone strength, microstructure of the distal femur, and the gene expression profiling of keel bone were measured. Compared to RCD hens, LCD hens had higher activity of both serum alkaline phosphatase and tartrate resistant acid phosphatase but lower serum calcium concentrations with reduced tibial and femoral mass, width and strength (P < 0.05). In addition, LCD hens had greater densities of osteoclasts, osteoblasts, connective tissue cells and osteoid in the trabecular bone (P < 0.05). The transcriptome analysis revealed that 563 unigenes were differentially expressed (DEG) in keel bone between LCD and RCD hens. The Kyoto Encyclopedia of genes and genomes (KEGG) pathway analyses revealed that these DEGs were mainly associated with the osteoporosis-related signaling pathways involved in the biological functions of the bone cellular and extracellular structural modulation. The Real-time PCR analysis further confirmed that the low calcium diet enhanced the mRNA expression of collagen teyp1 alpha 2 (COL1A2), integrin-binding sialoprotein (IBSP) and periostin (POSTN) but inhibited sclerostin (SOST) expression. These findings indicate that LCD hens have a higher bone turnover and micro-architectural damage compared to RCD hens. The results further evidence dietary supplement of calcium is a critical nutrient strategy for improving hen skeletal health.