Alterations to mineral balances can affect skeletal quality as minerals are the major component in bone and can influence cartilage development. Calcium makes up a large portion of bone, and homeostasis is tightly regulated with several mechanisms to maintain stable calcium concentrations in blood. Silicon associates mainly with collagen in soft tissues but has been implicated in bone development and cartilage quality. Previous research in horses documented that furosemide negatively impacted calcium balance for 3 days but did not determine when calcium balance returned to baseline, which may have long-term implications for bone of horses that regularly receive furosemide. Silicon has positive effects on bone mineral content and density and can increase collagen synthesis in multiple species, potentially affecting osteoarthritis in mature horses and bone quality in immature broilers. The overall purpose of the studies within this dissertation was to determine the extent to which impacts on mineral balance could affect both mature bone and cartilage as well as immature, growing bone. The three hypotheses tested within this dissertation include: 1) that Ca balance would be negatively impacted for at least 3 days but would be no different than controls within 7 days of furosemide administration; 2) that Si supplementation would increase bone formation markers and cartilage turnover through increased collagen degradation and formation markers and reduce lameness severity over time and as compared to controls in mature horses; and 3) and that increasing Si concentrations would improve bone quality measures in immature broilers as compared to controls and that these effects would be most prominent at the highest supplement concentration. Calcium balance in horses administered furosemide was more negative on d 1 than d 3 (P < 0.05), and fecal calcium concentrations were lower in furosemide-administered horses on d 7 as compared to d 1 (P < 0.001), indicating a potential mechanism to restore calcium balance. These findings corroborate previous studies on furosemide and calcium balance and provide evidence for a possible mechanism to recover net calcium losses after furosemide administration. In mature horses, silicon supplementation did not increase collagen degradation and/or synthesis markers in synovial fluid as compared to controls, indicating that cartilage turnover remained unaffected. While promising in bone and cartilage development in young animals, it may be too late for silicon supplementation to affect bone and cartilage in mature animals. In broilers, bone morphological and mechanical measures and density were unaffected by silicon supplementation, but supplementation did increase serum calcium concentrations and improved footpad dermatitis and hock burn welfare scores (P < 0.05). These differences demonstrate that silicon affects metabolism of other minerals and may be more beneficial for skin, rather than cartilage or bone. Overall, these studies show the difficulty of altering mature bone and cartilage composition and strength through alterations in mineral balance. Additionally, dietary silicon supplementation may not improve bone and cartilage quality but may be helpful in addressing problems associated with skin and connective tissue.
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