Effects of dietary energy and phosphorus content on blood chemistry and development of growing horses.

This study looks at how different amounts of energy and phosphorus content in diets affect the growth and clinical biochemistry of 42 young horses over a 30-week period, with data collected every 2 weeks. It reveals that variances in dietary phosphorus did not significantly affect the horses’ growth, food consumption and occurrence of musculoskeletal abnormalities.

Research Methodology and Results

• The experiment examined 42 light horse weanlings, fed on different diets that ranged from high-forage diets (between 73 to 77% alfalfa) to high-concentrate diets (between 63 to 65% grain and grain by-products). Phosphorus (P) content in these diets varied from low (.24 to .35%), normal (.68%), to high (.95 to 1.06%).
• Body weights of the horses and blood samples were taken every two weeks as a method to monitor the effects of the varied diets.
• The research indicated that the calcium and phosphorus digestibility were highest for horses that consumed the low phosphorus diets. However, only horses that consumed forage-low phosphorus diets might have absorbed insufficient phosphorus.
• It was observed that factors such as serum alkaline phosphatase activity, serum calcium, serum magnesium, and plasma copper concentrations were not influenced by the diet but on the other hand were altered among the different sampling periods.
• The concentration of serum calcium and phosphorus in the blood samples of all groups fluctuated up to week 10 before stabilizing at average levels of 2.77 and 2.03 mmol/liter, respectively.
• The study found that plasma zinc levels increased with the age of the horses and were 3.8 percent greater in concentrate-fed horses than forage-fed horses.

Findings and Conclusion

• Mild to moderate physitis and flexure limb deformities were noted in 88 percent of the weanlings, mainly between the 6th and 8th week of the study. However, most of these deformities were largely resolved by week 12.
• The study concluded that marginally deficient phosphorus intakes did not significantly alter productivity, feed intake, blood mineral concentration in the final 20 weeks, or the occurrence of musculoskeletal abnormalities in weanling horses.
• Thus, the research offers substantial insights into the dietary needs of growing horses, suggesting the resilience of young equines to variance in the phosphorus content of their diet.