Utilization of endogenous and dietary urea in the large intestine of the mature horse.

The research focuses on the metabolic processing of nitrogen in mature horses when they are fed with a low nitrogen diet or a diet supplemented with urea or soybean meal to meet their nitrogen requirements. It concludes that urea supplementation does not provide any beneficial effect to horses.

Study Design and Diets

• The study analyzes the metabolic response of mature horses against three types of diets – a low nitrogen diet, a diet supplemented with urea, and one supplemented with soybean meal.
• These diets were designed in such a way to meet the predicted nitrogen requirements of the horses.

Measurements and Observations

• The researchers observed that the digestibilities of Dry Matter (DM), organic matter, and neutral-detergent-fibre were similar across all three diets. This implies that the type of diet did not significantly influence the digestion process of these substances.
• However, nitrogen digestibilities and digestible nitrogen intakes were similar for the urea and soybean supplemented diets, and quite low for the low nitrogen diet. This indicates a more efficient use of nitrogen in diets supplemented with urea or soybean meal than the low-N diet.

Metabolism of Nitrogen

• For all three diets, plasma urea (a waste product of protein metabolism) was degraded in the digestive tract to ammonia, which was then utilized by the bacteria in the gut as a nitrogen source.
• Some ammonia was absorbed from the large intestine into the blood and converted back into urea, while some were incorporated into plasma proteins.

Effect of Diet on Urea Degradation

• The study found that horses fed on the low-N diet degraded more of their endogenous urea (internal urea produced by the horse’s own body) in the digestive tract than those fed on the urea or soybean supplemented diets.
• Horses fed on the urea diet had the highest degradation rate of urea, indicating an increased metabolic processing of urea in these horses.
• However, the amount of urea degraded in the digestive tracts of horses fed on the urea-supplemented and the low-N diets could not compensate for the lack of dietary crude protein in these diets. As a result, horses on these diets were found in a negative nitrogen balance.
• On the other hand, horses on the soybean diet showed a positive nitrogen balance, highlighting the value of protein-rich soybean meal in balancing horses’ nitrogen needs.

Summary and Conclusion

• In conclusion, the supplementation of urea in the diet did not provide any notable benefit to the horses. In contrast, the soybean supplemented diet was able to sustain a positive nitrogen balance in horses, suggesting it as a more beneficial feed supplement for horses’ nitrogen requirements.