Characterizing ammonia emissions from horses fed different crude protein concentrations.

This study explores the impact of different dietary protein levels on the emission of ammonia (NH) from horses. The researchers find that overfeeding crude proteins (CP) results in increased levels of urinary nitrogen and urea-N, which contributes to the release of more NH into the environment.

Objective of the Research

The aim of this study was to characterize the NH emissions from horses fed different concentrations of crude protein (CP). The researchers hypothesized that an increase in CP intake beyond required levels would lead to a rise in NH emissions from horse urine and feces. They also proposed that different bedding materials could affect these emissions.

Research Design and Methodology

• Nine adult gelding horses were used in this study, and the experimental setup followed a 3×3 replicated Latin square design. This type of setup allows for examining the effects of different treatments (in this case, varying CP levels in feed) on each test subject.
• The horses’ diets consisted of different ratios of bahiagrass and Tifton-85 bermudagrass hays, and a commercial vitamin mineral supplement. These diets were formulated to contain low, medium, and high amounts of CP (measuring 10.6%, 11.5% and 12% respectively).
• The experiment included an 11-day diet adaptation phase, followed by a three-day total collection of urine and feces from the animals.
• Total nitrogen (TN) and urea-N concentrations were determined from samples pooled by period, and for in vitro assessment of NH concentrations, fecal and urine samples were combined with either wheat straw or wood shavings.
• A vessel system was used to measure ammonia emission, with readings captured using a photoacoustic multigas analyzer. From this, the researchers calculated NH emission rate.

Findings

• The study found that as the horses’ crude protein intake increased, so did the excretion of urinary total nitrogen and urea nitrogen.
• Despite the same CP diet, NH concentrations in the vessel differed based on the bedding type. Straw bedding had higher NH concentration than wood shaving bedding.
• The cumulative NH emission rate also seemed to differ based on both diet and bedding types. Diets higher in CP and straw beddings resulted in higher NH emissions.

Conclusion and Implications

The research concludes that overfeeding horses with crude protein can lead to increased excretion of urinary total nitrogen and urea-N, which in turn potentially leads to greater releases of NH into the atmosphere. This has implications for stable management and feed strategies, suggesting the necessity to monitor and control dietary CP levels to maintain a sustainable environment around equine facilities.