Dietary protein can affect air quality

Reducing the amount of protein in your horse’s diet could, ultimately, protect his respiratory health, according to a new study.

Researchers at the University of Florida and University of Delaware teamed up to investigate the effects of dietary protein on the amount of nitrogen in urine and feces. Nitrogen is a component of ammonia, explains Jessie Weir, PhD. “Excess protein in the diet is broken down into nitrogen in the small intestine,” she says. “That nitrogen is then excreted as urea, which breaks down into ammonia in the stall. Ammonia is what causes the acrid smell that you can detect in a barn when the stalls need to be cleaned or the ventilation isn’t sufficient.”

Besides having a strong smell, ammonia is caustic. “It irritates the nose and lung tissue, causes excess mucus production and has been proven to contribute to respiratory problems, such as heaves,” says Weir.

For the study, the researchers fed nine horses three forage-based diets with different levels of protein. “The highest protein diet we fed was 12 percent, which isn’t really that high by industry standards,” says Weir. Throughout the study period, the horses wore a special harness that was used to collect their urine, which was then combined with either wood shavings or wheat straw and tested for ammonia levels.

The data showed that the higher protein diets led to significant increases in the nitrogen levels in urine. Also evident was the contribution that bedding materials make to ammonia emissions. “Straw bedding had higher levels of ammonia emissions than shavings for every diet we tested,” says Weir. “What happens is the urine falls through the straw to evaporate while shavings absorb it. It’s a tradition to bed young foals on straw, but that might not be the best choice if it’s going to lead to higher levels of ammonia.”

Weir says this study shows that cutting down on the protein in a horse’s diet could lower the amount of ammonia in his stall. “It is easy to overfeed protein and this is one more reason to try to reduce it if you can,” she says, adding that management practices can also help. “Cleaning stalls regularly is very important, and consider using an additive to neutralize ammonia. Ventilation is also critical. You smell ammonia more in the winter months, when the barn is shut up tight for human comfort. Open the doors and the windows.”

Reference: “Characterizing ammonia emissions from horses fed different crude protein concentrations,” Journal of Animal Science, August 2017

This article first appeared in the December 2017 issue of EQUUS (Volume #483)

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