Effect of diet on odorant emissions from cattle manure

Abstract

Ammonia loss from livestock manure is of special concern because it contributes to odour, can impact non-targeted environments through atmospheric deposition, and represents a potential loss of available nitrogen in manure used as fertilizer for crop growth. Our study investigated the effect of three barley-based diets on manure composition and the emissions of ammonia and volatile fatty acids (VFA) from beef feedlot manure. The results of our study suggest that the metabolizable protein requirements of heavyweight feedlot cattle (400 to 550 kg) were met when finished on a barley grain and barley silage diet [12.9% crude protein (CP)]. Therefore, the ability to reduce total N content of manure or manipulate the route of N excretion is limited, unless lower protein ingredients, such as corn silage or cereal straw, were incorporated into the diet to lower the basal diet CP concentration. There was no relationship between protein level and animal weight gain in our study. There was a positive relationship (P < 0.05) between level of intake protein and ammonium-N content of the surface-sampled pen manure. However, chamber data suggested that the higher ammonium-N content of manure did not translate to any significant difference in ammonia emissions, although the lowest emission rate for surface manure coincided with the lowest protein level. There was also no significant difference in VFA emission related to diet treatments. Key words: Ammonia, volatile fatty acid, odour intensity, cattle, manure, diet