Reducing ammonia emissions from dairy farms : insight into the Maltese islands dairy

Abstract

A major source of atmospheric ammonia pollution is the excreted nitrogen from dairy cows. Although the amount of ammonia evolved depends on the total amount of nitrogen excreted, studies show that the amount of urinary nitrogen contributes much more than the amount of fecal nitrogen. Urinary nitrogen depends exponentially on nitrogen intake; while nitrogen excreted in faeces and milk increase only linearly with nitrogen intake. Empirical equations describing these relationships are described. Although not precise, these equations are very useful to provide reasonable estimates of atmospheric ammonia emissions as a function of nitrogen intake. Typical feeding methods and quantities as used on Maltese dairy farms are described. It is shown that ammonia pollution may be decreased significantly by limiting nitrogen intake to less than 400g per day per milking cow, without significantly reducing milk quality. As a side benefit cost cutting is achieved by improved nitrogen efficiency of the cow. Other methods of reducing ammonia pollution from dairy cows, besides that of manipulation of nitrogen intake, are also discussed.