Role of Protein Intake in Containment of Ammonia Emissions in Dairy Cattle

In ruminants excess dietary Nitrogen (N) is excreted as urea mainly through urine. Urea, the major form of urinary N is rapidly converted to ammonia after excretion. Ammonia is an important environmental pollutant that impacts the quality of human and animal life .The NRC (2001) considered ammonia emissions from concentrated animal feeding operations (CAFO) as a major air quality concern. Ammonia can cause serious environmental problems and health issues in gaseous or particulate phases. Dairy cattle contributed 13% of the total NH3 emissions for the year 2002 while all animal operations including dairy contributed 55% of the total NH3 emissions. Thus decreasing N excretion from dairy cows will help reduce ammonia pollution. Ruminants are only 30% efficient in converting intake N to milk or tissue N and the remaining N is lost into the surroundings. Nitrogen efficiency could be as high as 80% in pigs, assuming similar potential, increasing N efficiency in lactating cows will decrease N excretion. Great improvements in N efficiency could be achieved by reductions in feed N if milk production could be maintained. In addition to the economic and environmental impacts, feeding excess Crude Protein may affect the fertility of dairy cows thus, it is beneficial to avoid excess dietary protein in lactating dairy cow diets without compromising milk production. Decreasing dietary RDP than recommended, proper Protein:carbohydrate ratio and feed additives will have positive economic and environmental impacts if diets can be constructed to maintain milk and milk protein production in dairy cows. Milk production may be maintained when essential AA requirements are met by maximizing ruminal microbial protein outflow.