Farm practices as they affect NH<inf>3</inf> emissions from beef cattle

Beef cattle farms in Canada are very diverse, both in size and management. Because the total biomass of beef cattle in Canada is larger than any other livestock sector, beef also has the potential for the largest environmental impact. In this study we estimate NH3 emissions associated with beef cattle production across Canada using data on farm practices obtained from a detailed survey answered by 1380 beef farmers in 11 Ecoregions. The farms were various combinations of cow/calf, backgrounding and finishing operations. The proportion of animals on pasture varied markedly among Ecoregions, especially for cows and calves, and this markedly affected the estimated NH3 emissions. The crop components of feed also varied among Ecoregions, but the resulting crude protein concentrations were quite consistent for both backgrounding and finishing cattle. Manure was stored longer in the west than in the east, and fall spreading of manure was notably more common in the west, especially when spread on tilled land. The estimated NH3 emissions per animal were relatively consistent across Ecoregions for confinement production, but because the proportion of animals on pasture varied with Ecoregion, so did the overall estimated NH3 emissions per animal. Temperature is a key factor causing Ecoregion differences, although husbandry and manure management practices are also important. Hypothetical best management practices had little ability to reduce overall emission estimates, and could not be implemented without detailed cost/benefit analysis.