Emissions of ammonia and odorous compounds from pig manure have attracted attention due to their negative effects on the environment and public health. Ammonia from the pig urine is one of the major environmental contaminants. Odorous compounds produced by microbial action on the organic matter in manure include volatile fatty acids, phenolic compounds, indole compounds, and hydrogen sulphide. The odorous compounds are primarily attributed to the dietary nutrient composition, gastrointestinal environment of pigs, and chemical reactions in the slurry. Several nutritional approaches used to mitigate the ammonia emissions are available. The first method involves reducing nitrogen excretion by lowering dietary crude protein concentrations and using digestive enzymes to improve protein digestibility and utilization in pigs. The second method involves supplementing diets with acidifying agents, such as benzoic acid or adipic acid, or lowering the dietary electrolyte balance to acidify the slurry. Finally, supplementation with materials containing urease inhibitor, such as Yucca schidigera extract and humic substances can inhibit urease activation in pig manure. Methods for reducing odorous compounds have also been suggested. Reducing undigested protein in pig manure is known to reduce odorous compounds. Selected feed additives may also function either by providing a terminal electrolyte acceptor for bacteria or by reducing the population of intestinal bacteria that produce odorous compounds in pig manure. Based on the present review, however, nutritional approaches for reducing odorous compounds in pig manure are not entirely convincing. Further research is required to investigate effective ways to reduce odorous compounds in pig manure.