Crossbred pigs 3 to 4 weeks of age were randomly assigned from outcome groups based on weight and sex to one of four dietary treatments either with or without added soybean oil or hulls. Nursery air quality was evaluated by measuring the concentrations of ammonia, carbon dioxide, settled dust, suspended particle size, and by microbiologically culturing air samples. Weekly performance data was also collected. ADG was unaffected by dietary treatment. ADFI was increased when soybean hulls were added to the ration with the difference being significant in trials 1 and 2 and over-all. Adding soybean oil to the ration produced slightly lower feed intakes over all trials but was not significant. Rations with added soybean oil reduced F/G, whereas, the addition of soybean hulls increased F/G for over-all trials. The response to soybean oil was less when soybean hulls were added. A comparison of rations 1 and 4 showed only slight differences in ADG, ADFI and F/G. The addition of soybean oil resulted in a 47% reduction in settled dust for trials 1 and 2 combined, and a 45% reduction for trial 3. Mean bacterial colony counts for each week and over-all for trial 3 were lower when soybean oil was added to the ration. Ammonia and carbon dioxide concentrations were not affected by dietary treatment. From the results of this experiment, the addition of soybean oil to starter diets improved nursery air quality and performance in some cases, however, gas concentrations were not different. / Master of Science