This paper represents the influence of swine nourishment with the low- and highly proteic diet on the size of ammonia emission during manure composting process. Research was carried out with usage of 4-chamber isolated bioreactor intended for model investigations of organic materials composting process. The influence of swine nourishment on the content of ammonium nitrogen in manure has been ascertained. Manure from animals feeding on highly proteic diet showed the considerably increased content N-NH4. Aside from the content of ammonium nitrogen all of the investigated manure types reached an intense termophilic phase. It has been observed that the most important factor influencing on high concentration of ammonia in composted manure is an initial content of ammonium nitrogen. The run of ammonia emission from composted manure was most intense during first 4-6 days of termophilic phase, whereby successively disappeared. The end of the termophilic phase was tantamount with ammonia concentration close to zero. Losses of nitrogen as result of ammonia emission amounted from 2,65 kg t-1 d.m. for the manure from low proteic diet to 5,0 kg t-1 d.m. of the manure coming from the highly proteic diet.