Dietary protein affects nitrogen excretion and ammonia emission from slurry of growing-finishing pigs

The effects of dietary protein on nitrogen excretion and ammonia emission f rom slurry of growing-finishing pigs were studied both in vitro and in a pi g house. The three diets had similar contents of NE, minerals, vitamins and ileal digestible lysine, methionine + cystine, threonine and tryptophan, b ut differed in CP content (16.5, 14.5 and 12.5%). In the balance experiment , 18 castrated males of about 55 kg body weight were allotted to the three diets. The experiment lasted 9 weeks, which were divided into three 3-week periods. In each period, urine and faeces were collected separately for 7 d ays in metabolism cages and mixed as slurry. A sample of this slurry was pl aced in a laboratory system to measure ammonia emission for 7 days. In the barn experiment, 216 pigs were housed in three compartments and fed the exp erimental diets. Ammonia emission was measured directly from the compartmen ts for 7 days during each of the 3-week periods. There was no effect of die tary CP level on faecal nitrogen excretion. Urinary nitrogen excretion and slurry pH decreased when dietary CP decreased. Both balance and barn experi ments showed similar effects of dietary CP on ammonia emission from slurry. Ammonia emission was reduced by 10-12.5% for each percent decrease in diet ary CP. It is concluded that lowering dietary CP and supplementing essentia l amino acids while maintaining normal growth rate reduces urinary nitrogen and ammonia emission from the slurry of growing-finishing pigs. (C) 1998 E lsevier Science B.V. All rights reserved.