Analysis On The Regularity Of Ammonia Emission And Effects Of Different Crude Protein Contents And Sources On Ammonia Emission From Chicken Manure

Ammonia is a major atmospheric pollutant that has adverse effects on human and livestock health and emission.This study aimed to investigate the effects of temperature and moisture content on ammonia emission in chicken manure and the pattern of ammonia emission at different times after manure discharge as well as the differences and mechanisms of flora composition,and to investigate the effects of diet composition on ammonia emission to provide support for rational control and improvement of air quality in breeding houses during emission.Experiment 1: Ammonia emission in manure at different temperatures and moisture content.Fresh manure was collected from 36-week-old hens in three groups for the temperature treatment（25℃,29℃ and 33℃）,three groups for the water content treatment（no deionized water,5% or 10% deionized water）and four groups for the temperature and water content treatment（25℃/33℃×0/10% deionized water）,with six replicates for each treatment,in a homemade gas collection device.The results showed that the amount of ammonia produced in manure per hour and the indexes of p H,urease activity,uric acid and ammonium nitrogen were measured.The results showed that the increase in temperature and water content of manure significantly increased the ammonia emission in manure（P < 0.01）,and there was a significant interaction effect between time after excretion,temperature and water content of manure on ammonia emission（P < 0.01）;the uric acid content of chicken manure significantly decreased（P < 0.01）,p H significantly increased（P < 0.01）,and 3h urease activity significantly increased（P < 0.01）with longer excretion time.activity（P <0.01）,ammonium nitrogen content（P < 0.01）,and total nitrogen content（P < 0.01）;the temperature increased,urease activity and uric acid content increased significantly（P < 0.01）,total nitrogen content in manure decreased significantly（P < 0.01）,ammonium nitrogen content increased significantly and ammonia emission increased significantly（P < 0.01）;the water content of The increase in water content significantly increased fecal uric acid content and urease activity（P < 0.01）,ammonium nitrogen content（P < 0.01）and ammonia emission（P < 0.01）from 3 h.There was a significant synergistic effect of temperature and fecal water content on fecal ammonia emission（P < 0.01）,with high temperature and high water content significantly increasing fecal urease activity and ammonium nitrogen content（P < 0.01）,ammonia emission was significantly increased（P < 0.01）.Experiment 2: Temporal variation pattern of fecal ammonia emission.Forty 56-week-old Hy-Line Brown layers were chosen for the experiment and fed in a single cage with eight hens in one replicate.The feces were gathered and observed to analyze the changes in fecal morphology and temporal patterns.Samples were collected at 0,50,170 and 480 minutes after fecal discharge to analyze the changes in physicochemical parameters and flora composition.The results showed that the manure disintegrated after 170 minutes of discharge,water was analyzed,the water content of the manure decreased significantly with time（P <0.05）,the p H value increased and then decreased（P < 0.05）,the urease activity and ammonium nitrogen content increased significantly after 170 minutes of discharge（P < 0.05）,and the total nitrogen content decreased significantly（P < 0.05）.The abundance of Firmicutes and Ruminococcus and Lachnospiraceae in the feces was significantly lower（P < 0.05）after480 min compared to the freshly excreted feces,and the abundance of Proteobacteria and Enterobacteriaceae was significantly lower（P < 0.05）.The abundance of Proteobacteria and Enterobacteriaceae increased significantly（P < 0.05）,and the urease activity and ammonium content were negatively correlated with Firmicutes.（P < 0.05）.Experiment 3 Effect of feeding diets of different compositions on ammonia emission in the feces of laying hens.Two experiments were conducted to investigate the effects of different crude protein and protein sources of diets on the emission of ammonia in chicken feces,respectively.In the experiment of different crude protein levels,288 8-week-old HyLine Brown layers were randomly divided into 2 groups with crude protein levels of 15.5%and 12.5%,respectively;in the experiment of different protein sources,432 12-week-old HyLine Brown layers were randomly divided into 3 groups: soybean meal group,cotton meal group and mixed meal group,respectively.All test hens were fed the corresponding test diets,and the feces were collected for 30 min and placed in a homemade gas collection device for the determination of fecal ammonia emission and physicochemical indexes.The results showed that the fecal ammonia emission increased and then decreased at different crude protein levels（P < 0.01）and reached the maximum value on the 4th day,the low protein diet significantly reduced the fecal ammonia emission（P < 0.01）,the fecal p H increased significantly（P < 0.01）,the urease activity increased significantly（P < 0.01）and the ammonium nitrogen content increased significantly（P < 0.01）in the first 4 days,and the fecal ammonia emission decreased by 24.81% during the test period.The ammonia emission was reduced by 24.81% during the experiment;feeding the mixed meal diet significantly increased the ammonia emission in manure after 6 d compared to the soybean meal group under different protein sources（P < 0.05）,and their manure water content was significantly lower（P < 0.05）and ammonium nitrogen content was significantly lower（P < 0.05）,and ammonia emission increased by 50.51% during the experiment.In summary,the rate of ammonia emission in chicken manure was low within 2 h after excretion,and after 2 h,the urease activity was enhanced and ammonia emission increased significantly;the increase in ambient temperature and manure moisture content increased manure ammonia emission through the change in manure urease activity and p H.The change in the composition and morphology of the fecal flora with time,the decrease in the abundance of Firmicutes,the increase in the abundance of Proteobacteria,the increase in urease activity and ammonium nitrogen content,may be the reason for the increase in ammonia emission;the level of feed protein and protein source affect the ammonia release,and the low protein diet reduces the fecal ammonia emission,while the mixed meal diet may increase the ammonia emission during storage after excretion.