Effects of crystalline amino acid supplementation to the diet on odour from pig manure

Odour emission from pig facilities should be taken into account due to the nuisance caused to the people living in the surroundings. Different compounds identified as odorants are intermediate or end products of aminoacid (AA) metabolism. Thus, the objective of the study was to determine whether the type of AA can influence odour from prig manure or manure characteristics.

The study involved a total of 18 barrows that were distributed into three treatments. The animals were penned individually, and each pen had a separate manure pit. Experimental treatments consisted in three diets; the control diet (CT) that was a basal diet with AA supplementation to provide the maximum protein gain, the Sulfur-AA (SAA) supplemented diet, which had three times the requirement of metionine and cystine, and a diet that contained two times the requirement of tryptophan, phenylalanine and tyrosine (TAA). All the AA supplementation was achieved by adding crystalline amino acids.

Collected samples from the manure pit were used to determine odor, ammonia, and manure composition analyses. Air samples, also obtained from the manure pit, were used to determine odour concentration, hedonic tone, and odour intensity.

Results showed that feeding the barrows the SAA diet resulted in an increase (P < 0.05) in the odour emission, odour intensity and reduced odour hedonic tone, the latter indicating that the odour resulted less pleasant. Manure characteristics were also affected by the diet, results showing increased total nitrogen (N) excretion in the SAA diet, and increased Ammonia-N concentrations in the SAA and TAA diets compared to CT. As expected, TAA diet provoked an increase in the concentration of cresols and indole compounds, and SAA diet determined an increase in the 4-ethyl phenol concentration compared to TAA diet.

At the light of the results it is clear that in order to reduce odour from pig manure, sulphur-AA should be formulated very near the requirement for the animal.