Dietary Protein Level and Season on Fecal Microbes and Odorous Compounds in Growing-Finishing Pigs

This study was done to investigate the effects of varying dietary protein levels (DPLs) and season on fecal microbes and odorous compounds in growing and finishing pigs. Thirty-six Landrace pigs were blocked based on their body weight and within each block assigned to one of the three dietary treatments (3 replicates (pens) per treatment). The DPLs used in the growing stage were 142.7, 155.4 and 174.9 gkg -1 while in the finishing stage were 97.3, 106.3 and 116.9 gkg -1 , respectively following a 3 x 3 factorial arrangement. In the growing stage, DPL and season did not alter the population of fecal aerobic bacteria, Salmonella spp, E. coli, other Gram-negative bacteria, total enterobactericiae and fungi. However, fecal coliform count increased significantly from 2.67 x 10 3 to 6.3 x 10 6 Colony Forming Unit (CFU)/g (p<0.75) during mid spring to early summer. In the finishing stage, fecal population of aerobic bacteria was reduced (p<0.09) from 1.5 x 10 9 to 2.93 x 10 8 CFU/g relative to decreasing dietary CP during mid summer. Pathogenic fecal E. coli was also effectively reduced from 3.1 x 10 7 to 6.2 x 10 5 CFU/g (p<3.43) but during midsummer only. Fecal lactic acid colony counts were not different during mid summer and late summer but were significantly increased from 2.6 x 10 8 to 7.7 x 10 8 CFU/g (p<0. 13), when DPL was increased from 97.3 to 116.9 gkg -1 during early autumn indicating a reduction in odorous compounds. DPL and body weight did not have pronounced effects on changes in the emission of iso-valeraldehyde, valeraldehyde, methyl isobutyl ketone, butanol, butyric and toluene from late spring to late summer. Only xylene was significantly reduced from 4.36 to 2.55 ugL-1 (p<0.34) across decreasing DPL during late summer. It was also further reduced to zero levels from late summer to early summer and late spring. The further reduced to zero levels from late summer to early summer and late spring. The above findings proved that reducing DPL and changes in season could cause a reduction in some fecal microflora and odorous compounds.