IMPACT of hydrolyzed feather meal
on odorous compounds in swine feces
A total of 120 pigs (BW=23.2 kg) were used to determine the impact of hydrolyzed feather meal on odorous compounds in fresh swine feces. Pigs were blocked by weight and randomly allotted, within block, to three dietary treatments (5 pigs/pen, 8 pens/treatment). Treatments consisted of corn-soybean meal-poultry fat basal diets containing 0, 4, or 8% hydrolyzed feather meal. Diets were fed in four phases (4 wk each) and were formulated to contain 1.00, 0.90, 0.75, and 0.60 apparent ileal digestible lysine for phase 1 to 4, respectively, with other amino acids provided at an ideal ratio. Available P and ME were kept constant within each phase. On wk 9 of the trial (phase 3 diets; contained 19.4, 18.9, and 21.6% CP for the 0, 4, and 8% feather meal treatments, respectively), fecal samples were obtained from at least 2 pigs per pen, pooled by pen, and analyzed for odorous compounds. Butanoic acid (19.7, 32.1, 39.6 ppm) and pentanoic acid (6.1, 8.0, 14.3 ppm) concentrations were greater (P < 0.05) in feces from pigs fed 8% feather meal compared to control pigs. The concentration of 3-methylbutanoic acid (1.6, 1.6, 4.0 ppm) was greater (P < 0.05) in feces from pigs fed 8% feather meal than feces from pigs fed 0 or 4% feather meal. Inclusion of 4% feather meal reduced (P < 0.05) the concentration of 3-methylphenol (7.6, 1.0, 2.9 ppm) compared to pigs fed control diets and inclusion of 8% feather meal reduced (P < 0.05) the concentration of 4-methylphenol (4.7, 3.5, 3.3 ppm) and decane (55.1, 39.0, 15.2 ppm) compared to control pigs. The concentration of indole (0.19, 0.07, 0.05 ppm) was reduced (P < 0.05) when 4 or 8% feather meal was included. Concentrations of other detectable compounds (acetic acid, propionic acid, 2-methylindole, 3-methylindole, nonanal, undecane, dodecane, tridecane, and tetradecane) were not affected (P > 0.11) by dietary treatments. Results clearly demonstrate that odorous compounds in feces can be affected by the inclusion of hydrolyzed feather meal in diets of growing-finishing pigs. The exact impact of these changes on odor perception remains to be elucidated.
Feather meal is a feed ingredient with a high protein content that has potential value for the swine industry. Traditionally, it has been recommended to limit the use of feather meal in growing-finishing pig diets to a maximum of 5% (Seerley, 1991). More recent research (Chiba et al., 1995) demonstrated that levels of feather meal as high as 15% could be used in finishing pigs (57 to 109 kg) without causing a reduction in pig growth. In a subsequent trial, Chiba et al. (1996) evaluated the inclusion of 0, 3, 6, 9, or 12% of feather meal in finishing pig diets. Growth and feed efficiency worsened as the inclusion of feather meal increased. However, an improvement in performance was observed at the 3% inclusion level. Up to 9% of feather meal could be included without negatively affecting carcass characteristics. A clear conclusion could not be reached from this experiment due to large variability in the data (Chiba et al., 1996). Although these studies suggest that feather waste could be used as a value added product in swine diets at limited inclusion rates, no direct research is available on the effects of feather meal on manure quality and odorous compounds. Hobbs et al. (1996) demonstrated that diets high in crude protein caused and increase in odorants produced compared to low protein diets. Because diets containing feather meal would typically be higher in protein content, one could speculate that both nitrogen excretion and concentration of odorous compounds would be increased with the inclusion of high levels of feather meal.
Therefore, the objective of this study was to determine the effects of hydrolyzed feather meal inclusion on odorous compounds in feces of modern lean growing-finishing pigs.
Materials and Methods
A total of 240 pigs (initial BW was 23.2±1.3 kg) was allotted based on BW and gender to a 2 x 6 factorial arrangement of treatments (4 pens per treatment; 5 pigs per pen) in a randomized complete block design. Modern genotype pigs were used in this trial and were considered typical of pigs used by the integrated swine industry in North Carolina. Factors consisted of: 1) gender (barrows or gilts) and 2) dietary treatment (0, 2, 4, 6, 8, and 10% of hydrolyzed feather meal inclusion). The feather meal used in this trial was produced by steam hydrolyzing raw feathers with added blood. This process breaks the keratin bonds between proteins in feathers and makes a highly digestible, high protein product. After hydrolyzing, the feather meal was ring-dried to below 10% moisture and screened.
Odorous compounds were analyzed in fecal samples obtained on wk 9 of the experiment as described by Rizzuti et al. (1999) using a gas chromatography-mass spectrometer (HP 6890Plus, Hewlett Packard Company, Palo Alto, CA). Standard solutions containing odorous compounds (acetic acid, propionic acid, iso-butyric acid, butanoic acid, 3-methylbutanoic acid, pentanoic acid, phenol, 3-methylphenol, 4-methylphenol, 2-ethylphenol, 3-ethylphenol, 4-ethylphenol, 2,6-bis(1,1-dimethylethyl)phenol, indole, 2-methylindole, 3-methylindole, 4-methylindole, decane, undecane, dodecane, pentane, gamma-butyrolactone, nonanal, 1-decene, tridecane, tetradecane, nonane, carbon disulfide, dimethyl disulfide, ethanethiol (ethyl mercaptan), propanethiol, butanethiol) were used to derive standard curves for quantifying the occurrence of these compounds in fecal samples.
Data were analyzed as a randomized complete block design using the GLM procedures of SAS (SAS Inst. Inc., Cary, NC). The model included sex, feather meal inclusion level and the sex by feather meal inclusion interaction. Significant differences between the different inclusion levels were determined following a significant F-test by using the least significant difference method.
Results and Discussion
Hobbs et al. (1996) demonstrated that increasing the crude protein content of the diet could lead to an increase in the production of odorous compounds. Phenols and indoles arise from protein degradation and have been found in freshly voided feces (Spoelstra, 1977). Volatile fatty acids are produced mainly in feces from fiber and protein degradation (Spoelstra, 1979). Therefore, measurement of odorous compounds in feces may be superior as an indicator of odor production, particularly because significant problems exist with air sampling methods and the fact that most odorous compounds appear to originate from feces (O’Neill and Phillips, 1992). On wk 9 of the trial (phase 3 diets; contained 19.4, 18.9, and 21.6% CP for the 0, 4, and 8% feather meal treatments, respectively), fecal samples were obtained from at least 2 pigs per pen, pooled by pen, and analyzed for odorous compounds. Butanoic and pentanoic acid concentrations were greater (P < 0.05) in feces from pigs fed 8% feather meal compared to control pigs (Table 1). The concentration of 3-methylbutanoic acid was greater (P < 0.05) in feces from pigs fed 8% feather meal than feces from pigs fed 0 or 4% feather meal. Inclusion of 4% feather meal reduced (P < 0.05) the concentration of 3-methylphenol compared to pigs fed control diets, and inclusion of 8% feather meal reduced (P < 0.05) the concentration of 4-methylphenol and decane compared to control pigs.
Table 1. Odorous compounds in feces from pigs fed different levels of feather meala
The concentration of indole was reduced (P < 0.05) when 4 or 8% feather meal was included. Concentrations of other detectable compounds (acetic acid, propionic acid, 2-methylindole, 3-methylindole, nonanal, undecane, dodecane, tridecane, and tetradecane) were not affected (P > 0.11) by dietary treatments. Compounds that were measured but not detected included 2-methyl propanoic acid, phenol, 4-ethylphenol, 3-ethylphenol, 2,6-bis(1,1-dimethylethyl)phenol, carbondisulfide, ethanethiol, dimethylsulfide, dimethylamine, butyrolactone, nonadecane, pentane, nonane, and 1-decene. In agreement with this study, Hobbs et al. (1996) reported greater concentrations of volatile fatty acids and branch-chain volatile fatty acids in slurry from pigs fed high protein diets. In addition, they reported increased levels of 4-methylphenol (p-cresol), indole, and skatole in slurry from pigs fed high protein diets. However, Sutton et al. (1999) observed no differences in phenolic compounds or sulfur-containing compounds in feces from pigs fed either 10, 13, or 18% CP diets. In contrast to these studies, we reported reduced levels of 3-methylphenol in feces from pigs fed 4% feathermeal, 4-methylphenol in feces from pigs fed 8% feathermeal, and indole in feces from pigs fed 4 and 8% feather meal. This is surprising, because only the diet with 8% feather meal contained a greater level of protein. Hammond et al. (1989) reviewed the origin of odorous compounds in livestock waste and reported that phenolic compounds are produced from tyrosine and phenylalanine, indole and skatole from tryptophan, and sulfides from the sulfur amino acids. Therefore, we expected these compounds to increase with increasing levels of feather meal inclusion. Sulfur containing compounds can contribute significantly to odor because of their low odor detection treshold and their relatively high concentration in livestock waste. However, the sulfur containing compounds we attempted to measure were not detected in fresh feces of pigs. Hobbs et al. (1996) reported that sulfides were produced primarily after a few days of anaerobic storage. In addition, sulfides could be detected primarily in the headspace and were not present at detectable quantities in the slurry (Hobbs et al., 1997) or in fresh feces (O’Neill and Phillips, 1992).
In summary, these results demonstrate that odorous compounds in feces can be affected by the inclusion of hydrolyzed feather meal in diets of growing-finishing pigs. The exact impact of these changes on final odor perception remains to be elucidated.
Chiba, L. I., H. W. Ivey, K. A. Cummins, and B. E. Gamble. 1995. Effects of hydrolyzed feather meal as a source of extra dietary nitrogen on growth performance and carcass traits of finisher pigs. Anim. Feed Sci. Technol. 53:1-16.
Chiba, L. I., H. W. Ivey, K. A. Cummins, and B. E. Gamble. 1996. Hydrolyzed feather meal as a source of amino acids for finisher pigs. Anim. Feed Sci. Technol. 57:15-24.
Hammond, E. G., C. Heppner, and R. Smith. 1989. Odors of swine waste lagoons. Agric. Ecosystems, Environ. 25:103-110.
Hobbs, P. J., T. H. Misselbrook, and B. F. Pain. 1997. Characterisation of odorous compounds and emissions from slurries produced from weaner pigs fed dry feed and liquid diets. J. Sci. Food Agric. 73:437-445.
Hobbs, P. J., B. F. Pain, R. M. Kay, and P. A. Lee. 1996. Reduction of odorous compounds in fresh pig slurry by dietary control of crude protein. J. Sci. Food Agric. 71:508-514.
O’Neill, D. H., and V. R. Phillips. 1992. A review of the control of odour nuisance from livestock buildings: part 3, properties of the odorous substances which have been identified in livestock wastes or in the air around them. J. Agric. Engng. Res. 53:23-50.
Rizzuti, A. M., A. D. Cohen, P. G. Hunt, and M. B. Vanotti. 1999. Evaluating peats for their capacities to remove odorous compounds from liquid swine manure using headspace solid-phase microextraction. J. Environ. Sci. Health, B34:709-748
Seerley, R. W., 1991. Major feedstuffs used in swine diets. In: E. R. Miller, D. E. Ullrey, and A. J. Lewis (Eds.), Swine Nutrition, Butterworth-Heinemann, Boston, MA. pp. 451-481.
Spoelstra, S. F. 1977. Simple phenols and indoles in anaerobically stored piggery wastes. J. Sci Food Agric. 28:415-423.
Spoelstra, S. F. 1979. Volatile fatty acids in anaerobically stored piggery wastes. Neth. J. Agric. Sci. 27:60-66.
Sutton, A. L., K. B. Kephart, M. W. A. Verstegen, T. T. Canh, and P. J. Hobbs. 1999. Potential for reduction of odorous compounds in swine manure through diet modification. J. Anim. Sci. 77:430-439.
 Previously presented at the International Symposium on “Addressing Animal Production and Environmental Issues”, Research Triangle Park, NC, Oct. 3 – 5, 2001.