Submitted to: Poultry Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/30/2003
Publication Date: 6/1/2004
Citation: Chavez, C., Coufal, C.D., Carey, J.B., Lacey, R.E., Beier, R.C., Zahn, J.A. 2004. The impact of supplemental dietary methionine sources on volatile compound concentrations in broiler excreta. Poultry Science. 83:901-910. Interpretive Summary: Over 8 billion broilers are reared each year for meat production in the U.S. Most odor nuisance reports concerning poultry farms are due to poultry manure. The primary source for odorous sulfur compounds in poultry manure is dietary sulfur amino acids, such as methionine (Met). This study evaluates the impact of different Met sources on broiler fecal volatile odor production. Broiler chicks were treated with four different Met sources and excreta samples were analyzed by an analysis method referred to as gas chromatography/mass spectrometry. Excreta from birds fed diets supplemented with liquid Met hydroxyl had significantly lower concentrations of odorous sulfur compounds than that from birds fed dry Met hydroxyl or sodium methioninate aqueous solution. These findings demonstrate that dietary methionine sources significantly influence odorous volatile concentrations in broiler excreta.
Technical Abstract: The impact of different methionine (Met) sources on broiler fecal odor volatiles was determined by evaluating the types of sulfur compounds produced in broiler excreta. Two experiments (exp.) were conducted using straight run broiler chicks raised in battery cages. In both experiments chicks were randomly distributed into 3 replications of 5 treatment groups with 16 birds per pen. The treatment groups were dry Met hydroxyl analogue (Dry MetHA), sodium methioninate aqueous solution (NaMet), liquid Met hydroxyl analogue (Liq MetHA), D,L-Met (D,L-Met), and no supplemental Met (control group). The Met activity of each Met source was 52, 45.9, 88, and 98%, respectively. All diets were formulated to either contain 0.8% (exp. 1) total Met activity or 0.5% Met activity in the starter and 0.38% Met activity in the grower (exp. 2) (except the control group, 0.35% Met activity), and otherwise met NRC nutrient requirements. Diets were fed ad libitum from day 1 to 6 weeks of age. There were no significant differences in body weights among the treatments. All excreta were collected in litter pans lined with aluminum foil. In exp. 1, at week 6, broiler excreta was collected for a 24 h period, and 4.5 g of broiler excreta from each treatment group was collected into 15 mL headspace vials. Samples were analyzed by gas chromatography/mass spectrometry. The volatile sulfur compounds that were identified and quantified in the broiler excreta were: hydrogen sulfide (H2S), carbonyl sulfide (COS), methyl mercaptan (CH3SH), dimethyl disulfide (CH3SSCH3), and dimethyl trisulfide (CH3SSSCH3). NaMet had significantly higher concentrations of H2S, COS, and CH3SSCH3 compared to all other treatment groups. Liq MetHA had significantly lower concentrations of H2S, COS, CH3SH, and CH3SSCH3 compared to the other treatment groups. Dry MetHA had the significantly highest concentration of CH3SH. D,L-Met had the significantly highest concentration of CH3SSSCH3 and the lowest concentration of H2S. The control group had the significantly lowest concentrations of CH3SH, CH3SSCH3, and CH3SSSCH3 compared to the other treatment groups. In exp. 2, at week 6, an electronic nose was used to evaluate a total of 15 air samples per treatment group. In addition fifteen air samples (containing 6 to 8 liters of air in a tedlar bag, 3 samples per treatment group) were collected for odor evaluation by a sensory panel. Electronic nose sensor data revealed that volatile compounds in broiler excreta from the control group were significantly different from the other four treatment groups. Evaluation of the air samples by a sensory panel determined that there was a statistically significant difference in odor threshold detection between the control group and the other four treatment groups. The dilution to threshold of control group, NaMet, Dry MetHA, Liq MetHA, and D,L-Met was 350, 492, 568, 496, and 526 odor units, respectively. These findings demonstrate that dietary Met sources significantly influenced odorous volatile concentrations in broiler excreta.