Feeding High Moisture Corn Instead of Dry Rolled Corn Reduces Odor Production in Finishing Beef Cattle Manure Without Sacrificing Performance

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1 1 2 3 Feeding High Moisture Corn Instead of Dry Rolled Corn Reduces Odor Production in Finishing Beef Cattle Manure Without Sacrificing Performance S. L. Archibeque, H. C. Freetly, D. N. Miller, and C. L. Ferrell The authors are Shawn L. Archibeque, Postdoctoral Fellow, Harvey C. Freetly, Research Animal Scientist, Daniel N. Miller, Microbiologist, and Calvin L. Ferrell, Research Animal Scientist, Nutrition Research Unit, USDA-ARS, U.S. Meat Animal Research Center, Clay Center, Nebraska. Corresponding author: Calvin L. Ferrell, USDA-ARS, U.S. Meat Animal Research Center, P.O. Box 166, Clay Center, NE ; phone: ; fax: ; ferrell@ .marc.usda.gov. ABSTRACT. We hypothesized that feeding steers high moisture (HM) corn in lieu of dry rolled (DR) corn would reduce both the amount of starch being excreted in the manure and the associated odor production. These innovative research methodologies could advance this area of research by demonstrating that dietary modification can substantially reduce the odor production from cattle finishing operations. One hundred, fortyeight composite steers were fed either the DR or HM based diets in 10 pens of 15 animals and eight Charolaissired steers were used in a supporting experiment to assess nutrient balance. Feeding HM corn reduced fecal excretion of starch from 448 to 292 g/d compared to steers fed DR corn. Steers fed HM corn tended to have a slightly lower average daily gain but final carcass weight, yield, and quality grade did not differ between treatments. In manure slurry incubations with soil and water, total VFA concentration was reduced in manure from the HM fed steers (97 mm) compared to DR fed steers (180 mm). Similarly, there was a decrease in total starch, alcohol, free glucose, and initial lactic acid concentration in the slurries from the HM manure. This was accompanied by an increase in the ph of the HM slurries. However, there was a slight increase in the branchchain VFA in the HM slurries. These data suggest that feeding HM corn is a viable method to decrease fecal starch and odor production in a finishing cattle system with modest impact on animal productivity. Keywords. Cattle Waste, Starch, Odor, Nutrient Balance INTRODUCTION Starch is the major energy component of grains and as such, the major source of energy to substantial portions of the beef feedlot industry, which feeds a large amount of grains to increase the energy density of the diet. However, the availability of starch in a grain for utilization by a growing steer is dependent on several factors. One of the most influential factors is the processing of grain. High-moisture corn is more rapidly degraded in the rumen (Stock et al., 1987a,b) than is dry rolled corn and has demonstrated improvements in beef cattle performance and efficiency (Ladely et al., 1995). Agricultural odors present an increasingly difficult and pressing problem. This problem will only continue to grow as people begin to live near areas that were previously used primarily for agricultural purposes. Odors from confinement livestock operations are produced primarily via an incomplete fermentation of livestock waste by bacteria (Mackie et al., 1998). This waste contains many nutrients that may be utilized by the bacteria for odor production, such as starch, proteins, nonprotein nitrogen, lipids, and nonstarch polysaccharides. Miller and Varel (2001) demonstrated that malodorous volatile fatty acids (VFA) are the dominant cattle manure fermentation products, which are produced primarily by fermentation of starch (Miller and Varel, 2001; 2003). Therefore, feedlot management and feeding 1 Mention of a trade name or manufacturer does not constitute a guarantee or warranty of the product by the USDA or an endorsement over products not mentioned. 1

2 practices that influence the utilization and/or excretion of starch by cattle may significantly affect the production of odor from these systems. The purpose of this study was to address the hypotheses that steers fed diets with less rumen bypass starch will release quantifiably less starch in their manure than steers fed diets higher in rumen bypass starch, which will result in decreased odor production from these manures. MATERIALS AND METHODS ANIMALS AND EXPERIMENTAL PROCEDURES A balance trial (Experiment 1) was conducted to determine nutrient balance and utilization of a dry rolled (DR) or high moisture (HM) corn finishing diet. Eight crossbred (1/2 Charolais 3/8 Angus 1/8 Piedmontese) steers were used in a switchback design with a 24 d adaptation period to each diet followed by a 6 d total collection of feces and urine. A feedlot trial (Experiment 2) used 148 MARC III (a four breed composite consisting of ¼ Angus, Hereford, Pinzgauer, and Red Poll) yearling steers to evaluate feedlot and carcass performance. This study was conducted as a split-plot design with diet fed to the pen as the whole plot effect (10 pens) and steers implanted with trenbelone-acetate (Finoplex-H), estradiol benzoate/progesterone (Synovex-S), or no implant as the subplot effect. The three implant strategies were used to evaluate the effects of diet over a variety of growth rates. The U.S. Meat Animal Research Center s Animal Care and Use Committee approved these experiments. Cattle feedlot soil and 10 fecal composite samples were collected 17 weeks into Experiment 2. Immediately after collection, the DM and OM content of the fecal composite was determined. Waterextractable constituents (alcohols, VFA, aromatic ring-containing compounds, L-lactate, and free glucose) and starch content of the particulate fraction were also measured (Miller and Varel, 2003). The volatile organic compounds (VOC) emitted from fecal composite samples were collected and sampled using a dynamic flux chamber (Woodbury et al., 2004) and solid phase microextraction (SPME) techniques. Briefly, the lower bowl was filled with manure (manure surface area = 523 cm 2 ), and allowed to equilibrate within the chamber for at least 10 min (air flow = 1.1 L/min). A SPME fiber (75 µm PDMS/Carboxen) from a portable field sampler (Supleco, Bellefonte, PA) was then inserted through a septum was exposed to the air stream for 5 min. Odor compounds bound to the SPME fiber were quantified by GC-MS. Relative total manure emissions and emissions of specific classes of compounds were compared based upon peak area (total ion current) corrected for any water vapor peak, if necessary. STATISTICAL ANALYSIS The MIXED procedure of SAS (SAS Inst. Inc., Cary, NC) was used for statistical analysis of data. For Experiment 1, the model included the independent variables; steer, period, and grain type, with steer and period treated as random effects. The model for Experiment 2 included grain type, implant treatment, and the two-way interaction with pen(grain) treated as a random effect. When treatment effects were significant, (P < 0.05) a difference was determined and a tendency for treatment to elicit a response was noted when P < RESULTS AND DISCUSSION In Experiment 1, steers fed the HM diet (4846 g/d) consumed less (P = 0.02) starch than those fed the DR diet (5407 g/d). This was accompanied by a concomitant increase (P = 0.03) in starch digestibility and a decrease (P < 0.01) in fecal starch from 91.7% and 448 g/d in the DR fed steers to 94.1% and 292 g/d in the steers fed the HM diet. Therefore, we were successful in generating a feeding system that resulted in lower levels of fecal starch. Although N intake was decreased (P < 0.01) in the HM steers (150 vs. 187 g/d), there was no difference in the amount of N retained between the two treatments (P = 0.55). 2

3 In Experiment 2, there was a tendency (P = 0.08) for the steers fed HM to have a reduced N intake, and there was similarly a tendency (P = 0.06) for a reduction in average daily gain from 1.53 kg/head in the DR steers to 1.44 kg/head. However, this was not a substantial enough difference to decrease final live weight (P = 0.19) or carcass weight (P = 0.23) between the two treatment groups. Also, the gain:feed ratio did not differ between the two treatment groups (P = 0.24). In addition, there were no significant differences in carcass composition characteristics between the two groups. This is similar to the findings of Owens et al. (1997) who summarized the effects of feeding grains with varying methods of processing on feedlot performance and noted no difference in feed efficiency and modest decreases in rate of gain and dry matter intakes when cattle were fed HM in lieu of DR corn. The ph of fresh fecal composites (Table 1) was lower (P = 0.02) in the DR feces (5.99) than the HM feces (6.35), which would enhance VFA volatility from the DR feces. This was evident by the substantial increase (P = 0.04) in total ion current area, an arbitrary measurement of total VOC output by the system, from in the HM feces to x 10 6 in the DR feces. The DR manure slurries had greater starch content than the HM slurries (Figure 1), until the starch was depleted to negligible levels. Consequently, the pattern of VFA increase was more rapid and occurred to a much greater extent in the DR slurries than in the HM slurries (Figure 1, P < 0.05). The increase in metabolic products was not limited to VFA. Glucose concentrations (Figure 2) rapidly increased in the DR slurries by day 3 and then dropped back to near negligible levels, which was accompanied by a similar spike in L-lactate concentrations. However, there was not a similar response in the HM slurries, which was expected, due to the aforementioned decrease in starch content of those slurries. There was also a similar pattern in ph, which decreased at a greater rate and to a greater extent in the DR slurries (data not shown). This was attributed to the increased production of lactate and VFA. This decrease in ph would also serve to increase the volatility of the VFA from the slurry. However, there was also a greater (P < 0.05) increase in the branched-chain VFA in the HM slurries than in the DR slurries (data not shown). Branched-chain VFA are a product of protein fermentation (Mackie et al., 1998) and this increase in the HM slurries may have been the result of alternative energy source utilization by the bacteria when less starch is available. These results were very similar to those reported by Miller and Varel in both cattle (2002) and swine (2001) manures. Like those studies, we have provided further evidence supporting the supposition that the starch content of manure largely influences production of potentially malodorous compounds from manure. Furthermore, we have provided a practical and readily usable method of reducing the starch content of beef cattle on finishing rations without substantially altering performance. 3

4 121 Table 1. Volatile odor compound production (percent of total volatile production) and ph of fresh fecal composites of steers fed high moisture or dry-rolled corn diets in Experiment 1. Treatment Item Dry Rolled High Moisture SE P-value a ph Dimethyl S Propanal Acetone Butanal Ethyl Acetate Butanone Ethanol Butanol Propanol Butanol Dimethyl S Dimethyl S Total S compounds Total alcohols Total ketones Total ion current area c Dry Rolled Starch High Moisture Starch Dry Rolled VFA High Moisture VFA Starch, mg/g DM VFA, mol/gdm Day of Manure Incubation Figure 1. Total starch and Volatile Fatty Acid (VFA) concentration of incubated manure composite slurries from steers fed high moisture or dry-rolled corn diets in Experiment 2. 4

5 Dry Rolled Glucose High Moisture Glucose Dry Rolled Lactate High Moisture Lactate Glucose, mmol/l Lactate, mmol/l Day of Manure Incubation Figure 2. Total glucose and L-lactate concentration of incubated manure composite slurries from steers fed high moisture or dry-rolled corn diets in Experiment CONCLUSION These data demonstrate that feeding a high-moisture corn based diet in lieu of a dry-rolled corn finishing diet will reduce the production of malodorous compounds in both fresh fecal composites and in a manure slurry that was incubated over time. This demonstrates a simple feeding practice for reducing odor production from confined cattle feeding operations. However, more research is needed to evaluate other feedstuffs that have high starch digestibilities, but not necessarily less total starch, such as steam flaked corn. ACKNOWLEDGEMENTS The authors wish to thank J. Barkhoff, J. Byrkit, C. Felber, C. Haussler, T. Post, and J. Waechter for their assistance. REFERENCES Ladely, S. R., R. A. Stock, F. K. Goedeken, and R. P. Huffman Effect of corn hybrid and grain processing method on rate of starch disappearance and performance of finishing cattle. J. Anim. Sci. 73: Mackie, R. I., P. G. Stroot, and V. H. Varel Biochemical identification and biological origin of key odor components in livestock waste. J. Anim. Sci. 76:

6 Miller, D. N., and V. H. Varel In vitro study of the biochemical origin and production limits of odorous compounds in cattle feedlots. J. Anim. Sci. 79: Miller, D. N., and V. H. Varel An in vitro study of manure composition on the biochemical origins, composition, and accumulation of odorous compounds in cattle feedlots. J. Anim. Sci. 80: Miller, D. N., and V. H. Varel Swine manure composition affects the biochemical origins, composition, and accumulation of odorous compounds. J. Anim. Sci. 81: Owens, F. N., D. S. Secrist, W. J. Hill, and D. R. Gill The effect of grain source and grain processing on performance of feedlot cattle: A review. J. Anim. Sci. 75: Stock, R. A., D. R. Brink, R. T. Brandt, J. K. Merrill, and K. K. Smith. 1987a. Feeding combinations of high moisture corn and dry corn to finishing cattle. J. Anim. Sci. 65: Stock, R. A., D. R. Brink, R. A. Britton, F. K. Goedeken, M. H. Sindt, K. K. Kreikemeier, M. L. Bauer, and K. K. Smith. 1987b. Feeding combinations of high moisture corn and dry-rolled grain sorghum to finishing steers. J. Anim. Sci. 65: Woodbury, B. L., D. N. Miller, R. A. Eigenberg, and J. A. Nienaber Development and application of an inexpensive chamber for analysis of VOC s. Proc., State of the Science of Animal Manure and Waste Management. San Antonio, TX. 6