The Effect of Paylean and Dietary Crude Protein Level on Odor Production and Nutrient Concentration in Anaerobically Stored Pig Manure

The pressure on swine producers to produce more environmentally friendly pork has increased in recent years as swine production units have become larger. Large pork production units have the potential to concentrate large volumes of manure in small land areas. Decreased land area for manure application contributes to nutrient build up in soil, which can lead to contaminating waterways from runoff and leaching into ground or surface waters. Odors from pork production units have threatened their existence in some areas and have often led to nuisance lawsuits against production units. The majority of odors from swine units are created from the anaerobic degradation of excreted nitrogenous, sulfur and carbohydrate compounds in manure. Paylean (ractopamine hydrochloride) has been shown to enhance nitrogen utilization for lean growth in finishing pigs, but the effect of Paylean on nitrogen and phosphorus excretion and odorous compound production in stored manure is unknown. The objective of this study was to determine the production of odorous compounds and the concentration of nutrients in stored manure from pigs fed a Paylean diet at two levels of crude protein (CP) during the late finishing period. Experimental Procedure Twenty-four DeKalb EB crossbred barrows (Initial BW = 185 lbs.) were adapted to stainless steel metabolism stalls for total collection of feces and urine. Pigs were adapted to stalls for eight days followed by a ten-day acclimation to one of the four following treatments: 1. 13.8% CP, 0.80% Lys (control) 2. 13.8% CP, 1.10% Lys with 18 g/ton (20 ppm) Paylean (ractopamine-HCl) 3. 16.1% CP, 1.10% Lys 4. 16.1% CP, 1.10% Lys with 18 g/ton (20 ppm) Paylean (ractopamine-HCl) A three-day total collection followed the diet acclimation period for use in simulated anaerobic pit systems. Pigs were fed at 2200 g/d and 4800 ml/d of water in four even feedings (700 h and 1600 h). Feces and non-acidified urine were collected twice daily prior to feeding. Urine was refrigerated at 38°F (3°C) and feces were stored at 50°F (10°C) during collection to maintain bacterial populations while minimizing bacterial activity. Feces and urine were blended based on the dry matter (DM) of feces to obtain a final slurried mixture of 7.5% DM. Manure from two pigs per treatment was paired for the slurry mixtures to obtain three pooled replicate samples per treatment. Simulated anaerobic pits were set up in four-liter glass jars using two liters of slurry from the last day of collection as the initial inoculum. Paired samples were used in duplicate jars for a total of 23 jars (n = 5, 6, 6, and 6 for diets 1, 2, 3, and 4; respectively). Additional slurry of each treatment was frozen in 38 mL aliquots and added to the jars three times a week (Mon., Wed., and Fri.). Jars were capped and air was pumped across the headspace of each jar at 200 cc/minute. Simulated pits were maintained for 64 days. Olfactometry air samples, total volatile fatty acids (VFAs), gas chromatography fibers, and mixed slurry samples were taken from each jar at d 0, 17, 35, and 64. Air samples were collected in 10 L Tedlar bags