Minimizing Odor from Swine Manure

Livestock Update, January 2003

Heather Harris and C. M. Wood, VA Tech

Two major elements that are of concern in nutrient management, phosphorus (P) and nitrogen (N), also contribute to the odor of swine manure. Nitrogen is particularly important because it is a component in ammonia. The amount of N and P that are excreted as waste are affected by three factors (Reese and Koelsch, 2000):

• The amount of N and P consumed;
• The proportion of the N and P consumed that are used for growth and reproduction; and
• The amount of N and P represented by secretions, sloughed cells and bacteria in the intestine.

During the lifespan of a pig, different nutrient levels are required at different stages of growth, so it has been suggested that pigs be fed on a phase feeding program. To encourage lower N excretion the pig should be fed the correct amount of amino acids at each phase of the feeding program. If the pig does not receive the proper amount of amino acids the N efficiency decreases while the N excretion increases (Reese and Koelsch, 2000).

The most limiting amino acid in swine diets is lysine. In meeting this one requirement, standard diets give rise to excesses of other amino acids. Replacing 100 lb of soybean meal with 3 lb of crystalline lysine and 97 lb of corn reduces N by about 16%, without affecting pig performance (Reese and Koelsch, 2000). Other amino acids such as crystalline tryptophan, threonine, and methionine can also be used to reduce N excretion but are high in cost.

Pigs lack the intestinal enzyme phytase, which breaks down phytate P in cereal grains and other plant sources. Using phytase with inorganic P sources can help reduce the amount of P excreted in the manure because inorganic P sources such as dicalcium phosphate can be added to the diet based on the amount of actual P available in the supplement (Reese and Koelsch, 2000). From an odor-control viewpoint, using less dicalcium phosphate is important because it contains sulfur, which is a component of many odor-causing compounds.

Although reducing N and P will help alleviate odor, other strategies are also needed. Using a natural, carbon-mineral (NCM) supplement known as Promax® in swine diets to reduce odor production is a fairly new concept. Professors at Texas Tech University used this compound as a feed supplement in a study that resulted in a 5 to 40 % reduction in air ammonia from pigs fed Promax® (Kim et al., 2002). Pigs (n=96) weaned at 21 days of age were used in this study. Half were assigned to a control group and half to the treatment (NCM) group. The NCM diet was supplemented with .05% NCM. The pigs were fed on a three-phase feeding program. Groups of eight pigs were placed in a ventilated environmental chamber for two days to measure the amount of ammonia in the air. Results showed no effect of treatment in the first 24 hours. However, the second 24 hour measuring period showed that there was 5 to 40% less ammonia in the air. The air ammonia was also affected by the amount of pig activity: the more activity, the more air ammonia that was present. Results indicated that this formulation of NCM may reduce air ammonia to differing degrees depending upon the time of day and pig activity levels. More research needs to be done, but Promax® appears to show some promise as an odor mitigating feed additive.

References
Kim, S. W., F. Ji and J. J. McGlone. 2002. Reducing odor in swine production: Effect of a natural carbon-mineral supplement on odor reduction. J. Anim. Sci. 80(Suppl. 1):111 (Abstr.)

Reese, D. E. and Rick Koelsch. 2000. Altering Swine Manure by Diet Modification. Neb. Coop. Ext. Pub. G99-1390-A. http://www.ianr.unl.edu/pubs/swine/g1390.htm. Accessed Nov. 2002.

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