Tackling Pig Manure Challenges with Enzymes

26 March 2013, at 12:00am

Economic analyses show the large potential for phytase in feed to reduce overall manure management costs resulting from environmental regulations, according to Gwendolyn Jones of Danisco Animal Nutrition.

Phosphorus-based nutrient management regulations increase the amount of land required to dispose of manure and will have a detrimental effect on pig farm profitability in areas of intensive animal production. Decreasing the phosphorus content of manure through nutrition with phytase is a powerful and cost-effective approach to reduce the amount of land required for pig production and therefore reduce the cost of manure disposal.

Environmental Regulations

Due to the rich phosphorus content of pig manure, application to meet crop nitrogen requirements can result in a net accumulation of phosphorus in the soil. Although phosphorus is much less prone to leaching out of soils than nitrogen, there are concerns that over-enrichment can lead to environmental problems. Phosphorus erosion from soil can enrich surface waters, causing algae bloom, upsetting the flora and fauna balance and degrading water quality.

The concentration of animals and manure into smaller areas increases the risk of environmental contamination and the nuisance potential of farms. This has lead to changes in the regulatory climate in many countries, enforcing stricter environmental regulations, which require animal operations to meet nutrient application standards when disposing of their manure by spreading it on cropland. As a result, the overall challenge of managing manure increases in pig operations.

Availability of Land

Phosphorus-based nutrient management regulations require that manure application be limited to the phosphorus (P) needs of the crop, preventing soil phosphorus accumulation and resulting run-off into water systems. These phosphorus-based plans will often demand that the excess manure be disposed of in other ways, or on other areas of land.

Under these circumstances, the costs of excessive phosphorus supplementation and excretion are much greater than just an increased feed bill for the farmer. These additional costs include the transportation of manure that is in excess of what can legitimately be applied to land and, potentially, subsequent disposal fees.

Manure disposal costs are highest where pig densities are at their greatest and crop-land for spreading manure high in phosphorus concentration is not as available. Farms with a small land-base relative to animal numbers will face a higher cost of compliance because they are more likely to have to pay third-party contractors to remove excess manure which cannot be spread due to lack of land availability.

Cost of Manure Disposal

One of the challenges of implementing regulations or recommendations to control agricultural pollution is to evaluate the economic impacts on the livestock sector. In the Netherlands the disposal of manure currently represents five per cent of pig production costs. The costs in the Netherlands are markedly higher than in other European countries and are set to increase further between now and 2013 (Wageningen University 2011). These costs amount to 23 €-cents per kg of slaughter weight.

In the US, switching from nitrogen based livestock manure policies to phosphorus based policies has been shown to increase the cost for compliance, ranging between $0.56 and $21.74 per unit of pig production capacity (Yap et al., 2004). The larger estimates represented the farms with the least flexibility in meeting regulations. Survey data used to assess the economic impacts of alternative regulations on manure application on Heartland pig farms in the US also revealed that phosphorus-based restriction would increase pig production costs and could affect the financial well-being of pig producers (Huang et al., 2003).

Strategies in Environmentally Efficient Countries

The ability to manage modern pork production systems for minimal environmental pollution has improved dramatically during the past decade in Denmark. According to a study by the Danish Pig Research Centre (2010), Denmark is now one of the world's most environmentally efficient pig producing countries. The study shows that nitrogen and phosphorus excretions from Danish pigs have been cut by 41 per cent and 46 per cent, respectively, since 1985 (Table 1).

Table 1. Development in nitrogen and phosphorus excretion per pig in Denmark, 1985-2010
(Source Danish Pig Research centre)
1985 2010 % change,
kg nitrogen per finished pig 5.1 3.02 -41
kg phosphorus per finished pig 1.05 0.57 -46

These reductions were made possible by five major factors:

  • the use of amino acids in feed, with consequent lower feed protein (nitrogen) contents
  • improved feed efficiency via genetic development, with an improvement of 0.1 feed units per kg growth every four years
  • altered housing systems and production methods, e.g. the replacement of traditional flooring by slatted floors and slurry systems
  • a higher body protein retention, with consequently lower levels of nitrogen excretion and
  • the addition of enzymes to feed.

Manure Management with Phytase

About 60 to 70 per cent of the total phosphorus in feedstuffs commonly used in pig diets exists as phytate phosphorus. Pigs are unable to use this phosphorus because they cannot break down the phytate molecule. The use of the enzyme, phytase, in pig diets helps to break down most of the phytate complex in the pig's digestive system, releasing phosphorus and other nutrients such as amino acids and calcium. Consequently, supplementation of phytase to growing-finishing pig diets allows feed formulators to reduce inorganic phosphate inclusion rates while maintaining animal performance similar to that observed with traditional formulations containing higher levels of inorganic phosphate. This helps to reduce the cost of feed and can reduce phosphorus excretion in manure.

Studies, including economic analyses carried out in Canada and the US, have shown that adding phytase to pig diets helps to reduce the incremental costs resulting from compliance with environmental regulations based on phosphorus-restriction and from the rising cost of mono-calcium phosphate (MCP), which in turn is linked to rising oil prices.

The Manitoba Livestock Manure Management Initiative in Canada compared the incremental cost per marketed pig of compliance with different phosphorus manure management strategies for farms with and without phytase in their feed. For the strategies where no extra land was available and manure needed to be transported over a certain distance, increased cost per marketed pig averaged C$1.2 in fattening pig operations. By adding phytase to the pig feed, the additional cost of complying with the nutrient standards could be decreased by around 43 per cent on average (Silvano et al., 2006).

Less Land Required with Phytase

A study in Holt country, Nebraska in the US carried out by the University of Nebraska showed that a pig producer was able to reduce the amount of land required for manure management from 300 acres to 186 acres per year, when reducing the amount of supplemented dietary phosphorus with the use of phytase in growing-finishing pig diets (Brumm, 2002). The pig manure was reduced by 34 per cent in phosphorus content in the phytase fed pigs compared to pigs fed the control diet.

A more recent study carried out in Germany (Table 2) demonstrated a significant reduction in phosphorus excretion in manure (-35 per cent) and the area of land required per 1,000 pigs (-35 per cent), when pigs were fed an E.coli phytase.

Table 2. Performance and amount of land required in response to replacing monocalcium phosphate (MCP)in diets of fattening pigs in Germany
(adapted from Stalljohann and Schulze-Langenhorst, 2011)
Control with MCP in the diet Phytase (Phyzyme XP)
without MCP in the diet
Start/end weight (kg) 29.0 / 120.7 29.1 / 120.8
Daily weight gain (g) 878 873
Feed conversion 2.58 2.54
Margin over feed cost/pig (€) 75.5 76.6
Carcass backfat (cm) 2.5 2.6
Carcass lean meat (%) 57.6 57.3
Bone ash (g/kg fat free dry matter) 581.9 587.0
Calcium (% in bone ash) 38.2 37.5
Phosphorus (% in bone ash) 17.8 17.5
P intake per pig (g) 1022 818
P-excretion per pig (g) 582 378
Amount of land required (ha/1,000 pigs)* 17.8 11.5
*with 75kg P2O5 fertilisation per hectare of agricultural land; 1 ha = 2.471 acres.


Environmental issues associated with pig production, and the disposal of manure, are becoming more regulated and complying with the resulting legislation is expensive and time consuming.

Advances in feed management increase the options available to pig producers for reducing nutrients in manure.

Economic analyses show the large potential for phytase in feed to reduce overall manure management costs resulting from environmental regulations.

March 2013