The increase in the number of larger pig production units has focused attention on properly applying manure in a manner that will not create excesses of any nutrients in the soil. The nutrient most commonly quoted is nitrogen, with phosphorus a close second.

Phosphorus is present in significant amounts in the ration ingredients fed to animals, however animals cannot digest the complexed molecule in which phosphorus occurs due to the lack of the proper enzyme. This necessitates the addition of mineral phosphorus to ensure an adequate digestible source of this nutrient for growth and maintenance.

European farms in some locations reached a point where excessive levels of phosphorus are limiting the expansion of animal agriculture. This has brought to the forefront research on ration additions that improve the digestion of ration nutrients and reduces the dependence on added ingredients.

One such additive that is showing promise is phytase. This is the enzyme which animals lack for improved release of plant-source phosphorus. Phytase has a varied response when added to the rations for pigs. Some grains have a natural level of phytase on the hull of the kernel while other grains have little or none. Examples of grains that are high in naturally occurring phytase are wheat and rye; barley is intermediate, while corn and soybean meal are low. Naturally occurring phytase helps overcome the indigestibility of plant phosphorus (phytic acid) and also some of its other anti-nutritive effects. As expected, wheat-based rations supplemented with added phytase have a low response while corn-based rations show large improvements in P digestibility. There are other minor effects including a slight improvement in nitrogen and amino acid digestibility.

Phytate P, a combination of phytic acid and its salts (phytate), is a major contributor to total plant phosphorus. Eeckhout and Depaepe (1994) report, for European grain and oil seeds, the proportion of total P represented as phytate in cereals is 59-70%, in legume seeds about 20-46% and from 34-66% in oil seed meals as measured in 51 samples.

The best responses to phytase supplementation are seen from corn/soy diets where P digestibility increased by 40% and for canola meal diets where P digestibility improves by 50%. Age groups respond differently to phytase supplementation and research will further quantify responses for us.

As this information becomes clear, it will be easier to identify what rate and category of pigs will give us our best economic return to phytase supplementation.

For further information on breeding management, contact your swine specialist.