Posted July 2008

The environmental effects of swine production are becoming increasingly important to pork consumers and producers alike.
Joel DeRouchey, associate professor of animal sciences and industry at Kansas State University, discussed ways for pork producers to manage the environmental footprint of their operations during a seminar June 5 at the World Pork Expo in Des Moines.
DeRouchey focused on lowering nutrient excretion of swine, determining impacts of Distiller’s Dried Grains with Solubles (DDGS) on nutrient management plans (NMPs), and determining the impact of the production phase on manure.
Some practices recommended by DeRouchey to lower nutrient excretion include reduction of particle size, reduction of feed wastage, split-sex or phase feeding, pellet diets, growth enhancers, and feeding of highly digestible ingredients including synthetic amino acids and phytase. Phytase is an enzyme that assists in breaking down phytate phosphorus.
Other technologies starting to be implemented include feeding of high fermentable carbohydrates such as soybean hulls and feeding of grains with higher bioavailability such as NutriDense Corn, DeRouchey said. NutriDense corn will increase amino acid digestibility and lower nitrogen excretion. This may help reduce the need for other amino acid additions.
DDGS in swine diets
The increasing use of DDGS and other by-products has raised questions of how these by-products impact manure and nutrient excretion.
“Use of DDGS has dramatically increased over the past few years due to the price relative to corn and other ingredients,” DeRouchey said. “When feeding ruminant animals, DDGS have a higher feeding value and can be used at higher inclusion levels than when feeding mongastrics.”
Use of DDGS will increase the dietary crude protein or nitrogen content in an animal’s manure because they are a poor lysine source. The increase in dietary crude protein is moderated in DDGS by using higher levels of synthetic lysine. A 15 percent DDGS diet with high synthetics will increase crude protein by one percent. This increase in crude protein could increase odor and ammonia emissions by as much as 10 percent.
“When we feed distillers, we will get more nitrogen, making the value of that manure higher,” DeRouchey said. “The use of DDGS does not impact land application when used at regular inclusion levels.”
DDGS are a good phosphorus source and allow for a decrease in supplemental dietary phosphorus.
Daily fecal excretion will increase 15 percent for every 10 percent of DDGS added to a swine diet. This is due to increased fiber content and reduced amino acid digestibility compared to corn and soybean meal.
DeRouchey offered these take home messages for the use of DDGS in swine diets:
  • The use of DDGS should not significantly affect the NMP/(Comprehensive Nutrient Management Plan (CNMP) of a swine operation.
  • Planners may need to update their planning tools to reflect farm-specific animal performance and feed technologies.
  • Book values for manure excretion and typical manure concentrations from five or more years ago are likely to not be representative of current manure production.

Manure sampling
Different types of operations differ in the amount of nutrients excreted. The time of year when samples are collected and the depth from which samples are collected also will affect reliability of manure samples.
Due to higher levels of anaerobic digestion, nitrogen levels in lagoons will be lower in warmer months. The opposite is true for phosphorus content as it will be at its highest levels during summer months. Knowing this information makes it even more important to take samples close to the time of application, as it may affect the application rate.
“As we look at differences in lagoon water, there is no reason we shouldn’t be seeing the same things in deep pits as well,” DeRouchey said.
Nutrients will tend to settle to the bottom of deep pits. When sampling manure, it is best to sample from an agitated pit to get a more accurate sample.
Production phases also will impact nutrient content in the manure.
“Nursery, wean-to-finish and finish were always higher,” DeRouchey said. “A potential argument is that we had some of our finishing diets over-formulated for phosphorus, so we excreted more.”
Zinc oxide levels were highest in the nursery production phase. High levels also were recorded in the wean-to-finish phase with a downward linear pattern from finish diets to farrow-to-finish then sow diets.
DeRouchey also found that manure from hoop barns has much higher nutrient content than previously reported for solid swine manure. Nitrogen levels were nearly double what is listed by the Midwest Plant Service and phosphorus levels were nearly three times higher.
“When you use book values for manure management planning in these cases, we are way off for solid bedded manure values,” DeRouchey said. “I would expect many producers will see the same thing.”
If you would like more information about environmental impacts of swine operations and ways to limit nutrient excretion, contact DeRouchey at
“Things have changed a lot in the last 10 years and I think they will continue to change,” DeRouchey said. “We recognize the value of a good manure sample.”