A research study conducted at New Fashion Pork in Jackson, MN, tested a new concept of fine-grinding either the corn portion or the whole diet when the diet contained higher levels of by-products in addition to corn to improve the energy value.

Kansas State University (KSU) researchers hypothesized that the new concept for feed processing would be to grind complete diets post-mixing and then pellet. Pelleting diets should be considered through most stages of production to improve average daily gain and feed:gain in light of ingredient prices where the cost of pelleting is more easily justified.

Study Parameters

For the study, 855 pigs weighing 56 lb. were placed on feed in a 111-day trial to evaluate the effects of corn particle size, complete diet grinding and diet form (meal or pellet) on finishing growth performance, caloric efficiency, carcass characteristics and economic payback.

Pens of pigs allotted by body weight and housed 19 pigs/pen were randomly placed on one of five dietary treatments with nine replications per treatment.

The diets were fed in a four-phase feeding program from Day 0 to 35, 35 to 65, 65 to 93 and 93 to 111.

Each diet phase included the same corn-soybean meal-based diet containing 30% distiller’s dried grains with solubles (DDGS) and 20% wheat midds for all five experimental treatments within each phase. The five treatments involved applying different processing techniques to the same diet: 1) roller-milled corn ground to approximately 650 microns fed in meal form; 2) hammer-milled corn ground to approximately 320 microns fed in meal form; 3) applying treatment #2 but fed in pelleted form; 4) applying treatment #1 but with the complete diet reground through a hammer mill to approximately 360 microns fed in meal form; and 5) applying treatment #4 but fed in pelleted form. All diets were prepared at New Fashion Pork’s feedmill in Estherville, IA.

At Day 93 of the trial, pens of pigs were weighed and the three heaviest pigs selected were shipped 350 miles to Triumph Foods in St. Joseph, MO, for slaughter.

Also, on Day 100, the next three heaviest pigs selected were shipped to Triumph Foods for slaughter. The remaining pigs were transported to Triumph Foods on Day 111 for slaughter.

Transportation distance and summer temperatures produced lower carcass yields than typical commercial production.

Overall, reducing particle size of the corn from 650 to 320 microns did not affect average daily gain or average daily feed intake, but did improve feed efficiency, caloric efficiency, feed cost/lb. of gain and IOFC (Table 1). Every 100-micron reduction in particle size improved feed efficiency by about 1%.

In the KSU study, fine-grinding the corn fraction significantly increased income over feed cost (IOFC) by $4.67, and pelleting this diet improved it further to $8.93 over the control diet. When evaluating the entire fine-ground diet, when in meal form IOFC only improved $0.69, but when that diet was pelleted, it had an IOFC of $8.08 compared to the same diet not reground and in meal form with almost 650-micron corn.

Pelleting the diet improved average daily gain, feed efficiency, caloric efficiency, final weight, hot carcass weight and loin depth and increased backfat.

Pelleting also reduced feed cost/lb. of gain and increased IOFC. Grinding the complete diet increased feed cost/lb. of gain and reduced IOFC and loin depth.

KSU researchers conclude that performance can be improved through a variety of feed-processing technologies.

“Fine-grinding corn and pelleting the diet improved efficiency of gain and economic return in finishing pigs,” said Jon De Jong, the graduate research assistant who led the KSU team. “The response to corn particle size is particularly significant because the diets used in the study included only 30 to 39% corn due to the inclusion of DDGS and wheat midds; however, fine-grinding the entire diet and feeding in meal form reduced feed intake.”

When the fine-ground diet was pelleted, feed intake improved, resulting in the highest growth rate of any treatment, researchers indicated.

Disappointing was the fact that feed efficiency and caloric efficiency were identical in pelleted diets, regardless of whether only the corn was finely ground or if the complete diet was finely ground.

This indicates that fine-grinding DDGS, wheat midds and soybean meal did not improve their energy value as measured by feed:gain.

This project was partially funded by the National Pork Board.

Researchers: J.A. De Jong, J.M. DeRouchey, M.D. Tokach, R.D. Goodband, S.S. Dritz, J.L. Nelssen and L. McKinnley, Kansas State University. For more information, contact De Jong by phone (616) 780-9063 or e-mail jadejong@ksu.edu.