Introduction

The dry milling process used in these studies involved tempering the corn in water (5, 7, or 10% added in the experimental test runs) in a small helical mixer turning at low rpm for up to 30 minutes. Tempered kernels were then augured into a Beall degerminator and subjected to a combination of abrasion and cracking forces. Material exiting the degerminator was collected as “tails” or “throughs” fractions and represented primarily endosperm. These fractions contain mainly starch and were expected to be most desirable to use in swine rations. Both tails and throughs were passed through an aspirator which used upward air flow to remove small particles and flakes of pericarp (containing most of the fiber).

Aspirated tails and throughs were passed through a roller mill set with a relatively wide (3 mm) gap so that endosperm particle size was reduced as little as possible, while germ was rolled flat. Germ material was rolled flat, rather than break into smaller particles, because germ absorbed water at the tempering step faster than endosperm, and germ contained high levels of fat. Material exiting the roller mill was passed over a #10 mesh sieve (1.68 mm openings) to remove germ from tails and throughs.

The pericarp portion (hulls) contained the greatest level of fiber (32.6% NDF) and a large portion of the phosphorus (Table 1). The germ fraction contained most of the phosphorus (0.92% P ) and a relatively high percentage of fiber. Thus, the remaining portions (tails and throughs) were low in fiber and phosporus and were expected to be superior products from both a nutritional and environmental perspective.

Digestibility of the corn fractions obtained from the dry milling process was tested in eight grower pigs. Samples were obtained from the end of the small intestine of these pigs for digestibility measurements (ileal digestibility) because limited uptake of nutrients takes place in the large intestine.

Ileal digestibility of dry matter was lower in the germ and hull fractions compared to tails, throughs, and regular corn (Table 2). Further, digestibility of phosphorus was extremely poor in the germ fraction, which also had lower overall amino acid digestibility.

In conclusion, the nutritional value of corn can be improved by removing the hull and germ. This would result in a product (tails and throughs fraction combined) with a 10% greater dry matter digestibility and 36% less fecal dry matter production (data not shown).

Reproduced Courtesy