You want to feed the least-expensive diet that promotes optimal pig growth. That only makes economic sense.

But if you cut or drop nutrients from the diet, make sure your pigs' growth rates don't drop off.

The Purina Swine Research Group did a trial that omitted supplemental vitamins and trace minerals in the finisher's final 45 days. Researchers found that pigs without supplements suffered slower growth.

The trial used 48 individually fed pigs, with 24 eating a control diet and 24 getting a supplement-free diet. Researchers exposed half of each group to an immunological challenge.

The pigs without the vitamin and trace mineral supplements posted lower final weights, average daily gains and feed intakes. Feed-to-gain ratios were poor as well. The results held for both the immune-challenged and healthy pigs.

Purina's recommendation, based on the trial, is to keep the vitamin and trace mineral supplements in the diet through the finishing phase. The key to saving money is not to omit these supplements; instead it's to supply them only at the levels the pigs need rather than overfeeding those nutrients.