Fat is often added to swine diets not only as a source of energy but also as an effective way of reducing the amount of dust in swine buildings. On-farm feed mixers can incorporate fat in either a liquid or dry form. Larger amounts (>7%) of fat in the diet may, however, prevent feed from flowing freely in storage bins and feeders, thus causing "bridging" in feeders.
Fat can rapidly become rancid when using feed-grade oils/fats if the fat is not protected from oxidation. Antioxidants added to the fat at the time of storage prevent the occurrence of rancidity. Routinely adding an antioxidant to all fat/oil sources upon their arrival is a good management practice. Another approach is to be sure that it was added when processed at the rendering plant.
The addition of fat to the mixer should be during the last part of the mixing process so that it can be rapidly incorporated and prevented from covering the sides of the mixer. It is best to mix the diet for a few minutes and then add the fat during the last two to three minutes of mixing.