Using crude glycerol in sow diets

What is glycerol?

Glycerol is a co-product of biodiesel production. For each gallon of biodiesel produced, about 0.66 pounds of crude glycerol are generated.

Glycerol could serve as an energy source in swine diets. Researchers in Iowa determined that the energy content of crude glycerol is about 95 percent of the energy present in corn. Starch and fats have been traditional sources of energy in U.S. swine diets. If biodiesel production continues, glycerol could become an important energy source for pork production.

Effects of glycerol in sow diets 

We evaluated the effects of glycerol in the diets of 345 sows. We assigned the sows to corn-soybean meal-based diets containing 0%, 3%, 6%, or 9% crude glycerol. The crude glycerol contained

• 86.1 percent glycerol
• 6.01 percent salt
• Less than 100 parts per million of methanol

Due to the high salt content of crude glycerol, we excluded supplemental salt from diets containing 6% and 9% crude glycerol. We imposed dietary treatments on day 109 of pregnancy. After sows farrowed their litters, we allowed them to eat as much of their assigned experimental diet as they wanted.

Results 

Including up to 9 percent crude glycerol had no significant effect on the sows:

• Weight or backfat loss.
• Litter size or weight at weaning.
• Time needed to rebreed after the pigs were weaned.

Dietary treatment tended to affect the daily feed intake of sows, mostly between sows fed 3 and 6 percent glycerol. There’s no apparent explanation for the lower feed intake of sows fed the 6 percent glycerol diet.

Dietary glycerol did not affect water use or breathing rates of sows.