Published: March 27, 2008 12:20 pm            

Pork Professor: Another biofuel co-product for feeding hungry pigs?

Originally published in the March 21, 2008, print edition.

Biofuels have taken this country by storm — it seems everyone in agriculture and a large portion of the general population are talking about biofuels and green energy.

The ethanol co-product, distiller’s dried grain with solubles, has become an important feedstuff for livestock including pigs.

Another biofuel receiving increasing attention is biodiesel. During biodiesel production, 100 pounds of fat or vegetable oil (usually soybean oil) is combined with 10 pounds of methanol to yield 100 pounds of biodiesel and 10 pounds of crude glycerol.

The fat source used for biodiesel production can be just about anything ranging from used restaurant grease to animal fat from a packing plant.

In Minnesota, most biodiesel production relies on soybean oil. While the biodiesel is used to power trucks and buses and tractors, the crude glycerol is left for other uses.

With the increasing popularity of biodiesel, there will be a mountain of glycerol to use. Currently, there are four plants in Minnesota with a capacity to produce 63 million gallons of biodiesel (and 22,000 tons of glycerol) annually.

On a national scale, 171 plants produce biodiesel with an annual production capacity of nearly 1.4 billion gallons, and will produce about 511,000 tons of glycerol when at full capacity. There are many uses for glycerol. However, the high cost of traditional feedstuff has encouraged livestock producers to consider glycerol as an energy source.

Glycerol could serve as an energy source for pigs, but limited research has been reported on its nutritional value in swine diets. Preliminary research done in Iowa with nursery pigs and growing-finishing pigs suggests that glycerol contains nearly as much energy as that found in corn.

This suggests that glycerol is easily digested and metabolized making it a readily available energy source for pigs with high energy needs such as rapidly growing pigs and lactating sows.

Glycerol also plays a role in water balance of the body. Several researchers have reported that consumption of glycerol enhances water retention in humans. Consumption of glycerol-containing water increased blood volume, and decreased heart rate, rectal temperature and urinary output of human endurance athletes during exercise in hot weather.

Lactating sows have a high demand for water to drive milk production, especially during summer with elevated environmental temperatures. We suspect that glycerol may benefit lactating sows under these heat stress conditions.

The influence of glycerol on water balance may extend to muscle tissue. European researchers fed glycerol to growing-finishing pigs and found a 25 percent reduction in drip loss of retail pork cuts and a 14 percent reduction in moisture loss during cooking when pigs received 5 percent glycerol in their diet. So, eating quality of pork may be improved if the pigs are fed glycerol before harvest.

We are currently conducting two studies to evaluate the utility of crude glycerol in swine diets. These studies are funded by pork checkoff dollars from the Minnesota Pork Board and West Central, a farmer-owned cooperative and soybean processor located in Ralston, Iowa.

Our first study used 300 lactating sows at the Southern Research and Outreach Center in Waseca during this past summer and early fall. Sows received diets that contained zero, 3, 6 or 9 percent crude glycerol from the SoyMor biodiesel plant near Albert Lea.

We measured sow and piglet performance in addition to selected blood characteristics in sows. Data from this study are being summarized currently.

Our second study involves 216 growing-finishing pigs at the West Central Research and Outreach Center near Morris that are being fed zero or 8 percent crude glycerol. Growing-finishing pigs receive the glycerol-containing diets from 50 to 260 pounds body weight or in the last six weeks of the finishing period.

We are measuring growth performance of pigs throughout the trial. In addition, we will study meat quality and eating quality of pork harvested from pigs fed glycerol for various lengths of time.

Preliminary performance data suggests no noticeable adverse effects of feeding 8 percent glycerol to market pigs.

It is clear to us that biodiesel production and the associated production of glycerol will increase dramatically in the foreseeable future. The production of biodiesel will utilize fats and oils that could otherwise provide energy to swine diets.

Similarly, ethanol production utilizes the starch of corn which would normally provide energy to swine diets.

Since the production of biofuels will consume a significant quantity of ingredients that would normally supply energy to drive pork production, it is imperative that pork producers seek out alternative sources of energy for feeding pigs. A thorough evaluation of results from our studies will give a good indication if crude glycerol can be a practical addition to diets for sows and finishing pigs.

We plan to have all our results summarized in the next few months. Stay tuned to the “Pork Professor” for results in coming months.

        

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