Mixing soybeans with dried distillers' grains and feed this to pigs might help cut feed costs for pork producers.
At Southern Illinois University Carbondale in the USA animal scientist Gary Apgar has been testing a blend of the ethanol by-product distillers' grains and soybeans, a traditional protein source for swine.
The combination turns out to be as nutritious as soybean meal and, because grains cost less than beans, it is cheaper.
“Soy meal runs about $300 per ton and contains about 47.5% crude protein, where DDGs cost about $125 per ton and contain 27% crude protein,” Apgar said. “If for $250 you can get 54% crude protein, it’s much more economical.”
Apgar’s work is part of a larger project aimed at solving two problems facing the ethanol industry: factory emissions in newer plants that exceed legal limits and the need to deal with the increased volume of by-products that will result from expanded ethanol production.
Apgar’s group, a consortium of private company representatives, university researchers and scientists from a national laboratory based in Peoria, is tinkering with the production process at a new ethanol plant in Wisconsin, hoping to cut emissions while turning the left-over grains into a more marketable livestock feed.
Newer plants generally use a dry mill process to produce ethanol, but the drying creates the most greenhouse gasses.
Wet milling solves the emissions problem, but the grains left behind spoil more easily than dried distillers’ grains and are harder to ship, thus reducing their value.
The researchers theorized that by shutting off the drying process early for about 15% of the residue, they could reduce emissions enough to meet emission standards.
Extrusion to increase value
By adding soybeans to the semi-wet grains, compressing the two and forcing them through an extruder, they hoped to create a feed with the higher nutritional value of wet grains plus the shelf life and handling ease of the dried variety.
“Extrusion involves both pressure and heat, “Apgar said. “This reaction can cause carbohydrates and proteins to bind to each other. When they don’t break down, they’re not available to the animal.”
To test the feed’s digestibility, Apgar analyzed faeces and urine produced by pigs fed wet grains, dried grains, or the extruded grains/soybean mix and those fed a grains/soy mix that hadn’t gone through the extruder.
He also wanted to know how much of the feed’s nitrogen was excreted by the pigs. Poor nitrogen digestion implicates a poor metabolic process in the pig.
Apgar found the mix performed better than he thought it would, proving significantly more digestible, in terms of the essential amino acids a pig needs, than the grains by themselves.
While roughly two-thirds of that effect came from the soybean meal, the fact that wet grains cost around $50 per ton as compared to $125 for dry grains means the mixed feed would cost less than rations consisting solely of either dried grains or soybeans.
When it came to nitrogen, Apgar found that although extruded feed containing distillers’ grains did lessen the amount of nitrogen the pig used, the excess tended to wind up in the faeces rather than the urine.
“That’s not a bad thing because the effluent can be used in crop production (as fertilizer), where a high nitrogen content better matches corn production needs,” Apgar said.