While DE and ME values for DDGS are fairly close to those of the parent grain, the high fibre and protein content make that energy less available to the pig.
Competition from the biofuels industry for traditional feed ingredients means that producers must now consider a range of alternative feed ingredients such as co-products from grain and pulse processing, says Dr. Martin Nyachoti from the University of Manitoba.
However, he told delegates at the recent Saskatchewan Pork Symposium that in order to maximize their effectiveness, it is important to characterize their nutritive value correctly. Nyachoti said the value of ingredients such as DDGS and expeller canola cake, which are high in protein, fat and fibre, are underestimated by traditional measurements.
“In particular, the continued use of digestible energy (DE) and metabolizable energy (ME) misrepresents their energy value,” Nyachoti said. “Determination of net energy (NE) for alternative ingredients is necessary to achieve predictable growth performance.”
The process of making DDGS from various grains and grain mixtures ferments starches to ethanol and concentrates the remaining protein, fibre and fat fractions by a factor of three. “Because the energy comes from these components rather than starch, the net energy system best expresses its value to the pig,” said Nyachoti. “Unfortunately the NE
Bernie Peet is president of Pork Chain Consulting Ltd. of Lacombe, Alberta, and editor of Western Hog Journal. values for DDGS are yet to be determined.” While DE and ME values for DDGS are fairly close to those of the parent grain, the high fibre and protein content make that energy less available to the pig. However, Nyachoti points out that trials at the U of M have demonstrated that a multi-enzyme supplementation in a 30 per cent wheat DDGS-based diet resulted in growth performance and apparent total tract digestibility of dry matter, energy, and crude fibre in growing pigs was commensurate to that of the control without DDGS.
“There is a need to investigate the potential of the fibre-degrading enzymes in mitigating the negative impact of DDGS fibre on energy availability and determine the NE value of DDGS with enzyme supplementation,” he said.
Another co-product that may be valuable is crude glycerol, which comes from biodiesel production, mainly from canola oil. “With the bulk of canola production being in Western Canada, it’s likely that supply of glycerol may in the future outstrip the demand for glycerol in the pharmaceutical industry,” Nyachoti said. “This will present the hog industry with an opportunity ingredient.”
Glycerol is an energy source for the pig and recent research suggests that it can be used in nursery pig diets. However Nyachoti said there are several obstacles to its use, in particular that it contains methanol, which is poisonous. Glycerol is not yet approved as a feed ingredient in Canada.
Expeller-pressed canola cake contains 10-15 per cent oil that can provide additional energy in swine diets, but there is limited information about its value. Compared to NRC values for solvent-extracted canola meal, the NE value is 40 per cent higher due to the higher oil content.
“The digestible contents of the most limiting amino acids are also fairly close between the two meals, Nyachoti said. “As such, expeller canola cake should essentially be a good source of energy and amino acids.”
One concern is that the high oil content may reduce fat quality in the carcass, but recent work at the University of Alberta showed that the use of up to 23 per cent expeller canola cake in the diet was not detrimental.
“However, the results also showed a strong linear decline in performance in feed intake and body weight gain as the level of the expeller canola cake increased,” Nyachoti said.
Trials with nursery pigs also showed that diets with expeller cake reduced feed intake by 10 per cent in the first 10 days after weaning compared to using solvent extracted canola meal. The researchers linked this to high levels of glucosinolates in the expeller meal.
Mixtures of oilseeds and pulses present an economical opportunity to fortify energy in swine diets, to compliment other protein sources, and to enhance pork quality, for example Omega-3 pork, Nyachoti says. Moreover, the use of a coextruded oilseeds-peas mixture overcomes the challenges of grinding and handling of oilseeds such as canola and flax in the feed mill because of their high oil content. Starch in the pulses absorbs most of the oil.
Various mixtures have been evaluated and work at the U of M concluded that for a combination of peas and canola meal the amino acid digestibility was intermediate to those of the two ingredients.
“Key concerns with these products which are yet to be established include the effect of heating conditions (during the extruding process) on their nutritive value, keeping quality and effect on growth performance and pork quality among others,” Nyachoti said.
Hulless oats, which have a lower fibre content and more fat and protein compared with conventional oats, may be used in pig diets, although there is limited information regarding their value.
“Trials at the U of M indicated that hulless oats have high apparent digestible amino acids and metabolizable energy compared to hulled oats,” said Nyachoti. “However, standardized ileal digestible amino acids and net energy value of the hulless oats are yet to be determined.”
Other useful sources of energy and protein are lentils and zero-tannin faba beans. Lentils have a slightly nutritional value than peas, while work at the U of A shows that zero-tannin faba bean may be included in late-nursery diets up to a level of 40 per cent without detrimental effects on weaned pig performance. “In growing-finishing pigs, zero tannin faba beans can fully or partially replace locally-grown pea or imported soybean meal as dietary supplemental protein source without negative effects on growth performance, carcass characteristics and pork quality,” said Nyachoti.