Distillers Dried Grains with Solubles and Grower-Finisher Diets
For most people it will come as a surprise to know that research into distillers co-products fed to swine has been conducted for more than 50 years. Early research in the mid 1940's was focused on the feeding value of distillers co-products fed to growing pigs. With the construction of large scale ethanol plants in the 1970's the production of distillers dried grains with solubles (DDGS) increased, leading to research into the effects of adding DDGS to grower-finisher and to starter diets. During the last decade, many new dry-grind fuel ethanol plants have been constructed, and in 2007 there were approximately 139 plants in the United States that produced more than 14.6 million metric tonnes of DDGS (Renewable Fuels Association, 2008).
In the last few years, numerous studies have been conducted to further evaluate the nutrient concentration, digestibility, feeding value and unique properties associated with feeding DDGS to pigs. A recent research summary by Hans Stein and Gerry Shurson (2008) compiled results from North American research in which DDGS was fed to weanling, growing and reproducing swine. Their review summarizes research on DDGS nutrient composition, digestibility and effects of inclusion rate at various stages of production.
With the increase in DDGS availability and the economic challenges in the swine sector DDGS is being used more extensively in grower-finisher diets to reduce feed cost. In their paper, Stein and Shurson (2008) gathered results from at least 25 experiments in which performance of grower-finisher pigs fed diets containing up to 30% of corn derived DDGS was measured (Table 1). In 23 of these experiments, DDGS was included in diets based on corn-soybean meal and in 2 experiments wheat-field pea based diets were used.
a Diets based on experiments published after 2000, which included a maximum of 30% DDGS in the diet.
Effects on Grower-Finisher Performance
In most studies grower-finisher performance was maintained or in one case increased. Some early research by Cromwell et. al. (1983) examining the use of DDGS in diets fed to grower-finisher pigs, demonstrated performance can be maintained when up to 20% DDGS is included in the diets. In the same trial if 40% DDGS was used performance was reduced. More recent experiments, in commercial facilities, confirmed that inclusion of up to 20% DDGS in diets fed to grower-finisher pigs did not reduce average daily gain (ADG), average daily feed intake (ADFI), or gain to feed ratio (G:F) provided the diets were adequately fortified with amino acids.
Based on the data provided the authors found it difficult to determine why pig performance was reduced in some experiments. Two of the studies examining the effects of inclusion up to 30% DDGS demonstrated inconsistent responses in ADFI and G:F but was likely due to variable energy concentration among the DDGS sources used. For other experiments where performance was reduced the authors hypothesized that it was possible that the DDGS used may have been of lower nutrient digestibility. Complicating matters, in some studies the diets were formulated in such a way that crude protein increased as DDGS was included in the diet. This confounded the results making it impossible to determine if the reduction in performance was due to the increase in DDGS inclusion or increase in crude protein concentration.
An important observation of the review was that in studies that found a reduced ADG, a reduction in ADFI was also observed. One possibility is that the poorer performance was due to reduced palatability of diets containing DDGS. Two experiments have shown that if given a choice, pigs prefer to consume diets containing no DDGS.
Effects on Grower-Finisher Carcass Characteristics
In the majority of research studies, carcass values for backfat depth, loin depth or lean percentage were not affected by the inclusion of DDGS. Backfat thickness of pigs fed DDGS was reduced in 1 experiment but in 14 other studies was not changed. Similarly, loin depth was not changed in 13 out of 14 studies and lean percentage was not changed in 12 out of 14 studies.
The dressing percentage of pigs was reported in 18 experiments in which DDGS was included in the diets. In 10 of these studies, no difference in dressing percentage was observed, while in 8 studies dressing percentage was reduced. It has been suggested that the inclusion of fiber rich ingredients in diets fed to pigs may be responsible for reducing dressing percentage due to increased gut fill and intestinal mass. This may in part explain the reduction in dressing percentage but it remains unclear why it is not the case in all of the studies.
Belly firmness was reported in only 3 studies but it is clear that pigs fed diets containing DDGS had reduced belly firmness. This observation is in line with data showing increased iodine value of belly fat when pigs are fed DDGS. This is likely a result of the relatively large quantity of unsaturated fatty acids in DDGS. It has been well documented that increased dietary unsaturated fatty acids will increase carcass iodine values. Iodine value is an important measure of carcass quality because high iodine values result in soft and less valuable bellies and loins. Current research efforts are looking into alternative nutritional strategies to reduce the negative effects of DDGS on iodine values. Much of the effort is looking at increasing the saturated fatty acid content of the diet to lower the iodine value. Removal of DDGS from the diet during the final 3 to 4 week prior to market will also reduce the negative impact of DDGS on carcass iodine values.
Putting it into perspective
Research has shown that distillers dried grains with solubles is an excellent source of energy and digestible phosphorus that can be fed to swine at all stages of production. As a result, depending on ingredient costs, DDGS can help to reduce overall feed cost and will most likely have the biggest economic advantage in grower-finisher diets. Based on the summary of DDGS research studies, growth performance and carcass quality can be maintained in most cases at inclusion levels of up to 20%. Pork fat becomes softer when DDGS is included in finisher diets so reducing DDGS inclusion levels in late finisher or withdrawing DDGS from the diets 3 to 4 weeks prior to market are two strategies that can be used to minimize this effect.
Renewable Fuels Association. 2008. Accessed January 26, 2009
Stein, H.H. and Shurson, G.C., 2008. Board Invited Review: The use and application of distillers dried grains with solubles (DDGS) in swine diets. J. Anim. Sci. In press.
Cromwell, G.L., Stahly, T.S., Monegue, H.J. and Overfield, J.R. 1983. Distillers dried grains with solubles for grower-finisher swine. Page 30-32 in Kentucky Agric. Exp. Stn. Progress Rep. 274. Univ. of Kentucky. Lexington.
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