A regional committee (North Central Coordinating Committee on Swine Nutrition [NCCC-42]), consisting of swine nutritionists from several universities, recently conducted an experiment to evaluate three dietary levels of distillerâ€™s dried grains with solubles (DDGS) for grow-finish pigs.
The study, funded in part by a grant from the Pork Checkoff, involved nine experiment stations in which 560 pigs were fed a common source of DDGS at levels of 0, 15, 30 and 45% in the diet. Pigs were fed the diets from 73 to 266 lb. in three phases involving 28 replicate pens of four to six pigs per pen for each of the four treatment groups.
Diets were formulated to have the same standardized ileal digestible (SID) lysine during each phase. Each participating station collected carcass data on two pigs from each pen and a sample of backfat from the 10th rib for fatty acid analysis.
Growth rate was reduced slightly at the higher levels of DDGS, but feed intake and feed efficiency were not significantly affected by DDGS level (Table 1). Carcass dressing percentage was not affected by treatment in this study. Backfat and loin eye area were reduced at the higher level of DDGS fed. The estimated percentage of fat-free lean in the carcass was not affected by level of DDGS in the diet.
Six stations measured belly firmness. Bellies (spareribs removed) were placed on a 3-in.-diameter PVC pipe mounted perpendicular to a board marked with a 1-in. grid matrix (pictured). Lateral and vertical flexes were determined from the degree of belly flex relative to the grid. A vertical flex of zero meant the belly was parallel to the floor and completely stiff. A lateral flex of 5 meant that the belly flexed to a point where there was 5 in. between the end of the belly and a vertical line directly below the PVC pipe.
Table 1 shows that both lateral and vertical flex of the bellies were greatly influenced by DDGS level. These flex measurements indicated an increased softness and more flexibility of the bellies as DDGS levels increased.
As level of DDGS increased in the diet, major changes in fatty acid composition of the backfat occurred. Linoleic acid (the primary polyunsaturated fatty acid in corn DDGS) more than doubled in the backfat of pigs fed the 45% DDGS diet vs. the control diet. This increase, along with a drop in saturated fatty acids, resulted in a higher iodine value in the fat of pigs fed higher levels of DDGS.
Iodine numbers up to 74 have been ranked as acceptable, with carcasses recording higher iodine numbers often being discriminated against by packers. In this study, regression analysis of the iodine values on level of DDGS in the diet indicated that an inclusion rate of 22% DDGS equaled an iodine value of 74.
The study showed that the iodine value increased by 4.3 points for every 19% DDGS included in the diet.
Results showed feeding high levels (up to 45%) of DDGS had little effect on growth performance or carcass traits, but belly firmness decreased with high levels of DDGS in the diet.
Additional research is needed to determine if processing characteristics of bellies and eating quality of bacon are negatively affected by feeding high levels of DDGS to finishing pigs.
Researchers: G.L. Cromwell, University of Kentucky; M.J. Azain, University of Georgia; O. Adeola, Purdue University; S.K. Baidoo, University of Minnesota; S.D. Carter, Oklahoma State University; T.D. Crenshaw, University of Wisconsin; S.W. Kim, North Carolina State University; D.C. Mahan, The Ohio State University; P.S. Miller, University of Nebraska; and M.C. Shannon, University of Missouri. For more information, contact Cromwell by phone (859) 257-7534, fax (859) 323-1027 or e-mail Gary.Cromwell@uky.edu.