An experiment involving 60 crossbred pigs was conducted at the University of Kentucky to assess the effects of feeding high levels of corn distillers dried grains with solubles (DDGS) on performance of growing-finishing pigs from 76 to 265 lb body weight, and on carcass and belly firmness, fatty acid composition of the fat, slicing efficiency of cured bacon, and eating quality of bacon slices, bratwurst sausage, and loin chops.
Fortified corn-soybean meal diets containing 0, 15, 30 or 45% DDGS were fed to growing-finishing pigs in three phases. A common source of DDGS analyzing 26.3% crude protein, 0.96% lysine, and 9.7% fat was used at each station. Diets were formulated to contain 0.83, 0.70, and 0.58% true ileal digestible lysine during the three phases with diets changed at 135 and 202 lb, respectively. The DDGS replaced corn and soybean meal, and crystalline lysine and tryptophan were added to maintain constant true ileal digestible levels of the amino acids in each phase. All pigs from each pen were killed for carcass and belly flex measurements. Samples of backfat and belly fat were obtained for fatty acid analysis and determination of iodine values.
Growth rate and feed intake were not affected by level of DDGS; however, efficiency of feed utilization decreased in pigs fed the higher levels of DDGS (P < 0.02). Backfat was reduced (but not significantly) and loin eye area increased (P < 0.05) in pigs fed DDGS, but carcass fat-free lean percentage was not affected by diet.
Bellies of the carcasses were measured for firmness. Flex measures indicated that the bellies became progressively more flexible and less firm as level of DDGS increased in the diets (linear, P < 0.01). Saturated and monounsaturated fatty acids in subcutaneous and belly fat decreased linearly (P < 0.001) and polyunsaturated fatty acids increased linearly (P < 0.001) with increasing DDGS in the diet. Iodine values (calculated from the fatty acid data) of outer backfat were 63, 70, 75, and 79 for the four treatment groups, a linear response to DDGS level fed (P < 0.001).
Slicing efficiency of cured bacon slabs was not affected by the softer bellies. In fact, the quality of the fresh bacon slices was improved (P < 0.001) in bellies from pigs fed DDGS in which the fat was softer and more unsaturated. Cooking shrink and distortion scores of cooked bacon were similar for the four treatment groups.
Eating quality of cooked bacon, bratwurst sausage, and loin chops as tested by an eight-member panel did not differ among pigs fed the four DDGS diets. There was no indication that tenderness, texture, juiciness, or off-flavor was impacted by dietary treatment.
The results of this study showed that rather high levels of DDGS (up to 45% DDGS in the diet) can be fed to growing-finishing pigs without having much of an effect on growth rate; however, the amount of feed required per unit of gain was increased with increasing amounts of DDGS in the diet. Carcass leanness was not greatly affected by level of DDGS; however, the high levels of DDGS in the diet resulted in higher proportions of unsaturated fatty acids in the body fat, higher iodine values in the backfat and belly fat, and softer, more flexible bellies. These responses were linearly (P < 0.01) related to the amount of DDGS in the diet. Regardless of the changes in fat composition, the slicing efficiency of cured bacon slabs, quality measures of fresh sliced bacon, and eating quality of bacon, bratwurst sausage, and loin chops did not seem to be negatively affected by feeding 30 to 45% DDGS to growing-finishing pigs.