Nutritional value of high protein ingredients fed to growing pigs in comparison to commonly used protein sources in swine diets

Two experiments were conducted to test the hypothesis that two high protein dried distillers with solubles and yeast mass added (GDDY) products fed to growing pigs had comparable amino acid (AA) digestibility and metabolizable energy (ME) to feeds commonly used in swine diets. In experiment 1, seven barrows with an initial body weight (BW) of 25 +/- 0.8 kg were fitted with a simple T-cannula at the distal ileum to allow for digesta collection. Experimental diets were N-free diets and six cornstarch-based diets containing six ingredients as the sole source of AA: spray dried GDDY, ring dried GDDY, corn distillers dried grains with solubles (DDGS), soybean meal (SBM), enzymatically treated soybean meal (ESBM), and fish meal (FM) provided at 4% of BW. The experiment was conducted as a 7 x 7 Latin square design with seven collection periods of 7 d (5 d adaptation and 2 d ileal digesta collection). In experiment 2, a total of 28 barrows (28.8 +/- 1.4 kg BW) were used in a two-period switch-back design with seven diets and four replicate pigs in each period (n = 8 reps per diet). Experimental diets were a corn-based basal diet and six corn-based diets containing spray dried GDDY, ring dried GDDY, DDGS, SBM, ESBM, and FM. Fecal and urine samples were collected using the marker-to-marker approach for 5 d after 7 d of adaptation to determine ME concentration. Overall, standardized ileal digestibility (SID) values were within the mean +/- SD of values for all ingredients evaluated. The SID of AA was greater (P < 0.05) in ESBM than the other protein feedstuffs (90.09% vs. 78.71%-81.51%). There were no significant differences in SID of AA (P > 0.05) in SBM, FM, spray dried GDDY, and ring dried GDDY (81.49%, 78.71%, 81.52%, and 79.20%). With respect to the most common first limiting AA for swine, the SID of Lys was greater (P < 0.05) in spray dried GDDY than ring dried GDDY and DDGS (83.56% vs. 77.33% and 68.53%, respectively). There were no significant differences (P > 0.05) for ME in corn (3,313 kcal/kg), ESBM (3,323 kcal/kg), and FM (3,454 kcal/kg) when compared with spray dried GDDY and ring dried GDDY (3,995 and 3,442 kcal/kg respectively). However, spray dried GDDY had greater DE and ME when compared to SBM. Collectively, this study demonstrates that GDDY products have an AA profile and digestibility comparable to SBM; ME in GDDY products is not different from corn. Therefore, GDDY has the potential as a feed ingredient for pigs, which could provide an alternative source of protein and energy in swine diets. Lay Summary Co-products such as distiller's dried grains with solubles (DDGS) from the ethanol industry are obtained through fermentation processes and removal of nonfermentable components; separation of soluble fiber and protein components can potentially increase their nutritional value in swine diets. With the development of new feed processing technologies, high protein DDGS with added yeast mass (GDDY) has been obtained by separating the protein fraction of DDGS. However, there is limited information on the nutritional value of these co-products for pigs. The first step in determining the suitability of novel co-product use in swine diets is to define the nutritional value. Therefore, the nutritional value of GDDY was determined by analyzing standardized ileal digestibility (SID) of amino acids (AA) and metabolizable energy (ME) in growing pigs compared with common protein and energy feeds used in growing pig diets. The results show that the AA profile and digestibility in GDDY products were not different from soybean meal (SBM) as is the case for lysine, the first limiting AA in pig diets. Similarly, ME concentration in GDDY does not differ from those in other energy sources. Therefore, GDDY could be an alternative source of protein and energy in swine diets, and the obtained data allow its inclusion in pig diets formulation. The high protein dried distillers grains with yeast mass added (GDDY) is a feedstuff with comparable energy and protein value to common protein and energy feedstuffs used in swine diets, particularly soybean meal and corn. The GDDY could be used as an alternative source of protein and energy in swine diets.