Effects of increasing the dietary energy density by replacing grass hay with soybean hulls and dried distillers grains with solubles on nutrient digestibility and rumen fermentation1

We hypothesize that soybean hulls (SH) and dried distillers grains with solubles (DDGS) can be used in lamb diets to increase dietary energy density compared with a traditional grass hay (GH) and soybean meal (SBM) diet without causing adverse effects on nutrient digestibility and rumen function. To test this hypothesis, four ruminally-cannulated wethers were used in a 4x4 Latin square design to determine the effects of replacing GH with SH and replacing SBM with DDGS on nutrient digestibility and rumen fermentation. All diets were formulated to contain 60% roughage and 40% concentrate on DM basis. Dietary roughage source, however, varied from completely GH to completely SH, and SBM was replaced by DDGS. Diets were formulated to contain 13.9% CP and an increasing amount of dietary energy as SH and DDGS replaced GH and SBM. The control diet was composed of 60% GH and 11.6% SBM (GHSBM). Treatment diets were 60% GH and 25.4% DDGS (GH-DDGS); 20% GH, 40% SH, 15.3% DDGS (SH40-DDGS); or no GH, 60% SH, 10% DDGS (SH60-DDGS). The SH, protein concentrate, and mineral portion of the diet was pelleted and mixed with the chopped GH, when GH was included in the diet. The SH60-DDGS diet was a completely pelleted diet. This trial was divided into four periods. Lambs were allowed 14 d to adapt to their respective treatment diet which was offered twice daily. Following adaptation, total feed, fecal, and urine samples were collected and weighed during the 4-d collection period and subsequently composited for nutrient analyses. On the day following collection of fecal and urine samples, rumen fluid was collected at -2, 0, 1, 4, 8, 12 h relative to feeding, for analysis of VFA and ammonia concentrations. Replacing GH with SH improved DM digestibility and the DE content of the diet. Although increasing SH in the diet decreased rumen pH, ADF and NDF digestibility was not affected adversely. Lower rumen pH did favor increased propionate concentrations in the rumen. These data are consistent with the hypothesis that DDGS and SH can be used to increase the energy density of lamb diets compared to a traditional GH and SBM diet without affecting nutrient digestibility and rumen pH adversely.