Effects of level of condensed distillers solubles in corn dried distillers grains on intake, daily body weight gain, and digestibility in growing steers fed forage diets1

Three experiments were conducted examining the effects of feeding different levels of dried distillers grains (DDG) and different proportions of condensed distillers solubles (CDS) added to DDG on performance and digestibility in forage-fed steers. In Exp. 1, a total of 120 individually fed crossbred steers (276 +/- 31 kg) were used in a randomized complete block design with a 4 x 5 factorial arrangement of treatments. Factors included DDG supplementation level (0.25, 0.50, 0.75, or 1.0% of BW daily) and proportion of CDS in DDG (0.0, 5.4, 14.5, 19.1, and 22.1% of DDG DM). A basal diet of 58.8% alfalfa hay, 39.2% sorghum silage, and 2% vitamin and mineral supplement (DM basis) was fed for ad libitum intake. As the level of DDG increased, intake of forage decreased linearly (P < 0.01), intake of DDG increased linearly (P < 0.01), and total DMI increased quadratically (P = 0.06). A DDG level x CDS level interaction (P < 0.01) was observed for ADG and G:F. The 0.0, 5.4, 14.5, 19.1, and 22.1% CDS treatments had the greatest ADG when DDG was supplemented at 0.75, 1.0, 1.0, 0.75, and 0.50% of BW daily, respectively. In Exp. 2, four crossbred steers (295 +/- 19 kg) were used in a 3-period switchback design. A basal diet of 58.8% alfalfa hay, 39.2% brome hay, and 2% vitamin and mineral supplement (DM basis) was fed at 95% of ad libitum intake. Treatments were DDG containing 0.0 or 22.1% CDS supplemented at 1.0% of BW daily. Apparent total tract digestibility was measured by total fecal collection. No differences between treatments were observed for digestibility of DM, OM, or NDF (P >/= 0.14). Digestibility of ether extract was greater (P = 0.02) in steers supplemented with DDG containing 22.1% CDS. In Exp. 3, two ruminally and duodenally cannulated Holstein steers (663 +/- 24 kg) were used to estimate DM and CP digestion of the DDG fed in Exp. 1 using the mobile bag technique. Basal diets were the same as fed in Exp. 1 and steers were supplemented with DDG at 0.5% of BW daily. Ruminal DM digestibility increased linearly (P < 0.01), and postruminal and total tract DM digestibility increased quadratically (P = 0.02 and P = 0.03, respectively) as the level of CDS increased. Level of CDS may affect growing steer performance because depressions in ADG and G:F were observed as intake of ether extract increased. A clear explanation for the interaction between the DDG supplementation level and the CDS level on growing steer performance was not evident in the digestion ex