Effect of graded levels of wheat-based dried distiller's grains in a barley ration on the growth performance, carcass quality and rumen characteristics of feedlot steers

Two trials were conducted to evaluate the effects of titrated levels of wheat-based dried distiller’s grains on feedlot performance, carcass characteristics and rumen fermentation parameters of cattle fed wheat-based dried distiller’s grains with solubles (DDGS). In trial 1, a barley grain-based diet (0% DDGS) was used as a control. It was formulated to 12% CP and 1.52 and 0.93 Mcal kg-1 net energy of maintenance (NEm ) and net energy of gain( NEg) respectively, during the backgrounding period and to 13% crude protein (CP) and 1.90 and 1.26 Mcal kg-1 NEm and NEg respectively, during finishing. Wheat-based DDGS replaced on a dry matter basis (DM) barley grain at levels of 8, 16, 24 and 32% during backgrounding and 6, 12, 18 and 23% during finishing. During backgrounding dry matter intake (P = 0.02), ADG (P = 0.04), and ultrasounded (US) longissimus. dorsi gain (P = 0.02) exhibited a cubic response to DDGS inclusion level with theoretical minima at 6.9, 8.1 and 6.9% DDGS respectively, and theoretical maxima responses at 27.2, 30.8 and 23.9% DDGS, respectively. Feed efficiency exhibited a quadratic response (P = 0.02) to DDGS inclusion level with a theoretical poorest response at 13.1% DDGS. Similar responses were noted during the first 56 d of the finishing period, however over the course of the finishing period no effect of DDGS inclusion level was noted on average daily gain (ADG), DMI, feed efficiency (FE), ultrasound measurements or on any carcass traits. Trial 2 examined the effects of graded levels of wheat-based DDGS (0, 7, 14, 21% DM basis) on rumen fermentation characteristics using rumen cannulated heifers. Rumen pH measurements indicated that the pH mean at or below 5.8 and 5.5 decreased as DDGS inclusion level increased to 14% DM. The highest values (