Effects of Increasing Dietary Energy Consumption on Intake, Digestion and Ruminal Fermentation in Limit-Fed Steers
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Effects of increasing dietary energy consumption on intake, digestion, and ruminal fermentation in limit-fed cattle were determined using 16 ruminally cannulated steers (359 kg ± 44 BW). All steers were fed a constant level of wheat straw (0.56% of BW) and one of four levels of concentrate (0.69, 0.88, 1.06, and 1.25% of BW) such that steers were fed 70, 85, 100, and 115% of NRC predicted NEm requirements in a one period, randomized complete block study. The concentrate portion of the ration consisted of dry-rolled corn (45%), dried distillers’ grains (42%) and a premix (13%). Diets and feeding levels were consistent with a companion mature cow project. The trial was 17 d long with 11 d for adaptation, 5 d to determine intake and digestion, and a 1 d ruminal fermentation profile. Dry matter intake increased linearly (P < 0.01) as per the design of the project from 3.70 kg/d for 70% to 4.19, 4.66, and 5.22 for 85, 100, and 115%, respectively. Digestion of DM increased linearly (P = 0.03) from 64 to 74% for treatments 70 and 115%, respectively. There were no significant differences for NDF and ADF digestion (P > 0.20). Digestion of GE increased linearly from 65% to 70, 67, and 75% for treatments 70, 85, 100, and 115%, respectively (P = 0.03). Correspondingly, digestible energy intake increased (P < 0.01) linearly from 9.6 Mcal/d for 70% to 15.6 Mcal/d for 115%. Mean ruminal pH decreased quadratically (P < 0.01) with increasing energy intake. Similar mean pH values were observed for 70, 85, and100%; 6.34, 6.38, and 6.36, respectively, and there was a decrease to 6.25 for 115%. No time × treatment interaction was observed (P = 0.17) for ruminal pH. The lowest ruminal pH was 6.15 and 5.95 at h 6 for 85 and 115%, respectively, whereas lowest ruminal pH for 70% was 6.05 at h 9, and 100% was 6.12 at h 12. There was a treatment × hour interaction (P < 0.05) for acetate to propionate ratio resulting from changes over time not a re-ranking of treatments. Mean acetate to propionate ratios decreased quadratically (P = 0.02) and averaged 3.28, 3.36, 3.02, and 2.98 for treatments 70, 85, 100, and 115%, respectively. Increasing concentrate provision increased diet digestion and energy consumption without producing changes in ruminal fermentation that could possibly impact long-term ruminal health.
Franks, Kelli Marie (2016). Effects of Increasing Dietary Energy Consumption on Intake, Digestion and Ruminal Fermentation in Limit-Fed Steers. Undergraduate Research Scholars Program. Available electronically from