Effects of increasing levels of corn dried distillers grains with solubles and monensin on intake, digestion, and ruminal fermentation in beef heifers fed high-barley grain diets1

Abstract

The objective of this study was to determine whether increasing corn-based dried distillers grains with solubles (DDGS) in high-barley grain diets reduces the merit of using higher levels of monensin by assessing intake, digestibility, and ruminal pH and fermentation in feedlot heifers. Five ruminally and duodenally cannulated Angus heifers (average BW of 599±36 kg) were used in a 5×5 Latin square with a 2×2+1 factorial arrangement. Treatments were control (CON, 10% barley silage, 90% barley-based concentrate, and 28 mg monensin/kg DM) and diets substituting 20% (LDG) or 40% (HDG) DDGS for barley grain with 28 mg (ML) or 48 mg (MH) monensin/kg diet DM: 1) CONML, 2) LDGML, 3) HDGML, 4) LDGMH, and 5) HDGMH. Contrasts compared LDG vs. HDG, ML vs. MH, interactions between DDGS and monensin, and the effect of increasing DDGS in the diet. Increasing DDGS quadratically (P<0.01) increased DMI. There was no interaction for DMI between the dietary inclusion rate of DDGS and the dose of monensin; however, DMI was reduced (P<0.05) for heifers fed MH vs. ML. Ruminal digestibility of OM, NDF, and starch linearly decreased (P<0.01), but intestinal digestibility linearly increased (P<0.01) with increasing DDGS, resulting in no differences in total tract digestibility. Ruminal digestibility of OM was greater (P<0.04) in heifers fed MH than ML; however, the total tract digestibility of OM was not affected. Intake of N, flows of total N, nonammonia N, and dietary N were linearly (P<0.02) increased, and the efficiency of ruminal microbial synthesis linearly (P<0.04) improved with increasing DDGS. Increasing DDGS inclusion linearly decreased (P<0.04) the acetate to propionate ratio. Inclusion of MH decreased (P<0.04) acetate and increased (P<0.05) NH3-N compared to ML, but high monensin did not affect mean ruminal pH, the duration of pH<5.8, 5.5, 5.2, or the area below the curve at pH 5.8, 5.5, and 5.2, indicating that there was no evidence that it modulated ruminal pH. These results suggest that feeding monensin at 48 vs. 28 mg/kg diet DM altered nutrient availability and site of feed digestion, likely as a result of reduced DMI and increased ruminal digestion of DM. High levels of monensin may reduce the risk of acidosis through a reduction in DMI, but in the present study this was not evident in differences in the ruminal pH profiles between heifers fed ML and MH diets.

Impact of hard vs. soft wheat and monensin level on rumen acidosis in feedlot heifers1

“…This translates into estimated feed efficiency improvements of −0.55, −0.64, and −0.73 kg DMI/kg gain for doses at 22, 33, and 44 mg/kg feed DM. The reduction in DMI with increasing monensin from 28 to 44 mg/kg DM in this study is in agreement with the conclusions drawn by that metaanalysis and is consistent with our studies that have examined the impact of elevated monensin on the DMI of feedlot cattle fed barley-based diets (Xu et al, 2013).…”

“…The reduction in the flows of OM, NDF, and starch to the duodenum with elevated levels of monensin reflects the decline in DMI, whereas extent of digestion of OM, NDF, and starch in the rumen was similar between these 2 monensin levels. This lack of an effect of monensin level on ruminal digestibility contrasts with previous reports that ruminal digestibility of OM and NDF declined with elevated levels of monensin when barley grain was substituted for a portion of the wheat distillers grain in high-grain diets (Xu et al, 2013). These authors suggested that the increase in ruminal digestibility of OM may have resulted from an increase in ruminal retention time of feed, thereby enhancing the extent of feed digestion by ruminal microorganisms.…”

Influence of feeding increasing levels of dry or modified wet corn distillers grains plus solubles in whole corn grain-based finishing cattle diets on pancreatic α-amylase and trypsin activity

“…Increasing inclusion of DGS results in changes in nutrient intake because of the differences in nutrient concentrations between DGS and other feed ingredients (mostly corn in the current experiment). Increasing inclusion level of DGS in the current experiment resulted in increased dietary protein intake and decreased starch intake (Salim et al 2012(Salim et al , 2014) which likely resulted in increased protein and decreased starch flow at the small intestine (Xu et al 2013). Past research has suggested that postruminal protein and starch flow as well as dietary energy intake are important factors in influencing pancreatic exocrine function in cattle Swanson et al , 2008b.…”

Comparison on the fatty acid profiles of liver, subcutaneous fat and muscle from feedlot steers finished on diets supplemented with or without cinnamaldehyde or monensin

“…In ruminants, dietary polyunsaturated fatty acids (PUFA) including linoleic acid (LA) and α ‐linolenic acid (ALA) can be biohydrogenated by ruminal bacteria, which increase biohydrogenation intermediates including vaccenic acid (VA) and conjugated linoleic acids (CLA) flow to duodenum . Several recent studies tested the effect of MO on rumen fatty acid profile and beef fatty acid profiles, and found little difference between treatments of MO with a high and a low doses . However, one study investigated the effect of CIN and MO on biohydrogenation of dietary forage PUFA in the rumen; it reported that supplementation of CIN or MO inhibited PUFA biohydrogenation and resulted in significant higher total PUFA compared to the control without CIN supplementation .…”