Multi-modifier Strategies to Improve Rumen Health, Growth and Carcass Attributes of Grain-fed Cattle

Abstract

<p>Rumen modifiers are included in rations for most feedlot cattle to reduce the incidence of ruminal acidosis and improve the efficiency of feed-use during finishing. There is a need to explore options to achieve maximum performance from existing rumen modifiers. A series of animal house studies followed by a feedlot finishing study were undertaken to quantify the effects of rotating and or of combining currently used rumen modifiers, while also evaluating tools for remote monitoring of ruminal acidosis risk.</p> <p>Key findings from this study include:</p> <p> The Allflex ‘eSense’ accelerometer ear tag provided a useful means of quantifying time cattle spent ruminating, showing a moderate correlation with visual assessment.</p> <p>The smaXtec bolus was not as useful in its application, with many individual boluses showing initial bias and time-associated drift in raw pH relative to a manual determination of pH <i>in-situ</i>. These biases were successfully overcome with correction from the paired samples taken throughout the study, and corrected data was used to conduct pH pattern analysis. </p> <p>The first of two intensive studies addressed changes in rumen fermentation when providing Monensin alone, in combination (with Lasalocid or Bambermycin), or in daily rotation (with Lasalocid or Bambermycin), during 28d adaptation periods to a high-grain diet in cannulated steers.</p> <p>A differentiation emerged between pairing of Monensin with Bambermycin compared to pairing Monensin with Lasalocid. The latter offered advantages, including the highest pre- and post-feeding ruminal pH (manual sample) and therefore the least risk of lactic acidosis, as well as the lowest redox potential, the lowest acetate percentage than treatments with Bambermycin. On these aspects, Monensin alone or in pairing with Lasalocid warrants further investigation.</p> <p>During the second intensive study where cattle were maintained on the Finisher ration for 28 days, the same pH responses did not persist, although Monensin cattle ate significantly more dry matter (DM) than other treatment groups. There were no effects on redox potential and, while rumen pH did not show treatment effects for the first 9h post-feeding, at 10 and 11h post-feeding Monensin had among the lowest rumen pH values. There was no effect of rumen modifier regime on daily methane production or methane yield (methane/kg DMI).</p> <p>A concluding large scale feedlot trial examined three rumen modifier treatments (Monensin alone, Lasalocid alone, and the two in daily rotation [L/R]) with average dry matter intake (DMI), daily gain (ADG), Feed: Gain (F:G) ratio and carcass attributes determined.</p> <p>Overall ADG and F:G for all treatments were superior to the industry average (mean ADG = 2.57 kg/hd/d; mean F:G = 4.5 on DM basis) for feedlot cattle, but ADG of Monensin cattle still tended (<i>P</i> < 0.10) to be greater than of Lasalocid and L/R Rotation cattle over the entire 109 days. </p> <p>Significant advantages (<i>P</i> < 0.05) were seen in feed conversion efficiency (+2.6%) throughout the entire trial with continuous inclusion of Monensin compared to Lasalocid alone or in Rotation.</p> <p>There were no differences in carcass characteristics or net economic benefit with modifier treatment, but cost of gain was significantly lower (-3.1%; <i>P</i> < 0.05) for Monensin cattle.</p> <p>Rotating ionophores, or inclusion of Lasalocid alone continuously, did not improve feedlot performance compared to continuously feeding Monensin alone.</p>