The duration of time that beef cattle are fed a high-grain diet affects the recovery from a bout of ruminal acidosis: Dry matter intake and ruminal fermentation1

Abstract

This study was conducted to determine if the duration of time cattle are fed a high-grain diet affects their susceptibility to and recovery from ruminal acidosis. Sixteen Angus heifers (BW ± SEM, 261 ± 6.1 kg) were assigned to 1 of 4 blocks and fed a backgrounding diet consisting of 60% barley silage, 30% barley grain, and 10% supplement (DM basis). Within block, cattle were randomly assigned to 1 of 2 treatments differing in the number of days they were fed the high-grain diet before an acidosis challenge: 34 d for long adapted (LA) and 8 d for short adapted (SA). All heifers were exposed to the same 20 d dietary transition to a high-grain diet containing 9% barley silage, 81% barley grain, and 10% supplement (DM basis). Ruminal acidosis was induced by restricting feed to 50% of DMI:BW for 24 h followed by an intraruminal infusion of ground barley at 10% DMI:BW. Heifers were then given their regular diet allocation 1 h after the intraruminal infusion. Data were collected during an 8-d baseline period (BASE), on the day of the acidosis challenge (CHAL), and during 2 consecutive 8-d recovery periods (REC1 and REC2). Acidosis induction increased daily duration (531 to 1,020 min/d; P < 0.001) and area (176 to 595 (min × pH)/d; P < 0.001) that ruminal pH was <5.5 relative to BASE. Relative to BASE, inducing acidosis also increased the daily mean (0.3 to 11.4 mM; P = 0.013) and maximum (1.3 to 29.3 mM; P = 0.008) ruminal fluid lactate concentrations. There was no effect of dietary treatment on ruminal pH, lactate, or short-chain fatty acid (SCFA) concentrations (P > 0.050). However, during BASE and CHAL, SA heifers experienced greater linear (P = 0.031), quadratic (P = 0.016), and cubic (P = 0.008) coefficients for the duration of time that pH was <5.5. In addition, a treatment × day interaction for the duration that pH was <5.5 during REC1 suggested that LA cattle tended to recover from the challenge more rapidly than SA cattle (P = 0.085). Regression analysis confirmed that the LA heifers experienced a quicker linear (P = 0.019) recovery from induced acidosis over time. These results indicate adaptation of the ruminal epithelium continues with advancing time as evidenced by more stable ruminal pH both before and after an induced bout of acute ruminal acidosis but does not affect susceptibility of cattle to ruminal acidosis.

Short-term adaptation of the ruminal epithelium involves abrupt changes in sodium and short-chain fatty acid transport

“…From CHAL to REC, ⌬G t increased linearly (⌬G t-CHAL-REC ; P ϭ 0.013), as did ⌬G t for BASE to CHAL (⌬G t-BASE-REC ; P ϭ 0.012). These data suggest that increasing the duration of time fed the moderate-grain diet did not improve resistance or reduce tissue sensitivity to an induced challenge ex vivo and supports recent in vivo results (47,48) and the notion that short-term exposure to more fementable diets compromises barrier function (29,31).…”

Ruminal acidosis: strategies for its control

“…Regression analysis confirms that the heifers exposed to the long period of adaptation, experienced a rapid linear recovery of ruminal pH with respect to time of the induced acidosis (Schwaiger et al 2013).…”

The duration of time that beef cattle are fed a high-grain diet affects feed sorting behavior both before and after acute ruminal acidosis1,2

“…Within block, average BW across treatments was balanced. Heifers on the LA treatment were fed a backgrounding (BG) diet (60% barley silage, 30% barley grain, and 10% supplement, on a DM basis; Schwaiger et al, 2013a) for 7 d before being transitioned to a barleybased, HG finishing diet (9% barley silage, 81% barley grain, and 10% supplement, on a DM basis; Schwaiger et al, 2013a) whereas SA heifers were fed the BG diet for 33 d before being transitioned to the HG diet. Differences in the duration of the BG period allowed a delay in the start of the dietary transition for the SA heifers so that the LA and SA heifers were fed the HG diet for 34 and 8 d, respectively, before their simultaneous induction of ruminal acidosis.…”

“…While acute episodes of severe ruminal acidosis are rare in dairy cattle, they are more prevalent (Nagaraja and Titgemeyer, 2007) and severe (Bevans et al, 2005;Wierenga et al, 2010;Schwaiger et al, 2013a) in feedlot cattle. Beef feedlot cattle frequently undergo acidotic challenges when transitioned from forage to concentratebased finishing diets (Bevans et al, 2005;Nagaraja and Titgemeyer, 2007).…”