Effects of Dietary Adaptation Programs on Feedlot Cattle Performance and Evaluation of Ruminal Monitoring Devices in an Acidosis Challenge

Abstract

Objective was to evaluate the performance and carcass characteristics of one hundred forty-four steers fed two diets and two adaptation methods over a 28 d period of adaptation to the finishing diet. Pens were randomly assigned to one of four treatments: traditional diet (TRAD) using the forage step-down (STEP) method, TRAD diet using the two-ration blending (2RB) method, wet distiller's grains with solubles (WDGS) diet (DG) using a WDGS step-down method (STEP), and DG diet using the 2RB method. During adaptation, steers fed DG had lower (P < 0.01) BW, DMI, ADG, and G:F than steers fed TRAD. Over the entire feeding period, steers fed DG adapted using STEP and those fed TRAD adapted using 2RB had greater ADG compared to steers fed TRAD adapted using STEP and steers fed DG adapted using 2RB (P < 0.01). Greater DMI were achieved for steers fed TRAD compared to steers fed DG (P < 0.01); however, there was no effect of adaptation diet or method on feed efficiency during the entire feeding period (P &le 0.71). Steers adapted using STEP had greater marbling scores compared to steers adapted using 2RB (P = 0.04). Results show diet type has an effect on the best method of adaptation; however, sulfur levels of the DG diet may have played a role in decreased performance. Steers fed DG during adaptation recovered in the subsequent feed period, performing similar to steers adapted using TRAD. A second experiment was conducted to determine the effects of an acidosis challenge on ruminal pH and temperature using ruminal pH and temperature monitoring devices. Twelve ruminally cannulated steers were offered the control diet at 2% BW/d prior to the challenge and starting 24 h after the challenge. Challenges were ruminal dosing of 2% BW of 65% concentrate diet (CON), a mixture of 50:50 dry rolled corn: wet distillers grains (DG/DRC), or 100% dry rolled corn (DRC) at 0 h. Bolus readings for ruminal pH (RpH) and ruminal temperature (RT) were recorded every minute for 72 h after dosing and compiled in 3 h increments for repeated measure analysis. Rumen pH was taken manually every 3 h for 72 h after dosing and analyzed with a repeated measures analysis. There were significant interactions of treatment h (P = 0.05), treatment day (P = 0.02) and day h (P = 0.03) for RpH. Main effects of treatment and d were not significant (P &le 0.48) for RT, however, there was a quadratic response (P < 0.01) at h 9 through 21, h 15 (39.64 &deg C) having greater RT (P < 0.01) compared to h 0 levels of RpH 5.2 and 5.6. These results indicate that increased availability of highly fermentable substrates in the rumen result in decreases in RpH and increases in RT. However, the type of fermentable substrate may change the relationship between rumen temperature and pH, particularly when substrates such as distiller's grains that have a low pH are included in the diet.