Ruminal Characteristics and Feedlot Performance of Feedlot Steers during Accelerated Step-up to High-Concentrate Diets Using Lactipro Advance®

Megasphaera elsdenii (ME) is the principal lactate-utilizing bacterium in cattle adapted to concentrates, and is marketed commercially as a probiotic (Lactipro Advance, MS Biotec) to facilitate transition to high-grain diets. In this study, ruminal characteristics and feedlot performance were measured for steers adapted to a high-grain diet using a traditional 22-d step-up program (C), and for steers adapted over 10 d with the aid of ME fresh culture administered as an oral gavage (F), an oral gavage of rehydrated lyophilized culture (R), or R combined with lyophilized culture powder administered daily as a ration top-dress (D) . Yearling steers (n = 435; initial BW = 408 ± 5 kg) were blocked by weight and randomly allocated to 64 concrete surfaced pens with 7 steers/pen and 16 pens/treatment. Step-up diets contained 40, 30, and 20% corn silage, and were followed by a finishing diet containing 10% corn silage and 90% concentrate. Ruminal fluid was obtained by rumenocentesis 26 h after steers received their first step-up diet, and inoculated into culture tubes containing lactate medium to determine differences in capacity for lactate metabolism over 24 h. Steers were fed once daily ad libitum for 156 d, then weighed, and transported 450 km to a commercial abattoir for harvest. Hot carcass weight and incidence of liver abscesses were determined at harvest and carcass traits were evaluated after 36 h of refrigeration. No differences were detected for feedlot performance (P > 0.20), liver abscesses (P = 0.45), or carcass traits (P > 0.20). Capacity for lactate utilization was increased with all forms of ME, as evidenced by increases in optical density (absorbance) of ME cultures, disappearance of lactate, and increase in butyrate production (P 0.01). In conclusion, steers dosed with ME can be stepped up to finishing diets in 10 d with no adverse effects on performance.

Item	C	F	R	D	SEM	P-value
G:F	0.1743	0.1733	0.1705	0.1705	0.0028	0.66
HCW, kg	433.9	436.6	438.9	435.3	4.29	0.63
Choice + Prime, %	49.1	51.0	52.7	46.6	5.00	0.82
Absorbance at 600 nm	1.30a	1.50b	1.53b	1.53b	0.04	< 0.01
Lactate, mM	22.6a	7.2b	10.5b	7.8b	3.17	0.01
Butyrate, mM	3.5a	8.8b	7.1c	7.5b,c	0.52	< 0.01
a,b Means within a row without a common superscript letter are different, P < 0.05