94 Effects of orally administered Megasphaera elsdenii during finishing diet realimentation on feedlot steer fecal consistency, clinical depression, and rumination

Abstract

Abstract The objective of the study was to determine the effects of oral administration of Megasphaera elsdenii NCIMB 41125 (ME) during finishing diet realimentation on fecal consistency, clinical depression, and rumination of feedlot steers. Steers [n = 60; initial body weight (BW) = 591 kg ± 38 kg] were assigned to microbial supplement treatment in a randomized complete block design. Treatments were 1) no ME (CON); and 2) orally administered microbial supplement (1 x 1010 colony forming units ME/capsule; LP) immediately before diet reintroduction. Preceding study initiation, steers consumed a finishing diet with 88% concentrate [dry matter (DM) basis] primarily consisting of whole shelled corn and corn silage for 200 d. Steers were transported from a local feedyard 27 km and upon arrival offered ad libitum long stem hay. Forty-eight h after arrival, steers were reintroduced to a 90% concentrate (DM basis) finishing diet with consisting of dry-rolled corn, dried distiller’s grains plus solubles, liquid supplement, and wheat hay. The diet was introduced initially at 1.5% BW on 0 d, and daily delivery was increased until cattle reached their intake plateau at which point a slick bunk management system was employed. At initial processing, all steers received respiratory and clostridial vaccines and were fitted with wireless rumination tags to track daily rumination throughout the 42-d study. Fecal consistency (FCS) and clinical depression scores (CD) were collected starting 24 h after diet initiation, and subsequent collections occurred at 24 h intervals until 168 h. Fecal consistency was recorded on 20 random pen surface fecal samples and CD was recorded for individual steer. Categorical distributions for FCS and CD were analyzed with the Fisher’s Exact Test. Rumination data was analyzed as a linear mixed model with fixed effects of treatment, days on feed (DOF), and their interaction with a random effect of block and DOF as a repeated measure. For all analyses, P ≤ 0.05 was declared significant and 0.05 > P ≤ 0.10 was considered a tendency. No difference (P ≥ 0.49) was observed for CD at all time points. Additionally, no difference (P ≥ 0.12) was observed for FCS at 24, 48, 72, 120, 144, and 168 h. Fecal consistency tended (P = 0.10) to differ at 96 h, with CON exhibiting a 67% decrease in FCS 1 and 2. No significant (P ≥ 0.78) treatment × DOF interaction was noted for daily minutes ruminating. A significant (P < 0.01) DOF effect was realized for daily minutes ruminating. Minutes ruminating differed (P < 0.01) between treatments, with CON steers ruminating 6% more minutes daily than LP steers. Oral administration of ME had minimal effects on FCS and CD and decreased daily rumination time in feedlot steers during finishing diet realimentation.