Effect of a direct-fed microbial (10-G Armor) on feedlot performance, carcass characteristics, and prevalence of Salmonella in fed-beef heifers

Crossbred beef heifers [N = 1,394; initial shrunk body weight (BW) 291 ± 9.9 kg] were used to investigate the efficacy of 10-G Armor (Life Products, Inc., Norfolk, NE; 10-G) upon feedlot performance, carcass characteristics, and fecal and subiliac lymph nodes Salmonella prevalence. Heifers were blocked by day of arrival and allocated to 1 of 20 pens (N = 70 heifers/pen) and assigned one of two treatments (10 pens/treatment) : no direct fed microbial (CON) or 2g/heifer/d of L. acidophilus, E. faecium, P. pentosaceus, L. brevis and L. plantarum respectively (Life Products, Inc., Norfolk, NE; 10-G). Twenty four animals were randomly selected from each pen for Salmonella sampling. Recto-anal mucosal swab samples (RAMS) were obtained at initial processing and harvest; subiliac lymph nodes were collected at harvest. In addition, pen surface fecal pats were collected and composited by pen (10 pats per composite, 5 composites per pen) on day 0, 52, 120 and 192. Data were analyzed as a generalized complete block design and pen served as the experimental unit. No differences were observed in live growth performance metrics (P ≥ 0.55). Yield grade distributions did not differ between treatments (P ≥ 0.62), however cattle fed 10-G tended (P = 0.06; 14.6 vs 18.9%) to have fewer USDA Select carcasses and more (P = 0.09; 73.6 vs 78.0%) USDA Choice carcasses. Cattle fed 10-G tended (P = 0.10; 9.2% vs 12.3%) to have fewer liver abscesses and had fewer (P = 0.04; 5.3 vs 8.5%) severe liver abscesses. Salmonella prevalence of RAMS did not differ between treatments at initial processing (P = 0.97; CON = 11.6%, 10-G = 11.5%) or at harvest (P = 0.91; CON = 99.0%, 10-G = 98.6%), however RAMS differed (P < 0.01) in Salmonella prevalence between the two collection times. Cattle fed 10-G had a lower frequency of Salmonella positive lymph nodes (P = 0.01; CON = 15.8%, 10-G = 7.4%) than CON. However, Salmonella log (mpn/g) of lymph nodes did not differ between treatments at harvest (P = 0.34; CON = 0.73, 10-G = 0.34). These data indicate that cattle fed 10-G have decreased rates of severe liver abscesses without altering live animal performance or carcass characteristics. Supplementation of 10-G significantly reduced prevalence rate of Salmonella recovered from the subiliac lymph nodes. The factors responsible for the observed difference in the effects of 10-G on Salmonella warrants further investigation

Comparison of tulathromycin and tilmicosin on the prevalence and severity of bovine respiratory disease in feedlot cattle in association with feedlot performance, carcass characteristics, and economic factors

The objectives of this study were to 1) quantify effects of metaphylactic treatment for bovine respiratory disease (BRD) on growth performance, carcass characteristics, and lung lesion prevalence and severity; 2) evaluate the association of lung lesion prevalence and severity with carcass characteristics; and 3) evaluate effects of therapeutic treatment on carcass characteristics and lung lesion prevalence and severity. The study was conducted at a commercial feedlot in the Texas Panhandle in which steers (n = 2,336) initially weighing 312.1 ± 9.6 kg were sourced from auction markets and allocated in a randomized complete block design to 1 of 3 treatments (no metaphylactic [no antimicrobial drug {ND}] treatment, tilmicosin at 10 mg/kg BW [TIL], and tulathromycin at 2.5 mg/kg BW [TUL]). Lungs of all steers were evaluated during harvest to assess presence and severity of pneumonic lesions in the anteroventral lobes and the presence and severity of pleural adherences. Compared to the ND treatment, steers treated via metaphylactic therapy had greater (P < 0.05) metaphylactic cost, ADG, shrunk final BW, dressed carcass yield, HCW, 12th rib fat, calculated empty body fat (EBF), and gross revenue, concurrent with reduced (P < 0.05) BRD treatment costs and financial losses from BRD death and railed cattle, cumulatively resulting in greater financial returns. Lung lesions were present in 64.3% of lungs and were distributed similarly between metaphylactic treatments (63.9%) and ND (65.1%) cattle. Steers with advanced lung lesions present at harvest were associated with reduced (P < 0.05) HCW, KPH, 12th rib fat, calculated yield grades, marbling scores, and calculated EBF as compared to steers without lung lesions. Steers pulled for BRD had increased (P < 0.01) incidence of advanced lung lesions, mortality, and railers with decreased (P < 0.05) HCW, 12th rib fat, KPH, marbling score, calculated EBF, and percentage choice carcasses when compared to non-BRD event steers. From the results of this study, controlling BRD through the use of metaphylactic treatments on arrival in heavier cattle improved financial returns primarily driven by reductions in cost of death loss and railers.