Comparative growth performance of backgrounded beef heifers treated with an injectable fixed-dose combination (0.2 mg/kg doramectin + 6.0 mg/kg levamisole hydrochloride) or single-active (0.2 mg/kg ivermectin) endectocide.

Gastrointestinal nematodes (GINs) can negatively impact all production classes of cattle, particularly growing cattle. A global decline in efficacy of broad-spectrum single-active anthelmintics requires alternative GIN control methods without the aid of novel drug classes. Here, we present a new fixed-dose combination injectable (FDCI) endectocide for cattle that combines doramectin (5 mg/ml) and levamisole hydrochloride (150 mg/ml). A 56-day comparative performance confinement backgrounding trial was conducted in stocker beef heifers (n = 1548) with confirmed GIN infections to (1) compare the Day 14 post-treatment effectiveness of the new FDCI endectocide to pen mates treated with the injectable single-active endectocide ivermectin, as evidenced by fecal egg counts (FECs) conducted for a randomly selected subset (10%) of both treatment groups, and (2) determine if the greater GIN control by the FDCI evidenced in the subsample improved growth performance in all FDCI-treated heifers. Heifers were procured in four cohorts, with a 10-week timeframe between enrollment of the first and last cohort. Treatment groups were comingled within dirt-floor pens (n = 31; 7-8 per cohort) and offered a standard backgrounding diet ad libitum for the study duration. Heifers with enrollment FEC ≥ 30 eggs per gram (EPG) were randomly allocated to receive the FDCI (n = 773) or ivermectin (n = 775) on Day 0. Day 0 FECs conducted on 10% of enrolled heifers (FDCI, n = 78; ivermectin, n = 79) were not different between treatment groups (p = 0.491). Day 14 FECs for the same heifers were reduced compared to Day 0 within each treatment group. Heifers given the FDCI had lower Day 14 AM FECs and higher FEC reduction test (FECRT) result (0.07 EPG; 0.999) than ivermectin-treated heifers (21.58 EPG; FECRT = 0.850). Mean body weight (BW) was not different between treatment groups on Day 0 (p = 0.2762) and Day 14 (p = 0.2010) but was significantly greater (p = 0.0007) for FDCI-treated heifers compared to ivermectin-treated heifers on Day 56. Compared to ivermectin-treated heifers, overall average daily gain from all evaluation periods (Day 0-14, Day 14-56, and Day 0-56) was greater (p ≤ 0.0052) in FDCI-treated heifers, and FDCI-treated heifers had 4.223 kg greater total weight gain over the 56-day study. The FDCI (0.2 mg/kg doramectin + 6.0 mg/kg levamisole hydrochloride) was highly effective in reducing GIN infections and thus promoted improved growth performance in beef heifers over a 56-day backgrounding period.

Synovex ONE Grower improves growth performance for at least 200 days in growing beef steers and heifers fed in confinement for slaughter.

Growth-promoting implants are broadly used in the feedlot industry to improve growth performance and to increase production efficiencies. With cattle being fed longer and to heavier weights, there is demand for extended-release implants that payout for at least 200 d. Our objective was to evaluate feedlot growth of Synovex ONE Grower, a moderate potency (150 mg trenbolone acetate [TBA] and 21 mg estradiol benzoate [EB]), extended-release, growth-promoting implant for 200 d. At four locations (Texas, Idaho, California, and Nebraska), 200 steers (n = 800; d 0 body weight [BW] = 320.2 ± 9.5 kg) and 200 heifers (n = 800; d 0 BW = 311.5 ± 9.5 kg) were blocked by BW and randomized to 1 of 2 treatments: 1) Control, empty subcutaneous needle inserted and extracted from the middle third of one ear; 2) ONE Grower, 150 mg TBA and 21 mg EB extended-release implant administered in middle third of one ear. Treatments were commingled within pen of the same sex (n = 4/site; 2/sex/site) in a split plot design replicated across four sites. Cattle were fed finishing ration ad libitum common to each geographical region at least once daily and were observed for any abnormal health events twice daily. Treatments were administered on d 0. Mid-study implant site evaluations were performed on d 35 or 41. Initial BW was recorded on d 0 and final BW was recorded on d 200 to 204. Cattle were harvested from d 201 to 231; however, carcass data were not collected due to slaughter facility complications brought on by the COVID-19 pandemic. Data were analyzed using the PROC MIXED and PROC GLIMMIX procedures of SAS (Version 9.4, SAS Institute, Cary, NC; P < 0.05), and animal was the experimental unit. There were no treatment × sex interactions (P ≥ 0.052) for any variable. Final BW on d 200 was greater (P < 0.01) for steers and heifers implanted with ONE Grower compared to Control; ONE Grower improved final BW by 5.7% for steers and 3.9% for heifers. Overall average daily gain (ADG) from d 0 to 200 was greater (P < 0.01) for ONE Grower steers and heifers compared to Control with an increase in ADG of 13.1% for steers and 8.9% for heifers. For cattle implanted with ONE Grower, implant retention rates at d 35 or 41 were 95.7% and 96.3% for steers and heifers, respectively. There was no difference (P ≥ 0.32) in percentage deads, removals, or bullers (steers) between treatments. Synovex ONE Grower improved final BW and ADG in feedlot steers and heifers fed for at least 200 d.

Limitations of bacterial culture, viral PCR, and tulathromycin susceptibility from upper respiratory tract samples in predicting clinical outcome of tulathromycin control or treatment of bovine respiratory disease in high-risk feeder heifers.

A cross-sectional prospective cohort study including 1026 heifers administered tulathromycin due to high risk of clinical signs of bovine respiratory disease (BRD), measured poor association between BRD clinical outcomes and results of bacterial culture and tulathromycin susceptibility from BRD isolates of deep nasopharyngeal swabs (DNS) and adequate association with viral polymerase chain reaction (PCR) results from nasal swabs. Isolation rates from DNS collected on day-0 and at 1st BRD-treatment respectively were: Mannheimia haemolytica (10.9% & 34.1%); Pasteurella multocida (10.4% & 7.4%); Mycoplasma bovis (1.0% & 36.6%); and Histophilus somni (0.7% & 6.3%). Prevalence of BRD viral nucleic acid on nasal swabs collected exclusively at 1st BRD-treatment were: bovine parainfluenza virus type-3 (bPIV-3) 34.1%; bovine viral diarrhea virus (BVDV) 26.3%; bovine herpes virus type-1 (BHV-1) 10.8%; and bovine respiratory syncytial virus (BRSV) 54.1%. Increased relative risk, at 95% confidence intervals, of 1st BRD-treatment failure was associated with positive viral PCR results: BVDV 1.39 (1.17-1.66), bPIV-3 1.26 (1.06-1.51), BHV-1 1.52 (1.25-1.83), and BRSV 1.35 (1.11-1.63) from nasal swabs collected at 1st BRD-treatment and culture of M. haemolytica 1.23 (1.00-1.51) from DNS collected at day-0. However, in this population of high-risk feeder heifers, the predictive values of susceptible and resistant isolates had inadequate association with BRD clinical outcome. These results indicate, that using tulathromycin susceptibility testing of isolates of M. haemolytica or P. multocida from DNS collected on arrival or at 1st BRD-treatment to evaluate tulathromycin clinical efficacy, is unreliable.

Low-dose oral interferon modulates expression of inflammatory and autoimmune genes in cattle.

While the safety and efficacy profiles of orally administered bovine interferon (IFN) alpha have been documented, the mechanism(s) that result in clinical benefits remain elusive. One approach to delineating the molecular pathways of IFN efficacy is through the use of gene expression profiling technologies. In this proof-of-concept study, different (0, 50, 200 and 800 units) oral doses of natural bovine IFN (type I) were tested in cattle to determine if oral IFN altered the expression of genes that may be pivotal to the development of systemic resistance to viral infections such as foot-and-mouth disease (FMD). Oral IFN was administered twice: Time 0 and 8h later. Blood was collected at 0, 8 and 24h after the first IFN administration, and DNA isolated from peripheral blood mononuclear cells (PBMCs) was employed in quantitative polymerase chain reaction (qPCR) microarray assays. Within 8h, 50 and 200 units of oral IFN induced significant (P<0.05) changes in expression of 41 of 92 tested autoimmune and inflammatory response-associated genes. These data suggest that orally administered IFN is a viable approach for providing short-term antiviral immunity to livestock exposed to viruses such as FMD virus (FMDV) until such a time that an effective vaccine can be produced and distributed to producers.

Cooperia punctata: effect on cattle productivity?

Cooperia spp. have become the most prevalent parasites in United States cow/calf operations as observed in the USDA NAHMS (National Animal Health Monitoring System) Beef Cow/Calf survey in 2008. This is at least in part due to the widespread use of macrocyclic lactones that have recently been shown to have a reduced activity against these parasites. The effects of Cooperia spp. on cattle productivity are largely unknown. This study was conducted to assess their effect upon cattle housed under conditions found in American feedlots. Two hundred yearling calves (average weight 460 lb/209 kg) were acquired from northwestern Arkansas and northeastern Oklahoma and were vaccinated and dewormed upon arrival at the feedlot. Animals were comingled and preconditioned for approximately one month, and were fed a standard growing ration throughout the study. Calves were randomly divided into two groups (n=80, infected and control) and each group was further divided into two replicate pens (n=40). Calves from the two infected pens were orally inoculated with a gavage of 1 × 10(5) and 0.825 × 10(5) infective larvae of a recent isolate of Cooperia punctata on day 0 and 14, respectively, with the two control pens receiving a similar volume of tap water. Data collected included biweekly fecal egg counts, daily individual feed consumption and weight gain over the 60-day test period. The presence of C. punctata (>99% of recovered worms) was confirmed by necropsy and recovery from the small intestine on days 35 and 60 post infection (PI) in a subset of animals. Egg counts were positive by day 14 PI and remained at numbers similar to values seen in field studies. The control group gained weight 7.5% more rapidly (p=0.02) than infected animals (3.24 lb/1.47 kg per day vs. 3.0 lb/1.36 kg per day, respectively). The Cooperia-infected calves also consumed 1.5 lb (0.68 kg) less dry feed per day than the control animals (p=0.02). These data suggest that C. punctata has a deleterious effect on both appetite and nutrient uptake or utilization. At necropsy (days 35 and 60), the draining mesenteric lymph nodes of infected animals were increased in size and the small intestinal mucosa was thickened and covered with a thick layer of mucus in the infected animals. The most prominent histological changes in the Cooperia- infected animals included a moderate increase in the number of intraepithelial lymphocytes and globule leukocytes, as well as aggregates of eosinophils within the lower lamina propria. The only significant difference was an increase in the goblet cell density at day 60. Anthelmintic sensitivity/resistance of the Cooperia isolate used was determined by treatment of one pen of infected calves with a macrocyclic lactone and the other pen with a benzimidazole at the completion of the study. The macrocyclic lactone treatment (n=40) did not remove the parasites (FECRT=8.8%), while treatment with a benzimidazole was very effective (FECRT=98.1%). This study demonstrated that C. punctata has a significant effect on cattle productivity, both reduced weight gain and decreased feed intake compared to controls.

Comparison of single vaccination versus revaccination with a modified-live virus vaccine containing bovine herpesvirus-1, bovine viral diarrhea virus (types 1a and 2a), parainfluenza type 3 virus, and bovine respiratory syncytial virus in the prevention of bovine respiratory disease in cattle.

Objective-To compare effects of administration of a modified-live respiratory virus vaccine once with administration of the same vaccine twice on the health and performance of cattle. Design-Randomized, controlled trial. Animals-612 mixed-breed male cattle with unknown health histories. Procedures-Cattle were randomly assigned to 1 of 2 treatment groups (single vaccination treatment group [SVAC group] vs revaccination treatment group [REVAC group]) during the preconditioning phase of production. All cattle were given a modified-live respiratory virus vaccine. Eleven days later, REVAC group cattle received a second injection of the same vaccine. During the finishing phase of production, cattle from each treatment group were either vaccinated a third time with the modified-live respiratory virus vaccine or given no vaccine. Health observations were performed daily. Blood and performance variables were measured throughout the experiment. Results-During preconditioning, no significant differences were observed in performance or antibody production between groups. Morbidity rate from bovine respiratory disease was lower for SVAC group cattle; however, days to first treatment for bovine respiratory disease were not different between groups. No significant differences in body weights, daily gains, or dry-matter intake between groups were observed during the finishing phase. Revaccination treatment group cattle had improved feed efficiency regardless of vaccination protocol in the finishing phase. Conclusions and Clinical Relevance-Vaccination once with a modified-live respiratory virus vaccine was as efficacious as vaccination twice in the prevention of bovine respiratory disease of high-risk cattle, although feed efficiency was improved in REVAC group cattle during the finishing period.