Elanco Animal Health Research Articles

Bovine Respiratory Disease (BRD) in Post-Weaning Calves with Different Prevention Strategies and the Impact on Performance and Health Status

Our study aimed to compare Bovine Respiratory Disease (BRD) morbidity, mortality, and growth in dairy and dairy beef cross-bred calves during the commingle period, 81–120 days of age, using two different BRD prevention strategies. The calves (n = 1799) were randomly assigned into groups: (1) Control (CON; received no vaccine or metaphylaxis); (2) Tulathromycin metaphylaxis (TUL; IncrexxaTM, Elanco Animal Health Inc., Greenfield, IN, USA); and (3) Mannheimia haemolytica vaccine (VACC; Nuplura® PH, Elanco Animal Health Inc., Greenfield, IN, USA). Calves were individually weighed three times during the study to estimate average daily gain (ADG). Deep nasopharyngeal swabs, thoracic ultrasonography, health scores, and treatment records were collected during the study. Ultrasound and health score results were not different across treatments. In this study, the TUL group had a lower cumulative BRD incidence than CON. The cumulative incidence and 95% CI of BRD during the commingle period, 81–120 days of age for CON, TUL, and VACC were 0.43 (0.38 to 0.47), 0.36 (0.38 to 0.40), and 0.39 (0.35 to 0.43), respectively. The ADG for CON, TUL, and VACC were 0.25 ± 0.15, 0.32 ± 0.15, and 0.17 ± 0.15 kg, respectively. There was no difference among the treatment groups for ADG. Management and environmental conditions were variable at this operation throughout the study period and likely impacted the calves. Earlier interventions may be needed when the BRD incidence is elevated in high-risk calves.

PSI-23 Growth implants can decrease enteric methane emissions intensity from finishing beef cattle

Abstract Growth promotants are a useful tool in cattle production to improve their environmental impact by decreasing emissions per unit of gain and increasing overall feed efficiency. The objective of this study was to assess the relationship between enteric methane emissions, feed intake, average daily gain (ADG), and feed efficiency of implanted and nonimplanted finishing steers. Cattle (n = 62) were housed at the Climate Smart Research pens at Colorado State University and blocked by body weight (BW) into two pens and randomly assigned to treatment. Each pen was equipped with GreenFeed automated head chambers and SmartFeed feed intake measurement (C-Lock, Rapids City, SD). The study was a completely randomized block design. Animals within each block were then randomly assigned a treatment: implanted with Component TE200 (IMP; Elanco Animal Health, Greenfield, IN) or not implanted (CON). Enteric emissions, dry matter feed intake, BW, and BW gain (ADG) were collected from each individual animal from the light and heavy blocks for 80 and 52 d, respectively. Data were analyzed in JMP Pro with the linear model function and significance was declared a P ≤ 0.05. IMP cattle had a greater average ADG (2.40 kg/d vs 1.77 kg/d, P < 0.0001) compared with CON cattle. A difference was observed in total methane (CH4) emissions between treatments (200.83 g CH4/d IMP and 187.45 g CH4/d CON, P = 0.02). Dry matter intake (DMI) was not different between treatments (P = 0.17). Methane emissions intensity for each treatment was 84.89 (IMP) and 106.90 g/kg of ADG (CON) was different (P = 0.0002), while CH4 yield (CH4 per kg of DMI) was not different (P = 0.12). Overall feed efficiency between treatments resulted in IMP animals having a greater feed efficiency (4.74 kg DM/kg ADG) compared with CON animals (6.32 kg DM/kg ADG, P < 0.0001). In summary, growth promotants decrease CH4 emissions intensity in finishing steers and increase animal feed efficiency without affecting daily DMI.

232 Evaluation of a phytogenic feed additive with essential oils and plant extracts on growth performance in single sourced steer calves fed a forage-based diet during the initial 53 d receiving period

Abstract The receiving period of a feedlot calf is one of the most stressful stages in the life of that animal and can result in respiratory disease caused, in part, by reduced feed intake and transit stress. Feeding a phytomolecule compound in combination with current therapeutic strategies may aid in controlling systemic inflammation and improve the performance of newly received calves. This study determined whether a phytogenic feed additive with essential oils and plant extracts (PFA) influences measures of growth and growth efficiency during the feedlot receiving phase. The two treatments were a control group fed no additive (CON) and a treatment group fed PFA additive at a rate of 0.25 g/45.4 kg of body weight (BW; PFA). Steers were transported 285 km from an auction facility to the Ruminant Nutrition Center in Brookings, SD where they were vaccinated against viral respiratory diseases and clostridial species, and administered pour-on anthelmintic. Steers were divided into 10 replicate pens of 8 steers (305 ± 30 kg) per treatment (n = 160 steers) in a randomized complete block design. The steers were fed a basal diet [dry matter (DM) basis] containing corn silage (74%), DDGS (21%), a liquid supplement (5%), and monensin sodium (Rumensin-90, Elanco Animal Health) at 25 g/907 kg (DM basis) for 53 d. Steers were fed 2X daily with intakes closely managed for the first 14 d during adaptation to the receiving diet then a slick bunk management strategy was applied for the remainder of the study. No mortality was observed in this study, and one steer was treated for respiratory disease from the CON group. There were no significant differences observed in BW, average daily gain (ADG), variation in ADG, dry matter intake, or feed conversion efficiency from d 1 to 29, 29 to 53, or during the cumulative receiving period (P ≥ 0.11) between the CON and PFA groups. NEm and NEg did not differ between the treatments (P ≥ 0.79). The ratio of observed-to-expected dietary net energy was also not affected by dietary treatment (P ≥ 0.71). The steers used in this study were in good health and had minimal morbidity (0.63%) with no mortality during the 53-d receiving study which contributed to the feed additive having no appreciable influence on the growth and health outcomes in this study.

Early vaccination of laying hens with the live bivalent Salmonella vaccine AviPro™ Salmonella DUO results in successful vaccine uptake and increased gut colonization.

Salmonella Enteritidis and S. Typhimurium are the two most clinically important zoonotic Salmonella serovars and vaccination of breeding and laying hens affords effective Salmonella control. The use of live vaccines has proven beneficial for a number of reasons, including ease of application, protection from the first day of life onwards and initiation of a strong local immune response. Live vaccines can be applied in the drinking water from the first day of life onwards, but some rearers choose to wait until the end of the first week to ensure sufficient water consumption. However, this practice leaves the birds unprotected during the crucial first week of life, where they are most susceptible to colonization by field strains. The aim of this study was to determine if successful vaccine uptake is achieved when layer pullets are vaccinated as early as day one. Three pullet flocks were vaccinated at 1, 2, 3 or 5 days-of-age with AviPro™ Salmonella DUO, a live vaccine containing attenuated strains of S. Enteritidis and S. Typhimurium (Elanco Animal Health, Cuxhaven, Germany). The vaccine was administered via the drinking water following manufacturer's instructions. Two days post-vaccination, 10 birds per flock were culled and caecal and liver samples taken, along with two pools of faeces per flock. Levels of vaccine strains were determined by quantitative and qualitative bacteriology. Vaccine strains were detected in all birds from all age groups indicating successful uptake of the vaccine. Levels of the S. Enteritidis vaccine were higher than levels of the S. Typhimurium vaccine, with the latter frequently only detectable following enrichment. There was an inverse correlation between age and caecal levels of vaccines, with the highest numbers seen in birds vaccinated at 1-day-of-age. Interestingly, S. Enteritidis vaccine strain levels in liver samples were highest when birds were vaccinated at 5 days-of-age. These results show that successful uptake of both vaccine strains was evident in all age groups. The earlier the chicks were vaccinated, the higher the vaccine levels in caecal contents. We therefore recommend vaccination of pullets as early as practicably possible to ensure protection against exposure to field strains.

Effects of zinc supplementation and implant abscess on the immune system and growth performance of growing beef steers.

Seventy-two Angus-cross steers (261 ± 14kg) were utilized to determine the effects of supplemental Zn sulfate on growth, trace mineral status, circulating immune cells, and functional innate immune responses. Steers were stratified by weight and implanted with a Component E-S with Tylan implant (Elanco Animal Health, Greenfield, IN) on day 0. Dietary treatments included: control (CON; no supplemental Zn), Zn100 (100mg supplemental Zn/kg DM), and Zn150 (150mg supplemental Zn/kg DM). Analyzed dietary concentrations of Zn were 58, 160, and 207mg Zn/kg DM, respectively. On days 13 and 57, blood from nine steers per treatment was collected for immune analyses (cell phenotyping and response to stimulus). On day 16, implant abscesses were evaluated by palpation and visual appraisal. Sixty percent of steers had abscesses; however, there were no differences in abscess prevalence due to treatment (P = 0.67). Data were analyzed as a split-plot design using the Mixed procedure of SAS 9.4 (Cary, NC) with effects of dietary treatment, abscess, and their interaction. There was a tendency (treatment × abscess; P ≤ 0.09) for steers without abscesses to have greater average daily gain (ADG; treatment × abscess P = 0.06) and gain:feed (G:F; treatment × abscess P = 0.09) from d 14 to 27 in CON and Zn100 while within Zn150 steers without abscesses tended to have lesser ADG and G:F than abscessed steers. There were no other treatment × abscess effects for growth performance, but steers with abscesses tended to have decreased final body weight (P = 0.10) and overall G:F (days 0 to 57; P = 0.08). There was no interaction of treatment and abscess on immune cell populations on days 13 or 58 (treatment × abscess P ≥ 0.11). On day 13, Zn150 steers had increased CD45RO + gamma delta (P = 0.04) T cells. Abscessed steers had increased CD21 + B cells (P = 0.03) and tended to have increased CD21 + (P = 0.07) and CD21 + MHCIIhi (P = 0.07) B cells in circulation. This study shows zinc supplementation and implant abscesses can alter the immune system and growth performance of growing beef steers.

Effect of forage quality and narasin inclusion on ruminal fermentation, nutrient intake, and total tract digestibility of Nellore steers.

The study aimed to evaluate the effects of forage quality and narasin inclusion on intake, digestibility, and ruminal fermentation of Nellore steers. Twenty-eight rumen-cannulated Nellore steers (initial body weight [BW] = 350 ± 32.4kg) were allocated to individual pens in a randomized complete block design, with 7 blocks, defined according to the fasting BW at the beginning of the experiment. The steers were randomly assigned within blocks to 1 of 4 experimental diets in 2 × 2 factorial arrangements, being the first-factor forage quality (MEDIUM = 81g of CP/kg of dry matter [DM], and HIGH = 153g of CP/kg of DM), and the second factor was the inclusion (N13 = diet plus 13mg/kg of DM of narasin) or not (N0) of narasin (Zimprova; Elanco Animal Health, São Paulo, Brazil). The experiment consisted of a 28-d period with 22 d for adaptation and the last 6d for data collection. No haylage quality × narasin interaction (P ≥ 0.68) was observed on DM and nutrient intake. Haylage quality affected (P ≤ 0.01) DM intake, with greater values observed for steers fed HIGH compared with MEDIUM haylage. There was an increase (P < 0.001) in OM, NDF, hemicellulose, and CP intake for steers consuming HIGH vs. MEDIUM haylage. Including N13 did not affect (P > 0.39) DM and nutrient intake of steers. No haylage quality × narasin interactions were detected (P ≥ 0.60) for total tract nutrient digestibility. However, steers fed with HIGH haylage showed an increase (P > 0.001) in DM and digestibility of all nutrients compared with MEDIUM. Steers fed a MEDIUM haylage had a greater (P < 0.01) proportion of acetate compared with steers fed HIGH during all evaluated hours. Steers fed HIGH haylage had a greater (P < 0.01) proportion of propionate at 0h compared with steers consuming MEDIUM, whereas at 12h, steers consuming MEDIUM hay had a greater (P < 0.01) proportion of propionate vs. HIGH haylage. A haylage quality × narasin and haylage quality × time of collection interactions were detected (P ≤ 0.03) for rumen ammonia concentration, which was reduced (P < 0.03) in N13 vs. N0 steers consuming HIGH haylage. Collectively, high-quality haylage allows increased consumption and digestibility, with more energy-efficient ruminal fermentation. In addition, narasin might be an important nutritional tool in forage-based diets to enhance the ruminal fermentation parameters of Bos indicus Nellore steers.

A meta-regression analysis to evaluate the effects of narasin on grow-finish pig performance.

Ionophores are feed additives that decrease gram-positive microbial populations by disrupting the ion transfer across cell membranes resulting in improved growth performance. Narasin (Skycis; Elanco Animal Health, Greenfield, IN) is an FDA-approved ionophore utilized for increased rate of weight gain and improved feed efficiency in growing-finishing pigs. A meta-regression analysis was conducted to evaluate the effects of added narasin in growing-finishing pig diets to predict its influence on average daily gain (ADG), feed efficiency (G:F), and carcass yield. A database was developed containing 21 technical reports, abstracts, and refereed papers from 2012 to 2021 representing 35 observations for growth performance data in studies ranging from 35 to 116 d in length (overall data). In addition, within these 35 observations, individual period data were evaluated (143 observations) using weekly, bi-weekly, or monthly performance intervals (period data). Regression model equations were developed, and predictor variables were assessed with a stepwise manual forward selection procedure. The ADG model using the overall data included ADG, ADFI, and G:F of the control group, added narasin dose, and narasin feeding duration categorized as longer or shorter than 65 d. Predictor variables included in the G:F model using overall data were ADG, ADFI, and G:F of the control group and added narasin dose. For carcass yield, the final model included ADFI and G:F of the control group, added narasin dose, and narasin feeding duration of longer than 65 d. In the period model for ADG, the predictors included ADG, ADFI, and G:F of the control group, added narasin dose, and average BW of the control group categorized into greater than or less than 105kg. For period data for G:F, the model selected ADG, ADFI, and G:F of the control group and added narasin dose. Based on the results, the overall response to added narasin for ADG and G:F was quadratic and tended to decrease as ADG and G:F increased. A similar quadratic response was observed for the individual period data. In summary, using median values from the database for predictor variables, this meta-analysis demonstrated narasin would be expected to improve ADG between 1.06% and 1.65%, G:F between 0.71% and 1.71%, and carcass yield by 0.31% when fed continuously for longer than 65 d.

PSI-8 Effect of Monensin Withdrawal on the Rumen Prokaryote Microbiome in Bos Indicus and Bos Taurus Steers Consuming Bermudagrass Hay

Abstract Monensin, a carboxylic polyether ionophore, is commonly added to ruminant diets as a strategy for improving animal production by altering ruminal fermentation. However, research concerning the effect of monensin withdrawal is limited. Therefore, the effect of monensin withdrawal and the subspecies of cattle on the rumen prokaryote microbiome was evaluated using ruminally cannulated steers (5 Bos indicus, BI and 5 Bos taurus, BT; 398 kg BW) consuming bermudagrass hay (13.7% CP). Subspecies were concurrently subjected to a two period, two treatment crossover design. Each 70-d period consisted of a 42 d adaptation phase with treatments including 0 (CON) or 200 (MON) mg·animal-1 monensin (Rumensin 90; Elanco Animal Health, Greenfield, IN) fed in 0.91 kg dried distillers grains with solubles daily. Withdrawal of monensin was then evaluated for a 28-d phase following adaptation. Rumen fluid was collected via suction strainer from the dorsal and ventral sacs of the rumen at feeding on d 1, 7, 14, 21, and 28 of the withdrawal phase and frozen until further analysis. Upon completion of the trial, samples were thawed and analyzed for microbial populations using massively parallel sequencing. The V4 region of the 16S rRNA gene was sequenced to analyze and compare rumen prokaryotic microbes within treatment groups and subspecies. Sequences were processed using QIIME 2 (q2) version 2021.2 and imported into R v4.1 for statistical analysis and graphical displays. Bray Curtis-based principle coordinate analysis (PCoA) provided visualization of microbial community clustering by monensin treatment and subspecies, facilitating identification of microbial community shifts resulting from treatments or subspecies. No monensin×subspecies×day interaction (P = 0.96) was observed. However, an effect of monensin (P = 0.01), subspecies (P ≤ 0.01), and day (P = 0.017) on the microbiome was present. The changes in microbial density that were observed with monensin withdrawal help to provide insight into the mode of action of monensin and its impact on potential methane mitigation in cattle.

260 Effect of Biochar Inclusion in Finishing Beef Cattle Diets on Enteric Methane Production and Performance

Abstract An experiment was conducted to evaluate the impacts of biochar on methane (CH4) and carbon dioxide (CO2) emissions and interim performance of finishing beef cattle. This experiment used crossbred beef steers (n = 128; initial BW= 347 kg ± 9 kg) fed a biochar sourced from pistachio shells (VGrid Energy Systems). The diet contained 61% dried rolled corn, 30% Sweet Bran (Cargill Corn Milling, Blair, NE), 5% wheat straw, and 4% supplement with Tylan (Elanco Animal Health) targeted at 9.7 mg/kg of dry matter (DM) and Rumensin (Elanco Animal Health) at 33.1 mg/kg of DM in a fine ground corn carrier. Two treatments consisted of a control (CON) group fed a diet containing no biochar and a biochar (BIO) group fed a diet with 0.5% biochar replacing 0.5% dried rolled corn in the diet. Cattle were implanted on d 0 with Revalor XS (Merck Animal Health). Pen was the experimental unit with 8 steers per pen and 8 replications. Interim data were collected on d 90 of the experiment. Four pen replications were rotated twice through a two-chambered barn equipped with open-circuit indirect calorimeters using a negative air pressure system. Within replicate, each pen of cattle was monitored in both chambers. LI-COR (Biosciences, Lincoln, NE) sensors were used to capture emissions (7700 Open-Path CH4 analyzer and 7500DS Open-Path CO2/H2O analyzer). Each replicate was monitored for 5 d in the pen chamber followed by 1 d manure contribution and 1 d used for baseline corrections. Cattle performance data were analyzed using the MIXED procedure of SAS with treatment as the fixed effect and emissions data were analyzed as a repeated measure. Feeding biochar tended to increase emissions of CH4 in g/d (194 g/d BIO and 176 g/d CON, P = 0.09) but had no other effects on CH4 in g/kg of dry matter intake (DMI) with 16.3 g/kg DMI BIO and 14.2 g/kg DMI CON (P = 0.27). Likewise, feeding BIO had no effect on CO2 as g/day (10854 g/d BIO and 10691 g/d CON, P = 0.78) or as g/kg of DMI (904 g/kg DMI BIO and 860 g/kg DMI CON, P = 0.34). Interim cattle performance showed no differences between treatments in interim body weight (529 kg BIO and 534 kg CON, P = 0.49) and average daily gain (2.02 kg/d BIO and 2.07 kg/d CON, P = 0.50). Dry matter intake (12.3 kg/d BIO and 12.1 kg/d CON, P = 0.45) was not different between groups, which resulted in no differences in feed efficiency (0.165 BIO and 0.169 CON, P = 0.23). Supplementing biochar at 0.5% of the diet DM did not decrease eructed CH4 (slight increase) or impact respired CO2. Interim animal performance was not impacted by feeding biochar.

308 Zinc Supplementation and Implant Abscess Effects on Growth Performance and Immune System of Growing Beef Steers

Abstract Zinc is beneficial in growth and immune system function in cattle. Angus-cross steers (n = 72; initial BW = 261 ± 14 kg) were used in this 58-day study to determine the effects of supplemental Zn on growth, trace mineral status, and circulating immune cell populations. On d 0, steers received a Component E-S with Tylan implant (Elanco Animal Health, Greenfield, IN) and were stratified by BW into twelve GrowSafe-equipped pens. Dietary treatments included: control (CON; no supplemental Zn), Zn100 (100 mg supplemental Zn/kg DM), and Zn150 (150 mg supplemental Zn/kg DM). Supplemental Zn was provided as Zn sulfate, and other trace minerals were supplemented at NASEM (2016) recommendations. Individual BW was recorded on days -1, 0, 12, 13, 27, 28, 56, and 57. Blood was collected from 9 steers per treatment on d 13 for immune cell population and function assays. Liver biopsies were conducted on 18 steers per treatment on d 14. On d 16, implant abscesses (ABSC) were evaluated, and all steers were treated with meloxicam (285 mg). Data were analyzed using the Mixed procedure of SAS (Cary, NC) with fixed effects of treatment and ABSC prevalence using steer as the experimental unit. Abscess prevalence among treatments was analyzed using Proc Glimmix. Sixty percent of steers had ABSC; ABSC prevalence was similar by treatment (P = 0.67). Steers without ABSC had greater (P = 0.04) ADG d 0 to 13 and tended to have greater (P = 0.09) ADG d 0 to 57. There was also a tendency (Trt × ABSC; P ≤ 0.09) for steers without ABSC to have greater ADG and G:F from d 14 to 27 in CON and Zn100 while within Zn150 steers without ABSC tended to have lesser ADG and G:F than ABSC steers. No other treatment by ABSC or treatment effects (P ≥ 0.14) for growth performance were observed. There were no treatment by ABSC effects for immune cell populations on d 13 (P ≥ 0.26). In Zn150 steers, activated natural killer and gamma delta T cells were increased (P ≤ 0.03) on d 13. Similarly, CD21+ MHC IIhi B cells tended to be increased in Zn150 steers (P = 0.08). Steers with ABSC had increased relative frequency of CD5+ and CD21+ B cells (P ≤ 0.05) and tended to have increased natural killer and CD21+ MHC IIhi B cells (P ≤ 0.09). In addition, steers without ABSC had greater liver Mn on d 14 than ABSC steers (P = 0.05). There were no other effects on liver trace mineral concentrations (P ≥ 0.17). These observations suggest Zn supplementation has greater impact on the cellular immune system, while ABSC have a greater effect on B cells and the adaptive immune system.

284 A Meta-Regression Analysis to Evaluate the Effects of Narasin on Grow-Finish Pig Performance

Abstract Ionophores are a separate class of non-medically important antibiotics used in animal production to increase growth rate. Narasin (Skycis; Elanco Animal Health, Greenfield, IN) is an ionophore labeled for increased rate of body weight gain and improved feed efficiency in growing-finishing swine. The mode of action of this ionophore is to increase energy availability by altering volatile fatty acid production in the hindgut in favor of propionate, which is the most efficient product of fermentation. Therefore, a meta-regression analysis was conducted to evaluate the effects of narasin inclusion in growing-finishing pig diets to predict average daily gain and feed efficiency. A database was developed that contained 21 papers from 2012 to 2021 representing 308 observations including both individual period data as well as overall trial data. For statistical analysis two models were created. The individual period model considered only data with single continuous narasin feeding periods while the overall trial model considered complete data sets representing periods with and without narasin feeding. Regression model equations were developed with the GLIMMIX procedure of SAS (Version 9.4, SAS institute, Cary, NC). Predictor variables were assessed with a step-wise manual forward selection for model inclusion. Predictor variables were required to provide an improvement of at least 2 Bayesian information criterion units to be included in the final model. For individual period data for G:F, the model selected included concentration of narasin in the feed, ADG and ADFI of the control group not provided narasin, and average BW of the control group categorized into greater than 105 kg or less than 105 kg (Table 1). There were 2 competing models to predict improvement in overall G:F. For model 1, significant predictors included concentration of narasin in feed and ADG of the control group. Model 2 for overall G:F included concentration of narasin in feed, ADG and ADFI of the control group. For the individual period model that predicted ADG, the predictors were concentration of narasin in the feed, ADFI, G:F of the control group and BW category for feeding period. The best fitting ADG model using the overall trial data included concentration of narasin in feed, ADFI and G:F of the control group, and feeding duration categorized as longer than 65 days or shorter than 65 days. Together, these models can be used to predict the response to narasin supplementation in finishing pigs. Based on the results, the overall response to narasin inclusion rate for ADG and G:F is quadratic in nature. Additionally, as ADG and G:F increase, the response to narasin supplementation decreases. In summary, using average values from the database for predictor variables, this meta-analysis demonstrates narasin would be expected to improve overall G:F from 0.74 to 1.13% and ADG from 1 to 3%.

160 Effect of Nexpro on Immune Response and Performance of Finishing Steers

Abstract This study aimed to determine the effect of NexPro on growth performance, carcass characteristics, and markers of immune function in finishing cattle. Angus-cross steers (n = 210) weighing 465 ± 48 kg were used for this 89-day study. Steers were blocked by BW into four treatments: SBM; a control diet with 11% soybean meal on DM basis; NP9 (9% NexPro), NP12 (12%), and NP15 (15%). NexPro replaced dry-rolled corn in the diet as NP inclusion increased. NexPro treatments each had 9 pens and SBM had 8 pens (6 steers per pen). On day 0, steers were implanted with Component TE-200 (Elanco Animal Health). The BW of all steers and bunk refusals were measured on d -1, 0, 26, 61, 75, and 89 and were used to calculate pen gain, DMI and feed efficiency for each period. One steer per pen was selected for blood collection and muscle biopsies collected on d 26 and 75. From d 61 to 89 steers received 300 mg/d of ractopamine hydrochloride (RAC; Actogain; Zoetis). Fresh blood samples were used for immune cell population determination using flow cytometry. Data were analyzed using the Mixed procedures of SAS with pen as the experimental unit and fixed effects of treatment and block. Performance data were analyzed using d 0 BW as covariate. During the pre-RAC period (d 0 to 61) steers fed the SBM treatment ate more (P &amp;lt; 0.001) than steers fed the NP diets. Steers on the SBM diet had the greatest ADG, with NP12 and NP15 intermediate, and NP9 lowest (P ≤ 0.06), with no treatment differences in G:F (P = 0.26). However, during RAC DMI improved in all NP treatments, and were not different (P = 0.32) from SBM. During the RAC period, ADG tended to be greater (P = 0.09) in NP15 than all other treatments, and G:F was improved (P = 0.01) in NP15 compared with other treatments. Carcass-adjusted BW and ADG, and HCW were less in NP9 (P ≤ 0.02) but similar between SBM, NP12 and NP15. Carcass-adjusted G:F did not differ by treatment (P = 0.50). On d 26, NP12 and NP15 had greater frequencies of live gamma-delta T cells, and on d 75, NP15 had the greatest frequency of these cells (P ≤ 0.016). All NexPro treatments had greater percentages of CD45RO positive B cells on d 75 (P = 0.03) and increased frequency of live total natural killer cells from d 26 to 75 (P = 0.06). The less than expected DMI and greater rumen undegradable protein in NexPro may have caused NP9 to be RDP deficient. However, the greater inclusions of NexPro supported excellent cattle gains, similar or better than SBM.

PSIV-19 Understanding Intestinal Health in Nursery Pigs Through Potential Non-Invasive Biomarkers

Abstract Mannans in feed ingredients can cause a feed-induced immune response (FIIR), resulting in intestinal inflammation. The addition of beta-mannanase can limit this anti-nutritional action, reducing the cost of activating the immune response. In the same way, non-invasive biomarkers are important tools that can provide early diagnosis of low-grade inflammation by mannans. The objective of this study was to assess potential non-invasive biomarkers in nursery pigs reared in different scenarios of low-grade inflammation. Female piglets (n = 396; 6.86 ± 0.9 kg; Large white × Landrace) weaned at 21 days of age were used for this trial. Treatments were organized in a factorial design with two diet types (simple or complex feed formulas containing 25 and 12% of soybean-meal, respectively) and two enzyme supplementation plans (control without supplementation or supplemented with beta-mannanase at 0.4 kg per feed of 1,000 kg Hemicell HT, Elanco Animal Health, São Paulo, Brazil). Fecal samples were collected from 10 pigs per treatment at the 21st experimental day. The fecal concentration of calprotectin, neopterin, free fatty acid, lactoferrin, and calcium binding proteins were determined using commercially available ELISA kits. Blood was sampled 6h after oral gavage of FITC-dextran at the 22nd experimental day to access intestinal permeability. The variables were subjected to the normality test (Shapiro-Wilk), analysis of variance (ANOVA), and Tukey's test. Differences among treatments were considered at 5 and 10% significance levels. Piglets receiving beta-mannanase had reduced fecal levels of calprotectin (-41%; P = 0.048), neopterin (-43%; P = 0.019), and free fatty acid (-34%; P = 0.050) in relation to the control group. A tendency was observed for the reduction of novel lactoferrin (-1%; P = 0.072) and calcium binding proteins (-35%; P = 0.095) when comparing control with supplemented animals. In addition, beta-mannanase supplementation decreased intestinal permeability (-10%; P = 0.053) compared with control treatment. However, there was no effects of diet type or diet by enzyme interactions (P &amp;gt; 0.10). The addition of beta-mannanase in the nursery phase reduced fecal biomarkers associated with gut health inflammation. However, there was no difference between diets indicating a simple diet may be used to reduce diet cost without compromising the intestinal health of the animals.

Evaluation of a new commercial source of monensin in lactating dairy cows and continuous culture fermenters

The objective of this experiment was to evaluate a new commercial source of monensin (MON) on performance of mid-lactation dairy cows and fermentation parameters of dual-flow continuous culture fermenters. In Experiment 1, 43 Holstein cows (25 multiparous and 18 primiparous; 175 ± 97 DIM; 45.3 ± 10 kg/d milk yield; 692 ± 68 kg BW; mean ± SD) were used in a randomized block design experiment with a 15-d covariate and a 9-wk treatment period. The first 3 wk of the treatment period were considered adaptation and the last 6 wk were used for data collection and analysis. Treatments were: Control (CTR; no MON added), Rumensin® 90 (RUM; 350 mg/d MON from Elanco Animal Health Inc.), and Monovet® 90 (MVet; 350 mg/d MON from Huvepharma® Inc. US). All cows were fed the same base diet throughout the experiment and treatments were top-dressed during the treatment period. Orthogonal contrasts were used to evaluate CTR vs. MON (RUM + MVet) and RUM vs. MVet. Compared with CTR, MON tended to increase milk yield (43.8 vs. 42.3 kg/d) but did not affect DMI or feed efficiency. The MVet treatment improved feed efficiency compared with RUM (1.70 vs. 1.58). Treatments did not affect milk fat content and yield, milk protein yield, MUN concentration, or energy-corrected milk yield. In Experiment 2, nine continuous culture fermenters were used in a randomized block design experiment with two 10-d periods. Fermenters were fed once a day approximately 100 g DM of the same diet fed in Experiment 1. Treatments were: CTR, RUM (2 mg/L MON from Rumensin® 90), and MVet (2 mg/L MON from Monovet® 90). Monensin did not affect DM, OM, NDF, ADF, and CP degradability or total VFA production (mmol/d), but decreased acetate, butyrate, and isobutyrate molar proportions and increased propionate molar proportion compared with CTR. Both sources of MON decreased acetate to propionate ratio compared with CTR (1.61 vs. 2.40). Adding MON increased daily production of propionate (74.1 vs. 108 mmol/d) and decreased that of butyrate and isobutyrate compared with CTR. Monensin supplementation decreased ammonia-N production (433 vs. 545 mg/d) compared with CTR. Overall, results indicate MON tended to increase milk yield and altered VFA profile in the rumen and in vitro, and that MVet is a suitable source of MON for dairy cows.

Effects of implant strategy in extended stocker cattle programs and subsequent carcass characteristics

Our objective was to understand the effects of different implant protocols in a long-duration stocker program on high-quality forage and potential carryover effects into later production phases. In Oklahoma (OK) and Mississippi (MS), steers were grazed on cool-season annual pastures in fall 2018 through spring 2019. Steers were ran- domly assigned to 1 of 3 implant treatments: (1) Synovex One Grower (Zoetis) at d 0, (2) Component TE-G (Elanco Animal Health) at d 0, or (3) Component TE-G at d 0 and again at d 82 (OK) or d 85 (MS). Steers from each treatment were commingled in 2 (OK) or 3 (MS) pastures for 159 (OK) or 161 d (MS). At the end of the grazing sea- son, steers were finished in commercial feedyards, where they were implanted identically upon arrival. Steers were slaughtered when the pen was visually estimated at 1-cm backfat. Carcass data included hot carcass weight, rib-eye area, back fat thickness, and marbling score. Implant program had no sig- nificant effect on animal performance (weight and ADG) during the stocker phase (P > 0.39), but marbling score tended to be greater in the single Component TE-G versus the other 2 treatments (425 vs. 408 and 410, SEM = 5.9, P = 0.07). No evidence was found to recommend an extended-release implant or stock- er-phase reimplanting even in a relatively long grazing phase (up to approximately 160 d), and producers should consider selecting the least-cost implant protocol.

35 Effects of Supplementing Pre- and Pro-Biotic Feed Ingredients on Performance, Health, and Physiological Responses in Feedlot Cattle

Abstract This experiment examined the effects of a synbiotic supplement (yeast-derived prebiotic + Bacillus subtilis probiotic), which replaced or was fed with feed-grade antimicrobials (monensin and tylosin), on performance and health responses of feedlot cattle. Angus-influenced steers (n = 192) from 4 different sources were weaned and transported 800 km to an experimental feedlot. Steers arrived on d 0 and a shrunk body weight (BW) was recorded. Steers were then ranked by source and shrunk BW and allocated to 1 of 24 drylot pens (8 steers/pen). Steers a received free-choice diet of 3 treatments: 1) monensin and tylosin (RT; 360 mg/steer/day from Rumensin and 90 mg/steer/day from Tylan; Elanco Animal Health, Greenfield, IN), 2) yeast-derived ingredient and B. subtilis probiotic (CC;8 g∙steer-1∙day-1 of Celmanax and 28 g∙steer-1∙day-1 of Certillus; Church and Dwight Co., Inc., Princeton, NJ), or 3) a combination of RT and CC (RTCC). Animals were adapted to diets in a stepwise manner which consisted of a receiving diet (d 0 to 56), two step-up diets (step-up: d 57 to 63; step-up 2: d 64 to 70), and a final diet (d 71 to slaughter). The cattle were slaughtered in four groups according to BW and balanced by treatments. More specifically, 33 steers were slaughtered on d 200, 33 steers on d 230, 63 steers on d 257, and 63 steers on d 285. Upon slaughter, hot carcass weight, backfat thickness, Longissimus muscle area, USDA marbling score, USDA yield/quality grades, and liver abscess score were recorded. Overall, feed intake during the duration of the experimental period (d 0 to slaughter) was greater (P &amp;lt; 0.01) in CC compared with RT and RTCC. However, no differences were observed for ADG (P = 0.61), final BW (P = 0.67), or morbidity (P = 0.15). With increases in intake but no differences in ADG the CC group had lower feed efficiency (P = 0.02) when compared with RT and RTCC. Upon slaughter, CC had higher marbling scores compared with RT (P = 0.04). Both the CC and RTCC cattle had larger Longissimus muscle area (P = 0.07) and more carcasses grading choice or better (P &amp;lt; 0.01) when compared with RT. Whereas, hot carcass weight, backfat thickness, and yield grade did not differ among treatments (P ≥ 0.20). There was tendency observed for liver abscesses (P ≤ 0.09) to be greater in CC compared with RT and RTCC. Overall, supplementing feedlot steers with RT and CC improved feed intake and some carcass measures despite the decreased feed efficiency experienced by these cattle but combining CC and RT did not yield any additional performance or health benefits.

37 Supplemented with Yucca Schidigera Extract to Feedlot Cattle Consuming Diets with or Without Monensin

Abstract This experiment compared performance and physiological responses of feedlot cattle receiving a saponin containing feed ingredient manufactured from purified extract of Yucca schidigera [Micro-Aid (MA); DPI Global, Porterville, CA] which replaced or was fed in conjunction with feed-grade antimicrobials. Yearling, Angus-influenced steers (n = 20) arrived at the experimental feedlot on d -19 and a shrunk body weight (BW; 309 ± 4 kg) was immediately recorded. Steers were ranked by BW and allocated to 4 groups of 30 steers each. Groups were housed in of 4 drylot pens equipped with GrowSafe automated feeding systems (4 bunks/pen) during the experiment (d -15 to 69). On d 0 groups were randomly assigned to receive a total mixed ration containing: monensin and tylosin (RT; 360 mg/steer daily from Rumensin and 90 mg/steer daily from Tylan; Elanco Animal Health, Greenfield, IN) and/or 4 g/steer daily of MA in a 2 × 2 factorial arrangement of treatments. During the experimental period non-supplemented (CON) steers received a total mixed ration containing no additives. Individual feed intake was recorded daily, and steer BW was recorded every 28 d and before slaughter. Steers were slaughtered according to BW and slaughter groups were balanced by treatments (36 steers on d 120, 36 steers on d 146, and 48 steers on d 174). Carcass traits were recorded upon slaughter. On d 55 eight rumen-cannulated heifers were housed with yearling steers (1 pair/pen). Pairs rotated among groups every 21 d, resulting in a 4 × 4 Latin Square design (n = 8 per treatment) with a 5-day washout between rotations. Rumen fluid was collected from pairs on d 55, 75, 90,110, 125, 145, 160, and 180 (beginning and end of each 21-day rotation) and pH was recorded immediately after collection. No RT × MA treatment interactions were detected (P &amp;gt; 0.10). Feed intake was decreased (P &amp;lt; 0.01) in steers receiving RT, whereas feed efficiency was greater (P = 0.02) in steers receiving RT. Carcass variables including hot carcass weight, backfat thickness, Longissimus muscle area, marbling, yield grade, and percent of carcasses grading choice or better did not differ among treatments (P ≥ 0.17). Rumen fluid pH was greater (P = 0.04) in steers receiving RT. Steers receiving MA had greater (P = 0.03) rumen fluid pH and decreased (P = 0.04) rumen fluid viscosity. Collectively, supplementing feedlot cattle with Yucca schidigera extract improved rumen pH and viscosity, but failed to impact performance or carcass measures in feedlot cattle.

105 Effects of Monensin on Intake, Growth Performance, and Health of Newly-Received Feedlot Calves

Abstract Monensin is an ionophore commonly fed to feedlot cattle to increase feed efficiency (gain:feed ratio; G:F) typically by decreasing dry matter intake (DMI) when fed at the commonly adopted dose of 33 mg∙kg DM-1. During the receiving period when intake is often suppressed due to management stressors, feeding monensin to light-weight feedlot calves may be detrimental to DMI and consequently to growth performance. The objective of this experiment was to evaluate the effects of feeding sodium monensin to newly-received feedlot calves. A total of 380 crossbred beef steers [initial body weight (BW) = 231 ± 25 kg and approximately 8 months of age] were sourced from local auctions in Delhi, LA and transported approximately 16 h to Clayton, NM. Upon arrival, steers were processed, blocked by off-truck shrunk BW, randomly assigned to 20 pens (19 animal∙pen-1), and pens were then randomly assigned to one of two dietary treatments (n = 10 pens/treatment): control (CON; no feed additive) or sodium monensin at 170 mg∙animal-1∙day-1 (MON; Rumensin 90; Elanco Animal Health, Greenfield, IN). The basal diet consisted of a complete starter feed composed predominantly of wet corn gluten feed (RAMP; Cargill Sweet Bran, Dalhart, TX). The experiment was 56 days in length. The amount of feed offered to each pen was adjusted based on the DMI of the previous day and bunks were managed to contain trace amounts of feed at 0600 h. Body weight was recorded on days 0, 14, 28, and 56 for average daily gain (ADG) and G:F calculation. Dietary net energy for maintenance (NEm) and gain (NEg) were estimated based on observed growth performance. Daily animal health evaluations were performed using a 4-point scale method based on depression, appetite, respiration, and temperature throughout the experiment. All data were analyzed as a randomized complete block design using SAS with pen serving as the experimental unit. Feeding MON did not affect feed intake (P = 0.58) compared with CON, yet ADG was increased (P &amp;lt; 0.01) by 12.5% in steers fed MON compared with CON. Thus, there was a 10.7% increase (P &amp;lt; 0.01) in G:F for MON, which corresponds with a greater (P = 0.02) observed NEm and NEg for MON compared with CON. Feeding MON tended (P = 0.07) to elicit a 2.9% increase in final BW compared with CON. Additionally, there was no treatment effect (P ≥ 0.57) on morbidity based on the number of therapeutic treatments among calves which were treated for indications of bovine respiratory disease. Moreover, treatments did not affect mortality rate. In summary, feeding monensin at 170 mg∙animal-1∙d-1 (26 mg∙kg DM-1) increases growth performance of light-weight, newly-received feedlot cattle without influencing DMI or animal health.

26 Effect of Monensin Inclusion on the Rumen Prokaryote Microbiome inBos Indicus andBos Taurus Steers Consuming Bermudagrass Hay

Abstract Monensin is a carboxylic polyether ionophore that has the ability to alter ruminal fermentation and microbial populations in the rumen. Current research shows monensin to have beneficial effects on feed efficiency, specifically, a reduction in average daily feed intake and an increase in gain. Ten ruminally cannulated steers [5 Bos indicus (BI), 5 Bos taurus (BT); 398 kg BW] were used to measure both the effects of monensin inclusion and subspecies’ differences when provided a forage-based diet (bermudagrass hay; 13.7% CP). Subspecies were concurrently subjected to a two period, two treatment crossover design. Each 70-day period, consisted of 20-days for treatment adaptation followed by 22-days for sample collection. Treatments included 0 (CON) or 200 (MON) mg·animal-1 monensin (Rumensin 90; Elanco Animal Health, Greenfield, IN) fed daily within 0.91 kg dried distiller’s grains with solubles. A withdrawal period (28 days) was allowed before the second period, to prevent carryover effects of monensin. Rumen fluid was collected via suction strainer from the dorsal and ventral sacs of the rumen at feeding on day 42, then subsequently frozen for later analysis. Upon completion of the trial, rumen fluid was thawed and analyzed for microbial populations using massively parallel sequencing. The V4 region of the 16S rRNA gene was sequenced to analyze and compare rumen prokaryotic microbes within treatment groups and subspecies. Sequences were processed using QIIME 2 (q2) version 2021.2 and imported into R v4.1 for statistical analysis and graphical displays. Bray Curtis-based principle coordinate analysis (PCoA) provided visualization of microbial community clustering by monensin treatment and by subspecies, facilitating identification of microbial community shifts resulting from the treatments. There was no significant interaction between monensin and subspecies (P = 0.42); however, effects of monensin (P ≤ 0.01) and subspecies (P = 0.04) did exist. Due to possible links to feed utilization and methane production, this alteration of rumen microbial communities in cattle is of great interest.

25 Effect of Cyclic Monensin Feeding onin Situ Degradability of Low-Quality Forage Fed to Ruminally Cannulated Beef Steers

Abstract Effects of cyclic monensin feeding on in situ disappearance kinetics of low-quality forage (LQF; 4.9% CP) were evaluated. Ruminally cannulated steers (n = 12; Bos taurus; 260 kg BW) consuming LQF were randomly assigned to of 3 treatments in a completely randomized design: CON (0 mg∙animal-1∙day-1 monensin; Rumensin 90, Elanco Animal Health, Greenfield, IN), 2) MON (200 mg∙animal-1∙day-1 monensin), or 3) CYC (200 mg∙animal-1∙day-1 monensin for 4 d and 0 mg∙animal-1∙day-1 monensin for subsequent 4 d). Steers were fed dried distillers’ grains with solubles (1 kg∙animal-1∙day-1) for monensin inclusion. Four 28-d replicated cycles were used allowing 9 days for treatment adaptation, 4 days for sampling, and 4 days for withdrawal of monensin within the CYC treatment group. Low-quality forage samples were weighed into 0 × 20 cm polyester bags in replicates of four for each sampling hour. On d 0, all replicates were placed into the ventral area of the rumen and replicates were removed 0, 4, 8,6, 24, 48, and 72 hours post feeding. Upon removal, bags were rinsed in ice water, and frozen until final replicates were removed. Subsequently, bags were washed utilizing a commercial washing machine, dried at 55°C to a constant weight and dried residues were analyzed for DM. Ruminal in situ DM degradation data over time were fitted to the first-order exponential model with discrete lag using the NLIN procedure of SAS 9.4, then model parameters were compared with PROC GLIMMIX model to compare dietary treatments with period included as a random variable. There was no effect of treatment (P ≥ 0.22) on potentially degradable DM, rate of DM degradation, DM residue, DM lag, or wash loss of DM. Results are consistent with findings in the concurrent in vivo study conducted by Hook et al. (2022). Further evaluation of NDF degradability is required to determine a clear effect of cyclic monensin feeding on steers consuming an LQF.