Beef Feedlot Research Articles

PSIV-25 Utilization of rumen protected lysine and methionine in beef feedlot diets: Impacts on steer performance

Abstract Our objective was to compare intake, gain, and feed efficiency of steers fed rumen protected lysine and/or methionine in 10% crude protein diet relative to performance of steers fed a diet with 13% crude protein without added amino acids. Beef steers [n = 161; body weight (BW) = 429.7 ± 44.5kg] were used in this experiment. Calves were randomly assigned to treatments consisting of 1) positive control diet (POS), formulated to contain 13.0 to 13.5% CP, 2) negative control (NEG) diet containing 10.2% CP, which also forms the basal diet for the remaining treatments, 3) rumen protected methionine (RPMet) 10.2% CP basal diet and 7.2 g/d supplemental methionine, 4) rumen protected lysine (RPLys) 10.2% CP basal diet and 18.5 g/d supplemental lysine, and 5) the combination of rumen protected lysine and methionine (RPMet+Lys) 10.2% basal diet with 7.2 and 18.5 g/d supplemental methionine and lysine, respectively. Initial and final BW were unaffected by treatment (P ≥ 0.24). Average daily gain for POS (1.93 kg/d P ≤ 0.02) was greater than those of NEG, RPLYS, and RPMET+LYS, but was similar to RPMET (1.86 kg/d; P = 0.17). Dry matter intake was greater in RPMET (12.1kg/d; P ≤ 0.10) compared with all other treatments. Gain-to-feed ratio was greatest in POS (0.170 kg gain:kg DMI; P ≤ 0.04). The impacts of rumen-protected amino acids on performance (intake, gain, and efficiency) of beef steers fed high-concentrate diets were inconsistent. Evaluating both lysine and methionine supplied independent of each other in various concentrations is critical before moving forward with recommendations for beef cattle. USDA is an equal opportunity provider and employer.

PSV-27 Optimizing corn silage utilization in beef feedlot diets: Evaluating the impact of exogenous glucoamylase addition on performance and digestibility

Abstract The addition of an exogenous glucoamylase enzyme preparation to feedlot diets that contain a high percentage of corn silage may improve digestibility and yield positive outcomes in growth and efficiency. However, it is unclear what concentration of corn silage in the diet would most benefit from exogenous glucoamylase. Crossbred steers [n = 180; body weight (BW) = 459 ± 11.8 kg] were divided into 30 pens (5 pens per treatment; 6 steers per pen) and assigned to one of six treatments arranged as a 3 x 2 factorial investigating 3 forage concentrations (15, 42, and 69% corn silage) and 2 exogenous glucoamylase additions (0 or 183 enzyme units/kg of dry matter per d). Steers were fed 42% corn silage, 30% corn, 23% dried distillers grains with solubles, and 5% supplement at feedlot entry and for 2 wk prior to initiation of the study. Steers on the 15% and 69% corn silage diets were transitioned to treatment diets by wk 3 of the study (d 15), with the first transition occurring on d 0. Diet transitions occurred once weekly. The animals were on feed for 105 ± 10.4 d and had ad libitum access to feed and water. Average daily gain (ADG), dry matter intake (DMI), and gain:feed were assessed both overall and for two distinct periods: d 0 to 50, and d 51 until slaughter. Data analysis was performed using the GLIMMIX procedure of SAS. From d 0 to 50, ADG, DMI, and gain:feed did not differ due to forage concentration or enzyme inclusion and there was no interaction (P ≥ 0.39). For d 51 to slaughter, enzyme inclusion interacted with forage concentration such that the enzyme improved ADG (P = 0.0003) and gain:feed (P = 0.01) for steers fed the 42% corn silage diet but did not effect ADG and gain:feed for steers fed the 15 or 69% corn silage diets. For d 51 to slaughter DMI was not affected by forage concentration, enzyme inclusion, or their interaction (P ≥ 0.21). When calculated for the entire study (d 0 to slaughter), increasing forage concentration decreased ADG and gain:feed (P ≤ 0.0006), but did not effect DMI (P = 0.22). Overall, enzyme addition did not impact ADG, DMI, or gain:feed and did not interact with forage concentration (P ≥ 0.50). Carcass characteristics were not affected by forage concentration, enzyme addition, or their interaction (P ≥ 0.19). Overall results suggest that an exogenous glucoamylase enzyme improves growth and efficiency of heavier feedlot cattle fed moderate amounts of forage later in the feeding period.

PSLBI-5 Ruminal papillae morphology of beef on dairy heifers with abscessed or non-abscessed livers

Abstract The ruminal papillae morphology characteristics of feedlot beef on dairy non-spayed heifers with liver abscess to those with non-abscessed liver were evaluated. Heifers were sourced from 27 lots which were harvested on six dates between November 2022 and February 2023. Upon harvest, a total of 94 rumen tissue samples from animals presenting liver abscesses and 110 rumen tissue samples from animals with non-abscessed livers were collected in pairs, as abscesses were identified within the harvesting facility viscera inspection line, following a randomized complete block design (block = lot within harvest date). Individual fragments (6 cm2) from the cranial sac epithelium of the rumen were collected, rinsed with deionized water, immersed in 70% alcohol, and preserved under refrigeration (4 oC) until analysis. Ruminal tissues were trimmed (1 cm2), in which the number of papillae was counted by three trained personnel, followed by the removal of 12 representative papillae specimens for further area electronic scanning (The University of Texas Health Science Center of San Antonio, Image Tool) to determine average papillae area, number per cm2 (AVP), average papillae area in cm2 (APA), absorptive surface area in cm2/fragment cm2 (ASA), and papillae absorptive surface area, % (ASA). Data were analyzed using the GLIMMIX procedures of SAS, with individual animal ruminal tissue used as the experimental unit, the fixed effect of ruminal condition, and the random effect of lot within the harvesting date. Average papillae number (P = 0.27), average papillae area (P = 0.74), absorptive surface area (P = 0.48), and papillae absorptive surface area (P = 0.43) were not affected by the presence of liver abscess. Severity of liver abscess distinguished as A -, A, or A+ scores compared with non-abscessed liver showed no difference on papillae number (P = 0.34), papillae area (P = 0.89), and absorptive area (P = 0.62). The presence of small or large liver abscesses did not affect the papillae area, size, or absorptive area (P ≥ 0.41). The liver lobe location of abscesses (cranial, caudal, both) did not affect (P ≥ 0.17) any of the ruminal morphological variables measured. The presence of liver abscesses, whether diffuse or localized, in beef on dairy heifers, did not affect (P ≥ 0.58) the development of ruminal papillae. The presence, severity, or location of liver abscess was not connected with ruminal papillae number, area, or absorptive surface area of beef on dairy heifers measured upon harvest time. The absence of ruminal papillae morphological changes in animals committed with liver abscesses may be further investigated with the characterization of potential cellular physical changes of the ruminal tissue and the integrity of the primary barrier in the digestive tract.

PSLBII-28 Effects of dietary protein manipulation on greenhouse gases and ammonia emissions from feedlot beef steers

Abstract Black Angus steers [n = 112; body weight (BW) = 401 ± 3.6 kg] were used in a randomized incomplete block design to evaluate the effects of 3 rumen available protein to microbial crude protein ratios (RAP:MCP) on growth performance, and gaseous emissions from feedlot steers. Steers were blocked by initial BW and randomly assigned to 1 of 3 treatment rations. Diets were fed rations either Deficient (-150 gּ animal-1ּ d-1; DEF), Balanced (0 gּ animal-1ּ d-1; BAL), or Excess (+150 gּ animal-1ּ d-1; EXS) in RAP: MCP. Steers were allocated and housed in cattle pen enclosures (CPE), and treatment diets were delivered daily as a total mixed ration. The present study consisted of two 42-d periods. Refusals were collected weekly and BW every 14 d. Gas measurements were obtained daily in sequential order from all CPE. Data were analyzed with R statistical software (4.2.3). The linear mixed effect model procedure within the “lme4” package was used with CPE as the experimental unit, treatment and week as fixed effects, and block and period as random effects. A contrast coefficient matrix was constructed to test for linear and quadratic effects. Initial, intermediary and final BW were not different for steers receiving the varying RAP:MCP (P ≥ 0.239). A treatment effect (P = 0.004) was observed for mean dry matter intake (DMI) where EXS steers consumed 0.46 kg more DM compared with BAL steers, but DEF steers had similar DMI to those fed EXS and BAL (P = 0.189). Average daily gain (ADG) was only affected by treatment (P = 0.007) on d 0 to 14 where steers receiving DEF gained 0.6 kg more than those fed BAL (P = 0.010), but those fed EXS had similar ADG. Similar to ADG, gain to feed (G:F) was affected by treatment (P = 0.012) only during d 0 to 14. Mean CH4 production from steers fed DEF and EXS were 20% and 13% greater (P = 0.010) compared with those fed BAL, respectively; however, CH4 from EXS vs. DEF steers was not different (P = 0.149). Mean cumulative NH3 emissions increased linearly by treatment with EXS steers emitting up to 52% more NH3 compared with those receiving DEF (P < 0.001). Similarly, EXS steers had increased SO2 emissions by up to 44% compared with those fed DEF (P < 0.001). Emissions of CO2, N2O, and H2S were similar (P > 0.100). The manipulation of RAP:MCP in the diets of feedlot steers can drastically reduce NH3 emissions without affecting growth performance and may be a valuable tool to reduce air pollution from beef production systems.

143 Short- and long-term effects of heat stress in cow-calf pairs adapted to tropical and subtropical regions

Abstract Chronic exposure to high temperatures and humidity can limit beef cattle performance in tropical/subtropical environments, regardless of breed. Despite better heat adaptability compared with Bos taurus cattle, heat-stressed Bos indicus cattle also experience an increase in body temperature above the physiological limit. As body temperature increases, cascades of behavioral and physiological events are triggered to lessen heat load but often at the expense of productive outcomes. Contrary to other species and feedlot beef cattle, the effects of heat stress on physiology and performance of grazing cow-calf pairs have not been evaluated in detail, particularly for Bos indicus cattle. Preliminary data showed opposite outcomes to heat stress in Bos indicus vs. Bos taurus cattle, limiting the implications of the existing data generated from studies using beef and dairy Bos taurus cattle. This presentation will share some nutritional and management practices to mitigate heat stress in grazing beef cattle. Practices mentioned herein include altering the timing of body weight (BW) growth pattern (stair-step, SST) and immunomodulatory feed ingredient (IFI) supplementation for replacement beef heifers, and maternal access to shade to reduce heat load. For 100 d before the breeding season, Bos indicus-influenced beef heifers grazing warm-season grasses received a constant supplementation amount or SST strategy (50 d of low then 50 d of high supplementation), with or without IFI. Under severe heat stress conditions, IFI supplementation reduced heifer vaginal temperature but did not increase their growth and reproduction, whereas the SST strategy lowered internal body temperature, enhanced growth performance and pregnancy success compared with a conventional constant supplementation practice. Our group is also focused on the critical need to determine the specific effects of heat stress mitigation during pre- and postnatal phases on physiology and performance of Bos indicus-influenced cow-calf pairs. Study 1 evaluated the impacts of maternal access to artificial shade from 83 d prepartum until 50 d postpartum on body thermoregulation, performance, and physiology of beef heifers and their first offspring. Removing maternal access to shade led to greater maternal respiration rate, vaginal and body surface temperatures and reduced maternal body condition score and calf BW at birth. Nonetheless, offspring born from cows with no access to shade were remarkably heavier during a 60-d post-weaning period and had decreased plasma indicators of inflammation and positive effects to humoral immune response. Study 2 is a multi-year, USDA/NIFA-funded study designed to capitalize on the ability of cattle to reprogram physiological/immunological systems following exposure to stress during gestation. Study 2 combined gestational and postnatal heat abatement to enhance the overall growth/immune/reproductive performance of grazing Bos indicus-influenced cow-calf pairs. Partial data on long-term growth and reproductive performance, physiology, metabolome, and microbiome of both cows and their female offspring will be shared in this presentation.

433 Use of polyclonal antibodies to improve the efficiency of rumen function

Abstract Technologies such as polyclonal antibody preparations (PAP) have been investigated as a tool to improve rumen function, by targeting specific bacteria or molecules. While PAP can be sourced from the serum of immunized mammals, isolating targeted avian-derived antibodies (immunoglobulin Y; IgY) from egg yolk gained popularity due to its reduced impact on hens and greater IgY concentration in yolks. Advantages of avian-derived PAP utilization include cost-effectiveness and convenient production, high stability, and reduced cross-reactivity compared with other PAPs. Furthermore, IgY does not activate the host immune complement system, as observed with PAP derived from mammalian serum. Several proposed strategies explain how PAP might protect the host. It is suggested that PAP can agglutinate bacteria, inhibit bacterial adhesion, suppress bacterial virulence factors, and neutralize toxins. Avian-derived PAP, mainly administered as a direct-fed product in beef and dairy cattle diets, has been studied for its impact on specific rumen microbial populations, especially during high-grain feeding. Research confirms the effectiveness of PAP-IgY in inhibiting the growth of targeted bacteria. In beef steers, feeding PAP-IgY against Streptococcus bovis and Fusobacterium necrophorum resulted in growth inhibition, while IgY against cellulolytic rumen bacteria also showed efficacy in reducing the growth of the targeted strains in vitro. In other studies, PAP-IgY targeting S. bovis and F. necrophorum increased ruminal pH in beef steers and heifers and dairy cows, while also cattle-fed PAP-IgY against F. necrophorum had reduced severity of liver abscesses. When performance was evaluated, PAP-IgY against S. bovis improved feed efficiency of feedlot beef steers, and milk production increased when dairy cows were supplemented with PAP-IgY against lipopolysaccharides, with no observed impact on cow health status. However, not all studies have consistently demonstrated positive effects of PAP-IgY on nutrient digestibility or on mitigating systemic inflammation during high-grain feeding. A recent study revealed that supplementation with PAP-IgY against Methanobrevibacter ruminantium M1 decreased methane output ex-situ and tended to increase molar proportion of propionate in beef steers. In summary, polyclonal antibody preparations, particularly avian-derived IgY, offer a promising alternative to improve rumen function and animal performance. This is evidenced by increased ruminal pH during high grain feeding, inhibition of targeted bacterial growth, and, most recently, methane reduction. However, not all studies demonstrate consistent effects regarding nutrient digestibility. Further research is needed to refine recommendations, including dosage and antibody combinations, and to explore the broader impacts of PAP-IgY supplementation on ruminal and systemic variables to optimize livestock performance.

Performance, Meat Quality and Meat Metabolomics Outcomes: Efficacy of 3-Nitrooxypropanol in Feedlot Beef Cattle Diets.

30 Nellore animals with an average weight of 407.25 ± 2.04 kg, were distributed in a completely randomized design across the following treatments: 1-Control (without inclusion of 3-NOP); 2-BV75 (inclusion of 3-NOP at 75 mg/kg DM); 3-BV100 (inclusion of 3-NOP at 100 mg/kg DM). No significant effects were observed between treatments on ingestive behavior. However, the notable effect on the BWfinal and ADG of animals supplemented with 3-NOP compared to the control group was measurable. Cattle beef receiving 3-NOP exhibited reduced methane emissions (p < 0.0001) for all variables analyzed, resulting in an average decrease of 38.2% in methane emissions compared to the control, along with increased hydrogen emissions (g/day) (p < 0.0001). While supplementation with BV100 demonstrated lower methane emission, the performance was lower than BV75 in DMI, BWfinal, ADG, and ADG carcasses. Partial separation of metabolomics observed between groups indicated changes in meat metabolism when comparing the control group with the 3-NOP group, identifying metabolites with a variable importance projection (VIP) score > 1. In conclusion, supplementation with 3-NOP effectively reduced methane emissions and did not negatively influence animal performance.

A survey of potential and frequency used of local feedstuffs in the concentrate formulations for beef cattle feedlot in Indonesia

Abstract In Indonesia, the most popular system of beef cattle farming is a feedlot system, in which cattle are fattened for 3-6 months before being marketed. For a feedlot system to be successful, the availability of feed throughout the production process is important. Local feedstuff is commonly utilized as concentrate feed for beef cattle. This study aimed to identify the types of local feedstuff, the factors affecting their selection and availability, and the supply chain, particularly in feedlots across Indonesia. The study involved surveys, through questionnaires, interviews, and observation. Farm, feed mill, and supplier of feed visits were made and the management were interviewed regarding the feed commonly used in the farm and feed mills. Descriptive analysis was used to describe the local feedstuff’s availability and potential in the feed supply. The research results show that the local feedstuff most frequently used in sequence were palm kernel meal (11.97%), solid tapioca waste/onggok (9.83%), molasses (8.97%), dried cassava chips (8.55%), coffee husks (7.26%), copra meal (7.26%), bran pollard (6.84%), rice bran (5.13%), rice husks (5.13%), and corn cobs (5.13%). The important factors for selecting the types of feedstuffs used were demand (26.3%) and availability (26.3%). The most important factor impacting the availability of feedstuff was the harvesting season (26%). Feedstuff suppliers consist of four types: producers, distributors, agents, and retailers who fill customer demand, with distributors being the most dominant choice.

Analysis of the Nutritional Quality of Local Feed Ingredients Commonly Used in the Concentrate Formula for Beef Cattle Feedlots in Indonesia

Indonesia's annual beef consumption is experiencing a steady rise. In 2021, the per capita beef consumption amounted to 2.56 kg per person per year, resulting in a total of 696 million kilograms consumed across the country. This quantity is equivalent to the slaughtering of approximately 3.98 million cattle annually. With the increasing growth of the feedlot industry, cattle farmers, including feedlot operators, have the opportunity to enhance the value of agricultural companies in Indonesia by utilizing local feedstuffs. The objective of this study was to assess the suitability and nutritional value of indigenous feed sources for beef cattle in Indonesia. The research utilized feedstuff varieties and characteristics sourced from feedlots spanning since 2012-2021. The employed methodologies encompassed surveys, interviews, and questionnaires. This research involved the collection of both primary and secondary data. The potential and quality of local feedstuff were described using descriptive analysis. This research showed that eight types of local feedstuff could be categorized as energy sources including dehydrated cassava chips with a total digestible nutrients (TDN) value of 84.2% and bran pollard with a TDN value of 66.6%. The fiber sources consisted of corn cob (37.7% crude fiber), coffee husk (38% crude fiber), cocoa bean shell (20% crude fiber), tapioca solid waste/onggok (22% crude fiber), and palm kernel meal (22.1% crude fiber). The protein source consisted of copra meal with a protein content of 22.4%. The physical test most frequently inspected the feed color (18.1%) and odor (18.1%). Moisture examination (24%) was the most frequently used of proximate analysis was employed to identify the chemical composition. In conclusion the existence of eight local ingredients which were categorized into three different types: energy source, protein source, and fiber source commonly used in the concentrate formula for beef cattle feedlots in Indonesia.

Digital dermatitis affects locomotion and gait traits of beef cattle in feedlots

Sparse scientific evidence of cattle in confined environments, like feedlot dirt pens, report on increased importance of digi­tal dermatitis (DD) besides foot rot as an infectious cause of lameness. Therefore, we investigated the associations between DD presence and locomotion, gait traits, feet and leg confor­mation, and hygiene related risk factors in feedlot cattle to pro­vide the industry with clear guidelines on identification of DD affected cattle.

Retrospective evaluation of the causes and distribution of lameness in beef and dairy cattle evaluated by ambulatory and in-house clinical services at a North American veterinary teaching hospital

Since lameness occurs so commonly and has such significant effects on cattle productivity and farm profitability, manage­ment and prevention of lameness is essential to the design of effective health and husbandry programs. Unfortunately, the causes and distribution of lameness lesions between beef and dairy cattle, as well as the different management groups within a specific production class, can differ dramatically. A recent report analyzing data from 17 dairies found infectious condi­tions, specifically digital dermatitis and foot rot, were the most common cause of lameness in first-lactation cattle. In contrast, non-infectious lesions, namely white line disease and sole and toe ulcers, were the most common cause of lameness in cows in their second or greater lactation. A report evaluating the inci­dence of specific causes of lameness in cattle on 6 commercial beef feedlots found that the most frequently identified causes of lameness were upper limb issues and deep digital sepsis. How­ever, when characterizing different causes of lameness in beef cattle outside of feedlots, there exists a dearth of published data. Therefore, the objective of this study was to describe the different causes and distribution of lameness in beef and dairy cattle presenting to either a primary care ambulatory service or in house referral services at a veterinary teaching hospital in the southeastern United States.

162 Effect of molasses-based liquid supplement vs. corn-based dry supplement on beef cattle feedlot performance, carcass characteristics, and intestinal length

Abstract Molasses-based liquid supplements contain sugars that can be fermented into butyrate, the primary source of energy for gastrointestinal (GIT) epithelial cells and may improve gut health and enhance beef cattle performance. The aim of this study was to examine how a molasses-based liquid supplement, in contrast to a dry-based supplement, impacts the performance, carcass characteristics, and intestinal length of beef cattle. Crossbred steers [n = 60; body weight (BW) = 381.7 ± 1.3 kg] were divided into 10 pens (5 pens per treatment; 6 steers per pen) and were assigned to one of two treatment groups: dry, which consisted of a 10% ground corn-based dry supplement, or liquid, which included a 10% liquid molasses-based supplement. All the steers were fed a high-forage diet (56%) and were transitioned to a high-grain diet (7%) on d 1 of the experiment. The animals were on feed for an average of 122 d and had ad libitum access to feed and water. Steers were weighed every 21 to 28 d, and feed intake, average daily gain (ADG), and gain to feed ratio (G:F) were assessed both overall and for two distinct periods: the initial period (IP) from d 0 to 69, and the subsequent or second period (SP) from d 70 until slaughter. Intestinal length was measured at the time of slaughter. Data analysis was performed using the GLIMMIX procedure of SAS. Body weight and ADG did not differ between treatments in either period, or overall (P ≥ 0.41). However, it is noteworthy that feed intake was greater for steers that received the dry supplement during both periods as well as across the entire study (P ≤ 0.04). In terms of G:F, steers provided with the liquid supplement demonstrated a tendency for improved efficiency in the second period (P = 0.09) and an overall greater efficiency (P = 0.04) compared with those receiving the dry supplement. Intestinal length exhibited no difference for both the small and large intestine (P ≥ 0.57). For carcass data parameters no differences were observed for hot carcass weight, dressing %, or %KPH (P ≥ 0.24). Fat depth tended to be greater (P = 0.06), and yield grade (P = 0.01) and marbling score (P = 0.03) were greater for the steers fed the dry supplement. Rib-eye area was greater (P = 0.03) for the liquid supplement group. Therefore, these findings suggest feeding a liquid based supplement to steers on a 93% concentrate diet decreases intake, maintains BW, and improves feed efficiency and carcass leanness compared with steers fed a dry supplement. However, the improvement in efficiency as a result of feeding a liquid based supplement was not caused by an increase in absorptive capacity through increased intestinal length.

57 Effect of diet mixing strategies on growth performance and carcass characteristic in feedlot steer

Abstract Our objective was to determine the effects of a feeding management strategy on growth and carcass quality and characteristics on finishing feedlot beef cattle. Angus-Simmental steers (n = 60), blocked by body weight (BW), were housed in individual pens and randomly assigned to treatments. Treatments were total mixed ration (TMR) or a non-mixed diet (Split). The diet contained 67.5% of dry rolled corn, 18% of distiller grains with soluble, 2.5% soybean meal, 7% hay, and 5% of mineral and vitamin mixed. The diet composition for both treatments was similar, the only difference was the use of a TMR or that the concentrate was fed separately from the hay on the Split treated calves. Feed intake was monitored through slick bunk management in both treatments. For the Split assigned calves, if any hay or concentrate was left in the bunk on two consecutive days, the total feed was decreased by 5%; maintaining always the 93% concentrate and 7% forage ratio. Steers were weighed monthly and feed samples were collected for nutrient composition analysis semimonthly. Monthly weights and intakes were used to calculate average daily gain (ADG) and gain to feed ratio (G:F). Steers were slaughtered per block when the average weight of the block reached 555 kg. Carcasses were evaluated 48 h post slaughter. Carcass yield and quality factors were evaluated at the 12th/13th rib interface. Data were analyzed as randomized complete block design. Considering the fixed effect of the feeding strategy and the random effect of block. We did not observe differences (P &amp;gt; 0.17) in growth performance or carcass characteristics variables due to management strategy (Table 1). The lack of observed differences due to treatment might be because the ratio of concentrate and forage intake was similar for both groups, in addition to the slick bunk management in both treatments, which forced steers to eat all their ration, independent of the treatment, to continue to receive the same amount of feed.

Effects of Cattle Breeds and Dietary Energy Density on Intake, Growth, Carcass, and Meat Quality under Thai Feedlot Management System.

This study determines the effects of varying dietary metabolizable energy densities on Holstein Friesian and Charolais crossbred beef cattle in fattening phases. The research focuses on nutrient utilization, ruminal fermentation, growth performance, carcass traits, and meat quality. Thirty-six steers were used in the feeding trial that lasted for six months according to a 2 × 3 factorial arrangement in a randomized complete block design (Factor A, cattle breeds (Holstein Frisian, Charolais crossbred); B, metabolizable energy density (10.5, 11.1 and 11.8 MJ/kg DM)) with six replications. The dietary energy density had no interaction with the cattle breeds (p > 0.05). Despite fewer carcass yields, Holstein Friesian crossbreds indicate superior eating quality to Charolais crossbreds on drip loss, meat iron content, and Warner-Bratzler shear force due to increased intramuscular fat content (p < 0.05) with similar meat color (p > 0.05). Increased dietary energy density positively impacts nutrient and energy intake and rumen fermentation (p < 0.05) but did not affect growth and carcass traits (p > 0.05). This research suggests the potential of Holstein Friesian crossbreds for intensive beef production, providing valuable insights into optimal feeding strategies for achieving quality meat outcomes. On-farm feeding trials are needed to develop a practical and economical Thai beef feedlot management system.

Beef cattle feedlot runoff impacts on soil antimicrobial resistance

AbstractField application of beef cattle feedlot runoff may transport manure‐borne microbes and antibiotic resistant bacteria to agricultural soils eventually impacting deeper soils and groundwater. To evaluate this potential, total soil, antibiotic resistance (AR), and fecal indicator bacteria (Escherichia coli and Enterococcus) and the presence/abundance of AR genes were examined to a depth of 1.8 m in an agricultural field receiving long‐term application of feedlot runoff and compared to a nearby pasture receiving no runoff. While plate counts of total soil bacteria and cefotaxime‐resistant, erythromycin‐resistant, and tetracycline‐resistant bacteria decreased with depth on both fields (p &lt; 0.001) by an average 2‐log10 colony forming unit g−1 to 1.8‐m depth, field differences were only observed with greater abundances of total soil and erythromycin‐resistant bacteria (p ≤ 0.026) in the runoff‐amended versus control field soils. Soil bacterial and fecal indicator bacterial isolates evaluated phenotypically for resistance to 12 antibiotics varied in range and sensitivity. Using a culture‐independent approach, erm(C) and tet(Q) were detected using polymerase chain reaction in 31% and 58% of runoff‐field samples throughout the soil profile. Detection of erm(C) and tet(Q) in the control field soil profile was less frequent (0% and 11%, respectively). Two other genes, erm(A) and tet(X) were not detected in any soil samples. Based upon these results, long‐term applications of beef cattle feedlot runoff may increase the total abundance of microorganisms in the surface and shallow soil, but the relative enrichment of AR was dependent upon the type of resistance evaluated and, more specifically, the genes targeted for analysis.

Variation in Pen-Level Prevalence of BRD Bacterial Pathogens and Antimicrobial Resistance Following Feedlot Arrival in Beef Calves.

Antimicrobials are crucial for treating bovine respiratory disease (BRD) in beef feedlots. Evidence is needed to support antimicrobial use (AMU) decisions, particularly in the early part of the feeding period when BRD risk is highest. The study objective was to describe changes in prevalence and antimicrobial susceptibility of BRD bacterial pathogens at feedlot processing (1 day on feed (1DOF)), 12 days later (13DOF), and for a subset at 36DOF following metaphylactic antimicrobial treatment. Mixed-origin steer calves (n = 1599) from Western Canada were managed as 16 pens of 100 calves, receiving either tulathromycin (n = 1199) or oxytetracycline (n = 400) at arrival. Deep nasopharyngeal swabs collected at all time points underwent culture and antimicrobial susceptibility testing (AST). Variability in the pen-level prevalence of bacteria and antimicrobial susceptibility profiles were observed over time, between years, and metaphylaxis options. Susceptibility to most antimicrobials was high, but resistance increased from 1DOF to 13DOF, especially for tetracyclines and macrolides. Simulation results suggested that sampling 20 to 30 calves per pen of 200 reflected the relative pen-level prevalence of the culture and AST outcomes of interest. Pen-level assessment of antimicrobial resistance early in the feeding period can inform the evaluation of AMU protocols and surveillance efforts and support antimicrobial stewardship in animal agriculture.

Use of probiotic lactobacilli as alternative to monensin in beef feedlot cattle

Use of probiotic lactobacilli as alternative to monensin in beef feedlot cattle

Prevalence of mycotoxins from silage in a small beef cattle feedlot over a storage season: a case study

Challenges exist worldwide for the storage of animal feed, though year-long feeding of livestock is especially difficult in northern climates, including Canada. Usage of silage allows for crops to be harvested at the optimal nutritional value and stored for extended periods in customized storage systems. This case study investigated various feed management practices typical of small beef cattle feedlot farms in Southwestern Ontario, Canada. Crop samples were collected monthly and analyzed for mycotoxins and fungal secondary metabolites by liquid chromatography mass spectrometry (LC-MS/MS). Stored barley contained modest concentrations of deoxynivalenol and related compounds, as well as near trace amounts of fumonisin. Stored hay contained low concentrations of deoxynivalenol and beauvericin from the field. Hot spots of the Penicillium metabolite citrinin were detected after 7–8 months of storage in barley (39.2 ng g−1). Citrinin was also detected after 7–8 months in hay (16.3–17.5 ng g−1) along with the appearance of trace amounts of other storage toxins, including penitrem A (8.84 ng g−1), griseofulvin (34.8 ng g−1) and sterigmatocystin (14.1–261 ng g−1). This case study was a unique opportunity to use ‘citizen science’ to observe the onset of postharvest fungi and associated mycotoxins in various storage conditions allowing for the farmer to make necessary modifications before major problems begin. An improved understanding of the storage conditions that foster fungal growth and mycotoxin production in this working farm led to better agronomic practices, ultimately improving feed quality, livestock health, and profitability.

Screening and selection of essential oils for an intranasal spray against bovine respiratory pathogens based on antimicrobial, antiviral, immunomodulatory, and antibiofilm activities.

The rise in antibiotic resistant pathogens associated with bovine respiratory disease (BRD) poses a serious challenge, particularly to the beef feedlot industry, as they currently depend on antibiotics to prevent BRD to mitigate the financial burden (approx. $1 billion annual loss) inflicted by BRD-associated high mortality and morbidity in feedlot cattle. Thus, there is an impetus need for the development of antimicrobial alternative strategies against BRD. This study aimed to screen and select candidate essential oils (EOs) for the development of an intranasal EO spray that can inhibit BRD pathogens and promote microbiota-mediated respiratory health. The effects of selected EOs (ajowan, cinnamon leaf, citronella, grapefruit, fennel, and thyme) on a bovine nasopharyngeal microbiota culture were evaluated using 16S rRNA gene sequencing. The microbiota culture was enriched by incubating nasopharyngeal swabs obtained from finishing beef heifers in brain heart infusion broth with and without EOs (0.025%, v/v). These EOs were then also evaluated for their immunomodulatory effects on bovine turbinate (BT) cells by analyzing the concentrations of 15 cytokines and chemokines in cell culture after 24 h incubation. The crystal violet assay was done to assess the antibiofilm activity of EOs against Escherichia coli UMN026 strain. Finally, 15 EOs were screened for their antiviral activity against the bovine viral diarrhea virus 1 (BVDV-1) using BT cells and a fluorescence-based method. Ajowan, fennel, and thyme resulted in a moderate reduction of overall nasopharyngeal microbiota growth with significant alterations of both alpha and beta diversity, and the relative abundance of predominant bacterial families (e.g., increasing Enterobacteriaceae and decreasing Moraxellaceae) compared to the control (p < 0.05). Co-incubation of BT cells with selected EOs resulted in minimal alterations in cytokine and chemokine levels (p > 0.05). Ajowan, thyme, fennel, and cinnamon leaf exhibited antibiofilm activity at concentrations of 0.025 and 0.05%. Reduction of BVDV-1 replication in BT cells was observed with thyme (strong), and ajowan and citronella (moderate) at 0.0125% concentration. Accordingly, ajowan, thyme, fennel, cinnamon leaf, and citronella EOs were selected for further development as an intranasal EO spray to prevent and control of BRD pathogens in feedlot cattle.

Effects of bacterial direct-fed microbial combinations on beef cattle growth performance, feeding behavior, nutrient digestibility, ruminal morphology, and carcass characteristics.

The effects of the dietary inclusion of a mixture of bacterial direct-fed microbial (DFM) on feedlot beef cattle growth performance, carcass characteristics, nutrient digestibility, feeding behavior, and ruminal papillae morphology were evaluated. Crossbred-Angus steers (n = 192; initial body weight (BW) = 409 kg ± 8kg) were blocked by BW and randomly assigned into 48 pens (4 steers/pen and 16 pens/treatment) following a randomized complete block design. A steam-flaked corn-based fishing diet was offered to ad libitum intake once daily for 153 d containing the following treatments: (1) Control (no DFM, lactose carrier only); (2) treat-A (Lactobacillus animalis, Propionibacterium freudenreichii, Bacillus subtilis, and Bacillus licheniformis), at 1:1:1:3 ratio, respectively; totaling 6 × 109 CFU (50mg)/animal-daily minimum; and (3) treat-B, the same DFM combination, but with doses at 1:1:3:1 ratio. Bacterial counts were ~30% greater than the minimum expected. Data were analyzed using the GLIMMIX procedure of SAS, with pen as the experimental unit, the fixed effect of treatment, and the random effect of BW-block, while preplanned contrasts comparing Control × treat-A or treat-B were used. Steers offered treat-A had increased carcass-adjusted average daily gain (P = 0.03) by 6.7%, gain efficiency (P < 0.01) by 6%, tended (P = 0.07) to have increased carcass-adjusted final BW by 15kg, and hot carcass weight (P = 0.07) by 10kg, while treat-B did not differ (P ≥ 0.17) from control. Overall dry matter (DM) intake (P = 0.36) and other carcass traits (P ≥ 0.13) were not affected by treatments. Steers offered treat-A tended to have increased digestibility of DM (P = 0.07) by 3%, neutral detergent fiber (P = 0.10), and hemicellulose (P = 0.08) by 9% compared with control, while treat-B did not differ (P ≥ 0.10) from control. No treatment × period interactions (P ≥ 0.21) or main effects of treatment (P ≥ 0.12) were observed during 24-h feeding behavior. Steers ruminated, ate, chewed, and were more active (P ≤ 0.01) during the second behavioral assessment (day 113), while drinking behavior was not affected (P ≥ 0.88). Ruminal papillae morphology and ruminal ammonia concentration (ruminal fluid collected at slaughter facility) were not affected by treatment (P ≥ 0.39). Steers offered the DFM treat-A had improved growth performance and it positively affected carcass weight and nutrient digestion. The DFM combinations did not seem to affect feedlot cattle feeding behavior or ruminal papillae morphology.