Beef Feedlot Research Articles

Identification of the production system of beef cattle by the stable isotope analysis

Abstract: The objective of this work was to evaluate the potential of the stable isotope technique to characterize beef cattle production systems in tropical conditions. For this, carbon and nitrogen stable isotopes were identified in non-defatted and defatted bovine muscles. A total of 45 cattle were evaluated in three production systems: pasture, conventional feedlot, and young beef bull feedlot (n = 15 per system). Samples from the Trapezius cervicis, Longissimus dorsi, and Semitendinosus muscles were collected to determine the isotopic composition of δ13C and δ15N. The isotopic data of the δ13C and δ15N of non-defatted and defatted muscles were subjected to the principal component analysis (PCA) and to the discriminant analysis (DA). The PCA allowed separating the three production systems based on the results obtained for the non-defatted and defatted muscles. A correct global classification rate of 100% and a cross-validation rate of 100% were obtained with the DA. The carbon and nitrogen isotopic ratio of non-defatted and defatted muscles allows for the precise identification of beef cattle production systems in tropical conditions.

The effects of zeranol and oestradiol implants on performance and nutrient digestibility of zero-grazed White Fulani cattle

Aim The aim of this study was to investigate the effects of two growth-promoting implants (zeranol and oestradiol-17β) on performance and feed digestibility of finishing White Fulani cattle in the feedlot. This was with a view to determining an alternative means of enhancing cattle performance without grazing the animals. Methods A 60-day feedlot trial was conducted using 27 stocker White Fulani bulls that were allotted randomly to three treatment groups (i.e. non-implanted, oestradiol-implanted and zeranol-implanted) in a completely randomised experimental design. Cattle were offered a compounded feedlot ration consisting of 14% crude protein ad libitum. The bulls were weighed initially and fortnightly thereafter for the duration of the study. Coefficients of dry matter and nutrients digestibility were determined using lignin as an internal marker. Data were analysed using the general linear model procedure of ANOVA and mean values were compared using Fisher’s least significant difference (l.s.d.0.05). Key results The average final liveweight, total weight gain, average daily gain (ADG) and average daily feed intake (ADFI) of implanted feedlot cattle were higher (P < 0.05) than for non-implanted cattle; and higher in oestradiol-implanted cattle compared with zeranol-implanted ones. The ADG was 29.16 and 20.48% higher, and the ADFI was 35.06 and 18.18% higher for oestradiol-implanted and zeranol-implanted feedlot cattle, respectively than for non-implanted cattle. Irrespective of the treatment, feed conversion ratio of experimental bulls remained below the range (4.5–7.5) established for feedlot beef cattle; an indication of better efficiency of feed utilisation by White Fulani cattle. The apparent digestibility of dry matter (59.76–64.31%) of the feedlot ration was in the order: non-implanted = oestradiol-implanted > zeranol-implanted while the apparent digestibility of crude protein (73.91–77.99%) was in the order: non-implanted > oestradiol-implanted = zeranol-implanted. Conclusions and implications The results of this study show that the use of an oestradiol implant in finishing zero-grazed White Fulani cattle was beneficial for improving growth performance. Both implanted and non-implanted cattle showed good coefficients of nutrient digestibility, indicating that the mode of action of the growth implants in enhancing performance characteristics does not depend on indices of digestibility.

Ractopamine Hydrochloride and Estradiol + Trenbolone Acetate Implants Alter Myogenic mRNA, <i>β</i>-Adrenergic Receptors, and Blood Metabolites

Two commonly used growth promotants in the United States beef industry are β-agonists and anabolic steroid hormones. Each has been shown to increase lean muscle deposition in cattle provided treatments of each growth technology, but much is still unknown of how steroidal implants and β-agonists work in combination. It was our goal to determine the effect of implant strategy and β-agonist administration in beef feedlot heifers (n = 264). A 3 × 2 factorial randomized complete block design was used with 2 levels of OPT and 3 different durations of terminal implant (TI) windows for a total of 6 treatment groups with 9 replications. Terminal implants (20 mg estradiol/200 mg trenbolone acetate implant, Component TE-200) were provided to heifers 140 d from slaughter (TI140), 100 d from slaughter (TI100), or 60 d from slaughter (TI60). Animals receiving the later two TI being first implanted on day 0 (8 mg estradiol/80 mg trenbolone acetate implant, Component TE-IH). The second treatment of the cattle received was the orally active beta adrenergic agonist, ractopamine-hydrochloride (RH) in the form of Optaflexx®(OPT; 0 (NO) or 200 (YES) mg/hd·d-1) over the final 28 days of the trial. Thirty animals were subjected to longissimus muscle (LM) biopsies on d 0, 40, 80, 112, and at slaughter on d 140 to view mRNA levels of myogenic related genes and protein quantities of the β1-adrenergic receptor (β1 AR) and β2-adrenergic receptor (β2 AR). On the same days, blood samples were taken from 108 animals to assess changes in plasma blood urea nitrogen (BUN), non-esterified fatty acids (NEFA) and progesterone due to treatments. Relative mRNA levels of myosin heavy chain IIX (MHC IIX), AMPKα, and IGF-I were increased (P P = 0.09) due to OPT. An interaction between TI d and OPT administration caused an increase (P β2 AR was decreased (P β1 AR protein intensity tended to be lower (P P P β-adrenergic receptors, and blood metabolites in finishing beef heifers.

PSXI-2 A computer vision system for feed bunk management in beef cattle feedlot

Abstract Feed bunk scoring is a common management practice in feedlots. Usually, the bunk score is assigned visually by a trained person. However, the subjectivity of bunk scoring and inconsistency across bunk readers can result in excessive variation on feed delivery. Such variation can result on feed waste, sub-optimal animal performance, and increased incidence of metabolic disorders. The objective of this study was to develop an artificial intelligence system to perform bunk management in real-time. RGB-cameras were installed above the feed bunk in a commercial feedlot, and a total of 4,280 images were acquired, together with visual bunk scores with four categories: empty (no feed remaining), low (scattered feed remaining), medium (30–50% of feed remaining), and full (> 50% of feed remaining). Cattle behavior at the feed bunk was also classified into four classes: empty (no cattle at the feed bunk); low (< 30% bunk occupied); medium (30–70% feed bunk occupied); full (above 70% feed bunk occupied). The labeled images were then used for model training and a new set of 105 images were used for validation. A deep neural network (DNN) called ResNet was implemented to generate the predictions using a transfer learning with weights from the ImageNet dataset. A cloud computing system was developed to acquire, process and store images every 15 minutes, and implement real-time predictions of bunk score and cattle behavior. Prediction accuracies across bank score categories were: 81.8% (empty), 82.4% (low), 88.8% (medium), and 90% (full). For cattle behavior, accuracies were: 83.7% (empty), 66.6% (low), 71.4% (medium), and 86.6% (full). Combining feed bunk score and cattle behavior can provide an important decision-making tool to improve nutritional management in beef cattle feedlot. The use of artificial intelligence can allow the development of fully automated real-time systems to enhance livestock operations.

PSV-28 Effect of a neuro-sensory additive on meat quality of feedlot finishing beef cattle

Abstract Combining natural additives with specific and selected neuro-sensory molecules is a possible solution to manage stress in feedlot beef cattle. The objective of this study was to assess the use of a neuro-sensory additive (VeO) on meat quality of finishing feedlot beef cattle. This study was conducted from May to August in the Premix Research Center, Patrocínio Paulista, Brazil. VeO is based on a specific extract from Rutacea family. 80 Nellore bulls were randomly assigned to a control group (C) and a treated group (V) with 40 animals in each (10 per pen). Both groups received the same total mixed ration supplemented with Fator P (Premix, Brazil) with the addition of VeO as the only difference for 100 days up to slaughter. 160 cuttings in Longissimus muscle were sampled from C carcasses and V carcasses (n = 20) and packed in PVC blister packs 48h post-mortem. Analyzed variables were red color (a*), yellow color (b*) and drip losses (%) at packing then 3 days, 5 days and 7 days after. Statistical analysis was performed through mixed procedure of SAS software. Interactions between treatment and time was observed for values a* (P = 0.003) and b* (P = 0.056) and drip losses as well (P = 0.03). Globally meat from animals fed VeO presented more stable red and yellow colors. From day 5, it presented more intense red and yellow colors in comparison to meat from control animals. At day 7 drip losses were reduced with treatment (V: 8.7% vs. C: 11.4%, P = 0.012). Results showed that the use of the neuro-sensory additive during finishing of feedlot beef cattle improved appearance of meat after slaughter, leading to possible extended shelf life.

PSIII-15 Effect of a neuro-sensory additive on behaviour and growth of feedlot finishing beef cattle

Abstract Combining natural additives with specific and selected neuro-sensory molecules is a possible solution to manage stress in feedlot beef cattle. The objective of this study was to compare the combination of a neuro-sensory additive (VeO) with a mix of natural additives (Fator P, Premix, Brazil) on behavior and performance. This study was conducted from May to August in the Premix Research Center, Patrocínio Paulista, Brazil. Fator P is made up of amino acids, organic minerals, probiotics, essential fatty acids and surfactant. VeO is based on a specific extract from Rutacea family. 80 Nellore bulls were randomly assigned to a control group (FP) and a treated group with 40 animals in each (10 per pen). Both groups received the same total mixed ration with the addition of a neuro-sensory additive (FPV) as the only difference. Adaptation period was considered as 21 first days out of 100 days total fattening period. Analyzed variables were eating (min/day) and rumination (min/day), average daily gain (g/day), dry matter intake (%BW) and feed conversion. Tukey test was used for comparison of means. During adaptation, animals spent 30.8 % more time ruminating. Feed conversion and DMI with FPV tended to be more efficient by 30.86% (P = 0.074) and 31.16% (P = 0.063) respectively. After 21 days, treated animals continued eating (P = 0.14) and ruminating more as well (P = 0.07). Over 100 days, bulls receiving FPV showed a higher average daily gain by 9.94% (+153 g/day, P = 0.07) consuming less feed per kg of growth (6.46 vs. 7.00; -7.7%; ns). Results showed that the use of the neuro-sensory additive with the mix of natural additives changed behavior of feedlot finishing bulls, leading to more efficient production with an increased average daily gain and an improvement of feed conversion.

PSXII-37 Effects of different sources of monensin on performance and carcass traits of feedlot beef cattle

Abstract This study evaluated the effects of monensin source on performance and carcass characteristics of Nellore bulls offered a high-concentrate diet during the finishing phase. On d 0 of the study, 240 Nellore bulls (initial BW = 363.2 ± 40.9 kg) were ranked and blocked according to initial BW, whereas within blocks animals were allotted into pens and randomly assigned into 1 of 3 treatments: 1) no ionophore feeding (CONT), 2) CONT diet plus 28 ppm (mg/kg DM) of monensin sodium-A (Rumensin ™ -200; Elanco Animal Health), and 3) CONT diet plus 28 ppm monensin sodium-B (generic). The experimental period lasted 104 d and was divided into a 21-d adaptation period and an 83-d finishing phase. During the adaptation phase, both monensin sources increased (P ≤ 0.01) BW change, ADG, and F:G ratio, reducing the DMI variation (P = 0.02). When the entire experimental period was evaluated, no treatment effects were detected (P ≥ 0.26) on final BW, BW change, total DMI, DMI as % BW, and ADG. Nonetheless, DMI variation was reduced as monensin was included in the diet (P = 0.01) and, as expected, only MON-A improved the efficiency of the animals by reducing the F:G ratio (P = 0.05) compared with CONT and by reducing (P = 0.05) the biological efficiency when compared with the MON-B group. Additionally, carcass ADG tended (P = 0.10) to be greater for MON-A compared with MON-B, no other differences in the carcass characteristics were observed (P ≥ 0.53). In summary, monensin feeding reduced DMI variation in the feedlot, but the source of monensin is important for the feedlot scenario, given that only MON-A significantly benefited the performance during the finishing phase of Nellore bulls offered a high-concentrate diet.

PSXIV-11 Supplementation of 25-hydroxy-vitamin-D3 and increased vitamin E as a strategy to increase carcass weight of feedlot beef cattle

Abstract Our objective was to evaluate the effects of supplementing 1mg of 25-OH vitamin D3 (HyD®) and increased vitamin E amount (2000 mg/animal/d) on cattleˈ performance and carcass characteristics when fed a 90-d feedlot finishing diet. A total of 140 Nellore bulls (IBW = 387 ± 28 kg) were distributed in 14 pens (10 animals/pen) in a randomized complete block design (7 pens per treatment). The basal diet was composed by 15% sugarcane bagasse, 72.8% ground corn, 7.6% soybean meal and 4.6 % mineral-vitamin premix (DM basis). The dietary treatments were: 1) Control: No addition of 25-hydroxy-vitamin-D3 (HyD®) and basal Vit. E amount (520 mg/animal per day); 2) HyD+Vit.E: Addition of 1 mg of HyD® plus increased Vit. E amount (2000 mg/animal per day). The animals were fed once daily and had free access to fresh water. Statistical analysis was performed using the MIXED procedure of SAS 9.4. Means comparison was evaluated by tukey test and declared significant at P < 0.05, and tendencies considered when 0.05 < P < 0.10. There was no difference on final body weight (~522.8 kg, P = 0.11), ADG (~1.54 kg/d, P = 0.17), DM intake (~9.9 kg/d, P = 0.41) and G:F (~0.156, P = 0.28) between treatments. Likewise, no differences were observed (P > 0.10) for dressing (~53.5%), REA (~65.5 cm²) and SFT (~4.10 mm). However, feeding HyD+Vit.E tended to increase (P = 0.07) carcass average daily gain (0.993 vs. 0.953 kg/d) and increased (P = 0.04) carcass weight by 4.2 kg compared with control (281.6 vs. 277.4 kg). In conclusion, the combination of HyD and increased vitamin E increases carcass production in feedlot cattle.

PSXII-12 Silages and roughage sources in the Brazilian beef feedlots

Abstract The aim of this survey was to identify silages and roughage sources adopted in the beef finishing diets. Eighty-two feedyards, located in 10 states, were surveyed from January to March 2019 for their feeding practices. Feedlot owners and nutritionists were interviewed by using a common survey form. The form consisted of 5 questions, including feedlot location, feedlot capacity and the number of animals serviced yearly, breed, silages and roughage sources, and roughage: concentrate ratio. Results were tabulated in an Excel spreadsheet for each feedlot. The number of responses per question, and the mean, minimum value, maximum value, and mode (most frequently occurring value) were calculated. Feedlot capacity ranged from 300 to 35,000 (mode = 3,000) and cattle serviced yearly per feedlot ranged from 400 to 90,000 (mode = 6,000). Nellore breed and crossbreed represented 74 and 26% % of finished animals, respectively. Roughage: concentrate ratio ranged from 40: 60 to 10: 90. Thirty-five percent of feedlots adopted 20: 80 ratio, followed by 15: 85 (16%) and 10: 90 (16%) ratios. Whole-plant corn silage was the most common roughage source (57%; Figure 1), followed by sugarcane bagasse (17%), tropical grass silages (16%), and whole-plant sorghum silage (11%). Nutritionists also cited hay (9%), sugarcane silage (5%), and fresh sugarcane (4%) as roughage sources. High-moisture corn, snaplage (grain, cob, husk, shank), and reconstituted grain corn were used by 20, 11, and 1% of feedlots, respectively. Reconstituted grain sorghum was included in 4% of the diets. Thus, 36% of feedlots adopted grain silages (corn and sorghum) in the diets. Overall, Brazilian feedlots have used high-energy finishing diets and corn is the most widely grown crop for silage. Feedlots have shown interest in using grain silages to maximize starch digestion, especially because Brazil grows flint corn and silage machinery industry has made available new equipment.

Short-term legacy effects of feedlot manure amendments on earthworm abundance in a clay loam soil

Long-term application of feedlot beef cattle manure amendments to cropland may enhance earthworm abundance by increasing soil organic carbon. The objective of this study was to determine the legacy effects of feedlot manure type [stockpiled (SM) vs. composted (CM)], bedding material [straw (ST) vs. woodchips (WD)], manure rate (13, 39, or 77 Mg ha−1), unamended control, and inorganic fertilizer treatments on earthworm abundance in a clay loam soil after 3–4 yr of discontinued applications following 17 annual applications. Earthworms were sampled (20 cm depth) in 2 yr (2017–2018), and ancillary soil properties also determined. The Aporrectodea genus was the dominant earthworm identified. Earthworm abundance was similar (P > 0.05) for amended and unamended or inorganic fertilizer treatments. Abundance at the 39 Mg ha−1 rate in 2018 was significantly (P ≤ 0.05) greater by four times for SM than CM with ST, but it was two times greater for CM than SM with WD. Abundance at the 13 Mg ha−1 rate in 2017 was significantly greater by 91% for ST than WD, but at the 39 Mg ha−1 rate, it was 10 times greater for WD than ST. In 2018, abundance was five times greater for WD than ST with CM, but it was similar with SM. Overall, short-term legacy effects occurred on earthworm abundance, but these effects varied with manure rate. Earthworm abundance was not increased by manure application, which suggested a carrying capacity not directly related to food resource.

Influence of feedlot manure amendments on runoff hydrology and sediment loss during transition between continuous and legacy phases

Little research has been conducted on the effect of beef feedlot manure amendments on runoff hydrology and soil loss during the transition between continuous and legacy application phases. We conducted a 6 yr (2013–2018) study and utilized surface (0–5 cm) soil collected from a long-term (since 1998) field experiment on a clay loam soil in southern Alberta, Canada. The treatments were stockpiled or composted feedlot manure with straw (ST) or wood-chip (WD) bedding applied at 13, 39, and 77 Mg ha−1 (dry weight). There was also an unamended control and inorganic fertilized treatment (IN). Disturbed surface soil was collected from all treatments after 15 (C15), 16 (C16), and 17 (C17) continual annual applications (2013–2015), and then 1 (L1), 2 (L2), and 3 (L3) yr (2016–2018) after manure applications were discontinued in 2015. The soil was packed into runoff trays, and a Guelph rainfall simulator (70 mm h−1) was used to generate 30 min of runoff. The time to runoff, total runoff depth, and flow-weighted mean concentrations (FWMCs) and mass loads of total suspended solids (TSS) were determined. Mean values of runoff variables were significantly greater for ST than WD in certain years for time to runoff (by 28%–127%), runoff depth (44%), TSS FWMCs (58%–137%), and FWMC loads (28%–230%). Mean TSS was generally significantly greater at the two lower than highest manure rates for FWMC (48%–135%) and loads (21%–253%). Overall, choice of bedding material showed the most potential to maximize infiltration and reduce water and sediment loss.

Antimicrobial use and stewardship practices on Australian beef feedlots.

Improving antimicrobial stewardship in the livestock sector requires an understanding of the motivations for antimicrobial use and the quantities consumed. However,detailed information on antimicrobial use in livestock sectors is lacking. This cross-sectional study aimed to better understand antimicrobial use in the beef feedlot sector in Australia. A self-administered questionnaire asking about antimicrobial use and reasons for use was designed and mailed to beef feedlot operators in Australia. Respondents were asked to report the percentage of animals treated, purpose of use, and disease conditions targeted for 26antimicrobial agents. In total, 83 of 517 (16.1%) beef feedlot operators completed the survey. Monensin (61.0%of respondents) and virginiamycin (19.5%of respondents) were the most commonly reported in-feed antimicrobials. In-feed antimicrobial agents were most frequently used by respondents for treatment of gastrointestinal diseases (52.8%). Antimicrobials were used for growth promotion by 42.1% of respondents, with most (85.7%) reporting the use of ionophores(a group of compounds not used in human medicine). Short-acting penicillin(69.1%), short-acting oxytetracycline, and tulathromycin (both 57.3%) werethe most common injectable antimicrobial agents used. Injectable antimicrobials were most frequently used to treat respiratory (72.3%) and musculoskeletal (67.5%) conditions. Overall,the use of antimicrobials was appropriate for the purpose indicated, and there was a strong preference for drugs of low-importance in human medicine. The data described here stand to be a strong influence on the implementation of an antimicrobial stewardship program in the sector.

Economic impacts of space allowance per animal on beef cattle feedlot

The objective of this study was to assess the economic outcomes of three space allowances (6, 12, and 24 m2 per animal) for outdoor feedlots-finished beef cattle. Simulations considered confinement systems with a static capacity of 5,000 animals per cycle and two 86-day cycles per year. Performance data were obtained from 1,350 uncastrated bovine males. An increase in space allowance elevated the fixed cost per animal. Fixed and variable costs represented 3% and 93% of the total operating cost, respectively. For variable costs, around 70% was used for purchasing cattle and 17% for purchasing feed. The operating profit per animal increased as space allowance increased (R$ 80.90, R$ 102.00, and R$ 109.00 for 6, 12, and 24 m2 per animal, respectively). The three feedlot systems recovered the initial investment and had a positive net present value. In addition, the internal rates of return were 22%, 27%, and 25%, and the probabilities of financial loss were 33%, 29%, and 26% for pen sizes of 6, 12, and 24 m2 per animal, respectively. Therefore, larger space allowances improve profitability and reduce the risk of financial loss.

Fatty acid profile of duodenal digesta and of meat of feedlot beef cattle fed diets containing different levels of concentrate

The objective of this study was to evaluate the fatty acid profile of duodenal digesta (experiment I) and of meat of beef cattle (experiment II) fed diets containing different levels of concentrate (220, 400, 590 and 790 g of concentrate/kg of dry matter of the diets). The experiment I was conducted with four Charolais-Nellore steers (460 ± 18.2 kg of BW), with a T-shaped duodenal cannula, using a double 4 × 4 Latin square as an experimental design. In experiment II, 16 crossbred Charolais-Nellore young bulls (192.44 ± 18.2 kg of BW) were randomly distributed in the experimental treatments (220, 400, 590 and 790 g of concentrate/kg of dry matter of the diets). The diets were isonitrogenous (120 g of crude protein/kg of dry matter). The intramuscular fat content was used as a covariant for the statistical analysis of the meat fatty acid profile. The duodenal content of fatty acid C17:0 decreased with increase of concentrate levels, while its content in the meat presented a quadratic variation with the increase of the concentrate levels of the diets, being the lowest values observed for the diet with 400 g of concentrate. The duodenal content of fatty acid C18:1 trans-11 decreased, whereas the content of this fatty acid in the meat increased with the increase of the dietary concentrate levels. The increase in the level of concentrate reduced the content of polyunsaturated fatty acids C18:3 n-3, C20:3 n-6, C20:4 n-6, and C20:5 n-3 EPA in both the duodenal digesta and meat. No difference was observed in the n-6/n-3 fatty acids ratio (mean of 13.96) of the meat between diets. The elevation of the level of concentrate in confinement diets reduces the nutraceutical quality of the meat of Charolais-Nellore young bulls slaughtered at 14-16 months of age due to the reduction of the polyunsaturated fatty acids content important for human health.

Calculation of Antimicrobial Use Indicators in Beef Feedlots-Effects of Choice of Metric and Standardized Values.

The potential for antimicrobial use (AMU) to lead to the development of antimicrobial resistant bacteria is an increasingly important priority in human and veterinary medicine. Accurate AMU quantification is essential to assessing the risk of antimicrobial resistance due to AMU. The quantification of AMU in production animals can be difficult, and feedlot beef cattle present a number of unique challenges. This paper presents selected parenteral data from western Canadian beef feedlots to illustrate variations in interpretation of AMU that can arise from the use of different metrics and standards. Specific examples presented compare the number of animal daily doses calculated from a given amount of antimicrobial drug (AMD) using actual and estimated weights of cattle at exposure, dose-based to weight-based indicators representing the same amount of antimicrobial, dose-based AMU indicators using different estimated durations of effect (DOE), and AMU indicators calculated using different standard weights of cattle at exposure. Changing these factors when calculating AMU indicators can have notable influences on the results obtained. Transparency about the methods used to calculate AMU indicators is critical to ensure that comparisons of use among different populations is meaningful and accurate.

Evaluation of Hair Characteristics and Animal Age on the Impact of Hair Cortisol Concentration in Feedlot Steers.

Hair cortisol is a novel biomarker of chronic stress. The objective of this study was to determine the effect of hair color and length, as well as, animal age on hair cortisol concentration in beef feedlot steers. Nineteen beef crossbred steers used for nutrition research and housed in a small feedlot setting were used for this study. Seven of the steers (680 ± 4.5 kg; ~9 years of age) were fitted with ruminal fistulas and duodenal cannulas. The other 12 steers (473 ± 3.1 kg; ~2.5 years of age) were fitted with only ruminal fistulas. Hair samples from each steer were collected throughout a period of 6 weeks from six different areas and analyzed for cortisol concentrations. One pre-determined area was shaved each week for 5 weeks (Weeks 1–5). During week 6, all five, previously shaved areas and an additional area was shaved to collect hair samples of various lengths. Hair length was recorded prior to the collection of each hair sample. Only data from the last week (Week 6) of collection were included in the analyses. Steers were categorized into one of three groups: old with black hair (OB, n = 3); old with white hair (OW, n = 3); young with black hair (YB, n = 12). Older steers exhibited greater hair cortisol concentrations than younger steers (P < 0.001). Hair cortisol concentration was not impacted by duration of growth (P = 0.33). Cortisol concentrations exhibited a weak, positive correlation with hair length (r = 0.33, P-value = 0.01). The average hair growth per week of beef steers in the winter months was calculated to be 0.90 mm. Further research should be performed to improve our understanding of the effect of hair characteristics, sampling methodologies and analysis techniques on hair cortisol concentrations.

Plasmid Distribution among Escherichia coli from Livestock and Associated Wastewater: Unraveling Factors That Shape the Presence of Genes Conferring Third-Generation Cephalosporin Resistance.

A key concern with agricultural wastewater storage ponds is that they may provide an environment conducive for horizontal exchange of antibiotic resistance genes (ARGs), thereby facilitating the emergence of antibiotic resistant pathogens. Central to this exchange are mobile genetic elements like plasmids; yet, the factors shaping their presence in agricultural environments remain poorly understood. Here, using Escherichia coli as a model bacterium, we examined genetic backgrounds and plasmid profiles of generic fecal and wastewater isolates and those possessing blaCTX-M and blaCMY-2 genes (which confer resistance to third-generation cephalosporins) to delineate factors shaping the environmental persistence of plasmid-associated ARGs in beef cattle feedlots. The wastewater environment exerted minimal influence on plasmid repertoires, as the number of plasmids and distribution of different incompatibility groups did not differ between generic fecal and wastewater isolates. The blaCTX-M and blaCMY-2 genes were associated with IncF and IncA/C plasmids, respectively, and host isolates possessing these ARGs had fewer plasmids than generic isolates, suggesting ARG-bearing plasmids may associate predominantly with such hosts to compensate for the metabolic burden imposed by these plasmids. Phylogeny also appeared to be a factor for blaCTX-M genes, as their bacterial hosts were restricted to particular genetic lineages, including the environmentally adapted ET-1 clade, as noted previously for these genes. Ultimately, these findings have important implications for evaluating human health risks of agricultural wastewater with respect to environmental persistence of ARGs and may help identify options for improving wastewater treatment.

Necrohemorrhagic enteritis outbreak in a cattle feedlot in Nova Crixás, Goiás, Brazil

ABSTRACT: This study described an outbreak of necrohemorrhagic enteritis in a beef cattle feedlot in Nova Crixás, State of Goiás, Brazil, with emphasis on epidemiological, lesional, and laboratory aspects. Visits to the property were carried out and a necroscopic examination was performed on the bovine cadavers (N=57), which presented similar macroscopic alterations. Epidemiological data were collected, mainly referring to the feeding management of animals, and tissue samples were submitted to histopathological examination. Samples of feces and intestinal contents were also collected for bacterial isolation and PCR genotyping to detect the etiological agent, being confirmed Clostridium perfringens type A strains in 100% of the samples. Furthermore, 33.3% of strains isolated from intestinal contents and 40% of those isolated from feces were positive for beta-2 encoding gene. Considering the history, macroscopic and microscopic findings, as well as bacterial isolation and PCR, the diagnosis of bovine necrohemorrhagic enteritis was determined.

Nitrogen Sidedress Directed by Corn Canopy Reflectance for Manured Fields

Fertilizer‐N equivalence of applied organic N is poorly predicted, often resulting in overapplication of fertilizer‐N. Research was conducted for continuous‐corn (Zea mays L.) at an irrigated location in eastern Nebraska with the objective of adapting variable rate in‐season N (ISN) application directed by remote sensing of crop canopy reflectance for manure‐applied fields. Beef (Bos taurus) feedlot manure was applied in 2015 at 0, 37, and 74 Mg ha–1 to main plots, and 0 to 120 kg ha–1 yr–1 pre‐plant N (PPN) was applied in 30‐kg increments to subplots. Sub‐subplot treatments were with and without ISN applied at V12. The ISN rates determined at V8 to V12 were well correlated, indicating that earlier canopy sensing can be used for later ISN application. The mean yield increase with ISN was 3.3 Mg ha–1. The crop responded to ISN within 10 d of application, but recovery was incomplete by tasseling when N deficiency stress was severe. If severe N stress occurs, the crop may benefit from ISN application before V12 for more recovery time. The mean ISN rate was 23% less with manure compared with no manure application. The results indicate a need to apply some ISN even when a sufficiency index indicated adequate N. The harvest index was greater with ISN compared with no ISN. Mean agronomic efficiency of ISN was 29.4 kg yield gain kg–1 N applied. The sensor‐ISN for corn was sensitive to manure N availability and is a means to achieve manure N use efficiency with high productivity.Core Ideas Availability of applied organic N to crop uptake is poorly predicted. Canopy reflectance can account for manure N supplied to the crop. Agronomy efficiency of sidedress N directed by crop reflectance is high for manured fields

Comparative diversity of microbiomes and Resistomes in beef feedlots, downstream environments and urban sewage influent

BackgroundComparative knowledge of microbiomes and resistomes across environmental interfaces between animal production systems and urban settings is lacking. In this study, we executed a comparative analysis of the microbiota and resistomes of metagenomes from cattle feces, catch basin water, manured agricultural soil and urban sewage.ResultsMetagenomic DNA from composite fecal samples (FC; n = 12) collected from penned cattle at four feedlots in Alberta, Canada, along with water from adjacent catchment basins (CB; n = 13), soil (n = 4) from fields in the vicinity of one of the feedlots and urban sewage influent (SI; n = 6) from two municipalities were subjected to Illumina HiSeq2000 sequencing. Firmicutes exhibited the highest prevalence (40%) in FC, whereas Proteobacteria were most abundant in CB (64%), soil (60%) and SI (83%). Among sample types, SI had the highest diversity of antimicrobial resistance (AMR), and metal and biocide resistance (MBR) classes (13 & 15) followed by FC (10 & 8), CB (8 & 4), and soil (6 & 1). The highest antimicrobial resistant (AMR) gene (ARG) abundance was harboured by FC, whereas soil samples had a very small, but unique resistome which did not overlap with FC & CB resistomes. In the beef production system, tetracycline resistance predominated followed by macrolide resistance. The SI resistome harboured β-lactam, macrolide, tetracycline, aminoglycoside, fluoroquinolone and fosfomycin resistance determinants. Metal and biocide resistance accounted for 26% of the SI resistome with a predominance of mercury resistance.ConclusionsThis study demonstrates an increasing divergence in the nature of the microbiome and resistome as the distance from the feedlot increases. Consistent with antimicrobial use, tetracycline and macrolide resistance genes were predominant in the beef production system. One of the feedlots contributed both conventional (raised with antibiotics) and natural (raised without antibiotics) pens samples. Although natural pen samples exhibited a microbiota composition that was similar to samples from conventional pens, their resistome was less complex. Similarly, the SI resistome was indicative of drug classes used in humans and the greater abundance of mercury resistance may be associated with contamination of municipal water with household and industrial products.