Canadian Cattle Research Articles

The prevalence and antimicrobial resistance of respiratory pathogens isolated from feedlot cattle in Canada

ObjectivesThe purpose of this study was to characterize the prevalence of antimicrobial resistance in Mannheimia haemolytica, Pasteurella multocida, and Histophilus somni isolated from healthy feedlot cattle over 2 years, and investigate factors potentially associated with recovery of resistant isolates.MethodsDeep-guarded nasopharyngeal (NP) swabs were used to sample feedlot cattle in multiple randomly selected feedlots (2019 n = 21, 2020 n = 26) at 2 timepoints. NP swabs were collected from 16 animals in each enrolled group upon entry processing and later in the feeding period. Cattle from the same groups (not necessarily the same animals) were sampled at both timepoints. Susceptibility testing was performed using the broth microdilution.ResultsA total of 1,392 cattle within 47 housing groups were sampled over 2 years, providing 625 bacterial isolates for investigation. Pasteurella multocida (27.4%) was the most frequently isolated BRD organism, followed by H. somni (9%) and M. haemolytica (8.5%). Resistance to ≥3 antimicrobial classes was detected in 2.4% of M. haemolytica, 3.4% of H. somni, and 21.3% of P. multocida isolates. Potential associations were investigated between recovery of resistant organisms and time of year at sampling (quarter), sampling timepoint (arrival or second sample), days on feed (DOF) at sampling, animal age categories, and BRD risk categories. There was a significant (p < 0.05) increase in resistance prevalence after arrival for macrolide drugs in M. haemolytica, and for ampicillin, danofloxacin, enrofloxacin, spectinomycin, gamithromycin, tildipirosin, tulathromycin and tetracycline in P. multocida isolates. Resistance was higher in calves than in yearlings for tulathromycin in H. somni, and for gamithromycin, spectinomycin, tulathromycin, tildipirosin, and tetracycline for P. multocida (p < 0.05) Resistance to tetracycline, tildipirosin, and tulathromycin decreased between 61–80 DOF and 81–100 DOF when compared to 20–40 DOF, whereas for spectinomycin, resistance was lower in cattle sampled between 61–80 DOF than those sampled at 20–40 DOF for P. multocida.DiscussionThe diversity of AMR profiles and associated risk factors between the BRD pathogens studied, underscores the importance of including all three organisms in future AMR studies in beef cattle.

Longitudinal screening of retail milk from Canadian provinces reveals no detections of influenza A virus RNA (April-July 2024): leveraging a newly established pan-Canadian network for responding to emerging viruses.

Highly pathogenic avian influenza (HPAI) H5N1 has caused the deaths of more than 100 million birds since 2021, and human cases since 1997 have been associated with significant morbidity and mortality. Given recent detections of HPAI H5N1 in dairy cattle and H5N1 RNA detections in pasteurized retail milk in the United States, we established the pan-Canadian Milk Network in April 2024. Through our network of collaborators from across Canada, retail milk was procured longitudinally, approximately every 2 weeks, and sent to a central laboratory to test for the presence of influenza A virus RNA. Between 29 April and 17 July 2024, we tested 109 retail milk samples from all 10 Canadian provinces (NL, NS, PEI, NB, QC, ON, MB, SK, AB, and BC). All samples tested negative for influenza A virus RNA. This nationwide initiative was established for rapid retail milk screening as per the earliest reports of similar undertakings in the United States. Our independent testing results have aligned with reporting from federal retail milk testing initiatives. Despite no known HPAI infections of dairy cattle in Canada to date, H5N1 poses a significant threat to the health of both humans and other animals. By performing routine surveillance of retail milk on a national scale, we have shown that academic networks and initiatives can rapidly establish nationwide emerging infectious disease surveillance that is cost-effective, standardized, scalable, and easily accessible. Our network can serve as an early detection system to help inform containment and mitigation activities if positive samples are identified and can be readily reactivated should HPAI H5N1 or other emerging zoonotic viruses be identified in agricultural or livestock settings, including Canadian dairy cattle.

PSVII-23 Discriminating meat from different Canadian cattle feeding systems by visible and near-infrared spectroscopy

Abstract Labeling of meat products is key to guarantee quality and origin. Rising production costs and an increase in world trade are leading to an on-going growth of meat fraud. Hence, the objective of this study was to evaluate the potential of visible and near-infrared (Vis-NIR) spectroscopy to discriminate meat from different Canadian cattle feeding systems. Steers (n = 45) were randomly assigned to three feeding systems: barley (n = 15), corn (n = 15) or grass-fed (n = 15). At 72 h postmortem, Vis-NIR spectra were collected on a) the longissimus thoracis (LT) muscle between the 12th and 13th ribs after 20 min of blooming (intact lean), and b) the adjacent subcutaneous fat from each in-bone ribeye. Afterwards, a steak from the anterior side of the striploin was collected and frozen at -20°C until analysis. After thawing at 4°C overnight, the striploin steak was ground and spectra were collected (ground meat). Four spectral replicates were acquired from each tissue sample with a portable LabSpec4 Standard-Res spectrometer (380–2,500 nm; 1 nm-bandwidth). The absorbances of the visible (Vis), near-infrared (NIR), and both regions combined (Vis-NIR) were later imported into the software PLS_Toolbox 9.3. under MATLAB R2023b. After the application of several mathematical pre-processing treatments, Partial Least Square-Discriminant Analysis (PLS-DA) and Support Vector Machine (SVM) discriminant approaches were performed. For the intact tissue, the best results were obtained using the Vis-NIR region with a combination of 2ndderivative+smoothing+mean center, and a PLS-DA with 6 latent variables (LV). This approach correctly classified 100% of the meat samples from each feeding group, with an area under the curve of a receiver operating characteristic curve (AUROC) of 1 in cross-validation (CV). Likewise, 100% of the fat samples from each feeding system were correctly classified in CV, using only the Vis region and 2ndderivative+smoothing+mean center by PLS-DA (5 LV and AUROCCV = 1). For ground meat, both PLS-DA (Vis, smoothing + mean center, 6 LV, AUROCCV = 1 or Vis-NIR, mean scatter correction, 6 LV, AUROCCV = 1) and SVM (Vis-NIR, smoothing + standard normal variate) correctly classified 100% of the samples from barley, corn and grass-fed in CV. The classification was successful only considering the Vis region due to the high homogenization of these samples. For fat, the significant variable importance in projection (VIP) scores were found at 423 to 612 nm, where carotenoids absorb energy. This would explain the accuracy of the Vis region for the classification of the fat samples. For intact and ground meat, significant VIP scores were found in both the Vis region, due to the myoglobin absorption, and NIR region (1,796 to 1,900 nm), due to the vibration of the hydrocarbon bonds from fatty acids. Hence, these results showed the potential of Vis-NIR spectroscopy to authenticate either fat, intact lean or ground meat from cattle fed different diets.

Frequency of isolation and phenotypic antimicrobial resistance of fecal Salmonella enterica recovered from dairy cattle in Canada

Salmonellosis is one of the leading causes of gastrointestinal infections in humans. In Canada, it is estimated that approximately 87,500 cases of salmonellosis occur every year in humans, resulting in 17 deaths. In the United States, it is estimated that 26,500 hospitalizations and 420 deaths occur every year. In dairy cattle, infections caused by nontyphoidal Salmonella enterica can cause mild to severe disease, including enteritis, pneumonia, and septicemia. Our study objectives were to determine the proportion of fecal samples positive for Salmonella in dairy cattle in Canada and determine the resistance pattern of these isolates. We used data collected through the Canadian Dairy Network for Antimicrobial Stewardship and Resistance (CaDNetASR). Pooled fecal samples from preweaning calves, postweaning heifers, lactating cows, and manure storage were cultured for Salmonella, and the isolates were identified using matrix-assisted laser desorption/ionization-time of flight mass spectrometry. Antimicrobial susceptibilities were determined using the minimum inhibitory concentration test, and resistance interpretation was made according to the Clinical and Laboratory Standards Institute. A 2-level, multivariable logistic regression model was built to determine the probability of recovering Salmonella from a sample, accounting for province, year, and sample source. The proportion of farms with at least one positive sample were 12% (17/140), 19% (28/144), and 17% (24/144) for the sampling years 2019, 2020, and 2021, respectively. Out of the 113 Salmonella isolates, 23 different serovars were identified. The occurrence of Salmonella appeared to be clustered by farms and provinces. The most common serovars identified were Infantis (14%) and Typhimurium (14%). Overall, 21% (24/113) of the Salmonella isolates were resistant to at least one antimicrobial. Resistance to tetracycline was commonly observed (17%); however, very limited resistance to category I antimicrobials (categorization according to Health Canada that includes third-generation cephalosporins, fluoroquinolones, polymyxins, and carbapenems) was observed, with one isolate resistant to amoxicillin and clavulanic acid. The proportion of Salmonella isolates resistant to 2 and 3 antimicrobial classes was 3.5% and 8.8%, respectively. Our study provided valuable information on the proportion of fecal samples positive for Salmonella, the serovars identified, and the associated resistance patterns across CaDNetASR herds, at regional and national levels.

Depletion of dexamethasone in cattle: Food safety study in dairy and beef cattle.

Dexamethasone is approved for cattle in Canada for several conditions, but no withdrawal times are currently provided on the approved labels. Recently, the list of Maximum Residues Limits for Veterinary Drugs in Foods in Canada was amended to include dexamethasone. The objectives of this study were to determine the residue depletion profile of dexamethasone after an extra-label dosage regimen in milk of healthy lactating dairy cattle (n = 18) and in edible tissues of healthy beef cattle (n = 16) and to suggest withdrawal intervals. Dexamethasone was administered intramuscularly at 0.05 mg/kg daily for 3 days. Milk samples were collected prior to treatment and every 12 h up to 96 h post-dose. Muscle, liver, kidney, and peri-renal fat tissues were collected from beef cattle at 3, 7, 11, or 15 days post-dose. Dexamethasone analysis was performed by liquid chromatography/mass spectrophotometry. Dexamethasone residues were detected in milk samples up to 36 h. Muscle and fat had no detectable dexamethasone residues while kidney and liver had detectable residues only on day 3 post-dose. A withdrawal interval of 48 h for milk in Canadian dairy cattle and 7 days for meat in Canadian beef cattle are suggested for the dexamethasone treatment regimen most commonly requested to CgFARAD™.

Stress Resistance and Virulence Gene Profiles Associated with Phylogeny and Phenotypes of Escherichia coli from Cattle

Seven serogroups of E. coli (Top seven E. coli) are frequently implicated in foodborne outbreaks in North America, largely due to their carriage of Shiga toxin genes (stx). This study aimed to profile resistance genes and virulence factors (VF), and their potential association with phylogeny and phenotypes of Top seven E. coli originating from cattle in Canada. 155 Top seven E. coli isolates previously characterized for heat and acid resistance and biofilm-forming ability were whole-genome sequenced and analyzed for phylogeny, VF, and stress resistance genes. The 155 E. coli strains belonged to six phylogroups: A (n = 32), B1 (n = 93), C (n = 3), D (n = 11), E (n = 15), and G (n = 1). Different phylogroups were clearly separated on the core genome tree, with strains of the same serotype closely clustered. The carriage of stx and the transmissible locus of stress tolerance (tLST), the extreme heat resistance marker, was mutually exclusive, in 33 and 15 genomes, respectively. A novel O84:H2 strain carrying stx1a was also identified. In total, 70, 41, and 32 VF, stress resistance genes and antibiotic resistance genes were identified. The stress resistance genes included those for metal (n = 29), biocides/acid (n = 4), and heat (n = 8) resistance. All heat resistance genes and most metal-resistance genes that were differentially distributed among the phylogroups were exclusively in phylogroup A. VF were least and most present in phylogroups A and D, respectively. No specific genes associated with acid resistance or biofilm formation phenotypes were identified. VF were more abundant (P < 0.05) in the non–biofilm-forming population and acid-resistant population.

Complete Genome Sequences of Mycobacterium bovis Strains Affiliated with Bovine Tuberculosis Outbreaks in Canada in 2016 and 2018.

Mycobacterium bovis is the primary causative agent of bovine tuberculosis, a zoonotic infectious disease that presents a risk to public health, livestock, and wildlife. Here, we report complete genome sequences of two Mycobacterium bovis strains affiliated with bovine tuberculosis outbreaks in Canadian cattle farms in 2016 and 2018.

Characterization of Escherichia coli and Other Enterobacterales Resistant to Extended-Spectrum Cephalosporins Isolated from Dairy Manure in Ontario, Canada.

Extended-spectrum cephalosporins (ESCs) resistance genes, such as blaCTX-M, blaCMY, and blaSHV, have been found regularly in bacteria from livestock. However, information on their distribution in dairy cattle in Canada and on the associated genome sequences of ESC-resistant Enterobacterales is sparse. In this study, the diversity and distribution of ESC-resistant Escherichia coli throughout manure treatments in six farms in Southern Ontario were assessed over a one-year period, and their ESC-resistance plasmids were characterized. The manure samples were enriched using selective media. The resulting isolates were screened via polymerase chain reaction for blaCTX-M, blaCMY, and blaSHV. No E. coli carrying blaSHV were detected. Escherichia coli (n = 248) carrying blaCTX-M or blaCMY underwent whole-genome sequencing using an Illumina MiSeq/NextSeq. These isolates were typed using multilocus sequence typing (MLST) and their resistance gene profiles. A subset of E. coli (n = 28) were sequenced using Oxford Nanopore Technologies. Plasmids were assembled using Unicycler and characterized via the resistance genes pattern, replicon type, plasmid MLST, phylogenetic analysis, and Mauve alignments. The recovery of ESC-resistant Enterobacterales (18 species, 8 genera) was drastically reduced in manure outputs. However, multiple treatment stages were needed to attain a significant reduction. 62 sequence types were identified, with ST10, ST46, ST58, ST155, ST190, ST398, ST685, and ST8761 being detected throughout the treatment pipeline. These STs overlapped with those found on multiple farms. The ESC-resistance determinants included CTX-M-1, -14, -15, -17, -24, -32, -55, and CMY-2. The plasmids carrying blaCTX-M were more diverse than were the plasmids carrying blaCMY. Known "epidemic plasmids" were detected for both blaCTX-M and blaCMY. IMPORTANCE The increase in antimicrobial resistance is of concern for human and animal health, especially when resistance is conferred to extended-spectrum cephalosporins, which are used to treat serious infections in both human and veterinary medicine. Bacteria carrying extended-spectrum cephalosporin resistance genes, including blaCTX-M and blaCMY, are frequently found in dairy manure. Manure treatment influences the loads and diversity of bacteria, including those carrying antimicrobial resistance genes, such as Enterobacterales and Escherichia coli. Any bacteria that survive the treatment process are subsequently applied to the environment. Enterobacterales carrying blaCTX-M or blaCMY can contaminate soil and crops consumed by humans and animals, thereby increasing the potential for antimicrobial resistance genes to integrate into the human gut microflora through horizontal gene transfer. This furthers the dissemination of resistance. Therefore, it is imperative to understand the effects manure treatments have on ESC-resistance in environmentally applied manure.

Using focus groups with dairy cattle veterinarians to explore learning about calf welfare.

Dairy calf welfare is a growing interest within the veterinary field. However, a limited understanding of the conception of calf welfare by dairy cattle veterinarians can hinder efforts to promote welfare improvements on farms. The aim of this study was to explore how focus groups can promote learning about dairy calf welfare issues among cattle veterinarians. Focus groups (n=5), that collectively had 33 participants representing five Canadian provinces and different geographical regions, were conducted as part of a continuing education workshop for Canadian cattle veterinarians. Two trained individuals undertook exploratory data analyses using applied thematic analysis and adult learning theory to develop a codebook of the data and identify the main themes. There were three main themes about learning that emerged from guided peer-discussion: (i) defining a shared concept of animal welfare from the veterinary perspective to diagnose the problem; (ii) understanding the problems of calf welfare by self-examination and group reflection; and (iii) negotiating the best approach to address the problems through sharing of ideas on improving calf welfare, including strategies for addressing welfare problems. In conclusion, focus groups can facilitate animal welfare learning within the veterinary profession.

Veterinarian perceptions on the care of surplus dairy calves

Both male and female calves that are not required in the dairy herd sometimes receive inadequate care on dairy farms. Veterinarians work with farmers to improve animal care, and farmers often view veterinarians as trusted advisors; however, little is known about the attitudes of veterinarians on surplus calves. This study investigated the perspectives of Canadian cattle veterinarians on the care and management of surplus calves, as well as how they view their role in improving care. We conducted 10 focus groups with a total of 45 veterinarians from 8 provinces across Canada. Recorded audio files were transcribed, anonymized, and coded using thematic analysis. We found that veterinarians approached surplus calf management issues from a wide lens, with 2 major themes emerging: (1) problematic aspects of surplus calf management, including colostrum management, transportation, and euthanasia, and suggested management and structural solutions, including ways to improve the economic value of these calves, and (2) the veterinarian's role in advising dairy farmers on the care of surplus calves, including on technical issues, and more broadly working with farmers to better address public concerns. We conclude that veterinarians are concerned about the care of surplus calves on dairy farms and believe that they have an important role in developing solutions together with their farmer clientele.

Dealing With Deadstock: A Case Study of Carnivore Conflict Mitigation From Southwestern Alberta

Livestock deaths are an unfortunate reality for livestock producers and dead livestock (i.e., deadstock) disposal options can have implications beyond the ranch itself. In Alberta, Canada, natural disposal (i.e., disposing of the carcass in a manner that allows for scavenging) has increased since the 2003 detection of bovine spongiform encephalopathy (BSE) in Canadian cattle. Prior to BSE, rendering companies removed deadstock for free. However, rendering companies started charging producers to remove deadstock to offset costs associated with new regulatory requirements enacted by the Canadian Food Inspection Agency, which has resulted in increased on-farm natural disposal of deadstock. This increase has ecological implications because deadstock are a major attractant for large carnivores. Carnivores feeding on deadstock are often near other agricultural attractants such as stored grain and feed, silage, and living livestock, which can exacerbate conflict potential and pose a risk to human safety. To help mitigate conflicts associated with deadstock, the Waterton Biosphere Reserve's (a local non-profit) Carnivores and Communities Program (CACP) supported expansion of community deadstock removal efforts beginning in 2009, including reimbursement of on-farm removal costs, bear-resistant deadstock bins, and a livestock compost facility (operational 2013–2014). Here, we present an evaluative case study describing the development, implementation, and results of the deadstock removal program, including the compost facility. We tracked the number of head of livestock removed each year, the number of participating landowners, the average cost per head, and total program costs. We also used an online survey to assess participants' perspectives of the deadstock removal program and future needs. To date, the CACP has removed &amp;gt;5,400 livestock carcasses, representing between 15.1 and 22.6% of available carcasses in the program area, and 67.3% of livestock owners indicated they currently use the deadstock removal program to dispose of deadstock. Average cost to compost an animal was significantly less than other removal methods ($36.89 composting vs. $79.59 non-composting, one-tailed t-test, unequal sampling variances: t = 4.08, df = 5.87, p = 0.003). We conclude by discussing both ecological and social implications for deadstock removal as a conflict mitigation measure and make suggestions for future management considerations.

168 Use of Genomic Tools to Improve Production Efficiency, Health Resilience and Carbon Footprint of Beef Production

Abstract The aim is to present validation studies that demonstrate the benefits of genomic retained heterozygosity, genomic enhanced expected progeny differences (gEPDs) for feed efficiency and carcass traits, as well as DNA pooling technologies, to the beef industry. Team members of Livestock Gentec are global leaders in beef genomics research as evidenced by their leadership roles on the Canadian Cattle Genome Project, 1,000 Bull Genomes Project, gEPDs for Commercial Cattle Project and the Functional Annotation of ANimal Genomes initiative. These large-scale projects have created databases of 380 whole bovine sequence genomes, &amp;gt;24,000 cattle genotypes imputed to sequence variants using Run 6 genotypes from 1000 Bull Genomes project, and &amp;gt;20,000 cattle with associated phenotypes for feed efficiency, carcass quality, cow fertility and methane emissions. The use of admixture analysis, genome wide association studies, and genomic prediction have resulted in new genomic tools that aid in mate selection, improve herd heterosis, female fertility, lifetime productivity and health resilience, and improve accuracy (acc. &amp;gt;0.36) of gEPDs for 18 traits in crossbred cattle. Genomic retained heterozygosity has a benefit of $161/female over five parities while decreasing morbidity of calves and improving the carbon intensity of beef production. Multi-trait selection studies using gEPDs for residual feed intake (acc. &amp;gt; 0.35) have demonstrated annual rates of genetic progress of 0.7%. Validation studies have reported that sires with superior gEPDs for increased marbling, decreased grade fat, increased ribeye and increased carcass weight (acc. &amp;gt; 0.45) produced progeny with improved AAA retail cut yield (59.9 vs 56.7%). DNA pooling shows potential for cheaper genotyping while providing information on pooled records related to sire contribution, heterosis and performance as influenced by genetics. The application of these genomic tools has potential to improve calf crop percentage, health resilience, and retail cut yield while decreasing the carbon footprint of beef production.

Prevalence and mechanisms of antibiotic resistance in Escherichia coli isolated from mastitic dairy cattle in Canada

BackgroundBovine mastitis is the most common infectious disease in dairy cattle with major economic implications for the dairy industry worldwide. Continuous monitoring for the emergence of antimicrobial resistance (AMR) among bacterial isolates from dairy farms is vital not only for animal husbandry but also for public health.MethodsIn this study, the prevalence of AMR in 113 Escherichia coli isolates from cases of bovine clinical mastitis in Canada was investigated. Kirby-Bauer disk diffusion test with 18 antibiotics and microdilution method with 3 heavy metals (copper, zinc, and silver) was performed to determine the antibiotic and heavy-metal susceptibility. Resistant strains were assessed for efflux and ß-lactamase activities besides assessing biofilm formation and hemolysis. Whole-genome sequences for each of the isolates were examined to detect the presence of genes corresponding to the observed AMR and virulence factors.ResultsPhenotypic analysis revealed that 32 isolates were resistant to one or more antibiotics and 107 showed resistance against at least one heavy metal. Quinolones and silver were the most efficient against the tested isolates. Among the AMR isolates, AcrAB-TolC efflux activity and ß-lactamase enzyme activities were detected in 13 and 14 isolates, respectively. All isolates produced biofilm but with different capacities, and 33 isolates showed α-hemolysin activity. A positive correlation (Pearson r = + 0.89) between efflux pump activity and quantity of biofilm was observed. Genes associated with aggregation, adhesion, cyclic di-GMP, quorum sensing were detected in the AMR isolates corroborating phenotype observations.ConclusionsThis investigation showed the prevalence of AMR in E. coli isolates from bovine clinical mastitis. The results also suggest the inadequacy of antimicrobials with a single mode of action to curtail AMR bacteria with multiple mechanisms of resistance and virulence factors. Therefore, it calls for combinatorial therapy for the effective management of AMR infections in dairy farms and combats its potential transmission to the food supply chain through the milk and dairy products.

Engineering and characterization of human \u03b2-defensin-3 and its analogues and microcin J25 peptides against Mannheimia haemolytica and bovine neutrophils

Mannheimia haemolytica-induced bovine respiratory disease causes loss of millions of dollars to Canadian cattle industry. Current antimicrobials are proving to be ineffective and leave residues in meat. Antimicrobial peptides (AMPs) may be effective against M. haemolytica while minimizing the risk of drug residues. Cationic AMPs can kill bacteria through interactions with the anionic bacterial membrane. Human β-Defensin 3 (HBD3) and microcin J25 (MccJ25) are AMPs with potent activity against many Gram-negative bacteria. We tested the microbicidal activity of wild-type HBD3, three HBD3 peptide analogues (28 amino acid, 20AA, and 10AA) derived from the sequence of natural HBD3, and MccJ25 in vitro against M. haemolytica. Three C-terminal analogues of HBD3 with all cysteines replaced with valines were manually synthesized using solid phase peptide synthesis. Since AMPs can act as chemoattractant we tested the chemotactic effect of HBD3, 28AA, 20AA, and 10AA peptides on bovine neutrophils in Boyden chamber. Minimum bactericidal concentration (MBC) assay showed that M. haemolytica was intermediately sensitive to HBD3, 28AA and 20AA analogues with an MBC of 50 µg/mL. The 10AA analogue had MBC 6.3 µg/mL which is likely a result of lower final inoculum size. MccJ25 didn’t have significant bactericidal effect below an MBC < 100 µg/mL. Bovine neutrophils showed chemotaxis towards HBD3 and 20AA peptides (P < 0.05) but not towards 28AA analogue. Co-incubation of neutrophils with any of the peptides did not affect their chemotaxis towards N-formyl-l-methionyl-l-leucyl-phenylalanine (fMLP). The data show that these peptides are effective against M. haemolytica and are chemotactic for neutrophils in vitro.

Comparative Pasture Management on Canadian Cattle Ranches With and Without Adaptive Multipaddock Grazing

Significant interest exists in the potential for specialized grazing systems, including adaptive multipaddock (AMP) grazing, to enhance grassland health and function. However, specific pasture management practices associated with AMP grazing at the ranch level remain poorly understood in comparison with more regionally representative management systems. As part of a larger study examining grazing effects on soil carbon, greenhouse gases, and other ecosystem attributes, here we report on differences in disturbance history and grazing management practices on a sample of AMP operators and their neighboring (n-AMP) ranches at 32 paired sites across the prairie provinces of western Canada. Most ranches studied (77.5%) relied on pastures composed of introduced (seeded) forage. On average, the AMP ranches surveyed were larger in size, supported greater animal numbers, and were more likely to use seeded forages comprising diverse mixes. Relative to n-AMP ranches, AMP ranches used 18.6-fold higher average stock densities in smaller paddocks (22.3 vs. 120.7 ha) while grazing over a grazing season that was 76 d longer, although computed stocking rates remained similar (P ≥ 0.10). AMP operators specifically used much shorter grazing periods (2.8 d) during the early growing season (i.e., before August 1) that were followed by a prolonged rest period (69 d) and could be used to compute a rest-to-grazing ratio for the first half of the grazing season for all ranches. This ratio, along with cattle stock density computed at the pasture scale, exhibited the greatest potential to differentiate the two groups of ranchers. Finally, both groups, and in particular ranchers within the AMP group, demonstrated high variability in management practices among individual operators, highlighting the importance of using specific management metrics rather than generalized descriptors of “grazing system type” to interpret their influence.

Influenza D virus in respiratory disease in Canadian, province of Québec, cattle: Relative importance and evidence of new reassortment between different clades

Influenza D virus (IDV), a segmented single-stranded negative-sense ribonucleic acid (RNA) virus, belongs to the new Delta influenza virus genus of the Orthomyxoviridae family. Cattle were proposed as the natural reservoir of IDV in which infection was associated with mild-to-moderate respiratory clinical signs (i.e. cough, nasal discharge and dyspnoea). In order to investigate the role of IDV in bovine respiratory disease, during the period 2017-2020, 883 nasal or naso-pharyngeal swabs from Canadian cattle with respiratory signs (cough and/or dyspnoea) were tested by (RT-)qPCR for IDV and other major bovine viral (bovine herpesvirus 1, bovine viral diarrhoea virus, bovine respiratory syncytial virus, bovine parainfluenza virus 3 and bovine coronavirus) and bacterial (Mannheimia haemolytica, Pasteurella multocida, Histophilus somni and Mycoplasma bovis) respiratory pathogens. In addition, whole-genome sequencing and phylogenetic analyses were carried out on five IDV-positive samples. The prevalence of IDV RT-qPCR (with cut-off: Cq<38) at animal level was estimated at 5.32% (95% confidence interval: 3.94-7.02). Positive result of IDV was significantly associated with (RT-)qPCR-positive results for bovine respiratory syncytial virus and Mycoplasma bovis. While phylogenetic analyses indicate that most segments belonged to clade D/660, reassortment between clades D/660 and D/OK were evidenced in four samples collected in 2018-2020. Relative importance of influenza D virus and associated pathogens in bovine respiratory disease of Canadian dairy cattle was established. Whole-genome sequencing demonstrated evidence of reassortment between clades D/660 and D/OK. Both these new pieces of information claim for more surveillance of IDV in cattle production worldwide.

COVID‐19 and the Canadian cattle/beef sector: A second look

After a year of adjusting to the shocks associated with COVID‐19 the Canadian cattle and beef sector faces a relatively optimistic future. This note examines the past year for this supply chain from the perspective of the consumer up to the cow‐calf producer by considering consumer reactions, labor market constraints, and supply responses. In the second quarter of 2020, the sector faced a significant challenge with continent wide shutdowns of beef packers reducing the U.S. beef supply by one‐third and Canadian beef slaughter by almost 60%. These shutdowns resulted in a sharp divergence between wholesale beef prices, which more than doubled, and fed steer prices, which declined by one third. Despite these dramatic shocks, the sector has returned to near normal conditions with prices and production levels similar to those observed prior to the pandemic. The near term prospects for 2021 are very similar to the current market situation.

Foot in Mouth: Animals, Disease, and the Cannibal Complex

Although the title of this paper invokes a disease of sheep as well as cattle, my primary concern is with the outbreak of another illness whose history in animal (and human) populations is more cryptic and more recent: so-called “mad cow” disease, or BSE (Bovine Spongiform Encephalopathy). Both the 2001 foot and mouth scourge in Britain and “mad cow” disease were (and are) widely represented in the media as disasters or catastrophes, in the case of foot and mouth for the sheep industry, and BSE for Britain’s beef producers. The detection of a single cow with BSE on a Washington (US) farm in 2004 had major financial repercussions for Canada’s farmers when the United States banned imports of Canadian cattle and meat products allegedly to protect its herds (and humans) from BSE and new variant Creutzfeldt- Jacob disease. The animals (especially sheep) caught up in the foot and mouth outbreak in Britain were slaughtered and then burnt in huge pyres, a holocaust similar to that following the mass killing of over a million cattle in Britain in 1987.

173 Greenhouse gas emissions and land use associated with the removal of growth-enhancing technologies from backgrounding and finishing cattle in Canada: A case study

Abstract Greenhouse gas emissions from backgrounding and finishing cattle with and without the use of growth-enhancing technologies (GET) were estimated using a whole-farm model, Holos (www.agr.gc.ca/holos-ghg). Model inputs were obtained from a four-year performance study using heifers (H) and steers (S) with six treatments (n = 40 hd treatment-1 yr-1): 1) H control (HCon); 2) H implanted (HTBA); 3) H melengestrol acetate (HMGA); 4) S control (SCon); 5) S implanted (STBA); and 6) S implanted + ractopamine hydrochloride (SRAC; conducted in the last two years). All cattle were finished to achieve a consistent number of days on feed (DOF; n = 233 ± 8). Lighter finish weights were observed for HCon and SCon. As a result, DOF were adjusted (-1 to 65 d) to achieve the same final weight as GET-treated cattle. Total emissions (kg CO2e head-1) were greater for Hcon_AdjHTBA (2967 ± 183) and HCon_AdjHMGA (2766 ± 84), than HTBA (2897 ± 184) and HMGA (2730 ± 81). Similarly, total emissions (kg CO2e head-1) for SCon_AdjSTBA (3169 ± 192) and SCon_AdjSRAC (3252 ± 202) were greater than STBA (2998 ± 153) and SRAC (3097 ± 185), respectively. On an intensity basis, (kg CO2e kg slaughter weight-1), emissions from GET-treated cattle [HTBA (4.49 ± 0.19), HMGA (4.39 ± 0.13), STBA (4.28 ± 0.17), and SRAC (4.31 ± 0.25)] were lower than HCon_AdjHTBA (4.60 ± 0.21), HCon_AdjHMGA (4.45 ± 0.18), SCon_AdjSTBA (4.52 ± 0.23), and SCon_AdjSRAC (4.52 ± 0.28), respectively. Furthermore, land-use (ha 100 kg slaughter weight-1) was reduced for GET-treated cattle (HTBA (0.068 ± 0.001), HMGA (0.067 ± 0.001), STBA (0.066 ± 0.001), and SRAC (0.067 ± 0.000)) compared to HCon_AdjTBA (0.071 ± 0.001), HCon_AdjMGA (0.069 ± 0.002), SCon_AdjTBA (0.072 ± 0.002), and SCon_AdjRAC (0.0073 ± 0.001), respectively. This study demonstrates that GETs can reduce the environmental footprint of beef cattle.

Enhancement of total lipid production in vegetative tissues of alfalfa and sainfoin using chemical mutagenesis

AbstractAlfalfa (Medicago sativa L.) and sainfoin (Onobrychis viciifoila Scop.) are two key forage legumes for the western Canadian cattle industry. Despite the high protein content, drawbacks to their use exist, including inefficient protein digestibility and energy use efficiency in the ruminant system, leading to economic losses and negative environmental impacts. Increasing the proportion of lipids in the diet of cattle is known to mitigate greenhouse gas emissions; however, the above two forage legumes possess only trace quantities of lipids in the shoot tissues used by the ruminants. In the current study, chemical mutagenesis was used as a conventional breeding approach to enhance lipid levels in the vegetative tissues of alfalfa and sainfoin. The mutagenesis procedures for these two forages need to be firmly established. We developed protocols for ethyl methanesulfonate (EMS)‐mediated mutagenesis by optimizing mutagen concentration and seed soaking duration. The EMS‐treated populations were assessed for morphological variants and total shoot lipid content (TSLC). Fatty acid composition was examined in a subset of plants with increased TSLC. Within 24 mo, the screening process identified mutagenized plants with significant increases in TSLC (3–5% on a dry weight basis), and a subset of these also displayed alterations in fatty acid composition in both species. These genotypes provide a novel source of germplasm for the future improvement of these two forage species.