Validation of a handheld refractometer to assess Merino ewe colostrum and transition milk quality.

Colostrum quality is generally defined by the IgG concentration in colostrum, and many methods have been used to assess it. Methods to measure colostrum quality both in the laboratory and in the field have been validated in cattle; however, this is only a recent topic of interest for sheep colostrum. Laboratory-based methods are often time consuming and require trained personnel compared with new handheld evaluation tools such as the digital Brix refractometer, which gives real-time results. The aims of this study were to (1) evaluate the relationship between the digital Brix refractometer and constituents indicative of quality (IgG, protein, fat, and lactose) in colostrum and transition milk, and (2) determine an appropriate Brix % cut-off value for the Brix refractometer in sheep colostrum and transition milk. The study used 50 colostrum samples (collected at 0 h postpartum, before lambs' sucking) and 169 transitional milk samples (collected at 4 and 24 h postpartum, after lambs had sucked) collected over 6 lambing trials in 2 years (2019 and 2020). We concluded that the Brix refractometer results correlated weakly with IgG concentration determined by radial immunodiffusion assay in colostrum collected at 0 h postpartum (r = 0.11) and in transition milk collected at 4 h postpartum (r = 0.12); however, a moderate to strong correlation was shown in transition milk samples collected at 24 h (r = 0.66). Brix % was significantly correlated with fat %, lactose %, and protein % at all timepoints. To determine an appropriate Brix % cut-off value indicating an IgG concentration of 20 mg/mL, we analyzed sensitivity and specificity of the Brix refractometer at 0, 4, and 24 h. In samples collected at 0 and 4 h, the highest combination of sensitivity, specificity, and accuracy was achieved at a Brix % cut-off value of 29%; in samples collected at 24 h postpartum, a Brix % cut-off value of 27% gave the highest sensitivity, specificity, and accuracy. Overall, the Brix refractometer has potential as a useful in-field tool for researchers and producers in both extensively and intensively managed flocks to measure and determine the quality of sheep colostrum and transition milk.

Analysis of immune-related microRNAs in cows and newborn calves.

Bovine colostrum contains a high concentration of immune-related microRNAs (miRNAs) that are packaged in exosomes and are very stable. In this study, 5 immune-related miRNAs (miR-142-5p, miR-150, miR-155, miR-181a, and miR-223) were quantified in dam blood, colostrum, and calf blood using reverse transcription quantitative PCR. Their levels in calf blood after colostrum ingestion were investigated to assess whether miRNAs are transferred from the dam to newborn calves. Three groups of Holstein-Friesian bull calves were bottle-fed 2 L of colostrum or milk from different sources twice per day. The group A calves received colostrum from their own dam and the group B calves were fed foster dam colostrum. Each pair of group A and group B calves were fed identical colostrum from the same milking of the corresponding group A dam for 3 d and then bulk tank milk for 7 d after birth. Group C calves were fed only 2L of "pooled colostrum" from multiple dams d 0 to 4 postpartum, and then fed bulk tank milk thereafter for 7 d after birth. The groups were fed colostrum from different sources and different amounts to assess possible miRNA absorption from the colostrum. All miRNAs were at the highest level in colostrum at d 0 and then decreased rapidly after d 1. The level of miR-150 had the largest decrease from 489 × 106 copies/µL (d 0) to 78 × 106 copies/µL (d 1). MicroRNA-223 and miR-155 were the most abundant in both colostrum and milk. Dam colostrum had significantly higher levels of miR-142-5p, miR-155, and miR-181a than the bulk tank milk. However, only the miR-155 concentration was significantly higher in the dam colostrum than in the pooled colostrum. The concentrations of miRNAs in the colostrum were less than in the cow blood (100- to 1,000-fold less). There was no significant correlation between the level of miRNAs in the dam blood and their colostrum, suggesting that miRNA is synthesized locally by the mammary gland rather than being transferred from the blood. MicroRNA-223 had the highest level in both calf and cow blood compared with the other 4 immune-related miRNAs. Calves were born with high levels of immune-related miRNAs in their blood, and there were no significant differences in miRNA levels between the 3 calf groups at birth or after they were fed different colostrum. This suggests that these miRNAs were not transferred from the colostrum to the newborn calves.

A novel phage-displayed MilA ELISA for detection of antibodies against Myc. bovis in bovine milk.

AIMS: The aim of this study was to assess a phage-displayed MilA protein of Myc. bovis in an indirect ELISA for the detection of Myc. bovis antibodies in milk samples. METHODS AND RESULTS: The desired sequence of milA gene was synthesized and cloned into pCANTAB-F12 phagemid vector. The expression of the MilA on the phage surface was confirmed by Western blotting. The recombinant phage was used in the development of an indirect ELISA to detect Myc. bovis antibodies in milk samples. There was a significant agreement between the results of phage-based ELISA and recombinant GST-MilA ELISA for the detection of Myc. bovis antibodies in milk samples. CONCLUSIONS: The inexpensive and convenient phage-based ELISA can be used instead of recombinant protein/peptide ELISA as an initial screening of Myc. bovis-associated mastitis. SIGNIFICANCE AND IMPACT OF STUDY: Mastitis associated with Myc. bovis is a continuous and serious problem in the dairy industry. Sero-monitoring of Myc. bovis infection cases are one of the key factors for surveillance of the infections in dairy farms. Despite the existence of some commercially serological assays for Myc. bovis antibodies, they have some limitations regarding their sensitivity and availability. The development of accurate diagnosis tools could contribute to control programmes of Myc. bovis-associated mastitis in the dairy herds.

Colostrum source and passive immunity transfer in dairy bull calves.

Colostrum is essential for good neonate health; however, it is not known whether different calves absorb the nutrients from colostrum equally well. In this study, the absorption of protein, IgG, and γ-glutamyl transferase was compared in newborn dairy bull calves for 1 wk after feeding colostrum from different sources. Thirty-five Holstein-Friesian bull calves were randomly allocated into 3 groups and fed colostrum within 4 h after birth. Group A calves (n = 12) were bottle fed colostrum from their own dam for 3 d. Colostrum from these group A cows was also used as foster cow colostrum for the group B calves (n = 12), such that each group A and B calf pair received identical colostrum from each milking of the respective group A dam (10% of birth weight per day). The group C calves (n = 11) were fed 1 bottle (2 L) of pooled colostrum and transition milk (referred to as pooled colostrum), as was the standard practice on the dairy farm. The pooled colostrum was collected from the other dairy cows on the farm 0 to 4 d postpartum and stored at 4°C for less than 12 h. Blood was sampled from calves before the first feeding and at 1, 2, 3, and 7 d after birth. Levels of total solids, total protein, and IgG were higher in the dam colostrum than in the pooled colostrum. At birth, there were no differences between the calf groups for any measurements, and all calves had very low IgG levels. After receiving colostrum, the glucose, plasma γ-glutamyl transferase, serum total protein, and IgG concentrations increased significantly in all calves. There were no differences in any blood measurements at any time point between the pairs of group A and group B calves that received colostrum from the same cow except for the IgG concentration 2 d after birth. However, the group A calves had a higher total serum protein level and IgG concentration than the group C calves for all the time points after the first feeding. The group B calves had a higher IgG concentration than the group C calves on d 1, 2, and 7 after birth. Compared with groups A and B, there was no difference in the proportion of calves in group C that failed to have passive immunity transferred adequately based on the IgG threshold (<10 g/L). Thus, the calves receiving identical colostrum from the same cow had the same levels of IgG, and even the pooled colostrum provided sufficient transfer of IgG as the calves were fed within 4 h after birth.

Predicting colostrum and calf blood components based on refractometry.

Provision of good quality colostrum is essential for the passive immunity and nutrition of newborn calves. In order to better predict the quality of colostrum and the transfer of passive immunity, the relationships between colostrum components and between calf serum components were examined in this study. Samples of bulk tank milk, colostrum pooled from several cows 0-4 d postpartum, and colostrum collected from individual cows twice daily for 3 d post-partum were compared. With the exception of fat percentage, there were strong correlations between the levels of the components in the pooled colostrum and in the individual cow colostrum collected 0-1 d postpartum. The correlations between total solids as measured by Brix refractometry and total protein, immunoglobulin G (IgG), lactose % and protein % in colostrum within 1 d postpartum and pooled colostrum were 0.92, 0.90, -0.88 and 0.98, respectively. These high correlations enabled these colostrum components to be accurately predicted from Brix % and therefore, the volume of colostrum required to feed neonate calves can be optimised based on Brix refractometry to avoid failure of passive immunity transfer. To assess whether the components obtained from colostrum were correlated in calf blood, newborn calves were separated from their dams before suckling and blood sampled before feeding (day 0), and on days 1 and 7, after receiving colostrum or milk twice a day. The correlations between glucose, total protein, IgG, and gamma-glutamyl transferase (GGT) levels in the calf blood were lower than the correlations observed between the colostrum components. The highest correlation was between serum protein measured by refractometer and serum IgG within one week postpartum. GGT activity was not a good indicator of serum IgG levels. However, serum protein refractometer measurements predicted serum IgG level with high accuracy, providing an on-farm test to determine that calves have received sufficient passive immunity and colostrum components.

Molecular characterization of antimicrobial resistance genes on farms and in commercial milk with emphasis on the effect of currently practiced heat treatments on viable but nonculturable formation.

Despite the considerable advances that have been made to improve dairy food safety, there is rising concern that pasteurization is not sufficient for the destruction of plasmid-mediated antimicrobial resistance (AMR) genes of resistant bacteria and could stimulate bacteria to enter into a viable but nonculturable (VBNC) state. In the current study, we surveyed the prevalence of 1 genomic and 9 plasmid-mediated AMR genes in 100 samples (bulk tank milk and milk filter socks) at the farm level and 152 commercial milk samples (pasteurized and UHT milks) and assessed the VBNC state in dairy bacteria. Results revealed that sul2 was the most prevalent plasmid-mediated gene in milk filter socks (96%), bulk tank milk (48%), pasteurized milk (68%), and UHT (43%) milk; in contrast, mecA was not detected in any sample. Additionally, commercial pasteurization (as currently practiced) failed to decrease the prevalence of the blaTEM-B1 (43%), tetK (30%), and tetA (55%) plasmid-mediated AMR genes; thus, commercial pasteurization may be one of the factors creating the VBNC state in some dairy bacteria. Continued research is necessary to identify bacterial species entering the VBNC state after pasteurization, to assess their potential hazard level and shed more light on the expression and possibility of horizontal gene transfer of those plasmid-mediated AMR genes.

A large-scale study of indicators of sub-clinical mastitis in dairy cattle by attribute weighting analysis of milk composition features: highlighting the predictive power of lactose and electrical conductivity.

Sub-clinical mastitis (SCM) affects milk composition. In this study, we hypothesise that large-scale mining of milk composition features by pattern recognition models can identify the best predictors of SCM within the milk composition features. To this end, using data mining algorithms, we conducted a large-scale and longitudinal study to evaluate the ability of various milk production parameters as indicators of SCM. SCM is the most prevalent disease of dairy cattle, causing substantial economic loss for the dairy industry. Developing new techniques to diagnose SCM in its early stages improves herd health and is of great importance. Test-day Somatic Cell Count (SCC) is the most common indicator of SCM and the primary mastitis surveillance approach worldwide. However, test-day SCC fluctuates widely between days, causing major concerns for its reliability. Consequently, there would be great benefit to identifying additional efficient indicators from large-scale and longitudinal studies. With this intent, data was collected at every milking (twice per day) for a period of 2 months from a single farm using in-line electronic equipment (346 248 records in total). The following data were analysed: milk volume, protein concentration, lactose concentration, electrical conductivity (EC), milking time and peak flow. Three SCC cut-offs were used to estimate the prevalence of SCM: Australian ≥ 250 000 cells/ml, European ≥200 000 cells/ml and New Zealand ≥ 150 000 cells/ml. At first, 10 different Attribute Weighting Algorithms (AWM) were applied to the data. In the absence of SCC, lactose concentration featured as the most important variable, followed by EC. For the first time, using attribute weighted modelling, we showed that the concentration of lactose in milk can be used as a strong indicator of SCM. The development of machine-learning expert systems using two or more milk variables (such as lactose concentration and EC) may produce a predictive pattern for early SCM detection.

Repurposing Ionophores as novel antimicrobial agents for the treatment of bovine mastitis caused by Gram-positive pathogens.

Increasing reports of multidrug-resistant bacterial infections in animals has created a need for novel antimicrobial agents that do not promote cross-resistance to critically important antimicrobial classes used in human medicine. In response to the recent emergence of antimicrobial resistance in several bovine mastitis pathogens, in vitro antimicrobial susceptibility was determined for four polyether ionophores (lasalocid, monensin, narasin and salinomycin) against Staphylococcus spp. and Streptococcus spp. isolated from clinical cases. In addition, erythrocyte haemolysis and WST-1 cell proliferation assays were used to assess in vitro mammalian cell cytotoxicity and biofilm susceptibility testing was performed using the minimum biofilm eradication concentration (MBEC™) biofilm assay. Lasalocid, monensin, narasin and salinomycin exhibited bacteriostatic antimicrobial activity against all pathogens tested, including methicillin-resistant staphylococci, with MIC90 values <16 µg/ml. Narasin and monensin displayed the least toxicity against mammalian cell lines and all compounds significantly reduced viable cell numbers in a Staphylococcus aureus biofilm. Based on in vitro characterization, all four ionophores offer potentially novel treatments against bovine mastitis but in vivo studies will be essential to determine whether acceptable safety and efficacy is present following intramammary administration.

Evaluation of effects of Mycoplasma mastitis on milk composition in dairy cattle from South Australia.

BACKGROUND: Mycoplasma mastitis is increasingly posing significant impact on dairy industry. Although the effects of major conventional mastitis pathogens on milk components has been widely addressed in the literature, limited data on the effects of different Mycoplasma and Acholeplasma spp. on milk quality and quantity is available. The aim of this study was to determine the casual relationship of Mycoplasma spp. and A. laidlawii to mastitis and compare them to subclinical mastitis caused by conventional mastitis pathogens from a single dairy herd in South Australia; Mycoplasma spp. and A. laidlawii were detected using PCR applied directly to milk samples. The herd had mastitis problem with high somatic cell count and low response rate to conventional antimicrobial therapy. A total of 288 cow-level milk samples were collected aseptically and used in this study. RESULTS: Conventional culture showed a predominance of coagulase-negative staphylococci, followed by coagulase-positive staphylococci, Streptococcus spp., Enterococcus spp., E. coli, and Klebsiella spp. PCR results showed a high prevalence of mycoplasmas (76.7%), including A. laidlawii (10.8%), M. bovis (6.2%), M. bovirhinis (5.6%), M. arginini (2%), and (52.1%) of cows were co-infected with two or more Mycoplasma and Acholeplasma species. Mycoplasma co-infection significantly increased somatic cell counts (SCC) similar to conventional mastitis pathogens and compared to non-infected cows with 389.3, 550.3 and 67.3 respectively; and decreased the milk yield with 29.0, 29.9 and 34.4 l, respectively. Mycoplasma co-infection caused significant increase in protein percentage, and significant decrease in fat percentage and total milk solids, similar to other conventional mastitis pathogens. In contrast, changes in milk composition and yield caused by various individual Mycoplasma species were non-significant. CONCLUSIONS: Mycoplasma mastitis had on-farm economic consequences similar to common conventional mastitis pathogens. Results of our study indicate that co-infection Mycoplasma mastitis caused similar effect on milk composition to other mastitis pathogens and we hope these findings raise the awareness of the importance of their detection on routine diagnostic panels.

Development of an improved Streptococcus uberis experimental mastitis challenge model using different doses and strains in lactating dairy cows.

Developing a reliable mastitis challenge infection model is required to test new intramammary antimicrobial preparations, other novel bovine mastitis treatments, and study mastitis pathogenesis. Three treatment groups of Holstein Friesian cows in active lactation were administered two doses (10(4) and 10(6) cfu/quarter) on a single occasion with one of the three Streptococcus uberis strains (BFR6019, MFF1283 and SA002) suspended in 5 ml of sterile PBS, administered via intramammary inoculation immediately after milking. All quarters that were challenged with S. uberis strains MLF1283 and BFR6019 showed clinical signs of mastitis on day 1 and 2 after the challenge. Strain SA002 had a lower rate of inducing clinical mastitis which was detected later than day 3 after the challenge. We successfully developed a rapid and reliable model for inducing experimental S. uberis mastitis with 100% success rate in cows in active lactation. On the basis of the correlation results between strains, RAPD fingerprinting results, clinical findings, and a 100% success rate of mastitis induction for low and high doses S. uberis strains MLF1283 and BFR6019, strain virulence seems to be a more important effect than challenge dose in induction of clinical mastitis following experimental challenge.

An overview of the detection of bovine respiratory disease complex pathogens using immunohistochemistry: emerging trends and opportunities.

The bovine respiratory disease complex (BRDC) is caused by a variety of pathogens, as well as contributing environmental and host-related risk factors. BRDC is the costliest disease for feedlot cattle globally. Immunohistochemistry (IHC) is a valuable tool for enhancing our understanding of BRDC given its specificity, sensitivity, cost-effectiveness, and capacity to provide information on antigen localization and immune response. Emerging trends in IHC include the use of multiplex IHC for the detection of coinfections, the use of digital imaging and automation, improved detection systems using enhanced fluorescent dyes, and the integration of IHC with spatial transcriptomics. Overall, identifying biomarkers for early detection, utilizing high-throughput IHC for large-scale studies, developing standardized protocols and reagents, and integrating IHC with other technologies are some of the opportunities to enhance the accuracy and applicability of IHC. We summarize here the various techniques and protocols used in IHC and highlight their current and potential role in BRDC research.

Effect of Feeding a Calcium Chloride Supplement on Sow Stillbirth Rate.

The present study was undertaken to determine the effect of daily calcium chloride (CaCl2) supplementation from day of entry into the farrowing house until day of farrowing (6.4 ± 0.3 d) on stillbirth rates. Landrace × Large White sows (parities 4 to 6; n = 53) were offered 40 g/d CaCl2 (n = 28) or served as controls (n = 25). The morning before their estimated farrowing date, a blood sample was obtained from 25 sows for calcium measurement and a urine sample from 22 sows for pH measurement. The feeding of CaCl2 decreased urinary pH compared to the control group (p < 0.001), indicative of an induced metabolic acidosis, but there was no effect of feeding CaCl2 on serum calcium concentrations or the incidence of stillbirths. Nonetheless, regardless of treatment, sows with higher serum calcium concentrations (>2.5 vs. <2.5 mmol) or lower urine pH (<7.0 vs. >7.0) had fewer stillborn piglets (p < 0.001 for both). While showing that low serum calcium levels will increase stillbirth rates, our data indicate that the administration of 40 g/d CaCl2 for 6 d prior to farrowing was not sufficient to increase serum calcium or decrease stillbirth incidence.

Assisting the Learning of Clinical Reasoning by Veterinary Medical Learners with a Case Example.

Effective clinical reasoning is essential for veterinary medical education, particularly in managing complex cases. This review explores strategies for learning clinical reasoning by veterinary medical learners, using a case example of mastitis to illustrate key concepts. Clinical reasoning encompasses cognitive, metacognitive, social, and situational activities, yet the literature on practical applications in veterinary education remains limited. The review discusses various stages of clinical reasoning, including data collection, problem representation, differential diagnosis, and management planning. It emphasizes the importance of integrating client-centered care and iterative evaluation into the clinical decision-making process. Key learning strategies include facilitation in using the domains of clinical reasoning-concepts, data collection, and analysis, taking action, and reflection on encounters. This review highlights best practices such as forward and backward reasoning, reflective practice, and the use of practical examples to enhance learners' diagnostic accuracy and patient outcomes. The insights provided aim to enhance the training of veterinary learners, ensuring they can navigate day 1 as well as complex cases with improved diagnostic accuracy and patient outcomes.

Histological characterisation of the horn bud region in 58 day old bovine fetuses.

The presence of horns in domestic ruminants, such as cattle, sheep and goats, has financial and welfare implications. The genetic interactions that lead to horn development are not known. Hornless, or polled, cattle occur naturally. The known causative DNA variants (Celtic, Friesian, Mongolian and Guarani) are in intergenic regions on bovine chromosome 1, but their functions are not known. It is thought that horns may be derived from cranial neural crest stem cells and the POLLED variants disrupt the migration or proliferation of these cells. Relaxin family peptide receptor 2 (RXFP2) is more highly expressed in developing horns in cattle compared to nearby skin and has been shown to play a role in horn development in sheep. However, the role of RXFP2 in horn formation is not understood. Histological analyses of cranial tissues from homozygous horned and polled cattle fetuses at day 58 of development was carried out to determine the differences in the structure of the horn bud region. Condensed cells were only observed in the horn bud mesenchyme of horned fetuses and could be the progenitor horn cells. The distribution of neural crest markers (SOX10 and NGFR) and RXFP2 between horned and polled tissues by immunohistochemistry was also analysed. However, SOX10 and NGFR were not detected in the condensed cells, and therefore, these cells are either not derived from the neural crest, or have differentiated and no longer express neural crest markers. SOX10 and NGFR were detected in the peripheral nerves, while RXFP2 was detected in peripheral nerves and in the horn bud epidermis. Previous research has shown that RXFP2 variants are associated with horn phenotypes in cattle an sheep. Therefore, the RXFP2 variants may affect the development of the epidermis or peripheral nerves in the horn bud.

Bovine Parainfluenza-3 Virus Detection Methods and Prevalence in Cattle: A Systematic Review and Meta-Analysis.

Bovine parainfluenza-3 virus (BPI3V) is an important respiratory pathogen in cattle, contributing to syndromes in the bovine respiratory disease complex (BRDC). Despite its significance, the understanding of its prevalence remains fragmented, especially within the larger framework of BRDC. This systematic review and meta-analysis aimed to determine the global prevalence of BPI3V in cattle using varied detection methods and to highlight associated risk factors. Of 2187 initially retrieved articles, 71 were selected for analysis, covering 32 countries. Depending on the detection method employed, the meta-analysis revealed significant variations in BPI3V prevalence. In the general cattle population, the highest prevalence was observed using the antibody detection method, with a proportion of 0.64. In contrast, in cattle with BRDC, a prevalence of 0.75 was observed. For the antigen detection method, a prevalence of 0.15 was observed, exclusively in cattle with BRDC. In nucleic acid detection, a prevalence of 0.05 or 0.10 was observed in the general and BRDC cattle populations, respectively. In virus isolation methods, a prevalence of 0.05 or 0.04 was observed in the general and BRDC cattle populations, respectively. These findings highlight the differences in the detection ability of different methods in identifying BPI3V. Other factors, such as country, study year, coinfections, farm size, the presence of respiratory signs, sex, and body weight, may also affect the prevalence. Most studies were anchored within broader BRDC investigations or aimed at detecting other diseases, indicating a potential under-representation of focused BPI3V research. BPI3V plays an important role in BRDC, with its prevalence varying significantly based on the detection methodology. To further understand its unique role within BRDC and pave the way for targeted interventions, there is an evident need for independent, dedicated research on BPI3V.

Preweaning Purified Fucoidan Drench: Effects on Growth, Immune Response, and Intestinal Morphology in Weaned Piglets.

Weaning stress imposes considerable physiological challenges on piglets, often manifesting in intestinal disturbances, such as inflammation and compromised barrier function, ultimately affecting growth and health outcomes. While conventional interventions, including antimicrobials, have effectively mitigated these sequelae, concerns surrounding antimicrobial resistance necessitate the exploration of alternatives. Fucoidan, derived from brown seaweed, offers promise due to its antioxidant and anti-inflammatory effects. Previous research has been limited to the in-feed supplementation of partially purified fucoidan extracted from brown seaweed. The focus of the present study is assessing the effect of a preweaning drench with highly purified (85%) fucoidan on piglet growth, immune response, and intestinal morphology post-weaning. Forty-eight male piglets at 17 ± 3 days of age (5.67 ± 0.16 kg) were assigned to a saline (control), fucoidan, or antimicrobial group, receiving treatment as a single 18 mL oral drench three days before weaning. Monitoring for seven days post-weaning included body weight measurements, blood sample collection for the inflammatory protein assay, and small intestine morphological analysis. The findings revealed that the preweaning fucoidan drench did not elicit adverse effects on piglets. However, neither fucoidan nor antimicrobial drenches significantly enhanced growth parameters, immune markers, or intestinal morphology compared to that of the control-treated piglets (p > 0.05). The lack of response may be attributed to the high health status of the experimental cohort and the limitation of a single dosage. Future research should consider a more challenging production setting to evaluate the viability and optimal application of fucoidan as an antimicrobial alternative in the pig industry.

Meta-Analysis on the Global Prevalence of Tetracycline Resistance in Escherichia coli Isolated from Beef Cattle.

Antimicrobial resistance (AMR) is an emerging global concern, with the widespread use of antimicrobials in One Health contributing significantly to this phenomenon. Among various antimicrobials, tetracyclines are extensively used in the beef cattle industry, potentially contributing to the development of resistance in bacterial populations. This meta-analysis aimed to examine the association between tetracycline use in beef cattle and the development of tetracycline resistance in Escherichia coli isolates. A comprehensive search was conducted using multiple databases to gather relevant observational studies evaluating tetracycline use and tetracycline resistance in Escherichia coli isolates from beef cattle. The rate of tetracycline resistance from each study served as the effect measure and was pooled using a random-effects model, considering possible disparities among studies. The meta-analysis of 14 prospective longitudinal studies resulted in a 0.31 prevalence of tetracycline resistance in Escherichia coli in non-intervention (no exposure), contrasting numerically elevated resistance rates in the intervention (exposed) groups of 0.53 and 0.39 in those receiving tetracyclines via feed or systemically, respectively. Despite the observed numerical differences, no statistically significant differences existed between intervention and non-intervention groups, challenging the conventional belief that antimicrobial use in livestock inherently leads to increased AMR. The findings of this study underscore the need for additional research to fully understand the complex relationship between antimicrobial use and AMR development. A considerable degree of heterogeneity across studies, potentially driven by variations in study design and diverse presentation of results, indicates the intricate and complex nature of AMR development. Further research with standardized methodologies might help elucidate the relationship between tetracycline use and resistance in Escherichia coli isolated from beef cattle.

Business Intentions of Australian Veterinary Students-My Business or Yours? A Cluster Analysis.

Little is known about veterinary entrepreneurial predisposition. Yet entrepreneurship and intrapreneurship (entrepreneurial behaviour of employees) foster business innovation and growth and support wealth creation and employment in both privately and corporately owned businesses which deliver contemporary veterinary services. We used responses from 515 final-year students in Australian entrepreneurship, nursing, and veterinary programs to capture entrepreneurial intention (EI), outcome expectations (OE-sb), entrepreneurial self-efficacy (ESE), and corporate/large organisation work intentions (CWIs). Veterinary respondents stood out for their high EI and high OE-sb, but low financial ESE and low CWI. Proportions of veterinary, entrepreneurship, and nursing respondents differed markedly across distinct cluster profiles representing entrepreneurial, intrapreneurial, both entrepreneurial and intrapreneurial, indifferent, and corporate employment intentions and attributes. Post hoc analysis revealed proportional cluster membership differences for respondents from different veterinary schools. Our findings raise questions regarding (1) the effectiveness of veterinary business curricula competencies which focus on expense management and (2) the implications of the mismatch of motivations and goals of new veterinary sector entrants whose low intent to work in a corporate environment is at odds with increasing corporate ownership of veterinary practices. To inform curricular change, we recommend further research to evaluate the relative impact of individual factors, admissions factors, and the formal or hidden curricula on entrepreneurial intention in veterinary final-year students.

Comparative Analysis of the Prevalence of Bovine Viral Diarrhea Virus in Cattle Populations Based on Detection Methods: A Systematic Review and Meta-Analysis.

Infectious diseases of cattle, including bovine viral diarrhea (BVD), pose a significant health threat to the global livestock industry. This study aimed to investigate the prevalence and risk factors associated with bovine viral diarrhea virus (BVDV) infections in cattle populations through a systematic review and meta-analysis. PubMed, Web of Science, and Scopus were systematically searched for relevant articles reporting the prevalence of and associated risk factors in studies published between 1 January 2000 and 3 February 2023. From a total of 5111 studies screened, 318 studies were included in the final analysis. BVDV prevalence in cattle populations was estimated using various detection methods. The analysis detected heterogeneity in prevalence, attributed to detection techniques and associated risk factors. Antibody detection methods exhibited a higher prevalence of 0.43, reflecting the cumulative effect of detecting both active and past infections. Antigen detection methods showed a prevalence of 0.05, which was lower than antibody methods. A prevalence of 0.08 was observed using nucleic acid detection methods. The health status of the examined cattle significantly influenced the prevalence of BVDV. Cattle with bovine respiratory disease complex (BRDC) exhibited higher antibody (prevalence of 0.67) and antigen (prevalence 0.23) levels compared to cattle with reproductive problems (prevalence 0.13) or diarrhea (prevalence 0.01). Nucleic acid detection methods demonstrated consistent rates across different health conditions. Age of cattle influenced prevalence, with higher rates in adults compared to calves. Risk factors related to breeding and reproduction, such as natural or extensive breeding and a history of abortion, were associated with increased prevalence. Coinfections with pathogens like bovine herpesvirus-1 or Neospora caninum were linked to higher BVDV prevalence. Management practices, such as commingling, introducing new cattle, and direct contact with neighboring farms, also influenced prevalence. Herd attributes, including larger herd size, and the presence of persistently infected cattle, were associated with higher prevalence. These findings indicated the importance of detection methods and risk factors in BVDV epidemiological studies.

Application of Exogenous GnRH in Food Animal Production.

Over several decades, exogenous GnRH and agonists have been employed for controlling reproductive cascades in animals, and treating some reproductive morbidities. The administration of GnRH is used in animals to counter ovarian dysfunction, induce ovulation, and to increase conception and pregnancy rates. GnRH and its agonists are used in the treatment of cystic ovarian degeneration and repeat breeder syndrome. The development of protocols for GnRH administration by intramuscular injection, intramuscular or subcutaneous implants, and intravaginal deposition has empowered their clinical use worldwide. Currently, exogenous GnRH products are a central part of several pre- and post-breeding programs for the enhancement of fertility, including the control of estrous cycles and timing of ovulation, development of fixed-time artificial insemination protocols, improved embryo survival, and the treatment of reproductive morbidity. The aim of the present review is to summarize the application of exogenous GnRH agonists in food animal production.