The welfare of ill and injured feedlot cattle: a review of the literature and implications for managing feedlot hospital and chronic pens.

By definition, ill and injured animals are on the negative valence of animal welfare. For beef cattle kept in feedlot settings, advances in cattle health management have resulted in a greater understanding and prevention of illness and injury. However, the management of cattle once they become ill and injured is an understudied area, and there are gaps in knowledge that could inform evidence-based decision-making and strengthen welfare for this population. The aim of this review is to provide a comprehensive overview of the acquired knowledge regarding ill and injured feedlot cattle welfare, focusing on existing knowledge gaps and implications for hospital and chronic pen management and welfare assurance. Ill and injured feedlot cattle consist of acutely impaired animals with short-term health conditions that resolve with treatment and chronically impaired animals with long-term health conditions that may be difficult to treat. A literature search identified 110 articles that mentioned welfare and ill and injured feedlot cattle, but the population of interest in most of these articles was healthy cattle, not ill and injured cattle. Articles about managing ill and injured cattle in specialized hospital (n = 12) or chronic (n = 2) pens were even more sparse. Results from this literature search will be used to outline the understanding of acutely and chronically ill and injured feedlot cattle, including common dispositions and welfare considerations, behavior during convalescence, and strategies for identifying and managing ill and injured cattle. Finally, by working through specific ailments common in commercial feedlot environments, we illustrate how the Five Domains Model can be used to explore feelings and experiences and subsequent welfare state of individual ill or injured feedlot cattle. Using this approach and our knowledge of current industry practices, we identify relevant animal-based outcomes and critical research questions to strengthen knowledge in this area. A better understanding of this overlooked topic will inform future research and the development of evidence-based guidelines to help producers care for this vulnerable population.

Influence of Single Dose Enrofloxacin Injection on Development of Fluoroquinolone Resistance in Campylobacter jejuni in Calves.

Fluoroquinolone (FQ) resistance in a major foodborne bacterial pathogen, Campylobacter jejuni, derived from cattle has recently become prevalent and poses a significant public health concern. However, the underlying factors for this increase are not entirely clear. To evaluate the effect of enrofloxacin treatment on FQ-resistance development in C. jejuni, 35 commercial calves were equally divided into five groups (Groups 1-5) and were orally inoculated with FQ-susceptible (FQ-S) C. jejuni. Eight days later, Groups 4 and 5 were challenged with Mannheimia haemolytica via a transtracheal route to induce a respiratory disease; after 8 days, Groups 2, 3, 4, and 5 were injected subcutaneously with enrofloxacin (7.5 mg/kg for Groups 2 and 4, and 12.5 mg/kg for Groups 3 and 5). Colonization levels by FQ-resistant (FQ-R) and FQ-S Campylobacter in rectal feces were determined via differential culture throughout the experiment. Before oral inoculation with C. jejuni, only five calves were naturally colonized by Campylobacter, four of which were also colonized by FQ-R C. jejuni (three in Group 1 and one in Group 3). Soon after the oral inoculation, almost all calves in the groups became stably colonized by FQ-S C. jejuni (~3-6 log10 CFU/g), except that the four calves that were pre-colonized before inoculation remained positive with both FQ-R and FQ-S C. jejuni. Following enrofloxacin administration, C. jejuni colonization declined sharply and rapidly in all treated groups to undetectable levels; however, the vast majority of the animals were recolonized by C. jejuni at comparable levels 72 h after the treatment. Notably, no FQ-R C. jejuni was detected in any of the calves that received enrofloxacin, regardless of the drug dose used or disease status of the animals. The lack of detection of FQ-R C. jejuni was likely due to the localized high concentration of the antibiotic in the intestine, which may have prevented the emergence of the FQ-R mutant. These findings indicate that single-dose enrofloxacin use in cattle poses a low risk for selection of de novo FQ-R mutants in C. jejuni.

Review of regulations and indications for the use of in-feed antimicrobials for production animals.

Antimicrobials have been fed to livestock for more than 60 years. Veterinarians and producers saw tremendous gains in health and performance, and usage became widespread. Over time, improved management reduced some of the benefit of many feed-through antimicrobials except for a few important diseases. As a result of concerns about antimicrobial resistance, the US FDA restricted the use of medically important antimicrobials. Starting in 2017, medically important antimicrobials were restricted to therapeutic purposes only, and only under the order of a veterinarian. The aim of this review is to provide an overview of commonly used antimicrobials in livestock feed and regulatory changes regarding the veterinary feed directive. When used judiciously, in-feed antimicrobials are an important tool to ensure the health and welfare of food animals while preserving the effectiveness for animals and humans.

Physical Traits and Reproductive Measurements Associated with Early Conception in Beef Replacement Heifers.

Developing and raising replacement heifers requires a large capital investment for producers. Therefore, it is imperative to discover traits and management practices to eliminate subfertile heifers prior to breeding and pregnancy determination. In this study, four years of data was analyzed from a centralized beef heifer development yard in the Midwest of the United States. The objective of this study was to analyze various heifer physical characteristics and management practices in order to quantify their impact on pregnancy and date of conception. Logistic regression models were built to investigate risk factors associated with conception to artificial insemination (AI), pregnancy by natural service after AI exposure, and pregnancy in the first 21-days of the breeding season. Age at entry, average daily gain from entry to breeding, pelvic width, and year were associated with AI pregnancy (p < 0.05). On the second model, average daily gain from entry to yearling weight, weight at breeding, weight at pregnancy diagnosis, and age at AI were significantly associated with pregnancy. There were no associations with reproductive tract score with any of the response variables analyzed. These results indicate there are physical measurements that can be used to improve the ability to select and develop heifers for improved reproductive performance.

Effect of Danofloxacin Treatment on the Development of Fluoroquinolone Resistance in Campylobacter jejuni in Calves.

Campylobacter is a leading cause of foodborne gastroenteritis. Recent studies have indicated a rise in fluoroquinolone-resistant (FQ-R) Campylobacter in cattle, where FQ is used to control bovine respiratory disease (BRD). To assess the effect of danofloxacin treatment on the development of FQ-resistance in C. jejuni, 30 commercial calves were divided into Group 1, Group 2, and Group 3 (n = 10), and were all inoculated orally with FQ-susceptible (FQ-S) C. jejuni; seven days later, Group 3 was challenged with transtracheal Mannheimia haemolytica, and one week later, Group 2 and Group 3 were injected subcutaneously with danofloxacin. Rectal feces were collected to determine relative percentages of FQ-R Campylobacter via culture. Before oral inoculation with C. jejuni, 87% of calves were naturally colonized by FQ-R C. jejuni. Two days after the inoculation, FQ-R C. jejuni decreased substantially in the majority of calves. Within 24 h of danofloxacin injection, almost all C. jejuni populations shifted to an FQ-R phenotype in both FQ-treated groups, which was only transitory, as FQ-S strains became predominant during later periods. Genotyping indicated that the spike seen in FQ-R C. jejuni populations following the injection was due mainly to enrichment of preexisting FQ-R C. jejuni, rather than development of de novo FQ resistance in susceptible strains. These results provide important insights into the dynamic changes of FQ-resistant Campylobacter in cattle in response to FQ treatment.

Validation of a gauze sponge sampling methodology to detect Tritrichomonas foetus by real-time PCR.

Bovine trichomoniasis is a concern for the cattle industry. Advances in testing systems have increased the ability to detect the disease in bulls. However, the greatest limitation is proper collection of an adequate sample. The low repeatability observed with most sample collection techniques can cause false-negative results. The aim of our study was to validate a sample collection technique that increases diagnostic sensitivity and is easier and safer to collect than preputial scraping. Commercial bulls (n = 111) of unknown infection status were sampled for detection of Tritrichomonas foetus using 2 different collection methods: 1) preputial scraping with a dry insemination pipette and 2) penile sponging with a 16-ply gauze sponge. Preputial scraping samples were collected by vigorously scraping preputial and penile mucosa using a rigid insemination pipette while applying negative pressure with a syringe. Penile sponge samples were obtained by swabbing the penile and preputial mucosa with a gauze sponge during full extension of the penis. All samples were processed using a commercial medium and submitted under similar conditions for PCR testing. Positive PCR results were detected in 37 of 111 (33%) bulls using the preputial scraping technique; however, 39 of 111 (35%) were positive using the penile sponging technique. The Newton-Raphson algorithm predicted that the sensitivity of the preputial scraping method was 0.919 (95% CI: 0.689-0.983) and the sensitivity of the penile sponging was 0.949 (95% CI: 0.818-0.987). These data indicate that the penile sponging technique is a reliable alternative to the preputial scraping method.

Validation of a portable pneumatic captive bolt device as a one-step method of euthanasia for use in depopulation of feedlot cattle.

OBJECTIVE: To validate the effectiveness of a penetrating captive bolt device with a built-in low-pressure air channel pithing mechanism (PCBD) as a 1-step method for euthanasia of cattle. DESIGN: Clinical trial. ANIMALS: 66 feedlot steers and heifers (weight, 227 to 500 kg [500 to 1,100 lb]) that were not expected to survive or finish the feeding period with their cohorts. PROCEDURES: Cattle were transported to a university facility and euthanized with the PCBD. For each calf, clinical variables were monitored and recorded immediately before and for at least 10 minutes after application of the PCBD. Following euthanasia, the head of each calf was removed and trauma to the brain and skull was assessed and scored. RESULTS: Death was successfully achieved with the PCBD without application of an ancillary technique in all 66 cattle; however, 4 (6%) cattle required a second or third shot from the PCBD because of technical errors in its placement. All shots from the PCBD that entered the cranial vault successfully rendered cattle unconscious without a return to sensibility. CONCLUSIONS AND CLINICAL RELEVANCE: Results indicated that the PCBD was an effective 1-step method of euthanasia for use in mass depopulation of feedlot cattle.

Serum concentrations of haptoglobin and haptoglobin-matrix metalloproteinase 9 (Hp-MMP 9) complexes of bovine calves in a bacterial respiratory challenge model.

BACKGROUND: Serum haptoglobin (Hp) and haptoglobin matrix metalloproteinase 9 complexes (Hp-MMP 9) have been identified as biomarkers with diagnostic potential in cattle with conditions resulting in an acute inflammatory response. The purpose of this study was to evaluate potential diagnostic applications of serum Hp and Hp-MMP 9 concentrations in calves with BRD and establish a timeline for their detection in calves experimentally challenged with Bibersteinia trehalosi and Mannheimia haemolytica. Thirty-five cross bred dairy calves were inoculated via tracheal catheterization with either a PCR confirmed leukotoxin negative B. trehalosi isolate, a PCR confirmed leukotoxin positive B. trehalosi isolate, a Mannheimia haemolytica isolate, a combination of leukotoxin negative B. trehalosi and M. haemolytica, or a negative control. Serum samples were collected throughout the study. Calves were euthanized and necropsy performed on day 10 post inoculation. RESULTS: M. haemolytica inoculated calves had increased lung involvement. Serum Hp and Hp- MMP 9 concentrations were elevated compared to the other treatment groups. Increases in serum Hp and Hp-MMP 9 concentrations for the M. haemolytica group were significantly different from other study groups on day 7 of the study. B. trehalosi inoculated calves did not have increased lung involvement compared to control calves, but the leukotoxin positive B. trehalosi group demonstrated increased serum Hp-MMP 9 concentrations from day 3 to the end of the study compared to the pre-inoculation concentrations. CONCLUSION: Serum Hp-MMP 9 concentration is a useful diagnostic tool for detecting early pulmonary inflammation in calves challenged with B. trehalosi and M. haemolytica. Serum Hp-MMP 9 may also be a useful tool in detecting subclinical pulmonary inflammation in challenged calves.

Randomized clinical trial to evaluate the pathogenicity of Bibersteinia trehalosi in respiratory disease among calves.

BACKGROUND: Bibersteinia trehalosi causes respiratory disease in ruminants particularly in wild and domestic sheep. Recently, there has been an increased number of B. trehalosi isolates obtained from diagnostic samples from bovine respiratory disease cases. This study evaluated the role of B. trehalosi in bovine respiratory disease using an intra-tracheal inoculation model in calves. Thirty six cross bred 2-3 month old dairy calves were inoculated intra-tracheally with either leukotoxin negative B. trehalosi, leukotoxin positive B. trehalosi isolate, Mannheimia haemolytica, a combination of leukotoxin negative B. trehalosi and M. haemolytica or negative control. Calves were euthanized and necropsy performed on day 10 of study. RESULTS: B. trehalosi inoculated calves did not have increased lung involvement compared to control calves. Additionally, B. trehalosi was only cultured once from the lungs of inoculated calves at necropsy. CONCLUSIONS: Based on these findings B. trehalosi may not be a primary pathogen of respiratory disease in cattle. Culture of B. trehalosi from diagnostic submissions should not be immediately identified as a primary cause of respiratory disease.

Effects of restricted antimicrobial exposure on antimicrobial resistance in fecal Escherichia coli from feedlot cattle.

OBJECTIVES: The primary objective was to evaluate differences in antimicrobial resistance among enteric bacteria recovered from feedlot cattle that were being raised without exposure to antimicrobial drugs (AMDs) and those reared using conventional practices. MATERIALS: Forty pens of feedlot cattle (4557 total animals) that were being fed without AMD exposures were selected for enrollment as were 44 pens of cattle (4913 total animals) being fed for production of conventional beef products at the same feedlots. Fecal samples were collected from the floors of pens approximately biweekly through the middle of the feeding period and again prior to slaughter. Samples were cultured to recover nontype-specific Escherichia coli (NTSEC) and Salmonella enterica, and isolates were evaluated for susceptibility to a panel of AMDs. RESULTS: Cattle enrolled in the study did not differ between groups in entry weight or finish weight, but cattle with restricted AMD and hormone exposures were fed for an average of 50 days longer than conventionally reared cattle (p < 0.001). Resistance among NTSEC isolates was most common to tetracycline, streptomycin, and sulfamethoxazole, and there were slightly higher prevalence of resistance among NTSEC isolates recovered from conventionally reared cattle. Therapeutic AMD exposures did not have a detectable impact on the prevalence of resistance among NTSEC. Although there were detectable temporal trends through the feeding period for resistance to tetracycline, naladixic acid, chloramphenicol, and cephalothin, the direction of trends differed among drugs and these trends were not associated with study groups. S. enterica was recovered rarely (0.73%) but at similar prevalences from cattle with both rearing methods. CONCLUSIONS: These findings suggest that conventional feedlot production methods (including parenteral and in-feed use of AMDs) do not predictably or uniformly increase the prevalence of antimicrobial resistance among fecal NTSEC when compared with rearing methods that restrict exposure to AMDs.

A survey of reasons why veterinarians enter rural veterinary practice in the United States.

OBJECTIVE: To identify factors associated with interest in or choosing a career in rural veterinary practice (RVP). DESIGN: Cross-sectional descriptive study. SAMPLE POPULATION: Veterinarians and veterinary students in the United States. PROCEDURES: Veterinary students and veterinarians in any area of practice were solicited to participate in an online survey through invitation letters sent to various veterinary associations. Proportions of respondents assigning high importance to various factors were analyzed for differences among gender, age, and background groups. RESULTS: 1,216 responses were received. In general, survey respondents indicated that RVP could be characterized as the practice of veterinary medicine in any community where agriculture represented a significant part of the local economy. Responses also indicated that RVP should not be confused with large animal or food animal exclusive practice. Most respondents (38.9%) developed an interest in RVP early in life (before 8th grade), with 13.0% reportedly developing their interest in RVP during veterinary school. The most highly ranked factors with regard to influence on developing an interest in RVP were having relatives with a farm background, having a veterinarian in RVP as a mentor, and exposure to RVP during veterinary school. Gender, generational category, background (rural vs urban), and livestock experience were significantly associated with when respondents developed an interest in RVP and with factors important in developing that interest. CONCLUSIONS AND CLINICAL RELEVANCE: Results of the present study suggested that various factors are associated with interest in and choosing a career in RVP. These factors should be considered when strategies for increasing interest and encouraging careers in RVP are planned.

A survey of reasons why veterinarians leave rural veterinary practice in the United States.

OBJECTIVE: To identify factors associated with veterinarians leaving a career in rural veterinary practice (RVP). DESIGN: Cross-sectional descriptive study. SAMPLE POPULATION: Veterinarians from the United States who no longer worked in RVP. PROCEDURES: Veterinarians in any area of practice were solicited to participate in an online survey through invitation letters sent to various veterinary associations. Those who indicated that they had left RVP were asked to rank the importance of various potential factors in their decision to leave RVP. RESULTS: 805 responses were obtained from veterinarians who had worked in RVP, of which 246 (30.6%) had left RVP. Most (231/246 [93.9%]) of those who reported leaving RVP had been in practice > 5 years, and 75.2% (185/246) had been in practice > 12 years. Eighty-three (33.7%) who left RVP pursued careers in urban areas, 72 (29.3%) entered academia, and 7 (2.8%) retired. Reasons for leaving RVP ranked by the highest proportions of respondents as being of high importance were emergency duty, time off, salary, practice atmosphere, and family concerns. Women ranked factors such as time off, mentorship, practice atmosphere, conflict with staff, and gender issues as being of high importance more often than men did. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggested that the perceived shortage of veterinarians in RVP may be in part influenced by a lack of retention, particularly among experienced veterinarians. Targeted efforts to tackle issues related to emergency duty, time off, salary, practice atmosphere, and family issues could help alleviate the efflux from RVP.

Calving and calving management of beef cows and heifers on cow-calf operations in the United States.

A national sample of cow-calf producers was contacted to participate in a study to describe selected calving management practices on operations throughout the United States. Information was gathered on calving season, frequency of dystocia, frequency of observation, timing of assistance, and calving facilities. Regional and herd size differences existed in all parameters evaluated. Most calves (63.9%) were born in the months of February, March, and April. Overall, 16.7% of heifers and 2.7% of cows required some level of assistance in calving. Heifers and cows were checked an average of only 3.6 and 2.5 times per 24 h period during the calving season. Producers allowed heifers to labor for an average of 2.8h prior to lending assistance in calving while cows were allowed an average of 3.5h before providing assistance. In addition, only 39.6% of calvings took place in specialized calving areas presumably to allow increased observation frequency, timely intervention and protection from the elements. Collectively, these management practices illustrate that opportunities exist to improve calf survivability and increase reproductive efficiency in many cow herds.