Characteristics of dairy calf ranches: morbidity, mortality, antibiotic use practices, and biosecurity and biocontainment practices.

The utilization of farming operations specializing in rearing dairy heifer calves has increased since the early 1990s. However, these operations have not been as well characterized as US dairy operations with respect to demographic and health-related measures, particularly during the preweaning period. The objective of this study was to characterize morbidity, mortality, antibiotic use, and biosecurity and biocontainment practices on operations rearing preweaned heifers only or preweaned heifer and bull calves (mixed) in the United States. A cross-sectional survey was performed using a standardized method that included a preletter, initial survey, postcard follow-up, and second survey delivered by mail. Additional follow-up contacts were attempted by telephone. Descriptive statistics for morbidity, mortality, antibiotic use, and biosecurity and biocontainment practices were computed at both the operation and calf levels. The overall response rate was 50%. Crude yearly mortality averaged 6.9% at the calf level, with the median operation reporting 3.6% mortality. Diarrhea was experienced by 18% of calves, with 73% receiving an antibiotic. The median operation reported 20% diarrhea morbidity with 83% receiving an antibiotic. Respiratory disease was experienced by 9.0% of calves, with 82% receiving an antibiotic. The median operation reported 5.3% respiratory morbidity, with 100% receiving an antibiotic. Heifer-only and mixed operations did not differ in operation median morbidity, mortality, or antibiotic treatment rates. Written antibiotic protocols were available on 65% of operations. Medicated milk replacer was used by 56% of operations. Passive immunity was routinely measured by 46% of operations. Direct contact between calves in housing units was not allowed by 45% of operations. Of all farms informed of disease concerns at the source farm, 76% changed their daily routine as a result. Almost all operations uniquely identified calves and recorded mortality. The heifer-only and mixed operations in this study were similar to US dairy operations for key health, antibiotic use, and biosecurity and biocontainment metrics. This research provides initial estimates of key demographics usable by calf ranches, veterinarians, and other professionals serving this segment of the US dairy industry.

Antimicrobial-resistant Salmonella is detected more frequently in feed milling equipment than in raw feed components or processed animal feed.

Food for human and animal consumption can provide a vehicle for the transfer of pathogenic and antimicrobial-resistant bacteria into the food chain. We investigated the antimicrobial susceptibility of 453 Salmonella isolates collected from raw feed components, equipment and finished feed from 17 commercial feed mills in Australia between 2012 and 2021. Previous studies have found Salmonella prevalence and the diversity of Salmonella serotypes are greatest in the raw feed components. We, therefore, hypothesised that we would find a greater proportion of antimicrobial-resistant Salmonella isolates in the raw feed components compared to other sample types. We found that of 453 isolates tested, 356 (0.80) were susceptible to all antimicrobials tested, 49 (0.11) were nonsusceptible to streptomycin only and 48 (0.11) were resistant to two or more antimicrobials. Of the 48 antimicrobial-resistant isolates, 44 were found in feed milling equipment, two in raw feed components and two in finished feed. Statistical analysis, using a logistic regression with random effects model, found that the population-adjusted mean probability of detecting antimicrobial-resistant Salmonella isolates from feed milling equipment of 0.39, was larger than the probability of detecting resistant isolates in raw feed components 0.01, (P < 0.001) and in finished feed, 0.11, (P = 0.006). This propensity for antimicrobial-resistant bacteria to colonise feed milling equipment has not been previously reported. Further studies are required to understand the ecology of antimicrobial-resistant Salmonella in the feed milling environment.

Pre-weaning morbidity and mortality of llamas and alpacas.

OBJECTIVES: To describe the morbidity and mortality patterns and identify factors associated with morbidity in pre-weaning llamas and alpacas. DESIGN: Cross-sectional observational study of 287 crias born on four farms in Ohio, USA. PROCEDURE: Historical data representing all crias born over a 6-year period were obtained from two llama farms and two alpaca farms in Ohio. Multivariable generalised linear mixed effects regression models were used to identify factors associated with morbidity outcomes. RESULTS: In total, 105 (37%) of the llamas and alpacas had some reported morbidity during the pre-weaning period, and mortality rate was 2.1%. In addition, 51 (18%) of llamas and alpacas experienced morbidity because of infectious disease, and 47 (16%) experienced morbidity during the neonatal period. The three most commonly reported morbidity events were undifferentiated diarrhoea (23%), umbilical hernia (16%) and unspecified infectious disease (15%). Difficult birth was an important risk factor for pre-weaning morbidity in this population. CONCLUSIONS: Camelid veterinarians and their clients can expect that pre-weaning health events are common among crias, although mortality is low. Crias experiencing difficult births may require additional monitoring for health events during the pre-weaning period.

Salmonella monitoring programs in Australian feed mills: a retrospective analysis.

The availability of safe, commercially prepared stock feed for production animals is an important step in ensuring animal health and welfare and the safety of food animal products for human consumption. Animal feed quality assurance programs include microbiological monitoring of raw materials, mill equipment and finished feed. Over a period of 16 years, 23,963 samples for Salmonella culture and serotyping were collected from 22 stock feed mills. A multivariable generalized linear mixed model (GLMM) was used to identify mill and sample type factors that increase the odds of detecting Salmonella. The odds of detecting a Salmonella positive sample was greatest in samples from raw materials and in mills that processed restricted animal material (RAM). The percentage of positive samples ranged from 7.2% in 2003 to 2.8% in 2017. Of the 1,069 positive samples, 976 were serotyped with 61 different Salmonella serotypes isolated. The serotype most frequently isolated from raw materials was S. Agona, (n = 108) whilst S. Anatum was the serotype most frequently isolated from equipment and finished feed (n = 156). The diversity of Salmonella serotypes differed between mills and different stages of the production line. Microbiological monitoring in the commercial preparation of animal feed in Australian stock feed mills guides the implementation of quality control measures and risk mitigation strategies thereby reducing the prevalence and diversity of potentially zoonotic bacteria such as Salmonella, enhancing food safety for both animal and consumer.

Effect of Continuous Digital Hypothermia on Lamellar Inflammatory Signaling When Applied at a Clinically-Relevant Timepoint in the Oligofructose Laminitis Model.

BACKGROUND: Although continuous digital hypothermia (CDH) protects lamellae from injury in the oligofructose (OF) model of sepsis-related laminitis (SRL), conflicting results exist from these studies regarding effects of CDH on lamellar inflammatory events. HYPOTHESIS/OBJECTIVES: To determine the effect of CDH on lamellar inflammatory events in normal and OF-treated horses when instituted at a clinically relevant time point (onset of clinical signs of sepsis in this model). ANIMALS: Standardbred geldings (n = 15) aged 3-11 years were used. METHODS: In a randomized, controlled discovery study, animals were administered either OF (OF group, n = 8) or water (CON group, n = 8) by nasogastric tube and CDH was initiated in one forelimb (ICE) 12 hours later. Lamellar tissue samples were collected 24 hours after initiation of CDH (ICE and ambient [AMB] forelimbs). Lamellar mRNA concentrations of inflammatory mediators and lamellar leukocyte numbers were assessed using qPCR and immunohistochemistry, respectively; values from four sample groups (CON AMB, OF AMB, CON ICE, and OF ICE) were analyzed using mixed model linear regression. RESULTS: Although lamellar mRNA concentrations of multiple inflammatory mediators (IL-1ß, IL-6, CXCL1, MCP2, COX-2) were increased after OF administration (OF AMB group versus CON AMB; P < 0.05), only 2 inflammatory mediators (IL-6 and COX-2) and lamellar leukocyte numbers were decreased with CDH (OF ICE versus OF AMB; P < 0.05). CONCLUSIONS AND CLINICAL IMPORTANCE: Continuous digital hypothermia initiated at a time point similar to that commonly used clinically (clinical onset of sepsis) resulted in a more focused inhibition of inflammatory signaling.

Dogs on livestock farms: A cross-sectional study investigating potential roles in zoonotic pathogen transmission.

Dogs are often present on livestock farms, where they serve important management and companion roles, yet may be involved in zoonotic pathogen transmission. Numerous factors can potentially alter the risk of exposure to zoonotic pathogens, such as the dog's access to livestock, close dog-human contact and an increasing immunocompromised human population. The objective of this study was to quantify and qualify dog ownership among livestock owners, their dog husbandry and biosecurity practices, the dogs' access to livestock and potential risks for zoonotic pathogen transmission. A questionnaire was developed and mailed to 2,000 presumed Ohio livestock owners. Data were collected on demographics, dog husbandry practices, attitudes surrounding zoonotic diseases and attachment to and preventive veterinary care for the dogs. There were 446 responders who met the study inclusion criteria as an Ohio livestock farm owner, with 297 (67%) also owning dogs. Approximately 52% of dog-owning households included at least one individual at higher disease risk (i.e., <5 years, ≥65 years, diagnosed with an immunocompromising condition). Most respondents had little/no concern for disease transmission from livestock to dogs (90%), from dogs to livestock (87%) and from dogs to people (94%). Dogs were allowed access to livestock by 70% of respondents and nearly all (96%; 198) indicated at least one higher risk dog-livestock management practice. In addition, many reported never leashing or fencing their dog (61%) and rarely to never picking up dog faeces (76%). Households with higher risk members reported similar husbandry, biosecurity and concern levels as households without those members (all p > .05). Numerous opportunities for zoonotic pathogen transmission and low level of zoonotic disease concern suggest a need for improved education and outreach for the livestock dog-owning community, particularly for higher risk households.

Antimicrobial-resistant Enterobacteriaceae recovered from companion animal and livestock environments.

Antimicrobial-resistant bacteria represent an important concern impacting both veterinary medicine and public health. The rising prevalence of extended-spectrum beta-lactamase (ESBL), AmpC beta-lactamase, carbapenemase (CRE) and fluoroquinolone-resistant Enterobacteriaceae continually decreases the efficiency of clinically important antibiotics. Moreover, the potential for zoonotic transmission of antibiotic-resistant enteric bacteria increases the risk to public health. Our objective was to estimate the prevalence of specific antibiotic-resistant bacteria on human contact surfaces in various animal environments. Environmental surface samples were collected from companion animal shelters, private equine facilities, dairy farms, livestock auction markets and livestock areas of county fairs using electrostatic cloths. Samples were screened for Enterobacteriaceae expressing AmpC, ESBL, CRE or fluoroquinolone resistance using selective media. Livestock auction markets and county fairs had higher levels of bacteria expressing both cephalosporin and fluoroquinolone resistance than did equine, dairy, and companion animal environments. Equine facilities harboured more bacteria expressing cephalosporin resistance than companion animal shelters, but less fluoroquinolone resistance. The regular use of extended-spectrum cephalosporins in livestock populations could account for the increased levels of cephalosporin resistance in livestock environments compared to companion animal and equine facilities. Human surfaces, as well as shared human and animal surfaces, were contaminated with resistant bacteria regardless of species environment. Detecting these bacteria on common human contact surfaces suggests that the environment can serve as a reservoir for the zoonotic transmission of antibiotic-resistant bacteria and resistance genes. Identifying interventions to lower the prevalence of antibiotic-resistant bacteria in animal environments will protect both animal and public health.

Use of group-randomized trials in pet population research.

Communities invest considerable resources to address the animal welfare and public health concerns resulting from unwanted pet animals. Traditionally, research in this area has enumerated the pet-owning population, described pet population dynamics in individual communities, and estimated national euthanasia figures. Recent research has investigated the human-animal bond and explored the community implications of managed feral cat colonies. These reports have utilized traditional epidemiologic study designs to generate observational data to describe populations and measure associations. However, rigorous scientific evaluations of potential interventions at the group level have been lacking. Group-randomized trials have been used extensively in public health research to evaluate interventions that change a population's behavior, not just the behavior of selected individuals. We briefly describe the strengths and limitations of group-randomized trials as they are used to evaluate interventions that promote social and behavioral changes in the human public health field. We extend these examples to suggest the appropriate application of group-randomized trials for pet population dynamics research.

Prevalence of AmpC- and Extended-Spectrum ß-Lactamase-Harbouring Enterobacteriaceae in Faecal Flora of a Healthy Domestic Canine Population.

In order to estimate the prevalence of AmpC- and ESBL ß-lactamase-producing Enterobacteriaceae in the faecal flora of a healthy domestic canine population, faecal samples were obtained from healthy dogs receiving routine parasitology screening at the Ohio State University Veterinary Medical Center, between January 2013 and April 2013. Samples were screened for the presence of AmpC and ESBL ß-lactamase phenotypes, and the clinically important genotypes, blaCMY and blaCTX-M , were confirmed via conventional PCR. Minimum inhibitory concentrations were determined for isolates and plasmids were characterized. Two hundred and twelve canine faecal samples were screened, of which 30 harboured isolates carrying the AmpC blaCMY , representing 14.2% of the population (95% CI: 9.4-18.9%). Nine samples harboured isolates that carried the ESBL blaCTX-M , representing 4.2% of the population (95% CI: 1.5-7.0%). Isolates containing blaCMY harboured multiple plasmid replicon types, while isolates containing blaCTX-M harboured few plasmid replicon types. Our results suggest that domestic dogs may serve as a reservoir for extended-spectrum cephalosporin resistance genes for other domestic animal populations as well as for their human companions. This represents a potential veterinary and public health risk that warrants further investigation and continued surveillance to ascertain the nature and extent of the risk. The high level of diversity of plasmid content among isolates harbouring blaCMY suggests broader dissemination relative to blaCTX-M isolates.

Interobserver Variation in the Diagnosis of Neurologic Abnormalities in the Horse.

BACKGROUND: The diagnosis of equine protozoal myeloencephalitis (EPM) relies heavily on the clinical examination. The accurate identification of neurologic signs during a clinical examination is critical to the interpretation of laboratory results. OBJECTIVE: To investigate the level of agreement between board-certified veterinary internists when performing neurologic examinations in horses. ANIMALS: Ninety-seven horses admitted to the Veterinary Teaching Hospital at The Ohio State University from December 1997 to June 1998. METHODS: A prospective epidemiologic research design was used. Horses enrolled in the study were examined by the internist responsible for care of the horse, and later by an internist who was not aware of the presenting complaint or other patient history. Data were analyzed by descriptive statistics, and kappa (K) statistics were calculated to assess interobserver agreement. RESULTS: Ninety-seven horses were enrolled in the study. Overall, examiners, also referred to as observers, agreed that 60/97 (61.9%) were clinically abnormal, 21/97 (21.6%) were clinically normal, and the status of 16/97 (16.5%) of horses was contested. There was complete agreement among the examiners with regard to cranial nerve signs and involuntary movements. Disagreement involving severity of clinical signs occurred in 31 horses, and 25 of those horses (80.6%) were considered either normal or mildly affected by the primary observer. When examining the results of all paired clinical examinations for 11 different categories, there was wide variability in the results. When examiners rated the presence or absence of any neurologic abnormalities, lameness, or ataxia, the agreement among observers was either good or excellent for 80% of horses. When assessing truncal sway, the agreement among observers was good or excellent for 60% of the horses. When examining the horses for asymmetry of deficits, agreement was either good or excellent for 40% of the horses. Agreement among observers was excellent or good for only 20% of the horses when assessing muscle atrophy, spasticity (hypermetria), and overall assessment of the severity of neurologic abnormalities. CONCLUSIONS AND CLINICAL IMPORTANCE: This study underscores the subjectivity of the neurologic examination and demonstrates a reasonable level of agreement that may be achieved when different clinicians examine the same horse.

Extended-Spectrum ß-lactam Resistance in the Enteric Flora of Patients at a Tertiary Care Medical Centre.

The dissemination of Enterobacteriaceae expressing resistance to extended-spectrum cephalosporins, which are therapeutically used in both human and veterinary medicine, is of critical concern. The normal commensal flora of food animals may serve as an important reservoir for the zoonotic food-borne transmission of Enterobacteriaceae harbouring ß-lactam resistance. We hypothesized that the predominant AmpC and ESBL genes reported in US livestock and fresh retail meat products, blaCMY-2 and blaCTX-M , would also be predominant in human enteric flora. We recovered enteric flora from a convenience sample of patients included in a large tertiary medical centre's Clostridium difficile surveillance programme to screen for and estimate the frequency of carriage of AmpC and ESBL resistance genes. In- and outpatient diarrhoeic submissions (n = 692) received for C. difficile testing at the medical centre's clinical diagnostic laboratory from July to December, 2013, were included. Aliquoted to a transport swab, each submission was inoculated to MacConkey broth with cefotaxime, incubated at 37°C and then inoculated to MacConkey agars supplemented with cefoxitin and cefepime to select for the AmpC and ESBL phenotypes, with blaCMY and blaCTX-M genotypes confirmed by PCR and sequencing. From the 692 diarrhoeic submissions, our selective culture yielded 184 isolates (26.6%) with reduced susceptibility to cefotaxime. Of these, 46 (6.7%) samples harboured commensal isolates carrying the AmpC blaCMY . Another 21 (3.0%) samples produced isolates harbouring the ESBL blaCTX-M : 19 carrying CTX-M-15 and 2 with CTX-M-27. Our results indicate that ß-lactam resistance genes likely acquired through zoonotic food-borne transmission are present in the enteric flora of this hospital-associated population at lower levels than reported in livestock and fresh food products.

Genotypic and epidemiologic characterization of extended-spectrum cephalosporin resistant Salmonella enterica from US beef feedlots.

In the US, nontyphoidal Salmonellae are a common foodborne zoonotic pathogen causing gastroenteritis. Invasive Salmonella infections caused by extended-spectrum cephalosporin resistant (ESCR) phenotypes are more likely to result in treatment failure and adverse health outcomes, especially in severe pediatric Salmonella infections where the extended-spectrum ß-lactams are the therapy of choice. To examine the genetic and epidemiologic characteristics of ESCR Salmonellae which may enter the food chain, we characterized 44 ceftiofur-resistant Salmonella isolates from the National Animal Health Monitoring System (NAHMS) 2011 beef cattle feedlot health and management study. As part of the NAHMS Feedlot 2011 study, 5050 individual fecal samples from 68 large (1000+ head capacity) feedlots were cultured for Salmonella spp. The resulting 460 positive samples yielded 571 Salmonella isolates with 44 (8%) expressing an AmpC ß-lactamase phenotype. These phenotypic blaCMY-2Salmonella isolates represented 8 serotypes, most commonly S. Newport (n=14, 32%), S. Typhimurium (n=13, 30%), and S. Reading (n=5, 11%), followed by S. Dublin, S. Infantis, S. Montevideo, S. Rough O:i;v:1;7, and S. Uganda. Carriage of the blaCMY-2 gene was confirmed for all isolates expressing an AmpC ß-lactamase phenotype by PCR. Additionally, all 44 isolates were shown to carry the blaCMY-2 gene on a large IncA/C plasmid, a gene/plasmid combination which has been previously reported in multiple species. Other plasmids, including IncN, FIC, and FIIA, were also detected in some isolates. Cattle fed chlortetracycline were less likely to be positive for a blaCMY-2Salmonella isolate in their enteric flora compared to those not receiving chlortetracycline during the feeding period. Carriage of blaCMY-2 was more prevalent in Salmonella isolates originating from lighter weight cattle, cattle fed tylosin and dairy breeds. Our characterization of the NAHMS Feedlot 2011 study Salmonella isolates with ESCR phenotype shows that while other cephalosporin resistance mechanisms have been reported in US cattle, specific serotypes harboring blaCMY-2 on IncA/C plasmids may be the dominant resistance genotype.

Comparative phenotypic and genotypic analyses of Salmonella Rissen that originated from food animals in Thailand and United States.

Salmonella enterica serovar Rissen has been recognized as one of the most common serovar among humans and pork production systems in different parts of the world, especially Asia. In the United States, this serovar caused outbreaks but its epidemiologic significance remains unknown. The objectives of this study were to compare the phenotypic (antimicrobial susceptibility) and genotypic attributes of Salmonella Rissen isolated in Thailand (Thai) and the United States (US). All the Thai isolates (n = 30) were recovered from swine faecal samples. The US isolates (n = 35) were recovered from swine faecal samples (n = 29), cattle (n = 2), chicken (n = 2), dog (n = 1) and a ready-to-eat product (n = 1). The antimicrobial susceptibility of isolates was determined using the Kirby-Bauer disk diffusion method with a panel of 12 antimicrobials. Pulse-field gel electrophoresis (PFGE) was used to determine the genotypic diversity of isolates. All Thai isolates showed multidrug resistance (MDR) with the most frequent antibiotic resistance shown against ampicillin (100%), sulfisoxazole (96.7%), tetracycline (93.3%), streptomycin (90%) and chloramphenicol (30%). About half of the isolates of USA origin were pan-susceptible and roughly 30% were resistant to only tetracycline (R-type: Te). Salmonella Rissen isolated from Thailand and the USA in this study were found to be clonally unrelated. Genotypic analyses indicated that isolates were clustered primarily based on the geographic origin implying the limited clonality among the strains. Clonal relatedness among different host species within the same geography (USA) was found. We found genotypic similarity in Thai and US isolates in few instances but with no epidemiological link. Further studies to assess propensity for increased inter-regional transmission and dissemination is warranted.

Distribution and Diversity of Salmonella Strains in Shipments of Hatchling Poultry, United States, 2013.

Multistate outbreaks of salmonellosis associated with live poultry contact have been occurring with increasing frequency. In 2013, multistate outbreaks of salmonellosis were traced back to exposure to live poultry, some of which were purchased at a national chain of farm stores (Farm store chain Y). This study was conducted at 36 stores of Farm store chain Y and was concurrent with the timing of exposure for the human outbreaks of salmonellosis in 2013. We used environmental swabs of arriving shipment boxes of hatchling poultry and shipment tracking information to examine the distribution, diversity and anti-microbial resistance of non-typhoidal Salmonella (NTS) across farm stores and hatcheries. Isolates recovered from shipment boxes underwent serotyping, anti-microbial resistance (AMR) testing and pulsed-field gel electrophoresis (PFGE). Postal service tracking codes from the shipment boxes were used to determine the hatchery of origin. The PFGE patterns were compared with the PFGE patterns of NTS causing outbreaks of salmonellosis in 2013. A total of 219 hatchling boxes from 36 stores in 13 states were swabbed between 15 March 2013 and 18 April 2013. NTS were recovered from 59 (27%) of 219 hatchling boxes. Recovery was not significantly associated with species of hatchlings, number of birds in the shipment box, or the presence of dead, injured or sick birds. Four of the 23 PFGE patterns and 23 of 50 isolates were indistinguishable from strains causing human outbreaks in 2013. For serotypes associated with human illnesses, PFGE patterns most frequently recovered from shipment boxes were also more frequent causes of human illness. Boxes positive for the same PFGE pattern most frequently originated from the same mail-order hatchery. Only one of 59 isolates was resistant to anti-microbials used to treat Salmonella infections in people. This study provides critical information to address recurrent human outbreaks of salmonellosis associated with mail-order hatchling poultry.

Performance of female Rhipicephalus sanguineus (Acari: Ixodidae) fed on dogs exposed to multiple infestations or immunization with tick salivary gland or midgut tissues.

This investigation compared the effects of repeated infestations to immunization of dogs with tick salivary gland or midgut extracts on the feeding and fecundity performances of female Rhipicephalus sanguineus (Latrielle). In each immunized group, three tick-naive dogs were immunized three times with tick salivary gland or midgut extracts, and twice challenged at 21-d intervals by allowing 80 female and 40 male adult ticks to feed on each host. The repeated infestation group of three naive dogs was infested five times at 21-d intervals by the same numbers of ticks. The repeated infestation group showed a trend of reduced tick performance after the third infestation, but some of the tick performance parameters had recovered by the fifth infestation. Tick attachment was reduced by immunization with either tick salivary gland or midgut extract. Immunization with tick salivary gland extract had the greatest impact on the feeding period and engorgement weight of the female ticks. Immunization with tick midgut extract resulted in the greatest reduction of tick fecundity parameters, which included preoviposition, oviposition, and egg-incubation periods in addition to reduced egg production and egg viability. These results confirm that dogs can become resistant to R. sanguineus, and demonstrate that immunization with tick salivary gland or midgut extract has different effects on tick feeding and fecundity.

The heterogeneity of bovine IgG2. VII. The phenotypic distribution of the A1 and A2 allotypes of IgG2a among beef cows with known clinical history.

A1 and A2 are allotypes of bovine IgG2a which differ significantly in their primary structure, allotope expression and the products of pepsin digestion. An analysis of 754 beef cows from 14 different breeds at the Meat Animal Research Center (MARC), Clay Center, NE, demonstrated a significant difference in the distribution of A1 and A2 among breeds but failed to find any correlation between the clinical disease history of the animals tested and their A-allotype. The proportion of all animals with either a history of infectious or respiratory disease (43.3 +/- 3.5 and 17 +/- 0, respectively) was the same among A1/A1, A1/A2 and A2/A2 animals. Similarly, there was no preferential association between allotype and clinical disease within any one breed. A very high incidence of A1 homozygotes was found among Angus (84%), Brown Swiss (100%), Limousin (87%), MARC I (87%) and Pinzgauers (88%). In contrast, Herefords had a high incidence of A2/A2 homozygotes (41%) as did Brahmans (46%) and Gelbveih (34%). The distribution of A1/A1, A1/A2 and A2/A2 animals within any breed was totally consistent with the concept that A1 and A2 represent Mendelian co-dominant alleles. These data suggest that, among vaccinated female beef cattle in a normal environment, A-allotypy plays no role in the propensity for clinical disease as defined in this study. It does not rule out such an association in non-vaccinated, severely stressed animals and in calves exposed to severe outbreaks of an infectious agent.

Risk factors for seroprevalence of ovine lentivirus in breeding ewe flocks in Nebraska, USA.

The prevalence of and risk factors for ovine lentivirus (OLV) infection in 1466 breeding ewes in nine US Meat Animal Research Center (MARC) flocks were determined using a recombinant transmembrane protein (PTM) enzyme-linked immunosorbent assay (ELISA) to detect serum anti-OLV antibodies and define infection. Based on multivariable logistic regression, confinement birth and rearing (odds ratio (OR) = 1.6), older weaning ages (OR = 1.1 week-1), and older age (OR = 1.3-2.5 year-1 beyond age 1 year) were significantly associated with higher OLV prevalence in ewes. Prevalence also varied significantly by flock, with Finnsheep and Texel ewes having the highest prevalences and Booroola Merino and Suffolk ewes having the lowest prevalences. These findings support the hypothesis that management control efforts should concentrate on events early in the life of sheep, as this period is associated with factors which can modulate the risk for OLV infection.

Effect of ewe ovine lentivirus infection on ewe and lamb productivity.

We used a previously described sensitive and specific ovine lentivirus (OLV) recombinant transmembrane (rTM) protein enzyme-linked immunosorbent assay (ELISA) to detect anti-OLV antibodies and define OLV infection in breeding ewes from nine US Meat Animal Research Center (MARC) flocks. We estimated the production impacts of dam rTM ELISA seropositivity on ewe and lamb productivity in the birth-to-weaning interval using production data from 1466 breeding ewes (of which 1242 actually lambed) and their 2452 lambs born in spring 1992 using several multiple linear and logistic regression models. By adjusting for lamb weaning age, gender, type of birth and rearing, birth difficulty, dam age, and flock, the component of ewe or lamb productivity related to ewe OLV infection alone was isolated. The rTM ELISA-negative ewes produced significantly more total weight of weaned lamb per ewe-lambing (3.84 kg) and per ewe ram-exposed (4.95 kg) compared to their OLV-positive flockmates. Negative ewes also weaned 0.11 more lambs per ewe-lambing and 0.09 more lambs per ewe ram-exposed, gave birth to 0.13 more lambs per ewe ram-exposed, and were more likely to lamb after breeding (odds ratio (OR) = 1.9) compared to equivalent OLV-positive ewes. Lambs reared by OLV-negative ewes weighed 0.15 kg more at birth, gained 8 g more per day through weaning, and weighed 0.59 kg more at 56-day weaning. Preweaning mortality was lower (OR = 0.8) among lambs born to OLV-negative compared to OLV-positive ewes, although this difference was not significant. Our results suggest that subclinical OLV infection has important detrimental effects on sheep production which occur in cumulative fashion from breeding through weaning and that OLV control efforts may be financially justified in some sheep flocks.

Persistent bovine viral diarrhoea virus infection in US beef herds.

In the summer of 1996, we screened 18,931 calves in 128 beef herds located in five US states for persistent bovine viral diarrhea virus (BVDV) infection. Of these, 76 herds were randomly selected from the client database of collaborating veterinary practices, and 52 herds were suspected by the collaborating veterinarians to have BVDV infection based on history or clinical signs. Serum was obtained from each calf in the cooperating herds prior to 4 months of age and tested for the presence of BVDV by microtiter virus isolation. Information about each of the herds (including management practices, vaccination history, and breeding- and calving-season production measures) were collected by the collaborating veterinarians using standardized questionnaires. A total of 56 BVDV-positive calves in 13 herds were identified on initial screening. Ten (19%) of the BVDV-suspect herds and three (4%) of the randomly selected herds had > or = 1 BVDV-positive calf at initial screening. Multiple BVDV-positive calves were identified in 10 of those 13 herds. Follow-up information was obtained for 54 of the 56 positive calves. Ten out of 54 (18%) died prior to weaning, and 1 (2%) was sold because of unusually poor growth. Thirty-three out of 54 (61%) of the initially positive calves remained BVDV positive at 6 months of age - confirming persistent-infection (PI) status. Dams of 45 of the 56 positive calves were tested, with 3 (7%) identified as positive - indicating most PI calves were products of acute dam infection during gestation. The proportion of cows that were pregnant at the fall 1995 pregnancy examination was 5% lower in herds with PI calves born during the 1996 calving season than in randomly selected herds without PI calves. Most of the calves we identified with persistent BVDV infections survived to weaning, and could provide a constant source of virus to the herd throughout the breeding season and early gestation.

Effect of breed, intake, and carcass composition on the status of several macro and trace minerals of adult beef cattle.

The objective was to determine the association between breed, intake, and carcass composition and the status of liver Cu, Zn, and Fe, and serum Cu, Zn, Ca, and Mg of 118 mature cows representing nine breeds of cattle. Breeds used were Angus, Braunvieh, Charolais, Gelbvieh, Hereford, Limousin, Red Poll, Pinzgauer, and Simmental. The cows were fed one of four levels of DMI: 58, 76, 93, and 111 g of DMI.wt-75.d-1. A ground alfalfa, corn, and corn silage diet was fed for up to 5 yr. There was no relationship between liver and serum concentrations of Cu, a negative correlation (P < .05) existed between liver and serum concentrations of Zn and a positive correlation (P < .01) existed between liver concentrations of Cu and Zn. Concentrations of serum Ca were positively correlated (Cu and Zn, P < .01; Mg, P < .05) with serum concentrations of Cu, Zn, and Mg, but negatively correlated (P < .01) with liver Fe. Liver Cu was higher (P < .05) for the Limousin breed than all others, except Angus. Liver Zn concentrations were higher (P < .05) for Limousin than for Pinzgauer, but no other breed differences were observed. Liver Cu concentration was not affected by daily intake, but liver Zn concentration increased (P < .05) with increased daily intake. Liver Fe concentration decreased (P < .01) in a curvilinear manner with increased daily intake. No breed differences in serum concentrations of Cu or Zn were observed.(ABSTRACT TRUNCATED AT 250 WORDS)