Transcriptional changes detected in fecal RNA from neonatal dairy calves of different breeds following gastrointestinal disease of varying severity.

Gastrointestinal (GI) disease is a major health concern in preweaned dairy calves. The objective of this fixed cohort study was to use RNA isolated from preweaned Holstein and Jersey heifer calf feces to study the molecular adaptations to variable clinical GI disease. The study was conducted on a commercial calf ranch in the western U.S. Enrolled calves were assessed twice daily for variations in demeanor, milk intake, and hydration. Fecal consistency scores were recorded at enrollment (day 1), and on the day (day 10) that a fecal sample was collected for differential gene expression (DGE). Calves with diarrhea on either day were classified as having either uncomplicated, localized GI disease (scours), or systemic GI disease (systemic enteritis). Eighty-four calves' fecal RNA was evaluated for DGE, of which 33 calves (n = 20 Holstein; n = 13 Jersey) were consistently healthy. The remaining 51 calves (n = 23 Holstein; n = 28 Jersey) experienced varying severity of GI disease during the sampling window. Genes of interest were related to the inflammatory response (i.e., IFNG, NFKB1, NOD2, TLR2, and TLR4) and cell membrane or cytoplasmic transport (i.e., AQP3, FABP2, KRT8 and SLC5A1). Breed-specific findings indicated that AQP3, IFNG, and TLR4 were upregulated in Holsteins with systemic enteritis, whereas KRT8 was downregulated in systemically affected Jerseys. Holsteins did not appear affected by scours aside from a tendency for DGE of toll-like receptors (TLRs) on the day of diarrhea. However, Jersey calves consistently demonstrated a tendency to upregulate IFNG, NFKB1, and TLR4 when affected with either scours or systemic enteritis. These findings were more pronounced in systemically affected Jersey calves and were observed as a delayed response to both scours and systemic enteritis. These findings support previous observations suggesting that Holstein calves may be better equipped than Jersey calves to rapidly fight pathogen invasion.

Describing motivation for health and treatment decisions and communication choices of calf-care workers on western United States dairies.

On large dairy farms, animal health assessments and treatments are made by farm employees. Little is known about how employees make decisions about illness detection or treatment, information critical to improving antimicrobial stewardship. The objectives of this study were to describe calf-care employee motivations for decisions associated with preweaned calf health and treatments, describe on-farm worker communication networks, and determine information sources used by these employees to support their decisions. Personal interviews were conducted with 103 calf-care employees on 28 farms in the western United States. The interview consisted of 10 motivation source type (MST) questions and questions about training, communication and educational opportunities. A latent class analysis created a summary for MST and resulted in 4 classes. Forty-three percent of calf-care employees fell into a class where responses were a combination of internal and intrinsic (personal beliefs or values and task fulfillment, respectively) and 23% were a combination of internal and goal internal (aligned with organizational goals). This latter class aligned health decisions with internal motivation and treatment decisions with goal internal. A network analysis summarized dominant communication relationships and established that feeders and treaters perceived more communication with supervisors than was reciprocated by supervisors, and that there was less communication between workers and management for tasks relative to daily work. Employee training was primarily done by herdsman, calf manager, or coworkers, and information for skill improvement and problem solving was sought from these individuals. Although veterinarians were not often involved in employee training, when they were involved, employees were likely to use them as an information source for skill improvement and problem solving. Few participants had ever used social media, but almost all had a device that could access the internet; more than 60% indicated interest in a social media platform for work-related information. Work motivation for many calf caretakers appeared to be sourced from personal beliefs, values, and job fulfillment, particularly when deciding to treat a sick calf. Investigation and incorporation of beliefs and values in training programs could help with alignment of protocols with actual treatment and further efforts to implement judicious use of antimicrobials.

A retrospective cohort study comparing dairy calf treatment decisions by farm personnel with veterinary observations of clinical signs.

Antimicrobials are frequently administered to calves with diarrhea, despite evidence suggesting questionable efficacy. Even if efficacious, providing the appropriate therapy to an animal requires accurate disease detection. The objective of this study was to use previously collected data and compare clinical scoring by a veterinarian to treatment decisions by on-farm personnel. Data describing daily clinical scores and farm treatments were previously collected from 4 farms for calves from birth to age 28 d. In this data set, a total of 460 calves were enrolled. Daily observations and clinical assessments were made on each farm by the same veterinarian, for a total of 12,101 calf observation days. Farm personnel made all treatment decisions based on their own observations, and these treatments were recorded by study personnel. Overall, the cumulative incidence of a calf exhibiting at least one abnormal clinical sign over the 28-d observation period was 0.93, with cumulative incidences of 0.85 and 0.33 for diarrhea and dehydration, respectively. The cumulative incidence of any treatment (including antibiotics and electrolytes) was 0.85, although the majority of treatments used an antimicrobial. The farm-specific probabilities that a calf with clinical signs of dehydration or diarrhea, respectively, received fluid or electrolyte therapy ranged from 0.08 to 0.27 and 0.03 to 0.12. These probabilities were greater for the day a clinical sign was first observed. The farm-specific probabilities that a calf with clinical signs of diarrhea received an antimicrobial was 0.23 to 0.65, and the probability that a calf exhibiting clinical signs of respiratory disease received an antimicrobial was 0.33 to 0.76. The first observation of diarrhea had similar probabilities to those for all observations of diarrhea. There was greater probability of treatment for calves with their first observed abnormal respiratory signs. Probabilities that treatment with antimicrobials, or fluids or electrolytes, was associated with an abnormal clinical sign were low-that is, calves received treatments in the absence of any abnormal clinical signs. This study illustrates incongruity between treatment decisions by calf treaters (the designated personnel on each farm responsible for calf health assessment and treatment decisions) and those of an observer using a clinical scoring system to identify calves with abnormal clinical signs. These findings indicate opportunities and the need for dairy farmers and advisors to evaluate calf treatment protocols, reasons for treatment, and training programs for calf health and disease detection, as well as to develop monitoring programs for treatment protocol compliance and health outcomes following therapy.

Calf care personnel on dairy farms and their educational opportunities.

As dairy herd sizes become larger and the organization of the business more complex, targeting communication and education to enhance animal care becomes more difficult. The purpose of this study was to describe selected demographics of calf care employees on large (>500 animals) and small (<501 animals) dairy farms that raise their own calves. Two to 8 individuals per farm involved with calf care, including owners, veterinarians, and calf managers, feeders, and treaters, were interviewed in either English or Spanish. Interviews were conducted in person on 53 dairy farms located in Arizona, Idaho, New York, Oregon, and Washington State. The number of preweaned calves on the farm ranged from 9 to 1,500 (median = 93). A total of 224 individuals were interviewed across 8 job titles. As farm size increased, personnel structure became more complex. Farms with >100 preweaned calves were 15 times more likely to have a calf manager title compared with farms with ≤100 preweaned calves. Eight farms designated the same person as calf manager, treater, and feeder, all with ≤100 preweaned calves. Thirty-two (60%) of the farms had at least 1 full-time calf feeder. Almost 30% of owners and over 40% of veterinarians interviewed were over 50 yr of age, whereas over 40% of the calf managers, feeders, and treaters were under 30 yr of age. Seventy-three percent of feeders and 72% of treaters spoke Spanish at home. For languages in which interviewees were comfortable speaking, more than 30% of owners and 33% of veterinarians were comfortable communicating in Spanish. For calf care employees, 60% of calf managers, 42% of feeders, and 38% of treaters were bilingual (English and Spanish), but most (72%) preferred to be interviewed in Spanish. The level of education varied by job title for those interviewed, but most of the calf care team had high school or less education. However, some diversity was observed in educational background within job title with almost 38% of the calf managers having at least some college education. The majority of feeders (88%) and treaters (83%) reported being trained by another employee and 66 and 58%, respectively, had not received any continuing education in the previous year. With the amount of diversity seen on these farms, understanding employees' educational backgrounds, language, and generational differences may be valuable when developing training for new procedures for animal health or other aspects of animal care.

Short communication: Predictors of time to dairy calf bucket training.

The time required to adequately bucket-train a dairy calf to drink its milk allotment is unknown. Additionally, factors that could predict calves who are slow to learn have not been identified. A prospective observational study was conducted to describe timing of bucket training and possible calf birth and colostrum quality factors that might predict calves requiring extra time to train. On one dairy farm, 1,235 calves were enrolled at birth in a prospective cohort study. Calving ease score, calf presentation at birth, twinning, calf sex, and dam parity were recorded by farm personnel. An as-fed colostrum sample for each calf was collected and evaluated for total solids, total plate bacterial count, and coliform bacterial count. Calf serum total protein values were obtained by d 2 to 3 of life. Calves were observed before the morning milk feeding for attitude/posture, and after feeding for assistance needed to drink milk from their bucket. Attitude/posture was significantly associated with whether a calf required assistance or not. Almost 60% (n = 724) of calves consumed their morning milk allotment (2 L) after d 3 of life without assistance. Significant factors associated with the odds of requiring assistance with drinking after 3 d of age included calf sex, being born a twin, and the week the calf was enrolled. Knowing how long it takes to train a calf to drink from a bucket could be useful in allocating the time or labor required to successfully train calves.

Technical note: Use of a digital and an optical Brix refractometer to estimate total solids in milk replacer solutions for calves.

The Brix refractometer is used on dairy farms and calf ranches for colostrum quality (estimation of IgG concentration), estimation of serum IgG concentration in neonatal calves, and nonsalable milk evaluation of total solids for calf nutrition. Another potential use is to estimate the total solids concentrations of milk replacer mixes as an aid in monitoring feeding consistency. The purpose of this study was to evaluate the use of Brix refractometers to estimate total solids in milk replacer solutions and evaluate different replacer mixes for osmolality. Five different milk replacer powders (2 milk replacers with 28% crude protein and 25% fat and 3 with 22% crude protein and 20% fat) were mixed to achieve total solids concentrations from approximately 5.5 to 18%, for a total of 90 different solutions. Readings from both digital and optical Brix refractometers were compared with total solids. The 2 types of refractometers' readings correlated well with one another. The digital and optical Brix readings were highly correlated with the total solids percentage. A value of 1.08 to 1.47 would need to be added to the Brix reading to estimate the total solids in the milk replacer mixes with the optical and digital refractometers, respectively. Osmolality was correlated with total solids percentage of the mixes, but the relationship was different depending on the type of milk replacer. The Brix refractometer can be beneficial in estimating total solids concentration in milk replacer mixes to help monitor milk replacer feeding consistency.

A Randomized Clinical Trial Evaluating the Effects of Oligosaccharides on Transfer of Passive Immunity in Neonatal Dairy Calves.

BACKGROUND: Bacterial contamination of colostrum is common and can decrease IgG absorption in neonatal calves. Strategies that mitigate this situation without complicating colostrum management will benefit dairy calf health and survival. OBJECTIVES: To evaluate the effects of supplementing colostrum with oligosaccharides (OS) on serum IgG concentration and apparent efficiency of absorption of IgG (AEA%) in calves fed unpasteurized colostrum and characterize these outcomes with respect to colostrum bacterial exposures. ANIMALS: One hundred twenty-three neonatal dairy calves. METHODS: Randomized, blinded, controlled clinical trial conducted at a commercial dairy operation. Calves were enrolled at birth in 1 of 4 treatment groups. Data were complete for 123 calves, which were distributed across the treatment groups as follows: mannan-oligosaccharides (MOS), n = 33; Saccharomyces galacto-oligosaccharides (SGOS), n = 31; Bifidobacterium galacto-oligosaccharides (BGOS), n = 28; and lactose control (CON), n = 31. A commercial radial immunodiffusion kit was used to determine colostrum and serum IgG concentrations. Conventional microbiology methods were used to enumerate colostrum bacterial counts. RESULTS: Bacterial counts were not significantly different among treatment groups. Total bacterial plate counts (TPC) were relatively low for the majority of colostrum samples, but TPC had a significant negative effect on serum IgG concentration and AEA% in the lactose-supplemented control group but not the OS treatment groups. CONCLUSIONS AND CLINICAL IMPORTANCE: These results suggest that a complement of OS structures may mitigate adverse effects of bacteria on transfer of passive immunity (TPI).

Escherichia coli O157:H7--Discerning Facts from Fiction: An Integrated Research and Extension Project for Multiple Audiences.

The O157:H7 (EcO157) epidemiology of Shiga-toxin-producing Escherichia coli (STEC) in cattle is complex, and myths about pre-harvest control are perpetuated. The objectives of this project were to identify perpetuated misinformation and inform four audiences about evidence-based risks and pre-harvest control of EcO157 by addressing: (i) EcO157 epidemiology and pre-harvest control; (ii) how food safety policy is created; and (iii) how to present accurate information about EcO157. An environmental scan using a daily Internet search helped identify themes for education. A literature review of pre-harvest control measures contributed to the development of educational materials (fact sheets, website, web presentations and conferences). Conference 1 was a webinar with 315 registrants, 10 countries including 41 US states and four Canadian provinces. Most participants felt confident in using their new knowledge, more than half felt confident enough to answer EcO157 questions from the public and many would recommend the recorded version of the webinar to colleagues. Conference 2 was live in the Washington, DC, area with most participants employed by the US government. All agreed that they better understood pre-harvest control, how food safety policy was made, and were confident they could create an effective message about STEC pre-harvest control. Videos were posted and received 348 Internet visitors within 2 months. Conference 3 was a webinar with a live audience and Twitter feeds, targeting people who give nutrition advice. Almost all ranked the programme good to excellent and relevant to their work. About 25% indicated that they would share: 'grass-fed beef is not safer than grain-fed', 25% would share information on effectiveness of cattle vaccines, and 14% would share information on message mapping. Across all conferences, major changes in knowledge included the following: there is no additional risk of EcO157 shedding from grain-fed versus grass-fed cattle, pre-harvest vaccination is efficacious, and production systems (pasture versus confinement) do not affect EcO157 shedding rates.

Antimicrobial Resistance Profiles and Diversity in Salmonella from Humans and Cattle, 2004-2011.

Analysis of long-term anti-microbial resistance (AMR) data is useful to understand source and transmission dynamics of AMR. We analysed 5124 human clinical isolates from Washington State Department of Health, 391 cattle clinical isolates from the Washington Animal Disease Diagnostic Laboratory and 1864 non-clinical isolates from foodborne disease research on dairies in the Pacific Northwest. Isolates were assigned profiles based on phenotypic resistance to 11 anti-microbials belonging to eight classes. Salmonella Typhimurium (ST), Salmonella Newport (SN) and Salmonella Montevideo (SM) were the most common serovars in both humans and cattle. Multinomial logistic regression showed ST and SN from cattle had greater probability of resistance to multiple classes of anti-microbials than ST and SN from humans (P < 0.0001). While these findings could be consistent with the belief that cattle are a source of resistant ST and SN for people, occurrence of profiles unique to cattle and not observed in temporally related human isolates indicates these profiles are circulating in cattle only. We used various measures to assess AMR diversity, conditional on the weighting of rare versus abundant profiles. AMR profile richness was greater in the common serovars from humans, although both source data sets were dominated by relatively few profiles. The greater profile richness in human Salmonella may be due to greater diversity of sources entering the human population compared to cattle or due to continuous evolution in the human environment. Also, AMR diversity was greater in clinical compared to non-clinical cattle Salmonella, and this could be due to anti-microbial selection pressure in diseased cattle that received treatment. The use of bootstrapping techniques showed that although there were shared profiles between humans and cattle, the expected and observed number of profiles was different, suggesting Salmonella and associated resistance from humans and cattle may not be wholly derived from a common population.

Targeting therapy to minimize antimicrobial use in preweaned calves: effects on health, growth, and treatment costs.

Prophylactic and therapeutic antimicrobial use in food animals is questioned because of the potential for development of resistant bacteria and future inability to use some antimicrobials for human or animal disease. The objectives of this study were to determine the effect of raising preweaned dairy calves without antimicrobials in the milk and minimizing therapeutic antimicrobial treatment on morbidity, mortality, weight gain, and treatment costs. Newborn calves (n = 358) were allocated to 1 of 4 groups, housed outdoors in individual hutches, and monitored for 28 d. Calves in the conventional therapy (CT) group were treated as per dairy protocol with sulfamethoxazole/trimethoprim, spectinomycin, penicillin, and bismuth-pectin for diarrhea. The targeted therapy (TT) group included bismuth-pectin for diarrhea and antimicrobial treatment only in cases of fever or depressed attitude. Within CT and TT groups, calves were equally assigned to receive neomycin and tetracycline in their milk for the first 2 wk of life (AB-milk) or no antimicrobials (NoAB-milk). Daily health evaluations included fecal consistency, respiratory disease, attitude, and hydration status as well as milk and grain consumption. A negative binomial model evaluated the total number of days with diarrhea days in each group. General linear models were used to assess average daily weight gain and grain consumption. Conventionally treated calves had 70% more days with diarrhea than TT calves, and AB-milk calves had 31% more days with diarrhea compared with NoAB-milk calves. The TT calves tended to have a higher average daily gain by 28 d and consumed more grain compared with CT calves. If antimicrobials were used only for diarrhea cases with fever, inappetence, or depression and no in-milk antimicrobials were used, a $10 per calf savings could be realized. Targeting antimicrobial therapy of calf diarrhea cases is prudent not only to save the drugs for future use but also to prevent the potential for antibiotic-associated diarrhea and reduce calf-rearing costs.

Evaluation of the effects of oral colostrum supplementation during the first fourteen days on the health and performance of preweaned calves.

Increasing concerns about antimicrobial resistance have led to the development and implementation of alternatives to antimicrobial use in animal production. The objective of this clinical trial was to determine the effect of colostrum supplementation of the milk replacer ration on morbidity, mortality, feed intake, and weight gain of preweaned calves. Ninety 1-d-old calves on each of 3 commercial calf ranches were randomly allocated to 1 of 3 groups. Treatment-group calves received 10 g of supplemental immunoglobulin G (IgG) in the form of 70 g of colostrum powder in the milk replacer twice daily for 14 d. The placebo-group calves received a nutritionally equivalent supplement lacking IgG in the milk replacer twice daily for 14 d. Control calves received milk replacer without supplements twice daily. Calves were housed in individual hutches and were weighed on d 1, 28, and 60. Serum was collected on d 2 for serum IgG determination. Daily health evaluations for the first 28 d of life were performed by study personnel blinded to treatment group assignment. Observed illness was treated based on health assessment, rectal temperature, and specific calf ranch protocols. Feed consumption (milk and grain) was recorded. Calves receiving supplemental colostrum had less diarrhea and received fewer antimicrobial treatments than control and placebo calves. The results indicated that calf diarrhea was associated with low serum IgG levels and low-weight calves. Grain consumption and weight gain over the first 28 d of life were significantly greater in colostrum-supplemented calves compared with control calves. No differences in mortality or respiratory disease incidence among groups were detected. Supplemental colostrum during the first 2 wk of life can reduce diarrheal disease in preweaned calves on calf ranches and thereby reduce the amount of antimicrobial treatments needed.

Comparison of Salmonella enterica subspecies enterica serovar Typhimurium isolates from dairy cattle and humans using in vitro assays of virulence.

Salmonella enterica subspecies enterica serovar Typhimurium (Salmonella typhimurium) can infect and cause disease in a wide range of host species however there have been suggestions that this serovar may have genes involved with host range or specificity [Tsolis, R.M., Townsend, S.M., Miao, E.A., Miller, S.I., Ficht, T.A., Adams, L.G., Baumler, A.J., 1999. Identification of a putative S. enterica serotype Typhimurium host range factor with homology to IpaH and YopM by signature-tagged mutagenesis. Infect. Immun. 67 (12), 6385-6393]. Our goal in this study was to determine if in vitro virulence assays would support this suggestion. Twelve human and 10 bovine isolates of S. typhimurium from a single county in California were evaluated using in vitro virulence assays of adhesion and invasion. The resulting data was combined with results from previously reported genotypic and phenotypic testing of the isolates and statistical analysis performed using multivariate general linear models. Human isolates had higher adhesion values in each of the statistical models tested (p<0.05) but no statistical differences were found in the invasion values of human and bovine source isolates. Both adhesion and invasion values differed between the two largest groups of isolates segregated on the basis of pulsed-field gel patterns. The findings suggest there may be genetically defined in vitro virulence attributes in S. typhimurium that are associated with host species.

Comparison of Salmonella enterica serovar distribution and antibiotic resistance patterns in wastewater at municipal water treatment plants in two California cities.

AIM: To determine Salmonella enterica serovars and antibiotic resistance (ABR) in the human waste stream. METHODS AND RESULTS: Sampling of influent wastewater at municipal treatment plants in two California cities was performed by collecting composite samples, over a 24-h period, from the treatment plants on five to six occasions. Serial water quantities were filtered and cultured with a Salmonella selective method and an oxytetracycline-supplemented Salmonella selective method. Antibiotic susceptibilities to 12 antibiotics were determined and the isolates were grouped based on ABR patterns. From 983 S. enterica isolated, 102 represented unique sampling-serovar-ABR patterns. Thirty-five different serovars were identified to be distributed over 17 different ABR patterns. The serovar distribution differed between the sampling sites, whereas there was no significant trend in levels of multiple ABR. CONCLUSIONS: Salmonella enterica was recovered with ease from small sample volumes of wastewater received by municipal water treatment plants. A large variety of serovars and ABR profiles were represented in the recovered Salmonella. SIGNIFICANCE AND IMPACT OF THE STUDY: The ease of sampling and recovery of Salmonella from municipal wastewater from treatment plants makes it a valuable sampling approach for monitoring the presence of Salmonella in the human population.

Genetic and phenotypic variability among Salmonella enterica serovar Typhimurium isolates from California dairy cattle and humans.

Fifty-six human and 24 adult dairy cattle isolates of Salmonella enterica serovar Typhimurium from a single county in California were compared using ribotyping, insertion sequence typing (IS200), pulsed-field gel electrophoresis, plasmid typing, phage typing, and antimicrobial resistance testing. The majority of the isolates fell into one of two groups which were phage types DT104 and DT193. Combining the information from all typing methods, a total of 45 different "clusters" were defined, with 35 of those including only a single isolate. The library of isolates had a high degree of variability, but antibiotic resistance and plasmid typing each defined single clusters in which human or bovine isolates predominated (chi2, P < 0.05).

Effect of rubber flooring on claw health in lactating dairy cows housed in free-stall barns.

Multiparous dairy cows between 10 to 30 d in milk (DIM) were enrolled in a clinical trial to evaluate the effects of rubber flooring on the development of claw lesions, locomotion scores, clinical lameness, and rates of hoof growth and wear. Two groups of cows were housed in identical free-stall facilities, except that 1 pen (rubber, n = 84) had rubber alley mats covering the entire concrete floor of the pen, whereas cows in the second pen were exposed to concrete flooring (concrete, n = 82) without rubber alley mats. All cows were evaluated 3 times between 10 and 30, 74 and 94, and 110 and 130 DIM for 1) the presence of claw lesions on their rear feet, 2) the occurrence of clinical lameness based on a locomotion score, and 3) rates of claw growth and wear as observed on the dorsal wall of the right lateral claw. No differences between flooring groups at the time of enrollment were detected for lactation number, mean DIM at first examination, body condition score, and proportion of cows with claw lesions at the first examination. Odds of developing claw lesions between examinations were not different for cows exposed to the rubber surface compared with those exposed to concrete. Cows on concrete, however, had greater odds of developing or exacerbating existing heel erosion than cows on rubber flooring. Regardless of the flooring surface, the lateral claw was more likely to develop lesions than the medial claw. Odds of becoming lame by the third examination and the proportion of cows requiring therapeutic hoof trimming because of lameness were greater for concrete-exposed cows than those on rubber. Cows on rubber flooring had decreased claw growth and wear between the first and last examination compared with cows on concrete. Regardless of flooring surface, second-lactation cows had greater wear rates than those in third or greater parities. Results of our study suggest that a soft flooring surface, such as interlocking rubber, is beneficial for hoof health.

Embryo survival from gossypol-fed heifers after transfer to lactating cows treated with human chorionic gonadotropin.

Objectives were to determine the effects of gossypol exposure during early embryo development on embryonic survival after transfer of frozen and thawed embryos to lactating dairy cows treated with human chorionic gonadotropin (hCG). Holstein cows (n = 269) were either treated or not treated with 3,300 IU of hCG on d 5 of the estrous cycle and received an embryo collected from heifers fed or not fed gossypol. Embryo donor heifers consumed either 0 or 12 g/d of free gossypol for 76 d prior to embryo collection, resulting in mean plasma gossypol concentrations of 0 and 7.38 microg/mL, respectively. Embryos were transferred on d 7 of the estrous cycle and pregnancy diagnosed 21 and 35 d later. Progesterone was analyzed in plasma collected on d 5 and 12 of the estrous cycle. Treatment with hCG increased the total luteal area on d 12 (818.0 vs. 461.1 mm2) because of increased number of corpora lutea (2.0 vs. 1.0) and increased area of the original corpora lutea (522.7 vs. 443.5 mm2). Plasma progesterone concentrations were similar between treatments on d 5, but increased by d 12 in hCG-treated cows (6.46 vs. 4.78 ng/ mL). Pregnancy rates on d 28 and 42 were not affected by hCG. However, after transfer into lactating cows, embryos collected from heifers not fed gossypol resulted in higher pregnancy rates at 28 d (33.3 vs. 23.1%) and 42 d (29.6 vs. 20.2%) of gestation compared with embryos collected from heifers fed gossypol. Our data suggest that the negative effects of gossypol on fertility are mediated by changes in embryo viability in spite of similar grade quality at transfer.

Comparison of reproductive performance by artificial insemination versus natural service sires in California dairies.

This study compared the calving to conception intervals for cows in AI pens with cows exposed to natural service sires, controlling for milk production, mastitis occurrence, parity and calving month effects. Records from 10 western United States dairy herds (mean herd size = 2058 cows) were evaluated retrospectively over an 18-month period. Eight bull breeding analysis cohorts were created (the first cohort 0-50 days in milk and the remaining cohorts at 25 days in milk intervals through 226 days). The cohorts contained non-pregnant cows that were first moved into bullpens during the described cohort period. Equal numbers of non-pregnant cows only exposed to AI during the cohort period were randomly selected from the pool of eligible non-pregnant cows. An AI cow was used only once in the data analysis, but was included in a bull breeding cohort at a later date if she remained non-pregnant and was transferred to a bullpen. Univariate and multivariate survival analysis was used to compare the calving to conception intervals. Cows in AI groups had higher hazard rates for pregnancy across all cohorts. Parity and milk production were significantly associated with risk for pregnancy. In herds that practice a mixture of AI and bull breeding, overall herd reproductive performance might be improved by allowing cows more opportunities at AI prior to moving them into clean-up bullpens.

Animal and farm influences on the dynamics of antibiotic resistance in faecal Escherichia coli in young dairy calves.

It is believed that the intensive use of antibiotics in the management of disease in pre-weaned calves contributes to high levels of antibiotic resistance in commensal and pathogenic bacteria. We described the temporal dynamics of antibiotic-susceptibility patterns seen in bovine enteric Escherichia coli in pre-weaned calves on dairy farms and dedicated calf-rearing facilities. Cohorts of 30 calves at each of six farms were sampled at 2-week intervals during the pre-weaning period. Faecal E. coli isolates were analyzed for antibiotic susceptibility to 12 antibiotics with the disk-diffusion method and grouped using cluster analysis of inhibition-zone patterns. The influences of calf age, farm-type, and individual-calf antibiotic therapy on the clusterings were assessed using stratified analyses and cumulative multinomial logistic regression using generalized estimating equation with antibiotic-resistance cluster as an ordinal-dependent variable. The model controlled for farm and cohort by a nested design and included a repeated measure on calf at each sampling occasion. E. coli from calves 2 weeks of age were more likely to be increasingly multiply resistant than E. coli from day-old calves (OR = 53.6), as were 4- and 6-week-old calves (OR = 29.8 and 16.4, respectively). E. coli from calves on dedicated calf-rearing facilities were more likely to be increasingly multiply resistant than E. coli from dairy-reared calves (OR = 2.4). E. coli from calves treated with antibiotics within 5 days prior to sampling were also more likely to be increasingly multiply resistant than E. coli from calves not exposed to individual antibiotic therapy (OR = 2.0).

A clinical trial evaluating prophylactic and therapeutic antibiotic use on health and performance of preweaned calves.

The objective of this clinical trial was to evaluate the influence of prophylactic and therapeutic antibiotics on health and performance in preweaned dairy calves on a calf ranch. One hundred twenty 1-d-old calves were enrolled into 3 management systems for antibiotic use and raised until 4 wk of age. Sixty calves were not eligible to receive prophylactic or therapeutic antibiotics. Thirty calves were eligible to receive individual antibiotic treatment for disease, but no prophylactic antibiotics in milk replacer. The remaining 30 calves received milk replacer medicated with neomycin and tetracycline HCl, and could be treated with antibiotics. Health status and treatments were monitored and recorded daily. The primary study outcomes were weight gain, morbidity, and mortality. The most important factor associated with morbidity and mortality was passive immune transfer through colostrum. In-feed antibiotics delayed onset of morbidity, decreased overall morbidity, and increased weight gain. Nonantibiotic therapies for clinical disease were associated with increased mortality and morbidity compared with antibiotic treatments. The study has shown that minimizing or eliminating the use of antibiotics in the feed requires measures to ensure adequate passive transfer of immunity, but that in the face of inadequate passive transfer of immunity, animal welfare may be endangered by replacing medicated milk replacer with nonmedicated milk replacer, and therapeutic antibiotics with nonantibiotic alternatives.

Assessing antibiotic resistance in fecal Escherichia coli in young calves using cluster analysis techniques.

This study uses cluster analysis techniques to describe the antibiotic susceptibility patterns seen in calf fecal Escherichia coli (E. coli). Cohorts of 30 dairy calves at six farms were sampled at 2-week intervals during the pre-weaning period. At each sampling occasion five fecal E. coli isolates per calf were analyzed for antibiotic susceptibility to 12 antibiotics using the disk diffusion method. All isolates had a profile consisting of the aggregate measured inhibition zone size for each of the evaluated antibiotics. Several cluster analytic algorithms were assessed to partition the E. coli isolates. For our data, Ward's minimum variance method met the objectives of the study. Relative to the number of possible combinations of resistance clusters, a parsimonious set of 14 patterns was developed. This set of E. coli isolates exhibited a limited set of resistance patterns to the different antibiotics indicating that certain resistance genes may be linked.