Factors influencing antimicrobial prescribing by veterinarians and usage by dairy farmers in New Zealand

<p>AIMS: To determine the factors associated with the selection of antimicrobials by dairy veterinarians, and the attitudes of those veterinarians and dairy farmers to antimicrobial usage and resistance.</p> <p>METHODS: Facilitated focus groups of dairy farmers (n=22) and an anonymous online survey of dairy cattle veterinarians (n=206 respondents) were used to determine prescribing behaviour, factors affecting prescribing of antimicrobials, and the attitudes of veterinarians and farmers to the use of antimicrobials and the risk of antimicrobial resistance (AMR).</p> <p>RESULTS: Amongst the 22 farmers, the most common primary reason for choosing an antimicrobial was veterinary advice (87%) followed by personal experience (68%). Farmers had limited knowledge or concern about the risk of AMR, particularly outside their farm, with only 47% and 26% agreeing or strongly agreeing that use of antimicrobials on their farm would increase the risk of resistance in their herd and in humans, respectively.</p> <p>Prescribing of antimicrobials by veterinarians was predominantly based on diagnosis (168/206; 82%), and response to previous therapy (134/206; 65%), while duration above the minimum inhibitory concentration (43/206; 21%) was also considered important. Non-clinical factors such as withholding period (52/206; 25%) and farmers’ preferences (45/206; 22%) also influenced prescribing. Antimicrobial culture and susceptibility testing was not widely used, with 126/166 (76%) having culture results for less than four of the last 10 clinical mastitis cases for which they prescribed antimicrobials. Attitudes about prescribing and AMR varied with years of practice, gender and employment status.</p> <p>CONCLUSIONS: Veterinarians primarily considered technical reasons when prescribing antimicrobials. However non-technical factors did influence prescribing, in particular client feedback about perceived efficacy and perceptions of cost/benefit. Farmers stated that veterinarians were the most credible source of advice for selection of antimicrobials, but that personal experience on their farm was also important.</p> <p>CLINICAL RELEVANCE: Farmers’ perception of efficacy of antimicrobials, based on clinical outcomes, is an important determinant of their preferred choice of product. Hence, where changes in on-farm use patterns are required, clear communication by veterinarians about prudent antimicrobial choice and usage will require initial education around classes of antimicrobials and risk of resistance, as well as information around assessing efficacy of antimicrobial usage. Many veterinarians are in businesses that do not have practice prescribing policies. Such policies would likely lead to more consistent and judicious use of antimicrobials.</p

Subclinical ketosis in post-partum dairy cows fed a predominantly pasture-based diet: defining cut-points for diagnosis using concentrations of beta-hydroxybutyrate in blood and determining prevalence

<div><p>AIMS: Firstly, to define, in dairy cows in the first 5 weeks post-calving fed a predominantly pasture-based diet, cut-points of concentrations of beta-hydroxybutyrate (BHBA) in blood, above which there were associations with purulent vaginal discharge (PVD), reduced pregnancy rates (PR) and decreased milk production, in order to better define subclinical ketosis (SCK) in such cattle; and secondly, to determine the prevalence, incidence and risk factors for SCK.</p><p>METHODS: An observational field study was conducted in 565 cows from 15 spring-calving and predominantly pasture-fed dairy herds in two regions of New Zealand during the 2010– 2011 dairy season. Within each herd, a cohort of randomly selected cows (approximately 40 per herd) was blood sampled to determine concentrations of BHBA on six occasions at weekly intervals starting within 5 days of calving. The key outcome variables were the presence/absence of PVD at 5 weeks post-calving, PR after 6 weeks (6-week PR) and after the completion of the breeding season (final PR), and mean daily milk solids production.</p><p>RESULTS: Two cut-points for defining SCK were identified: firstly concentration of BHBA in blood ≥1.2 mmol/L within 5 days post-calving, which was associated with an increased diagnosis of PVD (24 <i>vs</i>. 8%); and secondly concentration of BHBA in blood ≥1.2 mmol/L at any stage within 5 weeks post-calving, which was associated with decreased 6-week PR (78 <i>vs</i>. 85%). The mean herd-level incidence of SCK within 5 weeks post-calving was 68 (min 12; max 100)% and large variations existed between herds in peak prevalence of SCK and the interval post-calving at which such peaks occurred. Cows >8 years of age and cows losing body condition were at increased risk of SCK within 5 weeks of calving.</p><p>CONCLUSIONS: Cows with concentration of BHBA in blood ≥1.2 mmol/L in early lactation had a higher risk of PVD and lower 6-week PR. Cow and herd-level prevalence of SCK varied widely in early lactation.</p><p>CLINICAL RELEVANCE: Subclinical ketosis is common and is significantly associated with reproductive performance in mainly pasture-fed New Zealand dairy cattle. Controlling SCK may therefore result in improvements in herd reproductive performance. However considerable variation exists among herds in the incidence of SCK and in the timing of peak prevalence which means that herd-specific monitoring programmes are required to define herd SCK status accurately.</p></div

Use of equine chorionic gonadotropin in lactating dairy cattle: a rapid review

To use an evidence-based approach to evaluate the available research data on the efficacy of equine chorionic gonadotropin (eCG) to improve reproductive performance of dairy cows when added to oestrus synchronisation programmes for the treatment of cows not detected in oestrus. A rapid literature review was conducted to summarise the existing trial data, primarily the effect of eCG on conception rate (CR) to fixed time artificial insemination (FTAI) from oestrus synchronisation programmes in lactating dairy cows. Relevant papers were identified via databases and auxiliary search strategies, then information was collected using a standardised data collection form. Similar studies were grouped together to create a descriptive summary of CR to FTAI and secondary outcome measures, with the creation of forest plots to visualise results. A total of 15 studies were identified for review: nine examined the administration of 400–500 IU eCG as part of an oestrus synchronisation programme based on intra-vaginal progesterone-releasing devices, gonadotropin-releasing hormone and prostaglandin (P4-GPG programme). The variable methodologies in the trials evaluated posed difficulties in grouping studies for further analysis and meant that there was insufficient data for a full meta-analysis. A single study reported a statistically significant increase in CR to FTAI from the addition to eCG to a P4-GPG programme in cows with anovulatory anoestrous. Four studies evaluated the addition of eCG to P4-GPG programmes in cows without visible oestrous signs; risk differences for CR to FTAI were between −1.7% and 28.8%, with three out of four studies reporting a positive effect of eCG on CR to FTAI, but all 95% CI values crossed the line of no effect. Two studies reported on the effect of eCG on 42-day pregnancy rate following a P4-GPG programme; one reported a risk difference of −4.9% (95% CI = −10.6–0.8%), while the other reported a risk difference of 7.9% (95% CI = 0.8–15%). The results of published studies describing the effect of eCG in P4-GPG programmes on CR to FTAI are inconsistent and further well-designed, adequately powered studies with standardised outcome measures are required to investigate its effect.</p