The incidence and aetiology of clinical bovine mastitis on 14 farms in Northland,New Zealand

AIM: To estimate the incidence of clinical mastitis and the frequency of isolation of mastitis-causing organisms from clinical cases in one lactation season (July 2005 to May 2006) on 14 dairy farms from the Northland region of New Zealand.

METHODS: Cases of clinical mastitis were determined by trained farm personnel who recorded the identity of affected cows. Pooled milk samples from affected quarter(s) were aseptically collected by the farm personnel, for microbiology. Mean numbers of affected cows and quarters were compared at the population and farm level per 305 cow-days-at-risk (DAR).

RESULTS: One or more cases of clinical mastitis occurred in 559/3,765 (14.8%) lactating cows. The average incidence of clinical mastitis was 0.19 cases per 305 DAR. The incidence in rear quarters (56.2%) was 1.3 times (p=0.027) that of front quarters (43.8%). The incidence of clinical mastitis and numbers of affected quarters were signifi cantly infl uenced by the stage of lactation (higher in early lactation), age (higher in older cows) and farm. At the cow level, the most common isolates were Staphylococcus aureus (23.7%) and Streptococcus uberis (23.3%). No causative organisms were identifi ed in 19.9% of the samples. Each cow had an average of 1.8 quarters affected during a case of clinical mastitis.

CONCLUSIONS: This study demonstrated a higher incidence of staphylococcal clinical mastitis on dairy farms from Northland than has been reported in other regions of New Zealand.     

Effect of epidural and intravenous use of the neurokinin-1 (NK-1) receptor antagonist maropitant on the sevoflurane minimum alveolar concentration (MAC) in dogs

ObjectiveTo determine the effect of maropitant, an NK-1 receptor antagonist on the minimum alveolar concentration (MAC) of sevoflurane after intravenous and epidural administration to dogs.Study designProspective experimental study.AnimalsSeven, adult, spayed-female dogs (24.8 ± 1.9 kg).MethodsEach dog was anesthetized twice with sevoflurane in oxygen, with at least 10 days separating the anesthetic events. The minimum alveolar concentration (MAC) of sevoflurane was determined using the tail-clamp technique. During the first anesthetic event, the MAC of sevoflurane was determined initially and again after intravenous administration of maropitant (5 mg kg^?1) and an infusion (150 μg kg^?1 hour^?1). During the second anesthetic event, an epidural catheter was advanced to the 4th lumbar vertebra and MAC was determined after administration of saline and maropitant (1 mg kg^?1) epidurally. All MAC determinations were done in duplicate. The MAC values were adjusted to sea level and compared using student's t-test.ResultsThe baseline MAC for sevoflurane was 2.08 ± 0.25%. Intravenous maropitant decreased (p < 0.05) MAC by 16% (1.74 ± 0.17%). In contrast, epidural administration of either saline or maropitant did not change (p > 0.05) the MAC (2.17 ± 0.34% and 1.92 ± 0.12%, respectively).Conclusion and clinical relevanceMaropitant decreased the MAC of sevoflurane when administered intravenously to dogs but not after epidural administration.     

Effect of Oestrous-cycle Stage on the Response of Mares in a Novel Object Test and Isolation Test

In various species, sex, hormonal treatments and oestrous-cycle stage have been shown to affect the animal's response in behavioural tests. Few such studies have been performed in the horse. The main aim of the present study was to investigate whether oestrous-cycle stage affects mares' response to a novel object test and isolation test and, in part, to study whether mares, assumed to suffer from oestrous-related behavioural problems, respond differently in these tests when compared with controls. Twelve mares were tested twice, in oestrus and dioestrus, in a crossover design. Seven behavioural and two heart rate variables were measured for the novel object test and two heart rate variables for the isolation test. Oestrous-cycle stage and whether a mare was classified as a 'problem' mare did not affect the mare's response. However, test order, i.e. the cycle stage a mare was tested in first, affected its reaction. This effect could partly be explained by significant differences between test occasions 1 and 2 in three behavioural variables and one heart rate variable (p < 0.05) in the novel object test. The mares explored the novel object more and had a higher mean heart rate in the first test. Exploring the novel object more could largely be attributed to those mares tested in dioestrus first, perhaps indicating that the mares in oestrus were less receptive to the novel object. The reason for the differences between test occasions could be an effect of learning or habituation.     

Influence of general anesthesia on pharmacokinetics of intravenous lidocaine infusion in horses

OBJECTIVE: To compare the disposition of lidocaine administered IV in awake and anesthetized horses. ANIMALS: 16 horses. PROCEDURE: After instrumentation and collection of baseline data, lidocaine (loading infusion, 1.3 mg/kg administered during 15 minutes (87 microg/kg/min); constant rate infusion, 50 microg/kg/min) was administered IV to awake or anesthetized horses for a total of 105 minutes. Blood samples were collected at fixed times during the loading and maintenance infusion periods and after the infusion period for analysis of serum lidocaine concentrations by use of liquid chromatography with mass spectral detection. Selected cardiopulmonary parameters including heart rate (HR), mean arterial pressure (MAP), arterial pH, PaCO2, and PaO2 were also recorded at fixed time points during lidocaine administration. Serum lidocaine concentrations were evaluated by use of standard noncompartmental analysis. RESULTS: Serum lidocaine concentrations were higher in anesthetized than awake horses at all time points during lidocaine administration. Serum lidocaine concentrations reached peak values during the loading infusion in both groups (1,849 +/- 385 ng/mL and 3,348 +/- 602 ng/mL in awake and anesthetized horses, respectively). Most lidocaine pharmacokinetic variables also differed between groups. Differences in cardiopulmonary variables were predictable; for example, HR and MAP were lower and PaO2 was higher in anesthetized than awake horses but within reference ranges reported for horses under similar conditions. CONCLUSIONS AND CLINICAL RELEVANCE: Anesthesia has an influence on the disposition of lidocaine in horses, and a change in dosing during anesthesia should be considered.     

Technique and outcome of mitral valve replacement in dogs

Eight dogs with naturally occurring severe mitral regurgitation underwent mitral valve replacement with a mechanical valve prosthesis during cardiopulmonary bypass. Dogs received warfarin orally after surgery to maintain a prothrombin time-based international normalized ratio from 2.5 to 3.5. Seven dogs survived surgery. Left ventricular diastolic volume index decreased significantly from 206 +/- 91 mL/m2 before surgery to 121 +/- 47 mL/m2 after surgery. Left atrium-to-aorta ratio decreased significantly from 2.66 +/- 0.4 before surgery to 1.73 +/- 0.65 after surgery. Left ventricular systolic volume index was not significantly different after surgery (56 +/- 36 mL/m2), compared with before surgery (40 +/- 32 mL/m2). Median survival after surgery was 4.5 months (range, 0.75 months to 5.25 years). Six dogs died of confirmed or suspected thrombosis of the valve prosthesis. Dogs with severe mitral regurgitation tolerated mitral valve replacement well, but a high incidence of prosthetic valve thrombosis limited long-term outcome.     

Effects of diazepam and flumazenil on minimum alveolar concentrations for dogs anesthetized with isoflurane or a combination of isoflurane and fentanyl

OBJECTIVE: To determine the effect of a constant-rate infusion of fentanyl on minimum alveolar concentration (MAC) of isoflurane and to determine the interaction between fentanyl and a benzodiazepine agonist (diazepam) and antagonist (flumazenil) in isoflurane-anesthetized dogs. ANIMALS: 8 mixed-breed adult dogs. PROCEDURE: Dogs were anesthetized with isoflurane 3 times during a 6-week period. After a 30-minute equilibration period, each MAC determination was performed in triplicate, using standard techniques. Fentanyl was administered as a bolus (10 microg/kg of body weight, IV) that was followed by a constant infusion (0.3 microg/kg per min, IV) throughout the remainder of the experiment. After determining isoflurane-fentanyl MAC in triplicate, each dog received saline (0.9% NaCl) solution, diazepam, or flumazenil. After 30 minutes, MAC was determined again. RESULTS: Fentanyl significantly decreased isoflurane MAC (corrected to a barometric pressure of 760 mm Hg) from 1.80+/-0.21 to 0.85+/-0.14%, a reduction of 53%. Isoflurane-fentanyl-diazepam MAC (0.48+/-0.29%) was significantly less than isoflurane-fentanyl-saline MAC (0.79+/-0.21%). Percentage reduction in isoflurane MAC was significantly greater for fentanyl-diazepam (74%), compared with fentanyl-saline (54%) or fentanyl-flumazenil (61%). Mean fentanyl concentrations for the entire experiment were increased over time and were higher in the diazepam group than the saline or flumazenil groups. CONCLUSIONS AND CLINICAL RELEVANCE: Fentanyl markedly decreased isoflurane MAC in dogs. Diazepam, but not flumazenil, further decreased isoflurane-fentanyl MAC. Our results indicate that diazepam enhances, whereas flumazenil does not affect, opioid-induced CNS depression and, possibly, analgesia in dogs.     

A comparison of equine recovery characteristics after isoflurane or isoflurane followed by a xylazine-ketamine infusion.

OBJECTIVE: To determine whether infusion of xylazine (XYL) and ketamine (KET) for 30 minutes after isoflurane administration in horses would result in improved quality of recovery from anesthesia, without detrimental cardiopulmonary changes. STUDY DESIGN: Randomized, blinded experimental trial. ANIMALS: Seven healthy adult horses aged 6.4 +/- 1.9 years and weighing 506 +/- 30 kg. METHODS: Horses were anesthetized twice, at least 1 week apart. On both occasions, anesthesia was induced by the administration of XYL, diazepam, and KET, and maintained with isoflurane for approximately 90 minutes, the last 60 minutes of which were under steady-state conditions (1.2 times the minimum alveolar concentration isoflurane). On one occasion, horses were allowed to recover from isoflurane anesthesia, while on the other, XYL and KET were infused for 30 minutes after termination of isoflurane administration. Heart rate, respiratory rate, arterial blood pressure, pH, and blood-gases were measured and recorded at set intervals during steady-state isoflurane anesthesia and XYL-KET infusion. Recovery events were timed and subjectively scored by one nonblinded and two blinded observers. Data were analyzed using a restricted maximum likelihood-based mixed effect model repeated measures analysis. RESULTS: Infusion of XYL and KET resulted in longer recovery times, but there was no significant improvement in recovery quality score. CONCLUSIONS: Under the conditions of this study, infusion of XYL and KET does not positively influence recovery from isoflurane anesthesia in horses. CLINICAL RELEVANCE: This study does not support the routine use of XYL and KET infusions in horses during the transition from isoflurane anesthesia to recovery.     

The use of pulsed electromagnetic field (PEMF) therapy to provide post-operative analgesia in the dog

Buprenorphine is an effective analgesic when administered epidurally to humans. The purpose of this study was to compare epidural buprenorphine (B; n = 10) with epidural morphine (M; n = 10) for post‐operative analgesia in dogs undergoing cranial cruciate ligament repair. All dogs were premedicated with acepromazine (0.1 mg kg^?1 IM), induced with propofol (4–6 mg kg^?1 IV) and maintained with halothane in oxygen. Dogs were randomly assigned to receive B (0.004 mg kg^?1) or M (0.1 mg kg^?1) in the lumbosacral epidural space in a total volume of 0.2 mL kg^?1. End‐tidal halothane and CO₂ and temperature were recorded every 15 minutes until extubation (t = 0). A numerical rating pain score (SPS) was recorded at t = 0, 1, 2, 4, 6, 10 and 24 hours by a blinded observer. Dogs received rescue morphine (1.0 mg kg^?1 IM) if indicated by SPS and the time of rescue analgesic administration was recorded. Observable side‐effects such as urinary retention, sedation or pruritus were recorded. Data were analyzed with repeated measures anova . Mean ± SD body weight (kg) and age (yrs) for B dogs was 34.2 ± 10.8 and 5.5 ± 2.8; for M dogs these values were 36.6 ± 13.5 and 5.9 ± 3.3. Mean ± SD SPS for B dogs at t = 0, 1, 2, 4, 6, 10 and 24 hours were 1.2 ± 0.75, 3.2 ± 2.0, 4.5 ± 4.3, 4.6 ± 3.4, 4.7 ± 3.0, 5.0 ± 4.9 and 5.1 ± 3.5. For M dogs these values were 1.7 ± 0.5, 2.6 ± 2.0, 3.7 ± 0.75, 4.2 ± 2.2, 4.1 ± 3.0, 3.1 ± 2.1 and 3.9 ± 1.9. There were no significant differences between B and M with respect to SPS, times or frequency of rescue morphine administration, end‐tidal halothane and CO₂, or esophageal temperature. Fifty per cent of dogs in both groups required rescue morphine. Buprenorphine is as effective as morphine for epidural analgesia in healthy dogs undergoing hindlimb orthopedic surgery.     

Conventional and contemporary approaches for drought tolerance rice breeding: Progress and prospects

Drought is becoming a major threat to rice farming across the globe owing to the depletion of water tables in rice-growing belts. Drought affects rice plants at multiple stages, causing damage at morphological and physio-biochemical levels, leading to severe losses that exceed losses from all other stresses. The amalgamation of conventional breeding methods with modern molecular biology tools and biometrical methods could help accelerate the genetic gain for drought tolerance in rice. Many drought-tolerance traits with genetic determinants have been identified and exploited for tolerance rice variety breeding. The integration of genome-wide association study and genomic selection tools with speed breeding shortened the breeding cycle and aided in rapid improvement of genetic gain. In this review, we emphasized the progress made through classical breeding as well as the limitations and usefulness of current genomic methods in improving drought tolerance. We briefly addressed methods for identifying genetic determinants for drought tolerance and deploying them through genomics-assisted breeding programmes to develop high-yielding drought-tolerant rice cultivars.