The effects of age, isoflurane and sevoflurane on atracurium in lambs

ObjectiveTo determine the effects of age, sevoflurane and isoflurane on atracurium-induced neuromuscular blockade in 3–16 week-old lambs.Study designProspective randomized experimental trial.AnimalsTwenty-six Scottish blackface ewe-lambs were anaesthetized for spinal surgery when either 3–6 (mean age 4.6 weeks; n = 18) or 12–16 weeks (mean age 13.7 weeks; n = 15) of age; seven animals were anaesthetized at both ages.MethodsAfter intramuscular injection of medetomidine (10 μg kg^?1) anaesthesia was induced in the younger lambs either with isoflurane or sevoflurane in oxygen delivered by mask, and in the older lambs with ketamine (4 mg kg^?1), and midazolam (0.2 mg kg^?1) administered intravenously (IV). In both groups anaesthesia was maintained with fixed end-tidal concentrations of either sevoflurane (2.8%) or isoflurane (1.8%) delivered in oxygen. Before surgery meloxicam (0.6 mg kg^?1), morphine (0.5 mg kg^?1) and ketamine (1 mg kg^?1 followed by 10 μg kg^?1 minute^?1) were administered IV. The lungs were ventilated mechanically to maintain normocapnia. Neuromuscular block was achieved with a loading dose (LD) of atracurium (0.5 mg kg^?1 IV). The peroneal nerve was stimulated (train-of-four every 12 seconds). Evoked responses in the digital extensor muscles were evaluated by palpation and observation. Maintenance doses (MD) of atracurium (0.17 mg kg^?1 IV) were administered when the first twitch (T1) returned. The onset and duration of LD action (T1 absent) and the duration of MD were recorded. Data were analysed using Student's t test, Mann–Whitney U test, repeated–measures anova, Wilcoxon's matched pairs test or Pearson correlation coefficient as relevant (p < 0.05).ResultsOnset of LD action developed significantly (p < 0.05) more rapidly in isoflurane compared with sevoflurane-anaesthetized lambs (55 ± 18 cf. 80 ± 37 seconds). Duration of action of LDs and MDs was longer (p < 0.05) in lambs aged 12–16 than 3–6 weeks (33 ± 5.4 cf. 25 ± 6.4 and 26 ± 4.2 cf. 18 ± 5.5 minutes) but were independent of the anaesthetic used.Conclusions and clinical relevanceThe effect of atracurium is age-dependent in lambs being prolonged in older animals. The onset of neuromuscular blockade is more rapid in isoflurane compared with sevoflurane-anaesthetized lambs.     

Second Oestrus Synchronization and Precocious Embryo Viability after Puberty Induction in Gilts by the Use of Gonadotrophin Treatment

The use of exogenous gonadotrophins in puberty inducement and ovulation synchronization is a technique that has a positive influence on the management of swine. The purpose of this study was to verify the effects of a second gonadotrophin treatment [equine chorionic gonadotrophin (eCG) and luteinizing hormone (LH), intramuscularly (i.m.)] upon the second oestrus synchronization and fertility in gilts. Seventy-one NAIMA (Pen Ar Lan) gilts had their first oestrus (puberty inducement) induced by a hormonal treatment (eCG and LH). Then, they were randomly distributed into two treatments, with (T1) and without (C) gonadotrophin treatment at the second oestrus. The animals were fed with a single ration (16% of crude protein and 3286.73 kcal ME/kg), and timed artificial insemination performed at the second oestrus. Gilts were slaughtered for embryo recovery and ovary examination about 5 days after insemination. There was no evidence of a difference in the percentage of the second oestrus expression (T1 - 90.90% and C - 86.84%), the duration of the oestrus cycle (T1 - 19.62 +/- 0.82 days and C - 19.67 +/- 4.14 days), the percentage of follicular cysts (T1 - 15.15% and C - 18.42%) and number of ovulations (T1 - 14.60 +/- 5.7 and C - 13.23 +/- 4.8) between treatments (p > 0.05). However, the hormonal treatment (T1) showed minor oestrus dispersion and embryo viability (T1 - 8.4 +/- 5.6 and C - 11.2 +/- 4.6) (p < 0.05). These results indicate that the better synchronization and expression of the second oestrus when using gonadotrophins (eCG and LH) is followed by a lower embryo viability, which is probably the consequence of the heterogeneous follicle recruitment during the injection of eCG.     

Relative resistance of Dorper crossbred ewes to gastrointestinal nematode infection compared with St. Croix and Katahdin ewes in the southeastern United States

A study was conducted to evaluate relative resistance of Dorper crossbred (DO), Katahdin (KA), St. Croix (SC), and Hampshire (HA) ewes to natural and experimental gastro-intestinal (GI) nematode infection over a 20-month period. The objective of Experiment 1 was to evaluate breeds for resistance to infection acquired naturally from mixed grass pastures. In Year 1 (May-December 2000) de-worming of ewes occurred during wet, hot conditions in July and during late pregnancy in December. In Year 2 (January-December 2001), ewes were de-wormed after fecal egg count (FEC) for a breed group rose above 1000 eggs per gram (epg) or after blood packed cell volume (PCV) of an individual ewe fell below 20. FEC was determined every 28 days and PCV every 14-28 days. In both the years, ewes were pastured together, except during the 28-days breeding periods, on tall fescue, bermudagrass, or ryegrass, and rotated among pastures dependent on forage availability. Ewes were in good or excellent condition (body condition score of 3-4 out of 5) throughout the study. The objective of Experiment 2 was to evaluate the breeds for relative resistance to an experimental infection with Haemonchus contortus infective larvae. Both PCV and FEC were determined every 7 days from 14 to 42 days after inoculation with 30000 infective larvae per ewe. In Experiment 1, Year 1, FEC was slightly greater and PCV was lower from July to September in DO ewes (breed x time, P<0.001). In Year 2, de-worming occurred 14 days later in DO ewes compared with other breed types. Otherwise PCV and FEC were similar among the hair breeds and higher and lower, respectively, compared with HA ewes (breed x time, P<0.001). In Experiment 2, FEC and PCV were similar among hair breeds; FEC was lower and PCV higher in hair breeds compared with that of HA ewes (P<0.01). Relative resistance of mature Dorper crossbred ewes was comparable to that of Katahdin and St. Croix ewes and superior to that of Hampshire ewes.     

对兽药地方标准清理工作的思考

当前兽药地方标准清理工作已进入攻关阶段,但在清理地方标准的实际工作中尚存在一些问题,笔者分析了这些具体问题,认为在升标工作中,政府应当给予合理的政策扶持,加快地方标准清理工作进度,保护企业利益;企业应当着重做好品种筛选,合理安排临床试验资金投入;企业通过采取联合参与升标方式,减少资金投入;对于移植外省标准,可采取不同措施妥善解决;为保证升标工作顺利进行,农业部和各省兽医行政管理部门应做好升标培训指导工作.     

Use of FAMACHA system to evaluate gastrointestinal nematode resistance/resilience in offspring of stud rams

High levels of anthelmintic resistance in gastrointestinal nematodes (GIN) of small ruminants have created the need for animals with greater resistance to these parasites. The objective of this experiment was to evaluate the effectiveness of the FAMACHA system in identification of parasite resilient/resistant offspring, and thus identification of stud rams with greater resilience/resistance. Katahdin ewes bred in separate groups to two sires to lamb in spring (2004, 2005: Ram A and Ram B; 2006, 2007: Ram C and Ram D) at the USDA, Agricultural Research Station in Booneville, Arkansas produced 20-40 offspring/sire each year. Ewes and lambs grazed mixed grass (predominantly bermudagrass and ryegrass) pastures and were supplemented with corn/soybean meal between 30 days pre- and 60 days post-lambing (ewes) and starting 45 days of age until weaning (lambs; 95.0+/-0.6 days of age). Blood samples and feces were collected from the lambs to determine blood packed cell volume (PCV) and fecal egg counts (FEC) and FAMACHA scores were determined at 90, 120, and 150 days of age. Lambs were dewormed if anemic (PCV<19% or FAMACHA score >2) and data removed within 30 days after deworming. Data were analyzed for the 2004/2005 and 2006/2007 groups using general linear models with year, sex of lamb, and sire nested within year as variables. Sire differences were detected (P<0.05 or less) for PCV and FAMACHA at all time points, but not FEC. There tended (P<0.10) to be sire differences for FEC at 90 and 120 days of age, but not at 150 days of age. Lambs sired by Ram D were dewormed less by 150 days of age than those sired by Ram C. The FAMACHA system can be used to identify superior sires for parasite resilience/resistance, thus increasing flock resilience, and perhaps resistance.     

Associations between fungal and abiotic leaf spotting and the presence of mlo alleles in barley

The hypothesis that the increased use of the powdery mildew-resistance gene mlo has caused the increase in spotting diseases of barley over the past 20 years was tested in field trials. Near-isogenic lines with alleles of the Mlo gene for susceptibility or resistance to mildew in two parental backgrounds were trialled at four sites in Scotland and two in Ireland that were prone to spotting diseases, over 3 consecutive years. Mildew was controlled by sprays with quinoxyfen. Disease levels were low in the trials, the two most important diseases being scald caused by Rhynchosporium secalis and ramularia leaf spot caused by Ramularia collo-cygni . There were high levels of abiotic spotting. Lines with mutant mlo alleles consistently developed less Rh. secalis and Ra. collo-cygni , but more abiotic spots. This study indicates that the mlo mildew-resistance gene has not alone been responsible for the rise in spotting diseases over the past 20 years. Possible reasons for the rise are discussed, including the interaction of the mlo gene with the environment.     

Primary afferent depolarization evoked by a painful stimulus

Pulses of intense radiant heat applied to the plantar pad of unanesthetized spinal cats produced negative dorsal root potentials, increased excitability of cutaneous A fibers, and marked activation of ipsilateral flexor motoneurons. The same effects were obtained during cold block of A fiber conduction in the appropriate peripheral nerve. We conclude that adequate noxious activation of cutaneous C fibers depolarizes cutaneous A fibers.