大蒜素及其在畜禽生产中的应用进展

大蒜素是一种绿色环保药物和环保型绿色饲料添加剂,在畜禽养殖中应用十分广泛.本文综述了大蒜素的化学成分和理化特性、功能特点及其在畜禽养殖中的应用情况,并对其应用前景作了分析.     

Use of a transdermal matrix patch of buprenorphine in cats: preliminary pharmacokinetic and pharmacodynamic data

Six domestic shorthair cats, aged three to four years and weighing 5.1 to 7.4 kg, were used to assess the thermal antinociceptive effect of a transdermal buprenorphine patch, designed to supply 35 mug buprenorphine/hour, which was applied to the shaved thorax. The cats' thermal thresholds were tested before the patch was applied and two, four, six, eight, 10, 12, 14 and 16 hours after it had been applied, and then every six hours until it was removed after 72 hours, and for a further 24 hours afterwards. Blood was collected at each time to measure the plasma concentration of buprenorphine. The patches did not produce a significant change in the thermal thresholds of the cats throughout the testing period. The mean (sd) peak plasma buprenorphine concentration was 10 (0.81) ng/ml.     

Effects of intravenous lidocaine on the minimum alveolar concentration of isoflurane in cats

Lidocaine has been reported to decrease the minimum alveolar concentration (MAC) of inhalation anesthetics in several species and has been used clinically to reduce the requirements for other anesthetic drugs. This study examined the effects of intravenous lidocaine on isoflurane MAC in cats. Six cats were studied. In experiment 1, the MAC of isoflurane was determined. An intravenous bolus of lidocaine 2 mg kg^–1 was then administrated and venous plasma lidocaine concentrations measured to determine pharmacokinetic values. In experiment 2, lidocaine was administered to achieve target plasma concentrations between 1 and 11 μg mL^–1 and the MAC of isoflurane was determined in triplicate at each lidocaine plasma concentration, using the tail‐clamp method. End‐tidal isoflurane concentration was determined using a calibrated infrared analyzer. Systolic blood pressure (Doppler), SpO2 and end‐tidal PCO2 (calibrated Raman spectrometer) were measured prior to each MAC determination. Body temperature was maintained between 38.5 and 39.5 °C by supplying external heat as needed. MAC values at the different lidocaine plasma concentrations were analyzed by a repeated measures ANOVA , using the Huynh–Feldt correction. The MAC of isoflurane in these cats was 2.21 ± 0.17. For the target concentrations of 1, 3, 5, 7, 9, and 11 μg mL^–1, the actual lidocaine plasma concentrations was 1.06 ± 0.12, 2.83 ±0.39, 4.93 ± 0.64, 6.86 ± 0.97, 8.86 ± 2.10, and 9.84 ± 1.34 μg mL^–1, respectively. At these target concentrations, the MAC of isoflurane was 2.14 ± 0.14, 1.88 ± 0.18, 1.66 ± 0.16, 1.47 ±0.13, 1.33 ± 0.23, and 1.06 ± 0.19%, respectively. Lidocaine, at target plasma concentrations of 1, 3, 5, 7, 9, and 11 μg mL^–1, linearly decreased isoflurane MAC by –6 to 6, 7 to 28, 19 to 35, 28 to 45, 29 to 53, and 44 to 59%, respectively. Lidocaine significantly dose‐dependently and linearly decreases the requirements for isoflurane in cats. No ceiling effect was observed within the range of plasma concentrations studied.     

Suspected albuterol toxicosis in a dog

CASE DESCRIPTION: A 6-year-old male castrated Shetland Sheepdog was evaluated because of severe hypokalemia and progressive paresis. CLINICAL FINDINGS: Physical examination revealed fever, tachypnea, mydriasis, hyperemic mucous membranes, severe forelimb paresis, and hind limb paraplegia. The dog had superficial and deep pain sensation in all 4 limbs. Forelimb spinal reflexes were considered normal, but hind limb reflexes were normal to slightly hyperreflexive. The panniculus reflex was considered to be normal, and cranial nerve reflexes were intact. A CBC revealed mild leukocytosis and erythrocytosis, and serum biochemical analysis revealed severe hypokalemia. Thoracic and abdominal imaging did not reveal relevant findings. Blood pressure and ECG findings were within reference limits. Questioning of the owner revealed possible exposure to albuterol via ingestion of medication intended for the owner's horse. Results of serum testing via immunoassay were suggestive of albuterol toxicosis. TREATMENT AND OUTCOME: Treatment included IV administration of an electrolyte solution and supplemental potassium chloride. The rate of potassium chloride supplementation was slowly decreased as serum potassium concentration increased. No other medical intervention was required, and the dog made a rapid and complete recovery. CLINICAL RELEVANCE: Ingestion of albuterol can lead to profound physical and serum biochemical abnormalities. Appropriate historical information should be obtained to identify possible sources and routes of exposure to intoxicants. Albuterol-induced hypokalemia can be successfully managed medically.     

The climatic potential for beef cattle production in tropical Australia: Part II— liveweight change in relation to agroclimatic variables

Part I of this series demonstrated a method of simulating a ‘green season’ and a ‘dry season’ which corresponded closely to the main period of liveweight gain and loss respectively of cattle on native grass pastures. This paper attempts to further characterise these seasons, using agro-climatic variables derived from a weekly pasture growth index, as to their quantitative relation to cattle liveweight changes. Neither the duration of the green season nor the variable most closely related to cumulative pasture growth (‘growth weeks’) accounted for much of the variation in amount of gain in the green season. In the dry season, however, the amount of liveweight loss was closely related to the estimated number of weeks without green feed (‘dry weeks’). Extraordinary weight loss in the dry season occurred in the years with few growth weeks in the green season, indicating pasture quantity as well as quality limitations in dry season nutrition in these years. In comparison to the green season, marginal response in liveweight to additional green weeks was over two times as great when cumulated over an entire year; this suggests that the main benefit of prolonging the green season is its effect in shortening the dry season.The problem of generalising from the very few stations with cattle data is discussed.     

The climatic potential for beef cattle production in tropical Australia: Part IV— variation in seasonal and annual productivity

In Part II liveweight loss in the dry season was found in most years to be closely related to cumulative ‘dry weeks’; extraordinary weight loss occurred in the dry season in years in which there were a low number of ‘growth weeks’ in the previous green season. Annual liveweight gain was related to the total number of ‘green weeks’. In this paper the geographic variation in these three agro-climatic parameters is described using a network of 77 stations across northern Australia, and the year-to-year variability is examined for eight representative stations.Variation in dry season severity was greater than variation in green season productivity (growth weeks). Median ‘dry weeks’ in the dry season varied from 29 to nil over the area. ‘Green weeks’ in the dry season as a result of winter rain is an important phenomenon in a relatively small part of the area, but in this area year-to-year variability is extremely high.It is concluded that the objectives of the study, to extend existing agro-climatic methodology to interface with cattle production and to use this in surveying the climatic potential for this form of land use over the entire tropical region of Australia, were achieved to the extent that the existing animal production data allow.     

Effect of production temperature of seed potatoes on subsequent yielding potential

A two year experiment was conducted to test if the temperature environment under which seed potatoes are produced significantly affects the tuber development and yield of the resultant potato plants. Six temperature regimes were established in the controlled facility of the Biotron. Two generations ofSolanum tuberosum ‘Kennebec’ tubers were grown in these environments and the yielding ability of plants produced from these tubers was tested in greenhouse facilities. Plant growth and tuber yields were similar to those which might be expected under field conditions, and marked differences in the development and productivity as a result of the production environment of the seed tubers were apparent. However, no evidence was found to support the contention that seed potatoes originating from cooler environments had any increased potential to produce higher yielding plants than comparable seed from warm environments. Even within a generation, the highest yields were found in the warmest environments, somewhat modifying the concept that the potato is strictly a cool-season crop. Other possible non-pathogenic explanations for previously observed differences in seed quality as a result of the production environment are discussed.     

Environment. Sustainable development of the agricultural bio-economy

A U.S. farm policy shift to joint production of commodities and ecological services will advance sustainable agriculture.     

Quantitative characteristics of anesthetic induction with and recovery from isoflurane and sevoflurane in cats

Isoflurane (ISO) is the most commonly administered feline inhalant anesthetic in North America. A newer agent, sevoflurane (SEVO), may provide faster induction and recovery from anesthesia based on its physical characteristics. Accordingly, we compared some induction and recovery characteristics of ISO and SEVO in healthy cats. Six female DSH cats (17.9 ± 9.0 (mean ± SD) months, 3.7 ± 0.3 kg) received four randomly assigned treatments: ISO for 1 hour (IS), SEVO for 1 hour (SS), ISO for 5 hours (IL), and SEVO for 5 hours (SL). Anesthesia was induced in a chamber into which ISO or SEVO was delivered at 2.7 times the individual's MAC (determined previously) in 6 L minute^?1 O₂. Measured (Rascal II, Ohmeda) anesthetic concentration was reported after correction using a multiple gas, standard‐defined calibration curve. For induction, time (seconds) from introduction of inhalant to onset of incoordinated movement (IM), recumbency with movement (RM), recumbency without movement, loss of pedal reflex (PD), and intubation (ET) were recorded. Following intubation, anesthesia was maintained for the required time at 1.25 times the individual's MAC. For recovery, time (seconds) from discontinuation of the inhalant (with continuation of O₂) to first movement, extubation (EXT), start of incoordinated movement, head‐lift, sternal recumbency (SR), crawl, stand/walk with incoordination, and jump without incoordination were recorded. Esophageal normothermia was maintained. Data were analyzed by paired t‐test (induction) or One‐way Repeated Measures anova followed, when appropriate, by Tukey's test (recovery). p < 0.05 was regarded as significant. For induction, IM was not significantly different between ISO and SEVO (118 ± 28 seconds vs. 104 ± 28 seconds). All other induction times were significantly shorter with SEVO vs. ISO, e.g. RM (181 ± 31 seconds vs. 213 ± 31 seconds), PD (426 ± 68 seconds vs. 504 ± 70 seconds), and ET (434 ± 66 seconds vs. 515 ± 69 seconds). For recovery, there were no differences between ISO and SEVO for any stage of recovery, e.g. EXT (IS 588 ± 163 seconds vs. SS 425 ± 109 seconds), SR (IS 735 ± 215 seconds vs. SS 655 ± 337 seconds), and IL (710 ± 658 seconds vs. SL 807 ± 465 seconds). We concluded that quantitative recovery characteristics did not depend on whether cats are anesthetized with equipotent amounts of SEVO or ISO, but some induction end‐points were reached more quickly with SEVO.