Factors affecting pregnancy rate in Holstein-Friesian cattle mated during summer in a tropical upland environment   总被引：1，自引：0，他引：1  

WN ORR  RT COWAN  TM DAVISON 《Australian veterinary journal》1993,70(7):251-256

SUMMARY The relationships between some environmental factors and reproductive rates of dairy cattle during summer in a tropical upland area were studied using records for Holstein-Frieslan milking cows and non-lactating growing helfers maintained at the Kalri Research Station on the Atherton Tableland in north Queensland. The Station is situated in a tropical upland environment with warm, wet summers and dry, cool winters. Data were collected over a 12-year-period (1977 to 1988) for cows grazing nitrogen (N)-fertilised grass pastures and receiving either no supplement or about 3.5 kg molasses/cow/day. Cattle were mated over a 10-week period starting from mid-January to early February, with 32 to 36 cows and 5 to 42 heifers used in each year. There was considerable variation among years in the pregnancy rate after 3 Inseminations, with a low of 39% and a high of 94% pregnancy. This variation from year to year was reduced for cows grazing pastures receiving 300 kg N/ha/yr after molasses feeding commenced in 1984–85. Pregnancy rates after molasses Introduction were higher for cows grazing pastures receiving 300 compared with 100 kg N/ha/yr. Pregnancy rate in cows and heifers was reduced from 80 to 55% as mean daily maximum temperature increased from 26°C to 27.5°C. At mean maximum temperatures above 27°C for cows and 27.6°C for heifers pregnancy rates to 3 Inseminations were consistently below 60%. Much of the year to year variation in pregnancy rate was related to rainfall during the mating period. There was a positive association between pregnancy rate and rainfall up to 1000 mm, and this was associated with differences in growth rate of pasture. In years of very high rainfall, above 1500 mm, there was a depression in pregnancy rate, which may be related to the intense humidity in very wet years causing heat stress in cows and associated problems such as feet infections, or a deterioration in pasture quality. We conclude that much of the variation in pregnancy rate during summer may have been related to heat stress and the level of feed supply in the form of pasture and supplements.  相似文献   

Cardiopulmonary effects of romifidine/ketamine or xylazine/ketamine when used for short duration anesthesia in the horse          下载免费PDF全文

Carolyn L. Kerr  Wayne N. McDonell    Simon S. Young 《Canadian journal of veterinary research》2004,68(4):274-282

The cardiovascular changes associated with anesthesia induced and maintained with romifidine/ketamine versus xylazine/ ketamine were compared using 6 horses in a cross over design. Anesthesia was induced and maintained with romifidine (100 microg/kg, IV)/ketamine (2.0 mg/kg, IV) and ketamine (0.1 mg/kg/min, IV), respectively, in horses assigned to the romifidine/ ketamine group. Horses assigned to the xylazine/ketamine group had anesthesia induced and maintained with xylazine (1.0 mg/kg, IV)/ketamine (2.0 mg/kg, IV) and a combination of xylazine (0.05 mg/kg/min, IV) and ketamine (0.1 mg/kg/min, IV), respectively. Cardiopulmonary variables were measured at intervals up to 40 min after induction. All horses showed effective sedation following intravenous romifidine or xylazine and achieved recumbency after ketamine administration. There were no significant differences between groups in heart rate, arterial oxygen partial pressures, arterial carbon dioxide partial pressures, cardiac index, stroke index, oxygen delivery, oxygen utilization, systemic vascular resistance, left ventricular work, or any of the measured systemic arterial blood pressures. Cardiac index and left ventricular work fell significantly from baseline while systemic vascular resistance increased from baseline in both groups. The oxygen utilization ratio was higher in the xylazine group at 5 and 15 min after induction. In conclusion, the combination of romifidine/ketamine results in similar cardiopulmonary alterations as a xylazine/ketamine regime, and is a suitable alternative for clinical anesthesia of the horse from a cardiopulmonary viewpoint.  相似文献   

The clinical diagnosis of shock     

W McDonell 《The Journal of small animal practice》1974,15(5):293-301

Shock may be initiated by cardiac failure, hypovolaemia, or a primary change in peripheral resistance or venous capacitance vessels. Most of the clinical signs of shock occur as a result of sympatho-adrenal stimulation and peripheral tissue anoxia. Typically animals show an altered level of consciousness, tachycardia, poor peripheral perfusion (shown by a prolonged capillary refilling time) and poor organ perfusion (shown by oliguria). Cardiogenic shock is characterized by a fixed low cardiac output, hypotension, increased systemic resistance and an elevated central venous pressure. With hypovolaemic shock, central venous pressure, cardiac output and blood pressure fall while systemic resistance increases. Vasculogenic shock presents a varied clinical picture and there may be evidence of vasodilatation or vasoconstriction in mucous membranes. The haematocrit rises and there is rapid development of a marked metabolic acidosis. Résumé. Un choc peut s'indiquer par un arrêt du caeur, une hypovolémie, ou un changement primaire dans la résistance capillaire ou la capacité veineuse. La plupart des manifestations cliniques de choc se produisant comme résultat d'une stimulation sympatho-surrénale et d'une anoxie des tissus périphériques. D'une manière typique, on note chez les animaux un niveau alteré de toute leur connaissance, une tachycardie, une faible perfusion périphérique (indiquée par un temps prolongé de remplissage capillaire) et une faible perfusion des organes (indiquée par une uropénie). Un choc cardiogène se caractérise par un fonctionnement cardiaque fixe et au ralenti, une hypotension, une résistance accrue du système et une pression veineuse élevée et centrale. Avec un choc hypovolémique, la pression veineuse centrale, le fonctionnement cardiaque et la tension baissent tandis que la résistance du système s'accroît. Le choc vasculogène présente un ensemble varié de protocoles d'observation et il peut y avoir évidence de vasodilatation ou de vasoconstriction dans les membranes muqueuses. L'hématocrite s'élève et une acidose métabolique marquée se développe rapidement. Zusammenfassung. Schock kann sich in Herzschlag, Hypovolämie oder in einer primären Änderung im Kapillanviderstand oder in venöser Kapazität zeigen. Die meisten klinischen Anzeichen von Schock erscheinen als das Ergebnis von sympatho-adrenaler Stimulation und peripher Gewebeanoxie. Es ist typisch, dass die Tiere ein verändertes Mass von Bewusstsein, Tachykardie, schlechte periphere Perfusion, die sich in einer verlängerten kapillären Füllungszeit und schlechter Organperfusion, wie Oligurie, zeigen. Kardiogenischer Schock ist charakterisiert in starrem niedrigem Herzausstoss, Hypotonie, zunehmender systemischer Resistanz und einem erhöhtem zentralem venösem Druck. Mit hypovolämischen Schock fallen zentraler venöser Druck, Herzausstoss und Blutdruck, während systemische Resistanz zunimmt. Vaskulogenischer Schock stellt ein verschiedenes klinisches Bild dar und Gefässerweiterung oder Gefässverengerungen könnten sich beweisen. Der Hämatokrit steigt und es gibt eine rapide Entwickling von einer gekenntzeichneten metabolischen Acidose.  相似文献   

The effect of glycopyrrolate on heart rate and intestinal motility in conscious horses   总被引：1，自引：1，他引：0  

S. Singh  W. McDonell  S. Young  D. Dyson 《Veterinary anaesthesia and analgesia》1997,24(1):14-19

Glycopyrrolate (GLY) is a synthetic quaternary ammonium anticholinergic compound which offers a number of advantages over atropine, including less arrhythmogenic influence and lack of significant effect upon the central nervous system, eyes and foetus. Five healthy horses (7.4 ± 2.2 years, 462 ± 31.7 kg) were administered 2.5, 5 and 10 μg/kg doses of GLY iv in a randomised and blinded manner with at least 48 h between treatments. The electrocardiogram and heart rate were recorded on an oscilloscopic and chart recorder while gastrointestinal (GIT) motility was assessed by auscultation of 4 abdominal quadrants, assigning a subjective score from 0 (no motility) to 4 (normal motility). Heart rate, which was observed at baseline, 2, 5, 10, 15, 30 min, and 1, 2, 3, 4, 6, 9, 12, 18 and 24 h post GLY, revealed no change with the 2.5 μg/kg dose, and an increase with 5 μg/kg (59%) and 10 μg/kg (109%) for up to 1 h. The 2.5 and 5 μg/kg doses did not prevent the development of second degree atrioventricular block in some horses for up to 15 min, while the 10 μg/kg dose eliminated any pre-existing block within 5 min. There was a complete loss of GIT motility with the 5 and 10 μg/kg doses and partial loss with the 2.5 μg/kg dose. Subsequent return of motility was apparently dose-dependent with 50% of baseline motility score returning in 2.4, 6.4 and 11.5 h with 2.5, 5 and 10 μg/kg doses, respectively. Two horses receiving a 10 μg/kg dose developed abdominal discomfort. Passage of faeces and appetite were not significantly different with any dose. Glycopyrrolate did not induce any change in the pupillary response to a light source at any stage of observation. The results of this study indicate that 5 μg/kg induces a reasonable increase in heart rate without affecting GIT motility for an excessive length of time in awake, healthy, adult, unsedated horses.  相似文献   

Unilateral congenital elbow luxation in a Cavalier King Charles Spaniel          下载免费PDF全文

McDonell HL 《The Canadian veterinary journal. La revue veterinaire canadienne》2004,45(11):941-943

A 7-week-old, intact female, Cavalier King Charles Spaniel was evaluated for nonweight bearing lameness of the right forelimb. Type III unilateral congenital elbow luxation was diagnosed radiographically. After surgical reduction, temporary placement of a transarticular pin, and external splinting of the joint, full weight bearing was achieved. Radial head subluxation persisted.  相似文献   

Simple nonrebreathing valves for use with large mammals.   总被引：4，自引：4，他引：0       下载免费PDF全文

G J Gallivan  W Bignell  W N McDonell    T L Whiting 《Canadian journal of veterinary research》1989,53(2):143-146

Two simple nonrebreathing valves suitable for use with large mammals are described. These valves can be constructed in a reasonably well equipped workshop using materials that are readily available. The resistive pressure of both valves is less than 0.1 kPa at flow rates up to 15 L.s-1. Their main limitation is a relatively large dead space, although the dead space of valve B (290 mL) is less than the dead space of some commercially available valves. Healthy adult horses and cows compensate for the increased dead space by an increase in tidal volume.  相似文献   

The rapid and effective administration of a beta 2-agonist to horses with heaves using a compact inhalation device and metered-dose inhalers.          下载免费PDF全文

D B Tesarowski  L Viel  W N McDonell    M T Newhouse 《The Canadian veterinary journal. La revue veterinaire canadienne》1994,35(3):170-173

The purpose of the study was to administer therapeutic aerosol generated by metered-dose inhalers to horses exhibiting clinical signs of heaves using a compact inhalation device developed for human medicine. It was fitted to a custom face mask in order to study the effect of an inhaled beta 2-agonist, fenoterol. Pulmonary function testing was performed on six horses following an acute exacerbation of heaves, characterized by tachypnea, wheezes, crackles, and spasmodic cough. Horses inhaled fenoterol in 1 mg increments administered as one 200 microgram puff every 5-10 s with the recording of data 5 min after the cessation of drug inhalation. A significant effect of fenoterol was shown for maximum change in transpulmonary pressure, dynamic compliance, lung resistance, and work of breathing, and the wheezes and crackles disappeared when auscultation was performed at the end of the test. This study demonstrates a novel, highly effective method for the rapid administration of inhaled medication in horses.  相似文献   

An evaluation of the influence of medetomidine hydrochloride and atipamezole hydrochloride on the arrhythmogenic dose of epinephrine in dogs during halothane anesthesia.   总被引：2，自引：2，他引：0       下载免费PDF全文

G R Pettifer  D H Dyson    W N McDonell 《Canadian journal of veterinary research》1996,60(1):1-6

Alterations in the arrhythmogenic dose of epinephrine (ADE) were determined following administration of medetomidine hydrochloride (750 micrograms/M2) and a saline placebo, or medetomidine hydrochloride (750 micrograms/M2), followed by specific medetomidine reversal agent, atipamezole hydrochloride (50 micrograms/kg) 20 min later, in halothane-anesthetized dogs (n = 6). ADE determinations were made prior to the administration of either treatment, 20 min and 4 h following medetomidine/saline or medetomidine/atipamezole administration. Epinephrine was infused for 3 min at increasing dose rates (2.5 and 5.0 micrograms/kg/min) until the arrhythmia criterion (4 or more intermittent or continuous premature ventricular contractions) was reached. The interinfusion interval was 20 min. There were no significant differences in the amount of epinephrine required to reach the arrhythmia criterion following the administration of either treatment. In addition, the ADE at each determination was not different between treatment groups. In this study, the administration of medetomidine to halothane-anesthetized dogs did not alter their arrhythmogenic response to infused epinephrine.  相似文献   

Cardiorespiratory effects of a 5HT2 antagonist (R51703) in awake and anesthetized dogs.          下载免费PDF全文

T J Doherty  W N McDonell  D H Dyson  W D Black 《Canadian journal of veterinary research》1996,60(3):172-178

To investigate cardiorespiratory effects of an experimental 5-hydroxytryptamine receptor antagonist (R51703) with sedative properties, intramuscular doses of the drug were studied in 6 awake dogs of mixed breed, and in 6 anesthetized beagles. Two doses (0.2 and 0.4 mg/kg) of R51703 and a saline control were studied in the awake dogs using a randomized crossover trial. Subsequently, the higher dose of R51703 was included as a component of halothane anesthesia to determine whether the halothane sparing effect of R51703 produced a beneficial alteration of hemodynamic function. Data were obtained at equipotent halothane/R51703 (H/R) and halothane/saline (H/S) doses equivalent to 1.0, 1.5 and 2.0 MAC. In awake dogs, heart rates tended to be lower in dogs sedated with R51703, significantly so at 30 min for both doses, and at 90 and 120 min for the 0.2 and 0.4 mg/kg doses, respectively (P < 0.05). The cardiac index (CI) was lower at 60 min with both doses compared to the saline control group. Both doses of R51703 reduced mean blood pressure at 30, 90 and 120 min, and diastolic pressure at 30 and 90 min after administration; however, systolic blood pressure (SBP) was not altered. Overall, the cardiovascular alterations were minimal in conscious dogs and there was no evidence of respiratory depression. In the anesthetized dogs, at equipotent MAC, CI tended to be lower with H/R than with H/S, though the difference was not significant. Heart rate and stroke volume index also tended to be lower in the dogs treated with R51703, while systemic vascular resistance tended to be higher: these changes were not significant. Mean and SBP were higher at each MAC multiple in the H/R group. It was concluded that the halothane sparing effect of R51703 did not substantially improve hemodynamic function compared to the use of halothane alone at equipotent doses.  相似文献   

Effects of aerosolized histamine and carbachol in the conscious horse.          下载免费PDF全文

K B Mirbahar  W N McDonell  W Bignell    P Eyre 《Canadian journal of veterinary research》1985,49(2):211-218

Pulmonary function tests were performed in seven conscious, standing horses. Changes in pulmonary mechanics and ventilation volumes were measured after inhalation challenge with saline (baseline), histamine (1% w/v solution for 5 min) and carbachol (0.5% w/v solution for 3 min). Comparisons between baseline and posthistamine values revealed a significant (P less than 0.05) increase in nonelastic work of breathing (Wb), maximum change in transpulmonary pressure (max delta Ppl), and pulmonary resistance (RL), while dynamic compliance (Cdyn) decreased (P less than 0.05). Tripelennamine completely abolished these histamine induced changes suggesting the involvement of H1 receptors. A nonsignificant increase occurred in functional residual capacity. However, the amount of nitrogen retained in the lung at the end of a nitrogen washout test was significantly (P less than 0.05) greater after histamine when compared to baseline values. The effect of carbachol was qualitatively similar to that of histamine, Wb and max delta Ppl increased while Cdyn decreased (P less than 0.05). The increase in lower RL reached statistical significance (P less than 0.05) only at the beginning of expiration (/ 25% VT). The present investigation demonstrates that the physiological measurements of lung function could be carried out in conscious, unsedated horses and that the pulmonary function test methods could be used as a tool for study of drug induced changes in pulmonary mechanics.  相似文献