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Biomedical subjects

D R Hodgson

Publications and source records attributed to D R Hodgson.

At least 19 recordsLinked to original sources
PubMed1998

Skeletal muscle adaptations to prolonged training, overtraining and detraining in horses.

Thirteen standard-bred horses were trained intensively for 34 weeks and detrained for 6 weeks to study skeletal muscle adaptations to prolonged training, overtraining and detraining. Training included endurance (phase 1, 7 weeks), high-intensity (phase 2, 9 weeks) and overload training (OLT) (phase 3, 18 weeks). During phase 3, horses were divided into two groups, OLT and control (C), with OLT horses performing greater intensities and durations of exercise than C horses. Overtraining was evident in OLT horses after week 31 and was defined as a significant reduction in treadmill run time in response to a standardised exercise test (P<0.05). Relationships between peripheral (skeletal muscle) and whole body (maximum O2 uptake, V.O2, max, treadmill run time) adaptations to training were determined. Prolonged training resulted in significant adaptations in morphological characteristics of skeletal muscle but the adaptations were limited and largely completed by 16 weeks of training. Fibre area increased in all fibres while the number of capillaries per fibre increased and the diffusional index (area per capillary) decreased. Mitochondrial volume density continued to increase throughout 34 weeks of training and paralleled increases in V.O2,max and treadmill run time. Significant correlations were noted between mitochondrial volume and V.O2,max (R=0.71), run time and V.O2,max (R=0.83) and mitochondrial volume and run time (R=0.57). We conclude that many of adaptive responses of muscle fibre area and capillarity occur in the initial training period but that markers of oxidative capacity of muscle indicate progressive increases in aerobic capacity with increases in training load. The lack of differences between C and OLT groups indicated that there may be an upper limit to the ability of training stimulus to evoke skeletal muscle adaptive responses. There was no effect of overtraining or detraining on any of the adaptive responses measured.

Adaptation, Physiological↗
PubMed1998

Induced diarrhoea in horses. Part 1: Fluid and electrolyte balance.

Sodium, potassium and water balance, and measurements of acid-base status, haematocrit, packed cell volume and plasma total protein, were studied in four adult standardbred geldings following castor oil induced diarrhoea. Castor oil (2 mL kg-1) administration resulted in signs consistent with mild to moderate acute colitis. The total (combined faecal and urinary losses) losses of sodium and potassium ions were 2169 and 2864 mmol, respectively. Faeces constituted the major route for sodium loss, while urine was the major route for potassium loss at all times. Faecal dry matter potassium concentration did not vary significantly at any stage. Faecal dry matter sodium concentration increased significantly, coinciding with the onset of clinical diarrhoea. Faecal water loss increased significantly from 2.15 +/- 0.44 mL kg-1 h-1 to 5.15 +/- 0.92 mL kg-1 h-1 while clinical diarrhoea was observed. While plasma volume (PV) did not vary significantly in this study, there was a trend for PV to decrease while horses were clinically dehydrated.

Animals↗
PubMed1998

Induced diarrhoea in horses. Part 2: Response to administration of an oral rehydration solution.

Hydration status, electrolyte balance and acid-base balance were studied in four adult standardbred geldings with castor oil-induced diarrhoea. The horses received an oral rehydration solution (ORS) at a point when signs consistent with mild decreases in effective circulating fluid volume were first detected. Within 1.5 h of ORS administration, all horses exhibited a significant metabolic acidosis. At this time, mean values for venous blood pH, [HCO3], and standard base excess were 7.264 +/- 0.011, 17.7 +/- 0.3 mmol L-1, and -8.2 +/- 0.4 mmol L-1, respectively. Throughout the duration of the study, plasma volume did not change significantly, despite a decreasing trend, which tended to recover towards normal values 8 h after administration of the ORS. Signs of abdominal discomfort were observed in all horses following the last of three doses of ORS (8-10 L) administered at 30 min intervals. Faecal fluid sodium concentration increased significantly with diarrhoea, and reached values fourfold those in normal horses, while faecal dry matter sodium concentration increased exponentially following the onset of clinical signs. Despite this increase in sodium concentration, faecal fluid remained hypotonic at all stages. Our findings suggest that, while ORS can help restore systemic fluid balance, several factors influence their effectiveness. Two likely factors identified in this study were the ionic composition of the ORS as well as the rate of administration. We concluded that the electrolyte composition of current ORS may not be ideal to treat diarrhoea in horses and that administration of 8-10 of ORS every 30 min via nasogastric tube may result in too rapid small intestinal transit to allow sufficient time for absorption.

Acidosis↗
PubMed1998

Release of lubricating synovial surfactant by intra-articular steroid.

This study was undertaken to determine whether glucocorticosteroids promote the secretion of lubricating surfactant, i.e. surface-active phospholipid (SAPL), into the joint. A standard clinical dose (100 mg) of methylprednisolone acetate (MPA) in 2.5 ml of saline was injected into the load-bearing right radiocarpal joint of five horses and 2.5 ml of saline injected into each of the contralateral joints used as controls. Synovial fluid (SF) was aspirated from all 10 joints before injection and at intervals of 16 and 32 h after injection, and then analysed by standard methods. All test joints showed an elevated level of SAPL, the increases averaging 112% after 16 h and 76% after 32 h, which were highly significant relative to the control joints. A large increase at 16 h was also found in proteolipid as a possible further marker of surfactant release. Significant quantities of proteolipid were also found in human SF. Since intra-articular steroids can dramatically improve joint mobility in both humans and horses, it is proposed that part of the benefit may be derived from improved lubrication arising from the remarkable ability of SAPL to lubricate under high load. Other possible benefits of elevating surfactant levels in the joints include control of cartilage hydration, promotion of macrophage activity and the ability to scavenge oxygen free radicals.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1998

Surgical management of an abdominal abscess in a Malayan tapir.

A captive Malayan tapir was observed to have inappetence, weight loss, signs of depression, mild dehydration and diarrhoea. Haematological and serum biochemical tests showed anaemia, hypoproteinaemia, hyperfibrinogenaemia and neutrophilia with a left shift. Ultrasonic examination of the abdomen under anaesthesia revealed a well-encapsulated abscess. The abscess was marsupialised to the ventral body wall. Culture of the pus produced a mixed bacterial growth. Antimicrobial therapy was based on bacterial sensitivity results. Follow-up ultrasonic examinations showed resolution of the abscess. Ninety-one days after surgery the tapir began regurgitating food and water. An abscess originating from the stomach and occluding the lumen of the duodenum was identified at surgery. The abscess ruptured during surgical manipulations and the tapir was euthanased.

Abdominal Abscess↗
PubMed1998

Effects of two large doses of equine recombinant growth hormone on clinical, haematological and serum biochemical variables in adult horses.

OBJECTIVE: To evaluate the clinical, haematological, and serum biochemical effects of two large doses of recombinant equine growth hormone. DESIGN: Duplicated Latin square. SAMPLE POPULATION: Three Thoroughbred and three Standardbred mares aged between 12 and 17 years. PROCEDURE: Two horses were randomly assigned into one of three groups. On each of three successive days, each horse pair received one of two dosages of growth hormone or a saline placebo so that by the end of the experiment all three horse pairs had received both dosages and the saline placebo. Dose rates selected were 50 micrograms/kg, and 100 micrograms/kg. A clinical examination was performed and a venous blood sample drawn for a complete blood count and serum biochemical analysis before administration of growth hormone and at 1, 2, 3, 4, 6, 8 and 24 h after injection. Data were analysed by a repeated measures analysis of variance assessing the effects of dose and time. RESULTS: There was an effect of time on a number of clinical, haematological, and serum biochemical variables. There were significant effects of growth hormone on heart rate and serum glucose concentration but values for both variables remained within the reference range. CONCLUSION: The results of the present study suggest that equine recombinant growth hormone has a wide margin of safety and show that the single administration of up to five times the recommended dose rate has no significant effects on clinical, haematological, or serum biochemical variables.

Animals↗
PubMed1998

Serum gentamicin concentrations in compromised neonatal foals.

Twenty-one compromised neonatal foals hospitalised at the Rural Veterinary Centre (RVC) during 1993 were studied to determine i) serum gentamicin concentrations obtained when gentamicin was administered at 3.3 mg/kg bwt twice daily i.m.; ii) factors which contributed to inter-foal variation in serum gentamicin concentrations achieved and iii) clinical efficacy of gentamicin therapy in foals with confirmed septicaemia. Septicaemia was confirmed in 7 foals with positive blood cultures and suspected in 8 foals with a sepsis score > 11. Peak serum concentrations (Ps) were > 6 microg/ml in all foals and > 8 microg/ml in 60% of foals. Trough serum concentrations (Ts) were < 2 microg/ml in all foals. Factors found to produce inter-foal variation in the Ps achieved included age (< 24 h; decreased), bodyweight (< 38 kg; decreased) and severity of dehydration (8-12% bodyweight; increased). Clinical response was not associated with achievement of Ps > 8 microg/ml, but was negatively influenced by the severity of clinical signs of depression. None of the foals in this study developed septic arthritis or pneumonia during or after therapy. No serum biochemical evidence (i.e. elevated serum creatinine concentrations) of gentamicin-induced nephrotoxicity was noted during therapy.

Animals↗
PubMed1998

Flat, hurdle and steeple racing: risk factors for musculoskeletal injury.

A retrospective case-control study was conducted to identify and quantify risk factors for serious musculoskeletal injury sustained at 4 Australian metropolitan racetracks. During the period of study (August 1988-July 1995) there were 196 cases from flat racing, 52 cases from hurdle racing and 53 cases from steeplechases. The incidences of fatal musculoskeletal injuries per start for flat, hurdle and steeple races were 0.06, 0.63 and 1.43% respectively. Logistic regression identified harder track surfaces, horses being older than age 3 years, one racecourse (Flemington) and jumping races as significant risk factors which increased the risk of musculoskeletal breakdown. The incidence of fatal musculoskeletal injuries for flat races at the 4 study tracks was similar to that reported in the UK but less than the USA. Death rates for hurdle and steeple races in the study population were higher than in the UK. Strategies to reduce the incidence of serious musculoskeletal injuries may include avoidance of excessively hard track surfaces through closer regulation of track moisture content; implementation of more rigorous prerace lameness examinations of horses, particularly older horses; and altering the design and number of jumps in hurdle and steeple races. The quantification of risk, as we have reported here, is the first step towards addressing the causes of musculoskeletal breakdown and should help in applying a reasoned approach to intervention measures that may be effective in reducing racing injuries.

Analysis of Variance↗
PubMed1998

Role of prokinetic drugs for treatment of postoperative ileus in the horse.

All horses undergoing coeliotomy for an acute abdominal crisis are at risk of developing ileus and should receive therapy aimed at promoting gastrointestinal function by restoring fluid and electrolyte balance. Adequate analgesia and prevention against peritonitis, bacteraemia and endotoxaemia should be provided. Horses that at the time of surgery have a strangulating or non-strangulating small intestinal obstruction should be considered to be at greater risk of developing a persistent ileus that is refractory to treatment than those horses with lesions involving the large intestine. In horses considered to be at greater risk of developing a persistent ileus, the use of prokinetic agents should be considered. Agents that may be used to improve gastrointestinal motility include adrenergic receptor antagonists, cholinergic agonists, benzamides, dopamine antagonists, macrolide antimicrobials, opiate receptor agonists and antagonists, somatostatin analogues and local anaesthetics. There are limited studies into the use of these agents in the horse. Until further research provides more information on motility disorders following intestinal surgery and the efficacy of prokinetic agents in this species, only selective use of some of these drugs can be recommended.

Adrenergic Antagonists↗
PubMed1998

Effects of concentrated electrolytes administered via a paste on fluid, electrolyte, and acid base balance in horses.

OBJECTIVES: To test effectiveness of an electrolyte paste in correcting fluid, electrolyte and acid base alterations in response to furosemide administration. ANIMALS: 6 Standardbreds. PROCEDURES: Horses received electrolyte paste or water only (control). The paste was given orally 3 hours after furosemide administration (1 mg/kg of body weight, IM). Water was given ad libitum soon after the paste and 3 hours after furosemide administration to treated and control groups, respectively. Paste Na+, K+, and Cl- composition was approximately 2,220, 620, and 2,840 mmol, respectively. The PCV and plasma concentrations of total protein ([TP]), [Na+], [K+], [Cl-]), and bicarbonate ([HCO3-]) were determined, and urinary fluid and electrolyte excretion, fecal water, and body weight changes were measured. RESULTS: At the end of a 6-hour period, the paste-treated group had higher water consumption, which resulted in lower plasma [TP]; net electrolyte losses also were substantially less. With paste administration, [Na+] was approximately 2 mmol/L above a prefurosemide value of 137.3 mmol/L; control horses had values similar to the prefurosemide value. Plasma [Cl-] remained at the prefurosemide value, but values in control horses decreased by 7 mmol/L with water consumption. Plasma [K+] remained approximately 0.8 mmol/L below prefurosemide values in both groups. Venous [HCO3-] returned to prefurosemide values after paste administration, but alkalosis persisted in control horses after consumption of water only. Body weight loss was less after paste administration. CONCLUSIONS: Administration of electrolyte paste is advantageous over water alone in restoring fluid, electrolyte, and acid base balance after fluid and electrolyte loss attributable to furosemide administration.

Administration, Oral↗
PubMed1997

Risk factors associated with musculoskeletal injuries in Australian thoroughbred racehorses.

Risk factors for musculoskeletal injury in racing Thoroughbreds were investigated in a case-control study conducted at racetracks administered by the Australian Jockey Club. Univariable analysis of 137 cases from the official Veterinary Surgeon's reports and an equal number of randomly selected controls from the Australian Race Results identified field size, barrier position and class of race as being significantly associated with breakdown (P < 0.05). Multiple logistic regression was then used to investigate the effect of each putative risk factor whilst controlling for all others. Horses at greater risk were older, started from a wider barrier position, ran at the same distance as their previous race and raced in the highest class of race. There was no significant difference between tracks or significant association with track condition. The incidence of fatalities in the study population was less than that reported in the UK and USA.

Animals↗
PubMed1997

Failure of passive transfer in foals: incidence and outcome on four studs in New South Wales.

OBJECTIVE: To determine the regional incidence and effectiveness of treatment of failure of passive transfer (FPT) in foals. DESIGN: A study of disease incidence. ANIMALS: Eighty-eight foals and 57 mares from four studs in the practice area of the Rural Veterinary Centre were tested. PROCEDURE: Foals were tested for their serum IgG and total serum protein (TSP) concentration within the first 72 hours of life. Colostrum was collected from mares and specific gravity determined. FPT and partial failure of passive transfer (PFPT) of immunoglobulins was diagnosed when serum IgG concentrations were < 4 g/L and 4 to 8 g/L respectively. Owners of foals diagnosed with FPT were offered treatment with 1 to 2 L plasma (TSP > 70 g/L); 9 (64%) of the affected foals were treated. RESULTS: Fourteen foals (16%) had FPT whereas 15 (17%) had PFPT. There were significant differences between the mean TSP concentration in foals with FPT (42.6 +/- 4.2 g/L), PFPT (48.1 +/- 3.9 g/L) and those acquiring adequate passive immunity (58.9 +/- 5.5 g/l) (p < 0.01). Sixteen (29%) mares had pre-suck colostral specific gravity < 1.060 and 12 (71%) foals raised by these mares had FPT or PFPT. The incidence of severe disease (categorised by a sepsis score > 11, positive culture of bacteria from blood or disease requiring hospitalisation) in all foals in the first 2 months of life was 10%. However, none of the nine foals with FPT that received plasma experienced severe disease. In contrast, foals with PFPT had an increased susceptibility to severe disease (p < 0.001) when compared with normal foals. CONCLUSION: Treatment of foals with FPT may reduce the subsequent incidence of severe disease. Pre-suck colostral specific gravity and foal TSP may be used to predict the likelihood of FPT and PFPT. Even though the number of foals studied is small the results highlight the importance of optimal management practices in reducing the incidence of FPT and disease associated with this process.

Animals↗