Unexplained underperformance syndrome in sport horses: classification, potential causes and recognition

When inadequate training stress is applied and recovery time is insufficient, performance reduction and chronic maladaptation occurs. Known as overtraining syndrome (OTS), this complex condition afflicts horses in top training. The name of the syndrome implies causation and it is necessary to differentiate it from over-reaching, a term used in horses that, after suffering a loss of performance without an obvious clinical reason, recover their performance within 1 or 2 weeks. The term OTS should be used for horses in heavy training losing performance without an obvious clinical reason and which is sustained for > 2 weeks. Despite considerable scientific investigations, the underlying mechanisms are still poorly understood and there are no objective biomarkers for OTS. An imbalance between training and recovery seems to be the primary cause of this dysfunction. However, other factors such as transport, feeding, subclinical disease and general management may play a role. There is now sufficient evidence that red cell hypervolaemia is not a mechanism for the OTS in horses. A dysfunction of the hypothalamo-pituitary-adrenocortical axis is momentarily the only mechanism that may be related to the development of this syndrome. In the absence of a scoring system to assess the psychological status of horses, the most effective method for diagnosis is the thorough assessment of the history and presenting complaint (length of unexplained performance deficit, weight loss despite adequate feed intake, concurrence of unspecific subclinical problems, unsuccessful treatments and changes of behaviour). Standardised exercise tests are suggested to provide a way to detect subtle changes in hormonal responses in the individual, which may make an important contribution to the detection of early overtraining. But further longitudinal studies are needed to clarify mechanism(s) underlying OTS and to establish the potential for the use of a physiological test as a predictive tool of this disorder.     

Influence of smoke exposure on soil enzyme activities and nitrification

Summary Soil was exposed to red phosphorous/butyl rubber (RP/BR) aerosols at various relative humidities in a recirculating environmental wind tunnel. Soil microbial and enzymatic activities were measured immediately after exposure and periodically thereafter for 56 days. The nitrification potential was significantly reduced in soil amended with ammonium sulfate and exposed to RP/BR smoke, and could be related to a decline in soil pH. The rate of nitrate formation in unamended soil with time was also reduced, but by 57 days postexposure, concentrations were similat to those of unexposed controls in all but the thinnest soil lense. Soil dehydrogenase and phosphatase enzyme activities were sensitive to RP/BR smoke and in some treatments no activity was detected. The measured activities did not recover within the 56-day postexposure period and in some cases declined. Soil lense thickness was the greatest factor controlling the degree of RP/BR effects, indicating that injury to soil microbial and enzymatic activities may be surficial. Deposition of smoke particles increased with increasing relative humidity, which had a significant impact on the activities measured.     

Musculoskeletal responses of 2-year-old Thoroughbred horses to early training. 1. Study design,and clinical,nutritional, radiological and histological observations

AIMS: This is the first in a series of papers reporting studies in 2-year-old Thoroughbred racehorses that aimed to determine the response of musculoskeletal tissues to early training on grass and sand racetracks. In this paper, the experimental set-up of the whole study is described, and nutritional, workload, and clinical, radiographic and pathological outcomes are reported, including semi-quantitative assessment of macroscopic changes in articular cartilage.

METHODS: The study group comprised 14 two-year-old Thoroughbred fillies reared entirely at pasture. Of these, seven were selected by a licensed racehorse trainer to undergo a 4-week period of initial training in which they were taught to accept saddle and rider, followed by a 13-week period of flatrace training at a racetrack (Weeks 1–13); the other seven fillies were confined to large grass enclosures and were not trained. Nutrient, including macro- and trace-element intakes were estimated. Distances cantered or galloped and average velocities were quantified for the trained horses. All horses were observed daily, weighed approximately weekly, and underwent a clinical lameness examination at Weeks 5, 9 and 13. Distal forelimbs were radiographed prior to Week 1, during Weeks 7–8, and again at the end of the study, when macroscopic changes in articular cartilage of the proximal surface of the proximal phalanx were also scored after staining with India ink.

RESULTS: Dietary intakes met or exceeded recommended requirements for all nutrients except sodium, which was low in the trained horses. Bodyweight increased throughout the study in the untrained horses, and increased until Week 7 and then decreased slightly in the trained horses. Mean velocity data were used to define three stages of the training programme: Stage 1 comprised canter in Weeks 1–4; Stage 2 comprised canter in Weeks 5–8; and Stage 3 comprised canter in Weeks 9–13 and galloping twice weekly. Four of seven horses completed training. These covered a mean distance of 179.2 km at mean velocities (excluding gallops) of 7.63 m/sec (SD 0.58), 8.99 m/sec (SD 0.56), and 8.43 m/sec (SD 0.74) for Stages 1–3, respectively, and galloped 4.45 km at 14.4 (SD 0.1) m/sec. The three horses that did not complete training became lame in Weeks 9, 10 and 11, and covered 147.9 km at velocities of 7.38 m/sec (SD 0.44), 8.88 m/sec (SD 0.33) and 8.43 m/sec (SD 0.59) and galloped 2.1 km. Overall, slight or intermittent lameness in trained horses was noted on 76/655 (12%) of horse observation days. Swelling was evident on 284/655 (41%) of horse observation days in the metacarpophalangeal (MCPJ) and metatarsophalangeal (MTPJ) joints (92%), palmar metacarpal tendon region (7%) or carpus (1%). Swelling of the MCPJ or MTPJ was not associated with obvious lameness. Radiographic changes were minor and no gross lesions in bone or tendon tissue were evident except for one case of dorsal metacarpal disease. Post mortem, the cartilage of some MCPJ and MTPJ had obvious wear lines and high lesion scores, which were not consistently related to clinical evidence of pain, lameness or joint swelling. Mean lesion scores were not significantly different between the MCPJ and MTPJ, or between trained and untrained horses.

CONCLUSIONS: Workload can be readily quantified in racehorses under semi-commercial training conditions. Obvious lesions in cartilage of the MCPJ or MTPJ were present in some trained and some untrained horses and not consistently associated with clinical evidence of lameness, joint swelling or change in other connective tissues.

CLINICAL RELEVANCE: Workload data in racing horses are likely to be highly relevant for studying the pathogenesis of changes in bone, tendon and cartilage during training, for training management and for risk analysis in racehorse populations. Although obvious cartilage lesions produced little clinical effect, such lesions have previously been shown to be progressive and to prejudice athletic capability. Detection of such occult lesions in young horses will require more sophisticated detection methods.     

Evaluation of a new strategy to modulate skeletal development in Thoroughbred performance horses by imposing track-based exercise during growth

REASON FOR PERFORMING STUDY: No data exist on the intensity of exercise required or on possible harmful effects of increasing exercise in foals over the natural level when free at pasture. OBJECTIVES: To investigate whether an increase in workload over free pasture exercise in the period from directly after birth to the start of training is tolerated by Thoroughbred (TB) foals without increasing injury rate or producing other undesired side effects. METHODS: Thirty-three TB foals were allocated to one of 2 exercise groups directly after birth. One group (PASTEX) was raised on pasture and the other (CONDEX) kept under identical circumstances, but was additionally subjected to an exercise protocol of gradually increasing intensity. Foals were monitored periodically and scored for the presence of clinical signs related to the musculoskeletal system (joint effusion, pain at flexion, occurrence of physeal swelling), and radiographs taken at the end of the conditioning phase. Also, behavioural studies were performed to detect any changes in behaviour related to the exercise programme. Cortisol levels were measured in both groups, to assess the level of stress. RESULTS: Workload in the CONDEX group was significantly higher than in the PASTEX group (approximately 30%). Conditioning increased the likelihood for joint effusion in the antebrachiocarpal joint, but reduced tarsocrural effusion and physeal swelling at the lateral distal radius, the third metacarpal bone (medial aspect) and lateral and medial aspects of the third metatarsal bone. CONCLUSIONS: The 30% increase in workload did not affect the animals' welfare, effects of conditioning exercise on clinical musculoskeletal health were few and there were no adverse effects. POTENTIAL RELEVANCE: This study supports the feasibility of imposing early conditioning exercise in horses and is a benchmark for its effects on the development of equine musculoskeletal tissues.     

Quality and endosperm storage protein variation in Argentinean grown bread wheat. I. Allelic diversity and discrimination between cultivars

Genetic variability for endosperm storage proteins was analysed in 119 Argentinean grown bread wheat cultivars. For the HMW-GS, three, six and two alleles were observed at the Glu-A1, Glu-B1 and Glu-D1 loci, respectively, in 17 allelic combinations. The majority of these combinations were considered to be associated with good quality. For the LMW-GS, eight, seven and four alleles were provisionally observed at the Glu-A3, Glu-B3 and Glu-D3 loci, respectively, in 51 allelic combinations. Regarding quality, the alleles present at Glu-D3 were mainly those previously shown to be associated with good quality, whereas at Glu-A3 and Glu-B3, some alleles previously associated with poor quality were present at high frequency. Relatively few cultivars carried combinations for all the loci studied that would be expected to be associated with high quality. The mean genetic variation index (H) observed for the glutenin loci (0.589) was similar to values observed in other collections. Unweighted pair-group method using arithmetic averages (UPGMA) of the six loci plus the Chinese Spring-Cheyenne CSS–CNN difference showed that the 119 cultivars fell into 93 distinct combinations. For complete discrimination between all cultivars they would have to be analysed for additional loci. There remains scope for varietal quality improvement within this germplasm pool.     

Epidermal differential impedance sensor for conformal skin hydration monitoring

We present the design and use of an ultrathin, stretchable sensor system capable of conformal lamination onto the skin, for precision measurement and spatial mapping of levels of hydration. This device, which we refer to as a class of 'epidermal electronics' due to its 'skin-like' construction and mode of intimate integration with the body, contains miniaturized arrays of impedance-measurement electrodes arranged in a differential configuration to compensate for common-mode disturbances. Experimental results obtained with different frequencies and sensor geometries demonstrate excellent precision and accuracy, as benchmarked against conventional, commercial devices. The reversible, non-invasive soft contact of this device with the skin makes its operation appealing for applications ranging from skin care, to athletic monitoring to health/wellness assessment.     

BOVINE HERPESVIRUS 1 - INFECTION OF THE UPPER ALIMENTARY TRACT OF CATTLE AND ITS ASSOCIATION WITH A SEVERE MORTALITY

SUMMARY A severe cattle mortality in which 132 out of 340 animals died on a property in southern Queensland was investigated. Clinical signs shown by affected animals included fever, inappetance, depression, lethargy, salivation, diarrhoea, ataxia, and ulceration of the oral cavity. The most common lesions seen at autopsy of 6 affected animals were ulceration of the tongue, gums, dental pad and buccal mucosa, linear ulceration of the caudal third of the oesophagus, mild catarrhal enteritis and necrosis of lymph nodes draining areas of ulceration. Bovine herpesvirus type 1 (BHV 1) was isolated from 3 out of 5 animals from which virus isolation was attempted. BHV 1 was recovered from oesophageal ulcers, retropharyngeal lymph nodes, blood clot, and swabs from ulcers in the oral cavity but not from spleen, liver or mesenteric lymph node. Serum neutralising (SN) antibody to BHV 1 was detected in 4 out of 12 affected animals in the second of paired serum samples but not in the first. Mucosal Disease (MD) virus was not recovered from any of 17 animals from which isolation was attempted but moderate MD SN titres, without a rise on paired sera, were detected in affected animals. Fever, depression, inappetance, ulceration of the upper alimentary tract, and adrenal necrosis were produced in 2 susceptible animals following inoculation with third passage cell culture fluid containing BHV 1. A serological response to BHV 1, but not to MD virus was detected in one of the cattle infected experimentally.