No abstract

SummaryThe aim of this study was to evaluate pulmonary function in Standardbred trotters during graded exercise. The exercise test consisted of 4 work loads corresponding to lo%, 42%, 70% and 96% of the individual 002max. Oxygen uptake was detected from an open bias flow system without valves. Cardiovascular and haemodynamic data were recorded at walk and during steady state exercise in 7 horses. Pulmonary gas exchange was assessed by conventional blood gas variables (arterial and mixed venous blood gas tensions) and the ventilation-perfusion distribution vAIQ as estimated by the multiple inert gas elimination technique. The dispersion of perfusion and ventilation distribution respectively (SDQ) and the difference between measured PaO, and that predicted on the basis of amount of ventilation-perfusion mismatching and shunt that was observed (predictedmeasured), were determined. The latter reflects mostly diffusion limitation. At the highest work load the PaC02 increased to 50.3 tom. vAIQ inequality increased significantly with exercise [mean log = 0.32 f 0.03 (walk) and 0.46 f 0.06 (heavy exercise), PcO.Ol]. Alveolar-capillary diffusion limitation of oxygen was evident at and above exercise at 70% of v0zrnax. The arterial hypoxaemia seen during the highest work load was a result of a) hypoventilation, accounting for 4%, b) increase in vAIQmismatch, accounting for 41% and c) considerable diffusion limitation of oxygen, accounting for 55%.

Background: Sedation with α 2 -agonists in the horse is reported to be accompanied by impairment of arterial oxygenation. The present study was undertaken to investigate pulmonary gas exchange using the Multiple Inert Gas Elimination Technique (MIGET), during sedation with the α 2 -agonist detomidine alone and in combination with the opioid butorphanol.

The aim of this study was to study the physiological, especially thermoregulatory, responses during intense exercise in the clipped horse compared to the horse with winter coat. Six Standardbred trotters were studied before and after clipping. They performed an inclined incremental high intensity treadmill exercise test and were monitored during recovery. The clipped horse differed significantly (ANOVA) during exercise as compare to coated: less increase in central venous blood temperature, higher skin surface temperature, greater difference skin to ambient temperature and higher rate of nonevaporative heat loss. The clipped horse had significantly lower total cutaneous evaporative heat loss from walk to end of peak exercise and a shorter time for recovery for the respiratory rate using a paired t test. The clipped horse showed a tendency (P = 0.059) to decreased oxygen uptake during the stepwise increase in workload. We concluded that the clipped horse experienced less strain on the thermoregulatory system due to an enhanced heat loss. Some clipped horses in the study showed a more efficient power output; future studies with emphasis on respiration and oxygen demand are needed to explain this.

The purposes of this study were to elucidate the influences of age and sex on the mass specific blood volume parameters: total blood volume (TBV/BW, ml/kg), plasma volume (PV/ BW, ml/kg), total red cell volume (CV/BW, ml/kg) and maximal packed cell volume (PCV, 1/1, i.e. after total mobilisation of the splenic red cell reservoir) and to establish reference values for these in normally performing Standardbred trotting race horses.In total 205 horses were studied. They were all, according to their owners and/or trainers, performing satisfactorily in racing or training for shortly impending racing. Blood volume determination was done with the Evans blue dye dilution technique after exercise induced emptying of the spleen.Both age and sex were found to influence variation of these parameters significantly, with the possible exception of PV/BW, whereas the primary variation appeared to be in CV/BW. It was concluded that taking age and sex dependent variations into consideration will render prediction of normal values for the blood volume parameters in the athletic Standardbred trotter more reliable and the detection of abnormal deviations more precise if five age and sex groups are used for comparisons.