Abstract
OBJECTIVE: The objective of the study was to report normal ultrasonographic appearance and intra-cardiac dimensions in two dairy breeds and to calculate cardiac output (CO) using echocardiography. BACKGROUND: Intra-cardiac dimensions, time indices and CO estimation have not previously been reported in adult cattle. ANIMALS, MATERIALS AND METHODS: Echocardiograms were obtained from healthy adult dairy cows (10 Jersey (J) and 12 Holstein Friesians (HF)) in the body weight range of 400 to 700 kg. Standard echocardiographic images were obtained from the left and right hemithoraces. Velocity time integrals were obtained in order to calculate CO using pulsed wave Doppler of aortic flow in the J cows. Measurements obtained included pulmonary artery and aortic diameters, left and right ventricular diameters (and calculated fractional shortening and left ventricular ejection fraction), left atrial size and time indices assessing valve function. RESULTS: HF cows had significantly (p<0.05) larger pulmonary artery and aortic diameters, larger left atrial diameters and left ventricular internal diameters during diastole, but these were not different when corrected for body weight. Left and right ventricular dimensions, adjusted for body weight, were significantly larger (p=0.02 and p=0.035 respectively) in J cows when compared to HF cows. No differences were noted in the time indices between the two groups. No significant differences were noted in intra-operator variability and the only significant difference in inter-operator variability was in measurement of the pulmonary artery (p=0.03; ICC=0.63). CONCLUSIONS: It is possible to obtain repeatable, reliable echocardiograms in order that meaningful intra-cardiac dimensions can be obtained in adult dairy cattle.