Two-Dimensional, M-Mode, and Doppler Echocardiographic Reference Intervals in Adult Chickens (Gallus gallus domesticus) of Hobby Flock Breeds

The keeping of companion chicken flocks has recently grown in popularity, increasing the demand for advanced veterinary care. The clinical utility of echocardiography is currently limited by a lack of established reference intervals for adult chickens of non-commercial breeds. Therefore, the objective of this prospective observational study was to establish echocardiographic reference intervals for adult chickens of non-commercial breeds. Healthy adult chickens (n = 126) of both sexes and various breeds were administered intramuscular butorphanol (2 mg/kg) and midazolam (2 mg/kg) before undergoing echocardiography by a board-certified veterinary cardiologist. Using nonparametric methods, 95% reference intervals were determined, with the 2.5th (90% CI) and 97.5th (90% CI) percentiles serving as the lower and upper limits, respectively. The effect of body weight on linear cardiac dimensions was evaluated by regression analysis, and allometric equations scaled to body weight were derived for each variable. Intraclass correlation coefficients were used to quantify echocardiographic intra- and interoperator repeatability and intra- and interobserver measurement agreement. Body weight was a significant but not strongly correlative co-variate, and 95% prediction intervals for linear dimensions were determined by allometric scaling. Echocardiographic reference intervals were established from 126 chickens of non-commercial breeds.