Comparative Analysis of Production Performance and Physiological Responses in Snowy White Chickens Reared at Different Altitudes.

This study evaluated variations in phenotypic and physiological traits of Snowy White chickens reared under high-altitude conditions in Lhasa, China, at 3650 m and low-altitude conditions in Ya'an, China, at 600 m. Chickens reared at high altitude showed delayed sexual maturity and peak laying, as well as lower laying rate and hatchability. In contrast, egg weight at first laying was higher in chickens reared at high altitude. Organ index analysis showed that high-altitude chickens had a higher heart index but lower liver, stomach, and spleen indices than low-altitude chickens (p < 0.05). High-altitude chickens also had greater chest depth and chest circumference but shorter shank length and smaller shank circumference (p < 0.05). Multivariate analyses further indicated liver and spleen indices as major contributors to the separation between altitude groups. These results show that high-altitude rearing is associated with altered reproductive performance, organ development, and body conformation in Snowy White chickens. These findings may inform the evaluation, breeding, and management of layer chickens in plateau production systems.