THE EFFECTS OF THERMAL ENVIRONMENT ON THE GROWTH OF NEONATAL CHICKS .2. THE DEVELOPMENT OF THE VISCERA ORGANS

One hundred and fifty 1-day-old Hisex male chicks were used to investi gate the growth and development of viscera organs of neonatal chicks. The birds were exposed to five environments: control, 27 degrees C and 35 % RH, 27 degrees C and 85 % RH, 35 degrees C and 35 % RH, and 35 d egrees C and 85 % RH. The proportion of heart, liver, crop, stomach, i ntestine, yolk sacs, empty body weight, and viscera weight in body wei ght were determined after 48 and 72 h thermal exposure. The environmen tal temperature had significant effects on the development of viscera organs: the chicks in the 35 degrees C environment had lower stomach, intestine and viscera weight, and higher empty body weight compared wi th the chicks in the 27 degrees C treatment. It is suggested that the response of neonatal chicks to the high temperature was shown in the r apid development of viscera organs, especially in the development of t he gastro-intestinal tract. The humidity treatment had no significant effect on the development of viscera organs. The utilization of the yo lk was nor affected by the environmental temperature or the humidity w hen the neonatal birds were fed. Feed intake was increased by high tem perature during 48-h exposure (p < 0.05) compared with low temperature (27 degrees C). After 72-h exposure, the difference in feed intake be tween 35 and 27 degrees C treatment was not significant. It is suggest ed that the neonatal chicks could not make proper feed-intake adjustme nt in such a short time.