EFFECTS OF THERMAL CONDITIONING DURING HATCHING AND EARLY GROWTH ON HEAT TOLERANCE OF JAPANESE QUAIL

Abstract

The purpose of the present study was to investigate the effect of thermal conditioning on heat tolerance of Japanese quail. A 3 x 2 factorial experimental design included three incubation temperature treatments: low (L, 36.1°C), control (C, 37.7°C) and high (H, 39.4°C), and two housing temperatures: natural winter climate (N, average, 25.7°C) and constant high (H, 35.0°C). A total of 360 chicks were involved (60 in each experimental group). Data were collected on body weight, feed intake and conversion, rectal temperature, hematocrit, oviposition day time and mortality rate until 14 wks of age. Incubation treatments had significant impacts on most of the studied traits. Juvenile body weight was depressed in birds incubated at low temperature. From 6 wks, however, birds incubated at high temperature reached the highest body weights under housing heat stress indicating long-term adaptation effects of incubation under high temperature. High housing temperature exerted significant adverse effects on most of the studied traits. Rectal temperatures were significantly higher in heat stressed birds (42.57 vs. 41.92°C). Total mortality rate was increased under high temperature (22.8 vs. 17.8%). It was concluded that, adequately increased incubation temperature might help to increase heat tolerance in particular in adult Japanese quail by enhancing early physiological adaptation processes.