Effect of selection for 4-week body weight on growth, haematocrit and thermoregulation in Japanese quails

Effect of selection for 4-week body weight on juvenile growth, packed cell volume (haematocrit) and thermoregulatory ability of birds was studied in a selected and a control line of Japanese quails. Juvenile body weights at day old, 1, 2, 4 and 6 weeks of age were higher in growth selected line compared to control line and females have higher body weights than males at all stages except at 1-week of age. Relative growth rate (%) was highest for period 0–1 week. There were little differences between males and females for relative growth rate (%). Packed cell volume (PCV) was studied at four stages viz; 1, 3, 5 and 9-weeks of age. Average PCV at 1, 3, 5 and 9 weeks of age was 42.5, 42.6, 42.6 and 44.7 percent, respectively. The differences between growth selected and control line were non-significant at 1, 3 and 5 weeks of age while they were significant at 9-weeks of age. Males were having higher packed cell volume as compared to females. Growth-selected and control line quails were used for recording of cloacal and surface temperatures (foot pad). The core and surface temperatures were significantly higher in the afternoon than the morning by about 1.2 to 2.6% while the increase in the environmental temperature from morning (31°C) to afternoon (33°C) was 2°C (6.5% increase). However, the surface to core temperature ratio, which is indicative of maintenance of warmth in extremities in relation to body temperature, declined from morning to evening by 2.4%. The genetically improved line quails had significantly lower core as well as surface temperatures than the control line.