Effect of gradual acclimation to temperatures up to 44 °C on productive performance of the desert Bedouin fowl, the commercial White Leghorn and the two reciprocal crossbreds

The effect of daily exposures to increasing ambient temperatures (for 7 months) on egg production was evaluated in the desert Bedouin fowl of Sinai, a commercial White Leghorn and the two reciprocal cross breds. 2. High ambient temperatures did not adversely affect egg weight, laying rate or output per bird (g egg per day per g body weight) of the acclimated hens. 3. Best productivity was attained during periods of exposure to 38 to 40° C in all breeds. 4. Rates of decrease from maximal productivity to productivity at 42 and 44 °G differed with breed. Productivity of Leghorn and Leghorn x Sinai crossbred decreased curvilinearly above 40 °C, while productivity of Sinai and Sinai ( Leghorn crossbred decreased at 42 °C and then stabilised. 5. When changes in egg weight and laying rate were examined on an individual basis (comparison between successive months), the differences between Sinai and the Leghorn were more pronounced. 6. The results support previous findings that the Sinai breed and its crosses are able to withstand extreme environmental temperatures, reflecting genetic adaptation to desert conditions.