A Preliminary Study of Egg Production and Heat Tolerance in a New Breed of Fowl (Leghorn × Bedouin)

Physiological responses to high (40–45°C.) ambient temperatures were studied in acclimatized chronically cannulated laying Leghorn × Bedouin fowl. Normal values for body temperature (TB), respiratory rate (R.R.) and acid base parameters were determined in hens exposed to ambient temperatures (TA) of 25°C. Mean value for TB was 40.49°C. and R. R. ranged 11–26 breaths per min. Arterial pH, carbon dioxide partial pressure (PaCO2) and plasma bicarbonate ion concentrations [HCO3−] were: 7.549, 23.87 mm. Hg and 20.56 mM/L., respectively. Egg production studies under outdoor conditions, during 100 days, were carried out on 30 week old pullets. The rate of lay was 80.5%, and mean egg weight was 54.89 gms. The total egg output was 44.2 gm./hen day. This value was found to be about 44% higher than that calculated for laying Sinai Bedouin fowl. During long term exposure (8–10 hrs.) to high TAs (37–45°C.) TB increased within a range 2.1°C. higher than normal. Panting was indicated by an increased R.R., to 238–293 breaths per min., accompanied by synchronous gular fluttering. The thermal panting was accompanied by a slight decrease in PaCO2 to values of 19.15–21.44 mm. Hg which was compensated for by a lowering of bicarbonate ion concentration t o 17.11–18.86 mM/L. Arterial pH was regulated close to normal level i.e. 7.562 at 42°C. and 7.571 at 45°C. TA. The results suggest that the Leghorn × Bedouin offspring are well adapted to extreme dry heat conditions and are highly efficient in their egg production, as compared to their Bedouin parents.