Homeostatic mechanisms of desert and non-desert sheep and goats under harsh environmental conditions

الملخص EN

This experiment was carried out to compare heat tolerance of the local Sinai sheep and goats with those of Nile delta breeds (Rahmani sheep and Baladi goats).

Twenty animals (5 male of each group) were used in this study.

The age of sheep and goats ranged between 12 -18 months.

The coat of each animal (wool or hair) had been shorn to maintain its lengths constant at about 1.5-2 cm throughout the study period.

All the animals were exposed daily to direct solar radiation (DSR) from 12 : 00 h to 15 : 00 h for 7 successive days in August.

The averages ambient temperature and relative humidity were 31.75 oC and 46 %, respectively during this study.

Data on the following parameters were collected: rectal temperature (RT), respiration rate (RR), hemoglobin concentration (Hb), haematocrit value (Ht), thyroid hormones levels (T3 and T4) and acid-base balance (pH and HCO3) before and after exposure to DSR.

Results indicated that, exposure of animals to DSR increased significantly (P < 0.05) RT, RR and pH and decreased significantly Hb, Ht, T3, T4 and HCO3 irrespective of breed.

With respect to breed differences, changes in RT, HT, T3 and HCO3 after exposure to DSR were significantly lower in sheep compared to those in goats.

Moreover, location of breed affected the studied traits.

Sinai breeds had higher changes in RT, RR, T3, pH and HCO3 compared to Nile delta breeds irrespective of sheep and goats.

From this experiment, it could be concluded that, Sinai originated breeds of sheep and goats may have more tolerance to heat stress due to direct exposure to solar radiation than Nile delta originated breeds.