Heat Adaptability of Growing New Zealand White rabbits under Egyptian Conditions

The present study was conducted in the private Farm at Shyrkia, Governorate, Egypt during winter and summer seasons 2013. The work aimed to study the heat adaptability of growing male New Zealand White (NZW) rabbits.
Twenty growing male (NZW) were divided into two equal and similar groups. The 1^st group were subjected to mild winter climate (Temperature humidity index THI= 16.1) and the   2^nd group were exposed to hot humid summer (THI= 31.1). Results revealed that daily gain, daily feed intake and feed efficiency of growing NZW rabbits were affected negatively by exposure to hot climate. Respiration rate and rectal temperatureincreased (p ˂ 0.01) due to exposure to heat stress.
Red blood cell (RBC) counts, packed cell volume (PCV), hemoglobin, platelets, mean cell volume (MCV), mean cell hemoglobin (MCH) and mean cell hemoglobin concentration (MCHC) were significantly decreased during hot summer. Similarly, total leucocytes, nuetrophils and lymphocytes decreased significantly. While monocytes and basophils decreased unsignificantly,  esoinphils did not affected significantly by exposure to hot climate. Total; proteins (TP) glucose (Glu), albumin, globulins, A/G ratio, total lipids and cholesterol were decreased significantly, and triglycerides did not affected significantly by exposure to hot climate.
Liver function including alkaline phosphatase (ALP), acid phosphatase (ACP), alanine aminotransferase (ALT), aspartate aminotransferase (AST) and billrobin were decreased significantly due to heat stress exposure. Kidney functions which include creatinine and uric acid were decreased significantly due to exposure to hot climate. Activities of some blood minerals were decreased significantly as affected by heat stress i.e.; sodium, calcium, potassium and phosphorus.
 Activity of some blood hormonaes; cortisol, triiodothyroxine (T₃) and thyroxine (T₄) were significantly decreased during summer season. Results suggest that exposure of growing New-Zealand white rabbits to hot environmental conditions adversely affects physiological functions as reflected by the hematological, biochemical parameters, hormonal and various immunological function. These disturbances of internal physiological status of mammals led to impairment of all activities of these mammals.