HEAT-INDUCED CHANGES IN ALDOSTERONE
LEVEL AND MINERAL BALANCE IN
EGYPTIAN BUFFALO CALVES *

NESSIM, M.Z. and KAMAL, T.H.

Biological Applications Department, Nuclear Research Centre,
Atomic Energy Authority, Egypt.

Key words: Buffalo calves, Heat stress, Physiological response,
Aldosterone level, Mineral balances.

التغيرات الناشئة عن تعرض عجول الجاموس المصرى للعبء الحرارى
فى مستوى هرمون الألدوستيرون بالدم وميزان الأملاح

مجدى ذكى نسيم و تيمور حسين كمال

خلاصـة

تناولت الدراسة معرفة تأثير تعريض عجول الجاموس المصرى للعبء الحرارى الحاد لمدة 6 ساعات وذلك على مستوى هرمون الألدوستيرون بالدم وكذا تأثير العبء الحرارى لمدة أسبوع على درجة حرارة الجسم ومعدل التنفس وعلى ميزان الأملاح المعدنية وذلك بمقارنة هذه المؤشرات فى الجو المعتدل بمؤشرات الجو الحار على نفس الحيوانات.

أوضحت النتائج ارتفاع معنوى فى درجة حرارة الجسم ومعدل التنفس و مستوى هرمون الألدوستيرون بالدم و انخفاض معنوى فى ميزان الأملاح المعدنية لعجول الجاموس المصرى المعرضة للعبء الحرارى.

ABSTRACT

Eight male buffalo calves (13 months old) were used in the present study. The animals were maintained in metabolic cages inside a climatic chamber for 2 weeks under mild climate at 21ºC and 73% RH for 6 hours daily as an adjustment   period followed by 7 days at the same climatic conditions as a control period then followed by a heat exposure period for 7 days at 35-42ºC and 40-50 % RH for
6 hours daily. The animals were fed individually on concentrates and wheat straw. Plasma aldosterone was estimated on the first day after 6 hours of each mild and hot exposure periods. Sodium, potassium, calcium, phosphorus and magnesium balances were estimated on the last three days of control and heat exposure periods. Rectal temperature and respiration rate were recorded daily during both periods. The rectal temperature was raised (P<0.01) from 38.30 to 39.32ºC by the end of 6 hours heat exposure period. The respiration rate was increased (P<0.01) at the end of 6 hours of heat exposure from 25 to 110.81 breaths/minute. Aldosterone was increased (P<0.05) from 5.79 to 37.11 pg/ml whereas sodium, potassium, calcium, phosphorus and magnesium were decreased (P<0.01) by 19.16 %, 40.70%, 46.05 %, 35.69 % and 48.99%, respectively.