Natural Heat Stress Affects Physiological, Hematological and Hormonal Parameters in North African Ram Breeds
Natural Heat Stress Affects Physiological, Hematological and Hormonal Parameters in North African Ram Breeds
Walid Mâaoui1,2, Mohamed Amine Ferchichi2, Jihen Toumi3, Bayrem Jemmali2*, Naceur M’hamdi1 and Abderrahmen Ben Gara2
ABSTRACT
To study the ability of sheep to maintain their homeothermy in a North African natural heat stress condition, three Tunisian sheep breeds the Barbarin (BTR), Queue Fine de l’Ouest (QFO) and Noire de Thibar (NTB) were used. A total of twelve (4 per breed) rams were used in this study, for the period of 3 months from March to June. During this period, the ambient temperature varied from 12.5 °C to 32 °C, relative humidity from 49% to 94% and the temperature humidity index (THI) from 50 units to 85 units. The THI values exceeded the borderline of thermal stress, resulting a higher rectal and skin temperature, heart and respiratory rates (P<0.05). The rectal temperature (RT) varied from 39.41 °C to 39.38 °C for BTR, from 39.20 °C to 39.52 °C for QFO and from 39.51 °C to 39.72 °C for NTB. A significant (P<0.05) decrease in thyroxine (T4) from 16.58 pmol/l to 7.52 pmol/l for BTR rams, from 10.99 pmol/l to 6.34 pmol/l for QFO rams and from 12.43 pmol/l to 6.91 pmol/l for NTB rams. TSH hormone decrease significantly from a comfort situation to a stressful situation for BTR (0.124 mUI/l to 0.039 mUI/l), QFO (0.132 mUI/l to 0.065 mUI/l) and NTB (0.113 mUI/l to 0.057 mUI/l). No change in tri-iododthyronine (T3) and a no significantly decrease for cortisol hormone, from 6.91 ng/l to 2.83 ng/l for BTR, from 9.69 ng/l to 4.20 ng/l for QFO and from 7.65 ng/l to 2.42 ng/l for NTB. These responses allowed animals to efficiently dissipate heat, maintain a physiological rectal temperature, and avoid thermal stress. Blood samples were taken and analyzed during two different periods: no stress and heat stress to study the relationship between homeothermy and hematological (RBC, WBC, Hb, Ht, Pl, PCV, MCH, and MCHC), biochemical (glucose, cholesterol, total protein) and hormonal (T4, T3, Cortisol and TSH) parameters responses.
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