| Abstract |
This study was carried out at Sakha Experimental Station, Animal Research Institute, Ministry of Agriculture, located at the north part of the Nile-Delta, Kafr EI-Sheikh Governorate.
The study was carried out on 69 sheep and goats, 35 cross-bred 1/2 [Finnish landrace x Rahmani (FR)] sheep and 34 cross-bred 1/2 [Damascus x Baladi (DB)] goats. The mean age and body weight were 3.5 years and 52.20 kg for sheep and 3 years and 38.5 kg for goats, respectively. Animals were confined in semi-open pens day and night throughout the experimental period. Animals were fed during the hot season on clover hay (500 g/head/day) in addition to a concentrate mixture (500 g/head/day). In the cold season the animals were fed ad lib. on Egyptian clover (Trifolium alexandrinum) in addition to a concentrate mixture (250 g/head/day). Fresh tap water was available along the day for drinking.
Two experiments were carried out to study the adaptive responses of adult female sheep and goats under Egyptian conditions.
Responses to seasonal variation:
The variation in physiological responses between summer and winter are measured on animals to study the effect of seasonal changes.
Responses to direct solar radiation:
This experiment was carried out during the hottest month of summer season, (August, 1999). The physiological parameters were taken before and after 3 hrs of exposure to solar radiation. Measurements were taken at morning (11-12a.m.) before offering water and food. The animals were then exposed to solar radiation for 3 hrs (from 12 midday to 3 p.m.). Measurements were taken again on each animal in the same sequence.
Ambient temperature (AT), black body temperature (BBT) and relative humidity (RH) were recorded simultaneously while measuring the physiological responses.
The following physiological responses were determined:
Thermal responses and respiratory activities:
Rectal temperature (RT, °C), skin temperature (ST, °C), ear temperature (ET, °C), wool surface temperature (WT, °C) and hair surface temperature (HT,°C), respiration rate (RR), gas volume (GV), Tidal volume (TV), volume of inhaled oxygen VO2, volume of exhaled CO2 (VCO2), RQ, heat production (HP).
Blood parameters:
Hematocrit value and hemoglobin concentration Plasma measurements:
Plasma total proteins (TP), plasma albumin (AL), plasma globulin (GL), albumin/globulin ratio (A/G), creatinine concentration, Asprartate aminotransferase (AST), Alanine aminotransferase (ALT), Triiodothyronine (T3), thyroxine (T4), aldosterone, Na+ and K+ concentrations.
Results indicated that:
Seasonal responses:
In sheep, rectal temperature was significantly higher in summer than in winter, while in goats it was almost similar in both seasons.
. Skin temperature (ST), ET and coat temperature (WT /HT) of sheep and goats were significantly higher in summer than in winter.
. Respiratory activities (RR, GV and TV) as well as gas exchanges (Vo2, Vo2, RQ) and heat production of sheep and goats were significantly higher in summer than in winter.
. Blood Hb and Ht of sheep and goats were significantly lower in slimmer than in winter.
. Season had no significant effect on plasma proteins (TP, AI, GI and A/G ratio), kidney function (creatinine concentration) and liver function (ALT and AST). However, in sheep NG ratio tended to be lower in summer than in winter, while a reverse trend was noticed in goats.
. In both breeds, thyroid honnones (T3 and T4) were significantly higher in summer than in winter, except T4 in goats where the difference was insignificant. Season had no significant effect on T4/T3 ratio, but it tended to be higher in sheep and lower in goats in summer than in winter.
. In sheep, season had no significant effect on plasma aldosterone, while in goats it was insignificantly higher in summer than in winter.
. Under hot climate plasma Na+ concentration tended to be lower in sheep and higher in goats than in winter, while K+ concentration was higher in summer than in winter being significant in sheep only.
. In hot condition, sheep had significantly higher RT, ET insignificant, RR, G V, TV, VO2 insignificant, RQ (insignificant), HP (insignificant), GI and K+ than goats. While, AI, A/G ratio, T3, T4, aldosterone and Na+ were higher in goats than in sheep.
. In winter, a reverse trend was observed where RT, ST, T4, T4/T3 ratio and K were significantly higher in goats than in sheep. Also, TV, VO2, VCO2, HP, Ht, Hb, plasma proteins and T3 were insignificantly higher in goats than in sheep.
Responses to direct solar radiation:
. Exposure to solar radiation increased body temperatures (RT, ST, ET temperature), and respiratory activities and TV) of sheep and goats.
. In goats, exposure to solar radiation increased significantly gas exchange (VO2, VCO2, RQ) and HP, while an insignificant increase occurred in sheep.
. Exposure to solar radiation had no significant effect on Hb, Ht, Gl, liver function test (AL T and AST) and kidney function test (creatinine).
. Plasma total proteins (TP) increased significantly after exposure to solar radiation mainly due to a significant increase in Al so that A/G ratio increased after exposure however it was insignificant.
. Exposure to solar radiation decreased plasma T4 insignificantly and T3 significantly, which resulted in an insignificant increase in T4/T3 ratio.
. Plasma Na +, K+ and aldosterone tended to decrease insignificantly after exposure except in case of K+ in goats where the reduction was significant.
. In sheep, the insignificant increase in GV after exposure was due to a significant increase in RR. and TV, meanwhile in goats it was mainly due to a significant increase in RR while TV decreased.
. The effect of exposure to solar radiation on ST, RR, VO2, VCO2, HP, Na + and K+ was higher in goats than in sheep, while its effect on GV, TV, T 3, T 4 and aldosterone was higher in sheep than in goats.
In general, goats were more tolerant to. hot conditions than sheep. While under cold environment, goats were less tolerant than sheep to maintain their rectal temperature at the same level when compared to that in hot season, meanwhile sheep had lower rectal temperature in winter than in summer which minimize their need to increase heat production.
On the other hand, sheep found to be more tolerant to direct exposure of solar radiation than goats because the increase in skin temperature, respiration rate and heat production, while the decrease in thyroid hormones and aldosterone were lower in sheep than in goats probably due to the insulative properties of sheep wool coat.
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