الفهرس 
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Abstract
The present study was carried out at Maryout Research Station; Desert Research Center, Ministry of Agriculture and Land Reclamation. The study was conducted during spring and autumn seasons of the year 2017 on 24 adult not pregnant non lactating Barki ewes (12 in each season). Ewes were randomly divided to four groups (n=6 in each) and two groups were used in each season. In spring, the first group was kept unshorn and acted as control; the second group was shorn at the beginning of April. In autumn, the same procedures were used where one group acted as unshorn control group while the other group was shorn at middle of September. The studied parameters were compared between unshorn and shorn ewes in each season.The main objectives were to compare the effect of autumn shearing with ordinariy spring shearing on wool production and some wool characteristics, physiological responses, thermal gradients, some hematological traits, some hormonal profiles (tetra-iodothyronine and cortisol). Average ambient temperature (ºC), relative humidity (%) and total solar radiation (W/m2) were recorded daily and temperature humidity index was calculated to estimate the seasonal averages during the experiment period. Also live body weight was recorded as initial (IBW) and final (FBW) weight during each season and before and after shearing. Respiration rate, rectal temperature and skin temperature were measured during each season on days 15, 30, 45 and 60 after shearing in each season at 12:00 am to determine the physiological responses of the animals. Blood sample was taken at days 15, 30 and 60 after shearing from each animal to estimate RBCs and WBCs counts, hemoglobin concentration, PCV. Serum was separated to determine the concentrations of total protein, albumin, globulin, tetra iodothyronine (T4), and cortisol. Wool samples were obtained before shearing from the left mid-side position of each ewe during the experimental period to estimate mean clean yield, fiber diameter, standard deviation of fiber diameter, fiber length, crimp frequency, different fiber types ratio and medullation index. Staple length, staple strength, point of staple breakage and elongation rate were also measured.The obtained results could be summarized as the following:1. Shearing affected FBW (P<0.05) and BW change (P<0.01), being higher in unshorn than in shorn ewes. The effect of shearing was more obvious in autumn, as the shorn ewes lost higher (P<0.01) weight (2.85 kg) than the control ewes (0.39 kg).2. Shearing resulted in heavier (P<0.05) fleeces in autumn than in spring. No significant differences for the effect of shearing season were observed on wool clean yield (%).Average fiber diameter was coarser (P<0.05) in spring shorn fleeces (36.26 µm) than in autumn (30.22 µm)3. Autumn shearing improved the uniformity of fiber diameter where the standard deviation of fiber diameter decreased from 19.34 in spring to 13.07 in autumn.4. Fiber length and crimp frequency did not significantly differ between spring and autumn shorn wool5. Percentages of fine, heterotype and kemp fibers did not differ between spring and autumn shorn wool, while the percentage of medullated fibers was lower (P<0.05) in spring than in autumn, being 26.43 and 37.36%, respectively. Medullation index did not differ between spring (13.58) and autumn (13.80).6. Neither staple length nor staple strength was significantly affected by shearing season. Point of staple break and elongation rate were improved by autumn shearing, being 57.48 and 52.36% in spring and autumn, respectively. Elongation rate (ELR) increased from 17.64% in spring to 23.45% in autumn.7. Skin temperature was affected by season, being higher (P<0.05) in autumn (38.49 ºC) than in spring (38.08 ºC). Shearing decreased (P<0.05) ewes skin temperature, being 38.53 and 38.04 ºC in unshorn and shorn ewes, respectively.8. Thermal gradient between body core temperature and skin temperature was higher (P<0.01) in spring (1.24 ºC) than in autumn (0.42 ºC). Thermal gradient between skin temperature and ambient air temperature and between body core temperature and ambient air temperature were higher in autumn than in spring.9. All hematological parameters (count of RBC’s and WBC’s, Hb concentration and PCV), blood biochemicals concentration (total protein, albumin and globulin), and serum concentration of T4 and cortisol were not affected by shearing or season.CONCLUSIONThe previous results indicated that altering shearing time of Barki sheep from spring to autumn may be safely conducted without negative effects on wool production, physiological responses, blood constituents and animal homeostasis. Moreover, it improved greasy fleece weight, average fiber diameter, uniformity of wool fiber diameter, point of staple break and wool staple elongation rate compared with spring shearing.