الفهرس 
Material and methodsيوجد فقط 14 صفحة متاحة للعرض العام
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المستخلص
The present study was conducted on 36 Newzealand white rabbits assigned into three age group of two, three and four months, 12 rabbits for each group of the same age, there were 6 males and 6 females. For each sex, four rabbits were given orally a single dose of L-tyrosine, 100 mg/kg body weight and the other two rabbits, were left as control. All rabbits were kept under complete observation during the experimental period and data obtained were statistically analysed. 2-The obtained results came as follows:-
A- Clinical observations:- a-The body temperature increased significantly (P<0.01) with advancement of age; it seemed to be nearly the same in both males and females; the tyrosine-treated group showed a signif-icant(P<0.01)higher body temperature than that in the control. b-There was a steady increase in the body weight with advance ment of age;it seemed to be similar for both males and females the treated group revealed a significant (P<0.01) higher body weight when compared to control. c-In the treated group, the testicular descent in males and the first onset of male acceptance by females occurred much ear her during the second month of age than that in the control. d-Successful mounting and ejaculation of semen with sperms for the first time was recorded in the treated bucks at the begining of the third month of age, much earlier than that in the control. B-Morphological characters:- Both sizes of testes and ovaries increased significantly with advancement of age; tyrosine-treated groups revealed signif-icantly (P<0.01) an increase in the testicular and ovarian sizes when compared to those in the control. C-Histological findings:- a-Pituitary gland: The treated groups revealed an increase in the number, size and the secretory activity of somatotrophs, lactotrophs and LH gonadotrophs, in addition to a marked in-crease in the number size and the secretory activity of thyrotrophs, adrenocorticotrophs and FSH gonadotrophs during the second month of age. b-Testes : The seminiferous tubules of testis in rabbits treated by tyrosine at two months age revealed different stages of spermatogenesis with the formation of spermatozoa; the inter-stitial Leydig cells appeared larger in size in form of large clusters. c-Ovaries: In the tyrosine treated rabbits of two month age, numerous Graafian follicles with thickened zona pellucida were noticed, stroma appeared highly vascular; there was a marked increase in the number and size of the interstitial gland cells. 3- from the present results it can be concluded that tyrosine acts as a growth promoting factor and a hormonal inducing fac-tor, it can be used in rabbits for enhancing the puberty of both males and females. It can be recommeneded that tyrosine can be used on a large scale for regulating the reproductive
cycle of males and females in large animals.