تحديد مستوى هرمون17 بيتا-أستراديول في نعاج خطي إنتاج الحليب و اللحم لغنم العواس المحسنة

الملخص EN

A total of 48 Awassi ewes including 24 ewes of milk production lines(L1) and 24 ewes of meat production line(L2) in different parities (6 ewes/ parity/line) were used to determine the level of 17 β-estradiol (E2), and the effect of production line, parity, month of breeding season and their interactions.

Weekly blood samples (8 ml), were drawn regularly from the jugular vein using disposable vacutainer containing K3 EDTA as anticoagulant prior to morning feeding throughout the breeding season (June-September).

Each blood sample was centrifuged and the separated serum kept in plastic containers identified by the animal number, date of collection and stored at -20o C until hormonal assay using the enzyme-linked immunosorbent assay (ELISA).

Data were analyzed using the general linear model with repeated measure procedures.

The averages of hormone were calculated, analysis of variance was applied to determine the effects of studied factors and Tukey test was conducted to compare averages.

Results indicated that there was a significant effect (P < 0.05) for the production line, parity and their interactions on the level of studied hormone.

The level of E2 increased gradually as age advanced and it was in the blood of ewes of L1 > L2 and in Awassi ewes higher than in comparative breeds.

Its averages were 38.30 ± 1.55, 41.79 ± 1.03, 54.93 ± 2.95 and 55.69 ± 3.01 pg/ml.

in ewes of L1 aged < 1, 2, 3 , 4 years, respectively and 39.60 ± 1.32, 39.06 ± 0.91, 37.30 ± 1.01 and 53.30 ± 3.38 pg/ml in ewes of L2 of similar ages, respectively.

The results also showed a significant effect (p<0.05) for the month of breeding season on the level of E2 regardless of parity and the general averages of E2 in July (56.09 ±3.17 pg/ml) and in August (56.03 ±2.20 pg/ml) were higher than in June (41.51 ± 1.75 pg/ml) and September (37.08 ± 0.51 pg/ml).

A similar estradiol increase of tendency with the advance of breeding season was also observed in ewes of L2, but with lower levels than those in L1.It was conclude that the current applied genetic improvement program (GIP) based on line production might help in increasing the level of E2 of L1 to be higher than in ewes of L2.

Thus, more investigations are recommended to study the dynamic of ovarian activities, characteristics of ovarian follicles, the relative changes of reproductive hormones and the effect of these changes on ovulation rate and litter size among ewes of these two different production lines.