Effect of dietary urea on ovarian structures in Saidi ewes during follicular and luteal phases

Abstract EN

The aim of this study was to record the number of ovarian follicles, to evaluate the quality of oocyte and to determine serum concentrations of luteinizing (LH) and progesterone (P4) hormones in Saidi ewes fed on urea in relation to follicular and luteal phase.

Eighteen clinically healthy ewes of initial body weight 33.8 ± 2.71 kg and about 4 years age were randomly assigned to three groups ; the control group (G1) was given basal control diet which met energy requirements for body weight maintenance and the other two groups were fed on basal diet with 1 % (G2) and 1.5 % (G3) urea on dry matter (DM) basis.

The duration of this study was lasted for 3.5 months.

The estrous cycles of the ewes were synchronized using two injections of prostaglandin (PGF2α).

In each group, three animals were slaughtered 40 hrs.

after the second injection of PGF2α (follicular phase) whereas the remaining three animals were slaughtered 10 days after the second injection of PGF2α (luteal phase).

Upon slaughtering, blood sample and reproductive systems were collected.

Stages of estrous, weight of ovaries in addition to the numbers of follicles were recorded.

Follicles were categorized according to their diameter into ; < 2, 2-4 and > 4 mm.

Follicles (2-4 and > 4 mm) were aspirated for recovery of oocytes and recording their quality.

Oocytes were graded into cumulus enclosed; partially cumulus enclosed and denuded oocytes.

Ovulation rate was recorded through the number of corpora lutea or albicantia.

Concentrations of P4 and LH hormones were determined.

Differences in response to synchronization among groups were observed.

Numbers and diameters of follicles were decreased (P > 0.05) in G2 and (P < 0.05) G3 compared to G1.

Numbers of aspirated follicles, and quality of oocytes decreased in (P < 0.05) G2 and G3 compared to G1.

Ovulation rate showed no significant difference among experimental groups.

Concentration of P4 decreased (P < 0.05) in the G3 compared to G1 during luteal phase.

It could be concluded that dietary urea had a negative effect on the ovarian follicle numbers and diameters, oocyte quality and serum P4 concentrations.