The objectives of the present study were to investigate the effects of dietary urea supplementation (1.0% and 3.0%) on
oocytes quality, timing expected of embryo cleavages, offspring numbers and weights, blood components and rectal
temperature in mice. Sixty of growing albino mice were classified into three groups; the control group was given basal
control diet and the other two groups were fed on basal control diet supplemented with 1.0% and 3.0% urea. Body
weights were recorded at the beginning and after 5 weeks. Thereafter, five female mice of each group were injected
with 7.5 IU of pregnant mare serum gonadotropin (PMSG) for determination of oocyte quality after 48h of injection.
The fifteen female mice of each group were injected with 7.5 IU of PMSG followed by 7.5 IU of human chorionic
gonadotropin (hCG) after 48h and mated with males of proven fertility. Five mated females of each group were used for
determination of embryo cleavages to four cell stage and the other five mated females were used for determination of
embryo cleavages to eight cell stage upon 59-60 and 70 h of hCG injection, respectively. Rectal temperatures were
recorded and blood samples were collected. The remaining five mated females of each group were left for parturition.
The offspring number, litter size and male:female ratio were recorded. Hematocrit and hemoglobin concentrations
were determined in blood whereas urea, total protein, albumin, glucose calcium and phosphorus concentrations were
determined in plasma. The results indicated that offspring number and weight of litter size at birth were significantly
(P<0.05) increased in the urea groups compared to control group. Percentage of good quality oocytes was high (70%)
in control group compared to 3% urea group (60%). Dietary 3% urea was delayed cleavages to four-cell stage embryos
at the expected time. Dietary urea was significantly (P<0.05) increased concentrations of hematocrit and hemoglobin
in blood and urea, total protein, globulin, glucose, potassium and phosphorus in plasma. In conclusions, although 3%
dietary urea decreased oocytes quality and timing expected of embryo cleavages to four cell stages, it increased
significantly (P<0.05) offspring number and weight of litter size.