Abstract
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.
Highlights
Most previous reports have provided evidence that high protein diets, which result in elevated levels of plasma urea nitrogen, are related to decreased fertility in ruminants (McEvoy et al, 1997; Dawuda et al, 2002)
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
The results indicated that offspring number and weight of litter size at birth were significantly (P
Summary
Most previous reports have provided evidence that high protein diets, which result in elevated levels of plasma urea nitrogen, are related to decreased fertility in ruminants (McEvoy et al, 1997; Dawuda et al, 2002). The timing and mechanism(s) underlying the deleterious effects of excessive urea nitrogen on fertility remain unclear. Studies have examined the effects of urea nitrogen on oocyte maturation and embryo development in vitro (De Wit et al, 2001; Ocon and Hansen, 2003). High levels of plasma urea nitrogen changed the follicular, oviductal and (or) uterine environment, which impacted the competency of the embryos for continued development beyond day 7. Oocytes and embryos were recovered from superovulated donor mice fed diets supplemented with 1.0% and 3.0% urea. The collected oocytes and embryos were assessed for quality and stage of cleavages respectively
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