Disruption of Bovine Oocytes and Preimplantation Embryos by Urea and Acidic pH1

Department of Animal Sciences, University of Florida, Gainesville, 32611-0910
Journal of Dairy Science - J DAIRY SCI 01/2003; 86(4):1194-1200. DOI: 10.3168/jds.S0022-0302(03)73703-5

ABSTRACT Feeding cattle diets high in degradable crude pro- tein(CP)orinexcessofrequirementscanreducefertil- ityandloweruterine pH.Objectivesweretodetermine direct effects of urea and acidic pH during oocyte mat- uration and embryonic development. For experiment 1, oocytes were matured in medium containing 0, 5, 7.5,or10mMurea(0,14,21,or28mg/dlureanitrogen, respectively). Cleavage rate was not reduced by any concentration of urea. However, the proportion of oo- cytes developing to the blastocyst stage at d 8 after insemination was reduced by 7.5 mM urea. In addi- tion, the proportion of cleaved oocytes becoming blas- tocysts was decreased by 5 and 7.5 mM urea. For ex- periment 2, putative zygotes were collected ∼ 9ha fter inseminationandculturedinmodifiedPotassiumSim- plex Optimized Medium (KSOM). Urea did not reduce the proportion of oocytes developing to the blastocyst stage, although 10 mM urea reduced cleavage rate slightly. For experiment 3, dimethadione (DMD), a weak nonmetabolizableacid, was used todecrease cul- ture medium pH. Putative zygotes were cultured in modified KSOM containing 0, 10, 15, or 20 mM DMD for 8 d. DMD reduced cleavage rate at 15 and 20 mM and development to the blastocyst stage at all concen- trations. Results support the idea that feeding diets rich in highly degradable CP compromises fertility through direct actions of urea on the oocyte and

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    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.


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