In Exp. 1A, hybrid mice (N = 10) were provided with food and 25% (v/v) ethanol as the only source of liquid for 72 h, beginning at the detection of the copulatory plug (08:00 h, Day 1). Control mice received food and tap water. Food consumption (P < 0\m=.\001) but not total caloric intake (P > 0\m=.\05) was less for the alcohol-treated mice than the controls. Ethanol-derived calories averaged 35% of caloric intake during the 72 h of treatment. Alcohol-treated animals showed a dramatic weight

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... s until Day 5 while controls gained weight (P < 0\m=.\05), Ethanol consumption did not influence pregnancy rate, litter size or litter weight. In Exp. 1B, animals were treated as in Exp. 1A, but were killed at various times between 24:00 h, Day 1, and 08:00 h, Day 4. Trunk blood was used to determine haematocrit and serum to determine alcohol concentration. Haematocrit was greater (P < 0\m=.\05) for all alcohol-treated mice than for controls at all time periods sampled except one. Dehydration was therefore probably responsible for the weight loss seen in Exps 1A and 1B. Average blood alcohol concentrations fluctuated with time of day and day of treatment. Average maximum concentration was 91 \ m=. \ 4 mg ethanol/100 ml serum. In Exp. 2, hybrid mouse 2-cell embryos were cultured in vitro in 0 or 0\m=.\1%ethanol (Exp. 2A) and 0 or 1 \m=.\0%ethanol (Exp. 2B) for 8 days. There was no effect (P > 0\m=.\05) of 0\m=.\1%ethanol on the percentage of embryos reaching the morula or expanding, hatching or hatched blastocyst stages at various times as compared to control embryos. Fewer embryos (P < 0\m=.\05)developed to these stages when cultured in 1\m=.\0%ethanol. Embryos cultured as in Exp. 2 were transferred to Day-3 pseudopregnant recipients on the afternoon of Day 4 of development to determine their viability (Exp. 3). Alcohol-treated (0\m=.\1%) and control embryos survived equally well in utero except that a greater percentage (P < 0\m=.\05) of treated embryos implanted than did controls (37 vs 20% of all embryos transferred, respectively). Embryos cultured in 1\m=.\0%alcohol before transfer had lower (P < 0\m=.\05)implantation rates and lower (P < 0\m=.\05)fetal survival. Twelve control but only one alcohol-treated embryo survived to term. At blood concentrations up to 91 mg/100 ml and at in-vitro concentrations of 0\m=.\1%therefore, ethanol did not have any deleterious effects on preimplantation embryo development. When cultured in 1\m=.\0%ethanol, embryo development was inhibited but not completely.