EFFECTS OF SEASON ON EMBRYO RECOVERY RATE AND QUALITY IN BEEF-CATTLE

Seasonal effects on recovery rate and quality of embryos produced by b eef cows and heifers were studied. Donors were divided into three grou ps respecting character and body conformation: 1. breeds characterized with large framework (Charolais, Blonde d'Aquitaine, Simmenthal), 2. breeds with medium framework (Aberdeen Angus, Limousine), 3. Piemontes e heifers. FSH-P (Folicotropin, Spofa Prague) was applied for 4 days ( total dose in cows: 560 mg, total dose in heifers: 400 mg). Prostaglan din F-2alpha (Oestrophan, Leciva Praha) was added to the 5th dose of F SH. Three doses of frozen semen were used for insemination and repeate d insemination on Day 5 and Day 6 of the superovulation treatment. Emb ryos were recovered non-surgically on Day 7 post insemination. Data co llected in the period 1990-1996 in donors were analyzed with respect t o specific seasonal periods (spring, summer, autumn, winter). Rates of flushed heifers and cows are relatively high (84.7-100.0% and 86.0-96 .1%, respectively). III heifers, mean recovery rate amounted to ca. 6 ova/recovery (excluding winter season: 4.50 ova/rec.). Transferable em bryos (2.99 +/- 3.24) presented 78.4%, 58.0%, and 51.7% of embryos rec overed in spring, summer, and autumn period, respectively; the corresp onding ''winter'' value being 42.7% (P < 0.01, P < 0.05, P > 0.05). In cows, 6.61 +/- 7.26-11.07 +/- 6.23 ova were recovered in total; 1.46 +/- 2.48-5.86 +/- 3.63 transferable embryos. The highest rate of trans ferable embryos was found in summer (66.7%); somewhat lower rates were recorded in autumn (59.4%) and in spring (46.5%), the lowest in winte r (34.0% and 22.1% in specific sets). Rates of recovered ova and trans ferable embryos are very variable. Satisfactory results were found in all donor sets mainly in summer, autumn, and spring period; winter res ults were unsatisfactory.