EFFECT OF LEVEL OF DIETARY ENERGY AND PROTEIN ON EMBRYO SURVIVAL AND PROGESTERONE PRODUCTION ON DAY 8 OF PREGNANCY IN RASA-ARAGONESA EWES

The aim of this experiment was to investigate the effects of dietary p rotein and energy on ovulation rate and embryo survival to day 8 of pr egnancy, and the associated concentrations of progesterone in jugular, ovarian and uterine veins, in a Spanish breed of sheep. In mid-Octobe r, three groups of ewes were fed to provide 1.5 x (H; n = 9), 0.5 x (L ; n = 12) or 0.5 x plus 7.44 g CP/MJ ME (LP; II = 8) energy requiremen ts for maintenance of live weight from day -14 relative to a synchroni zed mating on day 0. A significant effect of nutrition on ovulation ra te was observed (H: 2.22 +/- 0.16; L: 1.50 +/- 0.16; LP: 1.88 +/- 0.12 corpora lutea; P < 0.05). Mean LH and progesterone concentrations wer e affected by nutrition on day 7, L ewes showing the highest mean LH l evel (P < 0.01), while H ewes presented the lowest mean LH concentrati on and the highest mean plasma progesterone concentration(P < 0.01). L aparotomies were performed on six animals of each group on day 8 to de termine the effect of nutrition on embryo development. A significantly higher percentage of embryos recovered from L and LP ewes presented a n earlier stage of development (morulae or early blastocysts) (P < 0.0 01), while 100% embryos of ii ewes were expanded blastocysts. The rati o expanded blastocysts/corpora lutea was significantly higher in H ewe s (0.86) when compared with L and LP groups together (0.57; P < 0.05). Mean progesterone concentration in the ovarian vein was 800-fold high er than mean jugular venous levels with no differences between groups. Samples from ovarian veins contralateral to corpus luteum-bearing ova ries showed mean progesterone concentrations significantly lower than samples opposite to corpus luteum (ipsilateral: 1037.84 +/- 138.45; co ntralateral: 30.4 +/- 11.22 ng/ml; P < 0.001). Mean progesterone conce ntration in the uterine vein was approximately 30-fold higher than in jugular and similar in both uterine horns and treatments. No effect of nutrition on pregnancy rate was observed (H: 89%; L: 92%; LP: 100%). These results suggest that neither dietary energy nor protein art: abl e to modify pregnancy rate or progesterone concentrations in ovarian a nd uterine veins right days after mating, However, the delay in embryo development observed in the embryos collected from L and LP ewes may give rise to compromised embryo growth and development some days later . (C) 1997 Elsevier Science B.V.