Many pasture plants have a history of causing infertility in grazing animals (eg, ‘clover disease’) and bioactive substances in newly developed forages might to contain also affect reproductive processes. We therefore studied fertilisation of sheep oocytes and subsequent embryo development in vitro and evaluated effects of crude ethanolic extracts of 5 mainstream forage species (Bituminari butuminosa, Medicago sativa, Chicorium intybus, Trifolium subterraneum, Trifolium pratense) and 2 novel species (Biserrula pelecinus and Eremophila glabra). We used a factorial design with 7 extracts at 2 concentrations (50 and 100 µg mL-1) repeated 4 times. Cumulus-oocyte-complexes from adult ewe ovaries were randomly allocated to treatments, fertilized and cultured in vitro. Cleavage, embryo development rates and total cell number (TCN) were recorded.
Compared to control (0 µg mL-1), the addition of 50 µg mL-1of B. pelecinus extract to the in vitro maturation medium increased the cleavage rate (P<0.05). At this concentration, no other extracts had an effect. B .pelecinus at 100 µg mL-1 also increased (P<0.05) the blastocyst rate and blastocyst efficiency (P<0.05). TCN was affected by treatment (p<0.001). TCN values for C. intybus at 50 µg mL-1 were (p<0.05) greater than Control values, whereas TCN values for M. sativa at 50 µg mL-1 were significantly lower than Control values. No other individual treatment effects were significant. There was no interaction between treatment and stage of embryo development.
The effects of B. pelecinus on oocyte fertility and embryo development suggests that it contains plant secondary compounds that could improve reproductive success in grazing sheep. C. intybus and M. sativa also seem to contain compounds that affect the early morphogenesis of developing embryos. Further investigation is needed to identify the specific bioactive compounds that might affect reproductive performance in ewes as a ‘duty of care’ prior to the release of new forage species into industry.