Lupin supplementation around joining and embryo survival in merino ewes

The literature review discusses studies of interaction between nutrition of the ewe in early pregnancy and embryo survival. Reports of elevated nutrition associated with increased or decreased embryonic mortality are examined and possible mechanisms relating nutrition to embryonic mortality are discussed. In Experiment One (Chapter three), the reproductive details in sheep (ovulation rate, embryo survival and returns to service) and progesterone measurements in blood were recorded as a means of assessing early embryo survival. The specific hypothesis tested was that lupin grain supplements for ewes after mating can lead to increased embryo mortality. The experiment also investigated whether this mortality can be reduced by strategic progesterone therapy using controlled internal drug release (CIDR). All ewes were fed lupins (500g/head/day) plus hay for seven days prior to joining. The diets of hay or hay plus lupins were fed to ewes during the early embryonic period (first 14 days of pregnancy). The overall ovulation rate (number of ova shed per ewe) was 1.06, indicating that despite being fed lupins, few ewes had multiple ovulations. Ewes fed lupins diet and given a progesterone supplement had a higher non-return to service rate (at day 21). This observation was not, however, reflected by the number of foetuses present at scanning at day 65 after mating. This implied that late embryonic mortality might have occurred in some ewes. The influence of nutrition on plasma progesterone in goats was investigated in Experiment Two (Chapter four). Ovariectomised does fed below maintenance (0.5M) rations and given exogenous progesterone (CIDR) had higher concentrations of peripheral progesterone compared with those fed higher levels (1.0M and 2.0M) of rations. This indicated that an increased hepatic clearance of progesterone, similar to that in sheep, may occur in the goat. In conclusion, the data collected in this study do not support the hypothesis that lupin grain supplementation could lead to decreased peripheral plasma progesterone concentrations and increased embryo mortality in ewes fed such diets. The data collected in the. study with ovariectomised does supported the hypothesis that feed intake could influence the clearance rate of peripheral progesterone concentration in a similar way to that observed in the sheep. This shows that sheep and goats have similar metabolic clearance rates of progesterone