Copper is stored in the liver. These levels deplete over winter and are lowest in winter and spring, when iron and molybdenum are highest.
CWD is not known to occur in New Zealand. It is a Transmissable Spongiform Encephalopathy (TSE) similar to Mad Cow disease (BSE) and Scrapie in sheep.
Vaccinations stimulate a sheep's own immune system to produce antibodies to fight infections.
The important trace elements in relation to conception rates in ewes are Selenium and Iodine and you need to ensure that deficiencies of these do not occur.
Toxoplasmosis is a protozoan disease of sheep that causes pregnancy loss. Sheep are a secondary host, with cats being the primary host that spreads the disease on the pasture, or in the feed in the case of hay.