Fail safe guides to grazing pregnant and lambing ewes on cereals – Phase II

Summary

​Grazing vegetative cereal crops is becoming an important strategic and tactical grazing option on mixed farms in Australia. However, metabolic disorders have been reported and many producers avoid grazing crops with reproducing ewes, others accept the risk and losses that go with it.

This project aimed to define the causes of metabolic risk and investigate options to minimise the risk. Mineral status of vegetative crops (wheat, barley and oats) and pregnant ewes grazing these crops was monitored on 18 farms in WA and NSW. Responses to supplements on six farms were also measured. Crops (particularly wheat grown in NSW) provided ewes with an unbalanced mineral supply of low Ca, Mg and Na accompanied by high K.

This combination increases the risk of hypocalcaemia and hypomagnesaemia. Partially consistent with this observation, ewes grazing crops had a low Ca status but did not show clear signs of low Mg status. Providing supplements containing Ca, Na and Mg improved the mineral status of the ewes and should be considered as a risk management strategy. Given that both endocrinological change and Ca status contribute to the onset of hypocalcaemia some evaluation of supplements under conditions of acute Ca stress are required.